Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic target?

Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic... DNA damage causes a local distortion of chromatin that triggers the sequential processes that participate in specific DNA repair mechanisms. This initiation of the repair response requires the involvement of a protein whose activity can be regulated by histones. Kinases are candidates to regulate and coordinate the connection between a locally altered chromatin and the response initiating signals that lead to identification of the type of lesion and the sequential steps required in specific DNA damage responses (DDR). This initiating kinase must be located in chromatin, and be activated independently of the type of DNA damage. We review the contribution of the Ser-Thr vaccinia-related kinase 1 (VRK1) chromatin kinase as a new player in the signaling of DNA damage responses, at chromatin and cellular levels, and its potential as a new therapeutic target in oncology. VRK1 is involved in the regulation of histone modifications, such as histone phosphorylation and acetylation, and in the formation of γH2AX, NBS1 and 53BP1 foci induced in DDR. Induction of DNA damage by chemotherapy or radia- tion is a mainstay of cancer treatment. Therefore, novel treatments can be targeted to proteins implicated in the regulation of DDR, rather than by directly causing DNA damage. Keywords VRK1 · H2AX · NBS1 · 53BP1 · p53 · Phosphorylation · DNA damage response · Ionizing radiation Abbreviations Introduction VRK1 Vaccinia-related kinase 1 DSB DNA double-strand break Genome stability DDR DNA damage response NBS1 Nijmegen breakage syndrome 1 (nibrin) Genome stability is essential for the maintenance of spe- NHEJ Non-homologous end-joining cies, but, at the same time, genetic variation is necessary for 53BP1 Tumor protein P53 binding protein 1 their evolution. Therefore, in all species, there are several ATM Ataxia-telangiectasia-mutated Ser/Thr kinase mechanisms aiming to protect DNA from genetic damage of endogenous or exogenous origin. Endogenous DNA damage is a consequence of the biological properties of cells, and includes oxidative stress, replication errors, transcriptional errors, or metabolism of DNA, to which cells are continu- ously exposed [1]. Alternatively, exogenous factors such as ultraviolet light, ionizing radiation, or chemicals also cause DNA damage to which exposure is frequently transient. The DNA damage has many different forms, single- or double- * Pedro A. Lazo strand breaks, nucleotide, or base modification [ 1]. To cope pedro.lazo@csic.es with all of them, cells have developed several specific DNA repair mechanisms, which increase their complexity in Experimental Therapeutics and Translational Oncology higher organisms because of the chromatin organization. Program, Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, 37007 Salamanca, Double-strand breaks constitute the most serious form of Spain DNA damage that has two alternative repair mechanisms Instituto de Investigación Biomédica de Salamanca (IBSAL), depending of the situation of the cell cycle. During repli- Hospital Universitario de Salamanca, 37007 Salamanca, cation, DNA double-strand breaks (DSBs) are repaired by Spain Vol.:(0123456789) 1 3 2376 I. Campillo-Marcos, P. A. Lazo homologous recombination (HR) using as template the other in the local chromatin organization. Chromatin can function chromatid. In non-dividing-cells or in G0/G1 phases, DSBs as a signaling platform that has effects not only on its remod- are repaired by non-homologous end-joining (NHEJ) [2]. eling, but can also send signals to other processes involved in Independently of the origin of DNA lesions, these lesions nuclear dynamics [14]. When cells encounter a stress such as have to be detected rapidly and efficiently before cells DNA damage, the activation of complex signaling networks divide, to avoid transmitting the damage to their progeny. triggers the detection and repair of the damage in a specific Because nuclear kinases are capable of rapidly and revers- and sequential process, before returning to the homeostatic ibly responding to changes in the cell and its environment, equilibrium. These networks integrate a wide variety of sig- and of integrating diverse stimuli, they are likely to be nals from inside the cell, transduced through protein kinases involved in sensing, triggering, regulating, and organizing [10–12], to ultimately control cell cycle arrest or progression the sequential steps that are needed for a correct and specific in the case of dividing cells [15]. Moreover, the chromatin- DNA damage response. signaling platform regulates DDR, cell cycle checkpoints, Cells are continuously exposed to DNA damage and it cell death, and senescence, among others. All these pro- can occur at any time during the cellular lifetime. The num- cesses are associated with the maintenance of genetic sta- ber of normal cell division is limited to approximately 40 bility and the transmission of a mutation-free genome to because of telomere shortening, which implies that, in the daughter cells. The major pathological consequence of DNA life of the organism, most cells are not dividing at the time of damage is the potential transmission of mutations to their exposure to DNA damage [3, 4]. Furthermore, cells are most progeny [16], which are implicated in aging and cancer [17]. of their lifetime in the G0/G1 phases, in which homologous In addition to the role of DNA damage in cancer, alterations recombination is not functional [5], but are exposed to DNA in DNA repair genes are also associated with neurodegenera- damage. Furthermore, stem cells have an enhanced response tive diseases [18], since neurons are not dividing in most of to DNA damage mediated by the NHEJ pathway [6]. There- the individual lifetime and have to repair these DNA lesions. fore, most of the DNA lesions will occur and have to be Most research into DNA damage responses has been studied repaired in the absence of replication. Very often, there is a in the context of replication and cell division [16]. large time interval between the moment in which DNA dam- In the highly organized eukaryotic chromatin, the most age occurs and the time when an individual cell replicates, vulnerable DNA is the fraction that is transcriptionally active in which most cells are non-dividing, and are thus able to at the time of exposure to damaging agents, particularly in pass the mutation to their daughter cells. Consequently, each resting or non-dividing cells, such as stem cells or neurons. cell has to deal individually with this problem and to respond In these locations, DNA has to relax and open to allow the independently of its particular situation, which is very vari- access of RNA polymerase and permit gene transcription. In able within a tissue. Cells are either resting or dividing, and these transcriptionally active regions, DNA is more exposed their individual position within a tissue implies that cellular and vulnerable, particularly in non-dividing or cells in G0/ interactions are heterogeneous depending on its location. G1. Therefore, in an individual resting cell, the response to DNA repair mechanisms have to function in all these dif- DNA damage does not have to be linked to cell division, ferent cellular contexts. In the particular case of neurons, differentiation state, or the cell location and its interactions by their exposition to oxidative stress, the accumulation of within a tissue. Even in dividing cells, the G1 phase last DNA damage might be a pathogenic mechanism for dete- several hours before entering replication. DNA damage has rioration of neurological functions associated with aging. to be detected, identified, and repaired immediately in all Recent evidence indicates that a significant proportion of the different types of situations. DNA damage is of endogenous origin [7, 8]. Francis Crick predicted that several redundant mechanisms must exist to repair damaged DNA and maintain genome integrity [9]. Cellular response to DNA damage Since then, several pathways have been identified [10– 13]. Induction of DNA damage is a mainstay of cancer treatment, The cellular reaction to DNA damage involves two major aims; one is to protect the DNA, and the other to protect and the specific targeting of regulatory proteins implicated in DDR can lead to the development of new drugs. cells and the organisms from the consequences of unre- paired DNA damage. The cellular protection against DNA Chromatin and DNA damage damage is mediated by arresting cell cycle in proliferating cells, so that damage can be repaired before its transmission The cellular response to DNA damage has to be initiated and to daughter cells. However, if DNA damage is excessive and cannot be repaired, the alternative response is medi- triggered at the site of the DNA lesion, independent of its type. DNA damage causes a local distortion of the double ated by the induction of cell death, and in that way, there is no progeny of mutated cells. These two types of responses helix, and of its associated nucleosomes, which is reflected 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2377 are associated with p53 and activated by different types of Chromatin DNA damage. DNA repair requires a sequential reorganization of chro- Transcription factors matin to allow for the different and consecutive steps in each DNA Damage Response repair pathway, which includes protection of damaged DNA, ac recognition of the type of lesion, recruitment of specific H2A H3 p53 repair mechanisms, ligation of DNA ends, and restoration P KAT5 to its normal chromatin organization. After DNA damage, in Sox2 P addition to the DNA lesion, the initial effect is a local distor - ac ATF2 P ATM tion of chromatin, which is the initiating event to trigger the P VRK1 cascade of DNA repair processes. As organisms increased P CREB NBS1 in their complexity, new regulatory elements are necessary P P Jun not only to coordinate different functions in DDR, but also γH2AX to adjust to their much more complex and dynamic structure FXR of chromatin. Therefore, new regulatory mechanisms that integrate and coordinate basic processes are necessary. In Fig. 1 VRK1 relation with transcription factors and DNA damage this context, new regulatory elements have evolved from pre- response proteins in chromatin existing proteins. A candidate for this role must be a chroma- tin protein with a reversible enzymatic activity. Among the which are organized in nucleosomes and in direct contact 518 kinase of the human kinome, vaccinia-related kinase-1 (VRK1) is a potential candidate for this role because of its with DNA, contributing to chromatin spatial organization. VRK1 is detected in the chromatin fraction forming a stable association to chromatin and its targets, with the exception of chromosomes condensed in mitosis [19, 20]. complex with histone H3 [29]. Moreover, VRK1 phospho- rylates histones H3 [27, 29, 30], H2A [31, 32] and H2AX [29]. Therefore, it is very likely that nucleosome organi- zation can be modified by covalent modifications because VRK1 roles in chromatin of histone phosphorylations by VRK1. This regulation of histone covalent modifications is essential for different func- The VRK1 chromatin kinase tions, normal or pathological, requiring a dynamic chroma- tin reorganization [33, 34]. VRK1 is a Ser-Thr kinase that belongs to the VRK family that diverged early from branch of the human kinome that An additional role of VRK1 as a chromatin kinase is its association with transcriptional complexes, where it inter- led the casein kinase family [21]. Bacteria and yeast have no VRK or p53 members, invertebrates such as D. mela- acts and phosphorylates several transcription factors that include p53 [28], CREB [35], ATF2 [36], c-Jun [37], Sox2 nogaster or C. elegans have one member, and mammals have three members in their respective families. The complex- [38], and the farnesoid X receptor (FXR) [39]. ity of VRK family [22] parallels that of p53 [23] and the autophagic DRAM (death-related autophagic modulator) VRK1 as a sensor of chromatin alterations [24]. This increased complexity during evolution is likely to reflect the need for additional regulatory or coordinating Chromatin in interphase has a very large size and DNA lesions can occur at any place, heterochromatin and euchro- roles as organisms and their functions became more com- plex. In mammals and C. elegans, it is known as Vrk-1 [25], matin, which are likely to have a different sensitivity to DNA damage. Alterations of DNA by strand breaks or chemical and in D. melanogaster as nucleosomal histone kinase 1 (NHK-1) [26]. modifications, such as oxidation, alkylation, or intercalation among others, will alter the chromatin organization by intro- VRK1 is a Ser-Thr kinase in nuclei [19] that is located on chromatin in resting cells and in all phases of the cell cycle ducing a local distortion [40, 41], which is a likely initiating event for triggering the complex processes of DNA repair covering all DNA, except when chromosomes are already condensed in mitosis [27, 28], in which VRK1 is ejected [42–44]. However, responding to DNA damage requires the coupling of chromatin distortion to a signal transduction from mitotic chromosomes. When chromosomes segregate, VRK1 returns to chromatin in daughter cells. VRK1 forms system, probably mediated by a nuclear chromatin kinase. A requirement for a sensor kinase is that its activation stable complexes with several different types of chromatin proteins, ranging from histones, transcription factors, and is independent of the type of DNA damage and, therefore, is not associated to any particular type of DNA damage. proteins involved in DNA repair processes (Fig. 1). The pro- teins more closely associated with DNA are histones [29], In this latter case, the kinase involved will participate in 1 3 2378 I. Campillo-Marcos, P. A. Lazo specific steps of a particular DNA damage, as is the case for [29]. ATM-null cells, such as the HT144 cell line, has a high ATM, ATR, or DNA-PK in the response to double-strand endogenous level of H4K16ac that is also lost by depletion +/+ DNA breaks [45]. In the particular case of VRK1, its kinase of VRK1 [29]. In ATM cells, this acetylation induced activity increases tenfold after induction of DNA damage by IR does not occur in the absence of VRK1 [29]. These independently of its type, which includes pyrimidine dimers results indicate that VRK1 is a good candidate to regulate caused by ultraviolet light, single-strand DNA breaks caused the enzymes involved in epigenetic modifications of chroma- by hydroxyurea treatment, or double-strand DNA breaks tin. DNA damage causes a local distortion of chromatin that induced by either doxorubicin or ionizing radiation [46]. can affect its different covalent modifications. Consequently, Early sensor mechanism of DNA damage must fulfill the regulation and coordination of histone modifiers such some basic requirements, be a nuclear enzyme that inter- as acetylases, deacetylases, methylases, and demethylases acts with basic chromatin components in nucleosomes, and is very poorly understood. Moreover, VRK1 also directly be a capable of an immediate signaling reaction that is also phosphorylates histone H2A in T120 [32], which is next to reversible. In this context, a kinase, such as VRK1, is a very K119 ubiquitinated, and both modifications are functional suitable candidate for this role [29, 46, 47]. alternatives, being T120 phosphorylation an activator of Other important early proteins at the site of specific types chromatin. Thus, two histones in nucleosomes, H3 and H2A, of DNA damage are Ku70/Ku80 (XRCC6/XRCC5), which are directly regulated by VRK1. Furthermore, histone H4 have to re-localize and interact with free DNA ends at the is not a phosphorylation target of VRK1, but its covalent breakpoints, mainly in double-strand breaks [48], a subtype modification by acetylation is sensitive to VRK1 in an ATM- of DNA damage, or in telomeres [48, 49]. It is unknown independent manner, since it is detected in ATM-null cells whether these proteins are targets of VRK1, but it is a real [29]. possibility. Ku70 and Artemis have multiple phosphoryla- It is important to remark that the sensor kinase activity tion sites, but the kinases involved in their specific phospho- has to be regulated by protein–protein interactions. In this rylation and their regulation are unknown. Telomeres are context, the C-terminal region of VRK1 has a low complex- naturally occurring DNA ends in chromosomes and there ity structure, which is very flexible and can adopt different is evidence for a role of VRK1 in their maintenance [50]. conformations [58]. This C-terminal region can fold and Moreover, VRK1 phosphorylates hnRNP A1 (heterogeneous block the active site of the kinase [58] and proteins inter- nuclear ribonucleoprotein A1) and facilitates its binding to acting with this region can modulate the activity of VRK1. telomeric ssDNA and telomeric RNA [50]. Two proteins that inhibit the VRK1 kinase activity have been identified, macrohistone H2A1.2 in interphase [ 59], VRK1, chromatin relaxation, and histone acetylation and Ran-GDP, but not Ran-GTP [60], which have an asym- metric nuclear distribution [61]. DNA damage and local disruption of chromatin are associ- ated with an increase in histone acetylation, which is medi- ated by KAT (lysine acetyl transferase) proteins. Histone VRK1 in DNA damage responses acetylation extends over an area of several hundred kilobases flanking the damaged DNA site [51, 52], which requires the VRK1 and histone H2AX local activation of KATs by a not yet identified mechanism. Defects in histone acetylation are associated with an increase VRK1 directly and stably interacts with histones H2AX in cellular sensitivity to DNA damage as a consequence of a and H3 in basal conditions, and is able to phosphoryl- defective DNA repair [53, 54]. Furthermore, acetylation of ate them in  vitro with purified proteins in Ser139 and histone H4 in Lys16 disrupts the interaction between H4 and Thr3, respectively [29]. The early response to DNA dam- H2A–H2B, and facilitates the relaxation of chromatin [55, age requires the phosphorylation of H2AX in Ser139 56]. Consistently, the inactivation of KAT5/Tip60 blocks (γH2AX). γH2AX covers large areas of DNA surround- the opening of chromatin at DSBs (double-strand breaks) ing the site of DNA damage [62] and protects DNA from that are required to facilitate the repair process [52]. Induc- exonuclease attack. This γH2AX organization can also tion of DNA damage by UV light or radiation causes an function as a platform for the recruitment of proteins increase in histone acetylation [52, 57]. Depletion of VRK1, that participate in sequential DDR steps, such as NBS1, a nucleosomal chromatin kinase, causes a loss of histones 53BP1, or BRCA1, among others [40, 63]. Phosphoryla- H3 and H4 acetylation, which are necessary for chromatin tion of histone H2AX in Ser139 (γH2AX) is a mark of relaxation, either in basal conditions or after DNA damage, an early reaction to DNA damage that can be detected by independently of ATM and p53 [29]. VRK1 knockdown formation of γH2AX foci [62, 64]. The phosphorylation also causes a loss of specific histone acetylations, including of H2AX and the formation of γH2AX foci induced by H4K16 acetylation (H4K16ac), induced by DNA damage ionizing radiation (IR) are lost by depletion of VRK1 and 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2379 can be rescued by kinase-active, but not by kinase-dead, VRK1 and NBS1 in early DDR VRK1 [29]. This effect of VRK1 is also independent of ATM, suggesting that VRK1 is an upstream participant. Cellular responses to DNA damage require the formation of VRK1 is also necessary for the activation of ATM and protein complexes in a highly organized fashion. In resting CHK2 in response to IR [46]. However, in the absence cells, VRK1 plays an important role in the formation of ion- of ATM, the γH2AX foci induced by IR have a smaller izing radiation-induced foci formed by γH2AX, NBS1, and size, which indicates that both kinases cooperate either in 53BP1 during DDR. The MRE11 complex holds together the formation or stabilization of the foci [29]. This latter the two free ends of the broken DNA. This complex, formed possibility might be a consequence of the effect of VRK1 NBS1–Mre11–Rad50, is highly dynamic and has a very on the stability of NBS1 [47]. In this context, VRK1 is a complex organization [66]. Phosphorylation of NBS1/nibrin novel chromatin component that reacts to its alterations is necessary for the recruitment of ATM to damaged sites and participates very early in DDR by itself and in coop- and for the stabilization of the repair complex [73]. VRK1 is eration with ATM [29]. activated by DNA double-strand breaks induced by ionizing radiation (IR) or doxorubicin, and specifically phosphoryl- ates NBS1 in Ser343 [47] and 53BP1 in serum-starved cells VRK1 and specific DNA damage response proteins and ATM-null and p53-null cells [46], indicating that they are independent of both p53 and ATM activation [47], and Because of the physical association of VRK1 with chroma- consistent with VRK1 role as an early step in the response tin, VRK1 has also been implicated in the regulation of DDR to DNA damage. Depletion of VRK1 causes a loss of NBS1 proteins. The VRK1 kinase has also been directly associated stability that is prevented by treatment with the MG132 pro- with different components in DDR pathways, which have teasome inhibitor [47]. This phosphorylation mediated by been studied in the context of the response to DSBs, in both VRK1 protects the NBS1 protein of RNF8-mediated ubiqui- resting and cycling cells as well as in ATM-null and p53- tination [47]. Therefore, it is likely that NBS1 phosphoryla- null cells. VRK1 physically interacts and directly phospho- tion by VRK1 contributes to the stabilization of foci, and rylates specific proteins participating at different sequential facilitates the recruitment of additional participants in the stages of DDR, which include H2AX [29], NBS1 [47], and specific DNA repair process, such as kinases of the PI3K 53BP1 [46, 65] in NHEJ [66, 67]; and all of these activating family, ATM, ATR, or DNA-PK, for specific signaling steps phosphorylations are lost by VRK1 depletion. Intermediate or pathways in DDR [45]. steps in DDR signal transmission are well known. The most common pathways in DNA damage response (DDR) impli- VRK1 and 53BP1 in NHEJ cate protein phosphorylation by different kinases such as ATM [10], ATR [11], and DNA-PK [12]; all members of the Double-strand breaks are the most serious form of DNA PI-3K family, which have been mostly studied in the context damage, particularly in cells that are resting or in the early of cell division and cell cycle checkpoints [15]. In response phases of the cell cycle, which includes differentiated rest- to double-strand breaks induced by ionizing radiation (IR), ing cells, as neurons, and stem cells. Under these conditions, the 53BP1 scaffold protein is recruited to IR-induced foci these DSBs are repaired by non-homologous end-joining (IRIF), and is an important marker for monitoring cellular (NHEJ); and one of its main components is 53BP1, a scaf- DDR by NHEJ. 53BP1 foci induced by ionizing radiation or fold protein that forms foci induced by DNA damage [74]. doxorubicin are intermediate steps in DDR activation [68, VRK1 stably interacts with 53BP1 in the region comprised 69] and are known to be regulated by ATM in response to between residues 955-1354, which is implicated in the DSBs [70], and by ATR in response to replication stress interaction with H2AX, but its phosphorylation site is in [71]. However, it is also known that DNA damage response Ser25/29 within the 53BP1N-terminal region and occurs can be ATM-independent [72]. The effect of VRK1 in DDR even in the absence of ATM (null cells) [46]. VRK1 deple- is insensitive to inhibitors of PI3KK proteins that target tion causes a defective formation of 53BP1 foci induced by ATM and DNA-PK [46]. This suggests that there are alterna- ionizing radiation or doxorubicin, both in number and size, tive kinases participating in DDR induced by ionizing radia- which requires a kinase-active VRK1 protein for their rescue tion. The complete molecular components that sequentially [46]. Moreover, this effect of VRK1 on 53BP1 foci is insen- participate in DDR, particularly regulatory proteins, remain sitive to ATM and DNA-PK inhibitors and is functional in unknown. In this context, VRK1 knockdown also prevents p53-null and ATM-null cells. All these data indicate that the the activating phosphorylations of ATM in Ser1981, CHK2 effect of VRK1 is independent of both ATM and p53 [46], in Thr68, and DNA-PK in Ser2056, all induced in response and that VRK1 activation in response to DNA damage is a to IR [46], suggesting that VRK1 is an early and upstream novel participant in the NHEJ mechanism of mammalian component in this DDR process. DNA damage responses [29, 46, 47]. 1 3 2380 I. Campillo-Marcos, P. A. Lazo stress or DNA damage, the basal intracellular level of the Cellular protection mediated by VRK1 and its p53 protein is very low, but it is always present. This basal target p53 low level of p53 is necessary to initiate a fast response to cellular stress by its immediate phosphorylation. The VRK1 forms a complex and phosphorylates p53 p53 phosphorylation in several residues within its TAD1 region (residues 1–46) is the main determinants of the The p53-mediated responses induced by DNA damage stress response [79]. To trigger an immediate reaction to have two major roles in the context of cellular protection DNA damage, the response will be greatly facilitated by (Fig.  2). The first one is preventing the transmission of the formation of a stable and inactive complex between damaged DNA to daughter cells during cell proliferation. p53 and one of its regulatory kinases that are activated by This p53 action is mediated by the induction of a cell cycle DNA damage. In non-damaged cells, the basal low p53 arrest, and forms part of cell cycle checkpoints [75, 76]. level is partially forming a stable complex with VRK1, The other role is the protection of the organism from the which are detected by reciprocal immunoprecipitations, consequences of accumulating cells with damaged DNA, and are detected in resting and cycling cells [81]. This which is mediated by induction of cell death [77]. The basal VRK1-p53 complex forms a basic early warning p53 transcription factor mediates these two main protec- system for detection of cellular stress and its activation is tive responses that are regulated by p53 immediate phos- induced by DNA damage caused by ultraviolet light, ion- phorylation in response to DNA damage. These cellular izing radiation, or doxorubicin treatments. All these types responses have a different temporal order because of the of DNA damage activate the kinase activity of VRK1, a covalent modifications, which are immediate as the stabi- previous step required for the specific phosphorylation of lization of p53, or require hours, such as the induction of p53 at Thr18 [28, 81]. Therefore, the subpopulation of specific gene expression. basal p53 that is forming a complex with VRK1 facili- The stabilization and activation of p53 is performed by tates a readiness state of p53 to initiate an immediate acti- several Ser-Thr kinases that target different residues within vating response in different cellular stress situations [28, the p53N-terminal transactivation domain (Fig.  2), and 81]. Furthermore, the p53 protein also indirectly plays an have different sequential roles [78– 80]. In the absence of important role in epigenetic regulation of chromatin [82]. Fig. 2 Kinase activation DNA damage induced by DNA damage and the regulation of p53 in G0/G1 cells. An enzyme (X) activated by VRK1, and that has not yet Local chromatin been identified, mediates the alteration AT M activation of ATM CHK2 Ub VRK1 Ub Ub Ub P P Ub Ub Ub Ub p53 p53 p53 p53 p53 mdm2 Target genes Proteasomal degradaon BAX CDKN1A MDM2 BBC3 (PUMA) (p21) NOXA Cell cycle Apoptosis arrest 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2381 autophagic proteins [94]. The reversion of activated p53 Phosphorylation of p53 by VRK1 prevents the interaction with MDM2 and regulates the switch also requires downregulation of p53 activating kinases, including VRK1 and ATM, so that dephosphorylated between ubiquitination and transcription p53 is not re-phosphorylated and becomes accessible to MDM2. In this context, p53 induces of the expression of Non-phosphorylated p53 binds to the human MDM2 (HDM2) ubiquitin ligase [83]. VRK1 uniquely and specifi- DUSP6 and WIP1 phosphatases targeting ATM [95–97], and that of the DUSP4 phosphatase targeting VRK1 [98, cally phosphorylates p53 in Thr-18 [28, 84, 85]. This Thr18 residue is critical to maintain the folding of the p53 α-helix 99]. However, downregulation of p53 activation is more complex and also requires additional deactivation of other required for its binding to a hydrophobic pocket in MDM2 [86]. The phosphorylation of p53 in Thr18 alters the align- kinases, which are mediated by phosphatases, and deacety- lation of p53 [94]. ment of hydrophobic residues in this α-helix, and this altered conformation permits the p53 binding to transcriptional The stabilization and accumulation of p53 by VRK1 in response to DNA damage is reverted by a novel p53-depend- cofactors. Moreover, this phosphorylation of Thr18 deter- mines the change in binding mode from ubiquitin ligases to ent activation of autophagy that removes its activating VRK1 [100], a p53 stabilizer, and thus permits p53 dephos- transcription factors, and additional p53 phosphorylation in Ser15 or Ser20 [87] contributes to the selection of specific phorylation and its downregulation by MDM2 [85, 100, 101]. Among the degradation processes regulated by p53 is transcriptional cofactors [88]. The specific phosphorylation of p53 in Thr18 places VRK1 upstream of additional phos- autophagy. In normal cells, autophagy contributes to regu- late basal levels of cytosolic and particulate proteins [102], a phorylation in Ser15 and Ser20 mediated by other kinases [79]. The activated ATM-CHK2, ATR-CHK1, or DNA-PK process that is further activated in response to several types of stress, including DNA damage. Autophagy is required pathways mediate the phosphorylation p53 in Ser15 or Ser20 [78, 79], and all of them are necessary to achieve the full for recycling of proteins implicated in negative cell cycle regulation, and can provide a survival strategy to tumor cells transcriptional activation of p53 [88]. These additional p53 phosphorylations, and their combination, select transcrip- [103]. By this process, regulated by p53, cells remove and digest endogenous proteins, particularly those that are very tional cofactors and activate p53-dependent genes such as CDKN1A (p21) expression [89], which induces a cell cycle stable, functioning as an important mechanism for tissue remodeling [103] and maintenance of cellular homeostasis arrest and senescence [90], and BAX that facilitates apopto- sis [91, 92], among others. The role of p53 in transcription [104], but it can also result in a form of cell death, thus hav- ing a dual role [105, 106]. in these processes has been extensively reviewed [93]. The kinase activity of all these p53 kinases, VRK1, ATM, The downregulation of VRK1 is a late response that is also mediated by the p53-dependent transcription of DRAM ATR, and DNA-PK, are inducible by DNA damage, but their spatial organization, coordination, and sequential activation (death-related autophagic modulator) [107]. DRAM is a small hydrophobic protein located in the membrane of require further studies for its complete understanding. In this context, because of its interactions with histones, VRK1 is a autophagosomes [108]. Expression of DRAM facilitates degradation of VRK1 in the lysosome, and the elimination of new component that participates very early in the response mechanisms to DNA damage, as well as in specific steps DRAM or Beclin1 prevents the downregulation of VRK1 by proteolytic degradation [85, 100] (Fig. 3). This degradation of DDR. of VRK1 takes place in the cytosol and is sensitive to the inhibition of nuclear export with leptomycin B and to lysoso- Activated p53 induces the downregulation of VRK1 mal inhibitors [100]. DRAM expression induced by p53 reg- ulates the degradation of stable proteins. DRAM is a novel Once DNA damage has been repaired, the cell cycle arrest induced by activated p53 has to be reverted. Otherwise, component of the cell autophagic response [107]. Autophagy is partly regulated by p53-induced DRAM expression [107], p53 will maintain the cell cycle arrest or even induce apop- tosis. This reversal requires the deactivation of p53, which and p53-induced VRK1 degradation requires entry in the endosomal–lysosomal pathway [85]. In this way, DRAM is mediated by its dephosphorylation and subsequent inter- action with MDM2. However, the phosphorylation of p53 downregulates VRK1 forming an autoregulatory loop [101] (Fig. 3). Moreover, this autophagic downregulation of VRK1 in Thr18 by VRK1 blocks its interaction with MDM2 and other phosphorylations, in Ser15 and Ser20 further is altered in tumors with p53 mutations that affect its DNA- binding domain, including all the most frequent mutations interfere with the interaction [88]. All these phospho- rylations have to be removed, to revert the p53-mediated detected in human cancer [85, 109], because they disrupt this autoregulatory loop. Consequently, tumors harboring responses, such as a cell cycle arrest, in viable cells. This is accomplished by the regulation by p53 of different target p53 mutations also have very high levels of VRK1, as it has been shown in head and neck squamous cell carcinomas genes that range from ubiquitin ligases, phosphatases, to 1 3 2382 I. Campillo-Marcos, P. A. Lazo Fig. 3 Downregulation of ATM VRK1 by DRAM1 in the DNA damage autophagic pathway induced DRAM1 by p53 and deactivation of p53 by phosphatases and ubiquitin WIP1 ligases the proteasome in DNA damage response. Solid black VRK1 lines represent the activation route. Dashed lines represent ATM the downregulatory routes and each color represents a MDM2 different route. Kinases: VRK1 and ATM. Phosphatases: p53 WIP1 (wild-type P53-induced VRK1 DRAM1 phosphatase 1) and DUSP4 (dual specificity phosphatase endosome DUSP4 4). DRAM1: damage-regulated autophagy modulator 1 Beclin1 p53 Ub-p53 lysosome proteasome [110] and lung cancer [109], which can also facilitate cell proliferation and cell cycle progression, where it plays sev- proliferation. eral roles [121]. VRK1 is required for G0 exit, behaving like In conclusion, the main mechanism of downregulation of an early gene such as MYC and FOS, which facilitate the p53 is mediated MDM2, but for this to occur, it is necessary progression in G1 and passing the restriction point [113]. to previously dephosphorylate p53 and its activating kinases, In this context, depletion of VRK1 prevents the expression all of which are regulated by p53 [94]. Once p53 is dephos- of CCND1 (cyclin D1), since VRK1 directly binds to the phorylated, it becomes available for its ubiquitination by human CCND1 promoter [32], and consequently, retinoblas- MDM2 and degradation in the proteasome, which has been toma cannot be phosphorylated [110]. Later, in cell cycle extensively reviewed and has become a target for therapeutic progression, VRK1 is also required for the phosphorylation intervention with drugs that interfere with the p53-MDM2 of histone H3 that facilitates the initiation of chromatin com- interaction, such as nutlins [111]. paction in G2/M [27] and cooperates with AURKB in the sequential remodeling of chromatin in the progression of mitosis [122]. Implications of VRK1 in cancer biology However, based on the biological actions of VRK1, either in cell proliferation or DNA damage responses indicates that The functions of VRK1 suggest that it is likely to actively depending on the cellular context, VRK1 might function as participate in tumor biology. Knockdown experiments indi- an oncogene or a tumor suppressor or predisposition gene. cate that VRK1 plays a major role in cell cycle progression VRK1 might behave an oncogene because of its roles in and proliferation [27, 112, 113]. Moreover, VRK1 elimina- the promotion of cell cycle progression and proliferation. tion by CRISPR/Cas9 identifies wild-type VRK1 as an over - However, in other contexts, VRK1 might behave as a tumor expressed oncogenic driver gene [114], consistent with its suppressor or a tumor susceptibility gene represented by the role in lung adenocarcinomas [115]. In most cell types, the effects mediated by p53 and those associated with genome human VRK1 gene is expressed at different levels and is not stability. These properties, in the context of cancer, can mutated in cancer, and it is overexpressed in many cancer contribute to a poorer prognosis of tumors overexpressing types of different origins correlating with a poorer prognosis VRK1 because of its contribution to the promotion of cell in breast [116, 117], lung [115], liver [118], glioblastoma proliferation and resistance to treatments based on DNA [119], head and neck [110], and esophageal cancer [120]. damage. Some driver genes are oncogenic in situations in which they Due to the essential role played by VRK1, attempts to are overexpressed by different mechanisms, as it occurs with generate knock-out mice have been unsuccessful. However, members of the MYC and EGFR families that promote cell the consequences of VRK1 deficiency in animal models proliferation. In the context of tumor growth, the human have been studied in gene-trap mice with a fifteen percent VRK1 protein has been implicated in the regulation of residual level of VRK1 [123–125]. In this model, deficient 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2383 animals were sterile, both male and female [123–125], pre- high probability of high toxicity and side effects. The elimi- venting additional studies. The role that VRK1 plays in nation of VRK1 causes a defective DDR that facilitates and response to DNA damage in this model was not studied. increases the sensitivity to DNA damaging agents, such as In one of the studies, the problem was identified as lagging ionizing radiation or doxorubicin [65]. Depletion of VRK1 chromosomes during meiosis leading to sterility [124], an sensitizes cells to these treatments because of defective DNA observation consistent with the role of VRK1 in dynamic repair, and thus permits the use of lower doses of toxic drugs chromatin reorganization. In addition, VRK1 regulates the to achieve the same result. This is important, because this attachment of chromatin to the nuclear envelop that is medi- sensitization also occurs in non-dividing cells, and might be ated by the phosphorylation of BANF1 [126]. The disrup- useful for targeting non-dividing cells within a tumor that tion of this process can also lead to alterations of chromatin later might cause a relapse. Moreover, the treatment with a reorganization in mitosis and affect cell viability [127]. lower dose of commonly used cancer drugs can contribute to a reduction of the toxicity associated with them. Facilitating some degree of DNA damage in tumor cells VRK1 potential as therapeutic target can contribute to the generation of new antigens and facili- in oncology tate the response to new therapies based on manipulation of the immune system, as supported by the evidence that Protein kinases, because of their structural characteristics, tumors with an intrinsic higher genome instability are better are candidates for development of inhibitors. Knockdown responders to these new therapies [133]. screening is a useful approach to identify potential thera- In conclusion, the pharmacological targeting of VRK1 peutic targets. Knockdown of VRK1 sensitizes cells to other will impair p53-mediated responses, prevent cell cycle pro- cancer treatments based on DNA damage such as ionizing gression and proliferation, and sensitize cells to treatments radiation or doxorubicin by impairing the DNA damage based on DNA damage, such as ionizing radiation and some response [46, 65]. Moreover, depletion of VRK1 inhibits chemotherapeutic drugs. The consequence of therapeutically cell proliferation [113, 128]. VRK1 has been identified as exploiting this target will be a better control of the tumor a potential target in a screening of synthetic lethal relation- if the new drugs are selective regarding both its molecular ships in a massive siRNA screening [129]. These observa- target and the specific tumor cell. tions suggests that inhibitors of VRK1 can be of potential Acknowledgements I.C-M was supported by FPI-MINECO-Fondo use in cancer treatments, by themselves or in combinations, Social Europeo predoctoral contract (BES-2014-06772). The labora- by facilitating inhibition of proliferation and at the same tory was supported by grants from Agencia Estatal de Investigación- time sensitizing cells to treatments based on DNA damage. MINECO (SAF2016-75744-R) and Consejería de Educación de la In cancer treatment, many drugs are directed to the main Junta de Castilla y León (CSI001U16, UIC-017) to P.A.L. driver as targets. However, cancer cells can be derailed if alternative pathways that impinge on basic processes of the Compliance with ethical standards tumor phenotype are targeted. These alternative targets will Conflict of interest The authors declare no conflict of interests. open a wide range of possibilities, as well as provide with alternatives to manage individual cases. Open Access This article is distributed under the terms of the Creative Kinases share a common structure in their catalytic Commons Attribution 4.0 International License (http://creativecom- kinase domain and are druggable proteins [130]. Therefore, mons.org/licenses/by/4.0/), which permits unrestricted use, distribu- the likelihood of cross inhibition with other kinases is very tion, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the high and makes many kinase inhibitors promiscuous. In the Creative Commons license, and indicate if changes were made. human kinome, there are kinases that are isolated from other major branches, among which is VRK1. The VRK family has some structural differences, which makes its members susceptible of highly specific inhibition with no promis- References cuity as detected in kinase assays or by structural thermal shift upon binding to inhibitors [131, 132]. However, at this 1. Friedberg EC, McDaniel LD, Schultz RA (2004) The role of time, there is no specific inhibitor for VRK1. Testing kinases endogenous and exogenous DNA damage and mutagenesis. Curr Opin Genet Dev 14(1):5–10. https ://doi.or g/10.1016/j. inhibitors that target the main kinome families did not detect gde.2003.11.001 any that has an effect in assays of VRK1 autophosphoryla- 2. Ciccia A, Elledge SJ (2010) The DNA damage response: making tion and VRK1 phosphorylation of p53 or H3 [30]. This is it safe to play with knives. Mol Cell 40(2):179–204. https ://doi. due to the very high inhibitor concentrations needed because org/10.1016/j.molce l.2010.09.019 of their low ani ffi ty, which required doses in the micromolar range that have a very high risk of cross inhibition and of the 1 3 2384 I. Campillo-Marcos, P. A. Lazo 3. Flores I, Blasco MA (2010) The role of telomeres and telomerase VRK1 (vaccinia-related kinase 1). Encyclopedia of sign- in stem cell aging. FEBS Lett 584(17):3826–3830. https ://doi. aling molecules, 2nd edn. Springer Science. https ://doi. org/10.1016/j.febsl et.2010.07.042 org/10.1007/978-1-4614-6438-9_561-2 4. Henriques CM, Ferreira MG (2012) Consequences of telomere 21. Manning G, Whyte DB, Martinez R, Hunter T, Sudarsanam S shortening during lifespan. Curr Opin Cell Biol 24(6):804–808. (2002) The protein kinase complement of the human genome. https ://doi.org/10.1016/j.ceb.2012.09.007 Science 298(5600):1912–1934. h t t p s : / / d o i . o r g / 1 0 . 1 1 2 6 / s c i e n 5. Orthwein A, Noordermeer SM, Wilson MD, Landry S, Enchev ce.10757 62 RI, Sherker A, Munro M, Pinder J, Salsman J, Dellaire G, Xia B, 22. Nichols RJ, Traktman P (2004) Characterization of three paralo- Peter M, Durocher D (2015) A mechanism for the suppression of gous members of the mammalian vaccinia related kinase fam- homologous recombination in G1 cells. Nature 528(7582):422– ily. J Biol Chem 279(9):7934–7946. https://doi.or g/10.1074/jbc. 426. https ://doi.org/10.1038/natur e1614 2M3108 13200 6. Soteriou D, Fuchs Y (2018) A matter of life and death: stem cell 23. Belyi VA, Ak P, Markert E, Wang H, Hu W, Puzio-Kuter A, survival in tissue regeneration and tumour formation. Nat Rev Levine AJ (2010) The origins and evolution of the p53 family Cancer 18(3):187–201. https ://doi.org/10.1038/nrc.2017.122 of genes. Cold Spring Harb Perspect Biol 2(6):a001198. https :// 7. Tomasetti C, Vogelstein B (2015) Cancer etiology. Variation doi.org/10.1101/cshpe rspec t.a0011 98 in cancer risk among tissues can be explained by the number 24. Mrschtik M, Ryan KM (2016) Another DRAM involved in of stem cell divisions. Science 347(6217):78–81. https ://doi. autophagy and cell death. Autophagy 12(3):603–605. https :// org/10.1126/scien ce.12608 25doi.org/10.1080/15548 627.2015.11374 12 8. Tomasetti C, Li L, Vogelstein B (2017) Stem cell divisions, 25. Gorjanacz M, Klerkx EP, Galy V, Santarella R, Lopez-Igle- somatic mutations, cancer etiology, and cancer prevention. sias C, Askjaer P, Mattaj IW (2008) Caenorhabditis elegans Science 355(6331):1330–1334. h t t p s : / / d o i . o r g / 1 0 . 1 1 2 6 / s c i e n BAF-1 and its kinase VRK-1 participate directly in post-mitotic ce.aaf90 11 nuclear envelope assembly. EMBO J 26(1):132–143. https://doi. 9. Crick F (1974) The double helix: a personal view. Nature org/10.1038/sj.emboj .76014 70 248(5451):766–769 26. Cullen CF, Brittle AL, Ito T, Ohkura H (2005) The conserved 10. Savitsky K, Bar-Shira A, Gilad S, Rotman G, Ziv Y, Vanagaite kinase NHK-1 is essential for mitotic progression and unifying L, Tagle DA, Smith S, Uziel T, Sfez S, Ashkenazi M, Pecker I, acentrosomal meiotic spindles in Drosophila melanogaster. J Frydman M, Harnik R, Patanjali SR, Simmons A, Clines GA, Cell Biol 171(4):593–602. https ://doi.or g/10.1083/jcb.20070 Sartiel A, Gatti RA, Chessa L, Sanal O, Lavin MF, Jaspers NG, 6067 Taylor AM, Arlett CF, Miki T, Weissman SM, Lovett M, Collins 27. Kang TH, Park DY, Choi YH, Kim KJ, Yoon HS, Kim KT (2007) FS, Shiloh Y (1995) A single ataxia telangiectasia gene with a Mitotic histone H3 phosphorylation by vaccinia-related kinase product similar to PI-3 kinase. Science 268(5218):1749–1753. 1 in mammalian cells. Mol Cell Biol 27(24):8533–8546. https:// https ://doi.org/10.1126/scien ce.77926 00doi.org/10.1128/MCB.00018 -07 11. Lakin ND, Hann BC, Jackson SP (1999) The ataxia-telangi- 28. Vega FM, Sevilla A, Lazo PA (2004) p53 Stabilization and ectasia related protein ATR mediates DNA-dependent phos- accumulation induced by human vaccinia-related kinase 1. phorylation of p53. Oncogene 18(27):3989–3995. https ://doi. Mol Cell Biol 24(23):10366–10380. https ://doi.or g/10.1128/ org/10.1038/sj.onc.12029 73MCB.24.23.10366 -10380 .2004 12. Lee SE, Mitchell RA, Cheng A, Hendrickson EA (1997) Evi- 29. Salzano M, Sanz-Garcia M, Monsalve DM, Moura DS, Lazo PA dence for DNA-PK-dependent and -independent DNA double- (2015) VRK1 chromatin kinase phosphorylates H2AX and is strand break repair pathways in mammalian cells as a function required for foci formation induced by DNA damage. Epigenetics of the cell cycle. Mol Cell Biol 17(3):1425–1433. https ://doi. 10(5):373–383. https://doi.or g/10.1080/15592294.2015.10287 08 org/10.1128/MCB.17.3.1425 30. Vazquez-Cedeira M, Barcia-Sanjurjo I, Sanz-Garcia M, Barcia R, 13. Soria G, Polo SE, Almouzni G (2012) Prime, repair, restore: the Lazo PA (2011) Differential inhibitor sensitivity between human active role of chromatin in the DNA damage response. Mol Cell kinases VRK1 and VRK2. PLoS One 6(8):e23235. https ://doi. 46(6):722–734. https ://doi.org/10.1016/j.molce l.2012.06.002org/10.1371/journ al.pone.00232 35 14. Bustin M, Misteli T (2016) Nongenetic functions of the genome. 31. Aihara H, Nakagawa T, Yasui K, Ohta T, Hirose S, Dhomae Science 352(6286):aad6933. https ://doi.or g/10.1126/scien N, Takio K, Kaneko M, Takeshima Y, Muramatsu M, Ito T ce.aad69 33 (2004) Nucleosomal histone kinase-1 phosphorylates H2A Thr 15. Abraham RT (2001) Cell cycle checkpoint signaling through the 119 during mitosis in the early Drosophila embryo. Genes Dev ATM and ATR kinases. Genes Dev 15(17):2177–2196. https :// 18(8):877–888. https ://doi.org/10.1101/gad.11846 04 doi.org/10.1101/gad.91440 1 32. Aihara H, Nakagawa T, Mizusaki H, Yoneda M, Kato M, Doi- 16. Jackson SP, Bartek J (2009) The DNA-damage response in guchi M, Imamura Y, Higashi M, Ikura T, Hayashi T, Kodama human biology and disease. Nature 461(7267):1071–1078. https Y, Oki M, Nakayama T, Cheung E, Aburatani H, Takayama KI, ://doi.org/10.1038/natur e0846 7 Koseki H, Inoue S, Takeshima Y, Ito T (2016) Histone H2A 17. Hoeijmakers JH (2009) DNA damage, aging, and cancer. N Engl T120 phosphorylation promotes oncogenic transformation via J Med 361(15):1475–1485. https://doi. org/10.1056/NEJMra0804 upregulation of cyclin D1. Mol Cell 64(1):176–188. https ://doi. 615org/10.1016/j.molce l.2016.09.012 18. Rass U, Ahel I, West SC (2007) Defective DNA repair and 33. Tessarz P, Kouzarides T (2014) Histone core modifications regu- neurodegenerative disease. Cell 130(6):991–1004. https ://doi. lating nucleosome structure and dynamics. Nat Rev Mol Cell org/10.1016/j.cell.2007.08.043 Biol 15(11):703–708. https ://doi.org/10.1038/nrm38 90 19. Varjosalo M, Sacco R, Stukalov A, van Drogen A, Planyavsky 34. Bannister AJ, Kouzarides T (2011) Regulation of chromatin M, Hauri S, Aebersold R, Bennett KL, Colinge J, Gstaiger M, by histone modifications. Cell Res 21(3):381–395. https ://doi. Superti-Furga G (2013) Interlaboratory reproducibility of large- org/10.1038/cr.2011.22 scale human protein-complex analysis by standardized AP-MS. 35. Kang TH, Park DY, Kim W, Kim KT (2008) VRK1 phosphoryl- Nat Methods 10(4):307–314. https://doi.or g/10.1038/nmeth.2400 ates CREB and mediates CCND1 expression. J Cell Sci 121(Pt 18):3035–3041. https ://doi.org/10.1242/jcs.02675 7 20. Cantarero L, Moura DS, Salzano M, Monsalve DM, Campillo-Marcos I, Martín-Doncel E, Lazo PA (2017) 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2385 36. Sevilla A, Santos CR, Vega FM, Lazo PA (2004) Human vac- of repair proteins and repair of DNA double-strand breaks. Nat cinia-related kinase 1 (VRK1) activates the ATF2 transcriptional Cell Biol 8(1):91–99. https ://doi.org/10.1038/ncb13 43 activity by novel phosphorylation on Thr-73 and Ser-62 and 53. Bird AW, Yu DY, Pray-Grant MG, Qiu Q, Harmon KE, Megee cooperates with JNK. J Biol Chem 279(26):27458–27465. https PC, Grant PA, Smith MM, Christman MF (2002) Acetylation ://doi.org/10.1074/jbc.M4010 09200 of histone H4 by Esa1 is required for DNA double-strand break 37. Sevilla A, Santos CR, Barcia R, Vega FM, Lazo PA (2004) repair. Nature 419(6905):411–415. https://doi.or g/10.1038/natur c-Jun phosphorylation by the human vaccinia-related kinase 1 e0103 5 (VRK1) and its cooperation with the N-terminal kinase of c-Jun 54. Ikura T, Tashiro S, Kakino A, Shima H, Jacob N, Amunugama (JNK). Oncogene 23(55):8950–8958. https ://doi.org/10.1038/ R, Yoder K, Izumi S, Kuraoka I, Tanaka K, Kimura H, Ikura sj.onc.12080 15 M, Nishikubo S, Ito T, Muto A, Miyagawa K, Takeda S, Fishel 38. Moura DS, Fernandez IF, Marin-Royo G, Lopez-Sanchez I, R, Igarashi K, Kamiya K (2007) DNA damage-dependent Martin-Doncel E, Vega FM, Lazo PA (2016) Oncogenic Sox2 acetylation and ubiquitination of H2AX enhances chroma- regulates and cooperates with VRK1 in cell cycle progression tin dynamics. Mol Cell Biol 27(20):7028–7040. https ://doi. and differentiation. Sci Rep 6:28532. https ://doi.org/10.1038/org/10.1128/MCB.00579 -07 srep2 8532 55. Robinson PJ, An W, Routh A, Martino F, Chapman L, Roeder 39. Hashiguchi T, Arakawa S, Takahashi S, Gonzalez FJ, Sueyoshi RG, Rhodes D (2008) 30 nm chromatin fibre decompaction T, Negishi M (2016) Phosphorylation of Farnesoid X receptor at requires both H4-K16 acetylation and linker histone evic- serine 154 links ligand activation with degradation. Mol Endo- tion. J Mol Biol 381(4):816–825. https ://doi.or g/10.1016/j. crinol 30(10):1070–1080. https://doi.or g/10.1210/me.2016-1105 jmb.2008.04.050 40. Shi L, Oberdoerffer P (2012) Chromatin dynamics in DNA dou- 56. Shogren-Knaak M, Ishii H, Sun JM, Pazin MJ, Davie JR, Peter- ble-strand break repair. Biochim Biophys Acta 7:811–819. https son CL (2006) Histone H4-K16 acetylation controls chromatin ://doi.org/10.1016/j.bbagr m.2012.01.002 structure and protein interactions. Science 311(5762):844–847. 41. Deem AK, Li X, Tyler JK (2012) Epigenetic regulation of https ://doi.org/10.1126/scien ce.11240 00 genomic integrity. Chromosoma 121(2):131–151. https ://doi. 57. Li X, Corsa CA, Pan PW, Wu L, Ferguson D, Yu X, Min J, Dou org/10.1007/s0041 2-011-0358-1 Y (2010) MOF and H4 K16 acetylation play important roles 42. Raschella G, Melino G, Malewicz M (2017) New factors in in DNA damage repair by modulating recruitment of DNA mammalian DNA repair—the chromatin connection. Oncogene damage repair protein Mdc1. Mol Cell Biol 30(22):5335–5347. 36(33):4673–4681. https ://doi.org/10.1038/onc.2017.60https ://doi.org/10.1128/MCB.00350 -10 43. Ceccaldi R, Rondinelli B, D’Andrea AD (2016) Repair pathway 58. Shin J, Chakraborty G, Bharatham N, Kang C, Tochio N, choices and consequences at the double-strand break. Trends Cell Koshiba S, Kigawa T, Kim W, Kim KT, Yoon HS (2011) NMR Biol 26(1):52–64. https ://doi.org/10.1016/j.tcb.2015.07.009 solution structure of human vaccinia-related kinase 1 (VRK1) 44. Polo SE, Jackson SP (2011) Dynamics of DNA damage response reveals the C-terminal tail essential for its structural stability proteins at DNA breaks: a focus on protein modifications. Genes and autocatalytic activity. J Biol Chem 286(25):22131–22138. Dev 25(5):409–433. https ://doi.org/10.1101/gad.20213 11https ://doi.org/10.1074/jbc.M110.20016 2 45. Falck J, Coates J, Jackson SP (2005) Conserved modes of recruit- 59. Kim W, Chakraborty G, Kim S, Shin J, Park CH, Jeong MW, ment of ATM, ATR and DNA-PKcs to sites of DNA damage. Bharatham N, Yoon HS, Kim KT (2012) Macro histone Nature 434(7033):605–611. https: //doi.org/10.1038/nature 03442 H2A1.2 (MacroH2A1) protein suppresses mitotic kinase 46. Sanz-Garcia M, Monsalve DM, Sevilla A, Lazo PA (2012) VRK1 during interphase. J Biol Chem 287(8):5278–5289. Vaccinia-related Kinase 1 (VRK1) is an upstream nucleoso-https ://doi.org/10.1074/jbc.M111.28170 9 mal kinase required for the assembly of 53BP1 foci in response 60. Sanz-Garcia M, Lopez-Sanchez I, Lazo PA (2008) Proteom- to ionizing radiation-induced DNA damage. J Biol Chem ics identification of nuclear Ran GTPase as an inhibitor of 287(28):23757–23768. https://doi.or g/10.1074/jbc.M112.353102 human VRK1 and VRK2 (vaccinia-related kinase) activities. 47. Monsalve DM, Campillo-Marcos I, Salzano M, Sanz-Garcia M, Mol Cell Proteom 7(11):2199–2214. https ://doi.org/10.1074/ Cantarero L, Lazo PA (2016) VRK1 phosphorylates and pro-mcp.M7005 86-MCP20 0 tects NBS1 from ubiquitination and proteasomal degradation in 61. Kalab P, Pralle A, Isacoff EY, Heald R, Weis K (2006) Analy - response to DNA damage. BBA Mol Cell Res 4:760–769. https sis of a RanGTP-regulated gradient in mitotic somatic cells. ://doi.org/10.1016/j.bbamc r.2016.02.005 Nature 440(7084):697–701. h t t p s : / / d o i . o r g / 1 0 . 1 0 3 8 / n a t u r 48. Fell VL, Schild-Poulter C (2015) The Ku heterodimer: function e0458 9 in DNA repair and beyond. Mutat Res Rev Mutat Res 763:15–29. 62. Rogakou EP, Boon C, Redon C, Bonner WM (1999) Megabase https ://doi.org/10.1016/j.mrrev .2014.06.002 chromatin domains involved in DNA double-strand breaks 49. Celli GB, Denchi EL, de Lange T (2006) Ku70 stimulates fusion in vivo. J Cell Biol 146(5):905–916. https ://doi.org/10.1083/ of dysfunctional telomeres yet protects chromosome ends from jcb.146.5.905 homologous recombination. Nat Cell Biol 8(8):885–890. https 63. Nakamura AJ, Rao VA, Pommier Y, Bonner WM (2010) The ://doi.org/10.1038/ncb14 44 complexity of phosphorylated H2AX foci formation and DNA 50. Choi YH, Lim JK, Jeong MW, Kim KT (2012) HnRNP A1 phos- repair assembly at DNA double-strand breaks. Cell Cycle phorylated by VRK1 stimulates telomerase and its binding to 9(2):389–397. https ://doi.org/10.4161/cc.9.2.10475 telomeric DNA sequence. Nucleic Acids Res 40(17):8499–8518. 64. Paull TT, Rogakou EP, Yamazaki V, Kirchgessner CU, Gel- https ://doi.org/10.1093/nar/gks63 4 lert M, Bonner WM (2000) A critical role for histone H2AX 51. Downs JA, Allard S, Jobin-Robitaille O, Javaheri A, Auger A, in recruitment of repair factors to nuclear foci after DNA dam- Bouchard N, Kron SJ, Jackson SP, Cote J (2004) Binding of age. Curr Biol 10(15):886–895. https ://doi.org/10.1016/S0960 chromatin-modifying activities to phosphorylated histone H2A -9822(00)00610 -2 at DNA damage sites. Mol Cell 16(6):979–990. https ://doi. 65. Salzano M, Vazquez-Cedeira M, Sanz-Garcia M, Valbuena A, org/10.1016/j.molce l.2004.12.003 Blanco S, Fernandez IF, Lazo PA (2014) Vaccinia-related kinase 52. Murr R, Loizou JI, Yang YG, Cuenin C, Li H, Wang ZQ, Herceg 1 (VRK1) confers resistance to DNA-damaging agents in human Z (2006) Histone acetylation by Trrap-Tip60 modulates loading breast cancer by affecting DNA damage response. Oncotarget 5(N7):1770–1778. https ://doi.org/10.18632 /oncot arget .1678 1 3 2386 I. Campillo-Marcos, P. A. Lazo 66. Williams GJ, Lees-Miller SP, Tainer JA (2010) Mre11–Rad50– 83. Moll UM, Petrenko O (2003) The MDM2–p53 interaction. Mol Nbs1 conformations and the control of sensing, signaling, and Cancer Res 1(14):1001–1008 effector responses at DNA double-strand breaks. DNA Repair 84. Lopez-Borges S, Lazo PA (2000) The human vaccinia-related (Amst) 9(12):1299–1306. https ://doi.or g/10.1016/j.dnar e kinase 1 (VRK1) phosphorylates threonine-18 within the mdm-2 p.2010.10.001 binding site of the p53 tumour suppressor protein. Oncogene 67. Williams GJ, Hammel M, Radhakrishnan SK, Ramsden D, 19(32):3656–3664. https ://doi.org/10.1038/sj.onc.12037 09 Lees-Miller SP, Tainer JA (2014) Structural insights into NHEJ: 85. Valbuena A, Vega FM, Blanco S, Lazo PA (2006) p53 down- building up an integrated picture of the dynamic DSB repair regulates its activating vaccinia-related kinase 1, forming a new super complex, one component and interaction at a time. DNA autoregulatory loop. Mol Cell Biol 26(13):4782–4793. https :// Repair (Amst) 17:110–120. https ://doi.or g/10.1016/j.dnar e doi.org/10.1128/MCB.00069 -06 p.2014.02.009 86. Kussie PH, Gorina S, Marechal V, Elenbaas B, Moreau J, Lev- 68. Schultz LB, Chehab NH, Malikzay A, Halazonetis TD (2000) ine AJ, Pavletich NP (1996) Structure of the MDM2 oncopro- p53 binding protein 1 (53BP1) is an early participant in the tein bound to the p53 tumor suppressor transactivation domain. cellular response to DNA double-strand breaks. J Cell Biol Science 274(5289):948–953. https ://doi.or g/10.1126/scien 151(7):1381–1390. https ://doi.org/10.1083/jcb.151.7.1381 ce.274.5289.948 69. Wang B, Matsuoka S, Carpenter PB, Elledge SJ (2002) 87. Teufel DP, Freund SM, Bycroft M, Fersht AR (2007) Four 53BP1, a mediator of the DNA damage checkpoint. Science domains of p300 each bind tightly to a sequence spanning both 298(5597):1435–1438. https://doi.or g/10.1126/science.10761 82 transactivation subdomains of p53. Proc Natl Acad Sci USA 70. Mochan TA, Venere M, DiTullio RA Jr, Halazonetis TD (2003) 104(17):7009–7014. https ://doi.org/10.1073/pnas.07020 10104 53BP1 and NFBD1/MDC1-Nbs1 function in parallel interact- 88. Teufel DP, Bycroft M, Fersht AR (2009) Regulation by phos- ing pathways activating ataxia-telangiectasia mutated (ATM) in phorylation of the relative affinities of the N-terminal transacti- response to DNA damage. Cancer Res 63(24):8586–8591 vation domains of p53 for p300 domains and Mdm2. Oncogene 71. Ward IM, Chen J (2001) Histone H2AX is phosphorylated in an 28(20):2112–2118. https ://doi.org/10.1038/onc.2009.71 ATR-dependent manner in response to replicational stress. J Biol 89. Del Sal G, Murphy M, Ruaro E, Lazarevic D, Levine AJ, Schnei- Chem 276(51):47759–47762. https://doi.or g/10.1074/jbc.C1005 der C (1996) Cyclin D1 and p21/waf1 are both involved in p53 69200 growth suppression. Oncogene 12(1):177–185 72. Riballo E, Kuhne M, Rief N, Doherty A, Smith GC, Recio MJ, 90. Ferbeyre G, de Stanchina E, Lin AW, Querido E, McCurrach ME, Reis C, Dahm K, Fricke A, Krempler A, Parker AR, Jackson SP, Hannon GJ, Lowe SW (2002) Oncogenic ras and p53 cooperate Gennery A, Jeggo PA, Lobrich M (2004) A pathway of double- to induce cellular senescence. Mol Cell Biol 22(10):3497–3508. strand break rejoining dependent upon ATM, Artemis, and pro-https ://doi.org/10.1128/MCB.22.10.3497-3508.2002 teins locating to gamma-H2AX foci. Mol Cell 16(5):715–724. 91. Miyashita T, Reed JC (1995) Tumor suppressor p53 is a direct https ://doi.org/10.1016/j.molce l.2004.10.029 transcriptional activator of the human bax gene. Cell 80(2):293– 73. Wen J, Cerosaletti K, Schultz KJ, Wright JA, Concannon P 299. https ://doi.org/10.1016/0092-8674(95)90412 -3 (2013) NBN phosphorylation regulates the accumulation of 92. Miyashita T, Krajewski S, Krajewski M, Wang HG, Lin HK, MRN and ATM at sites of DNA double-strand breaks. Oncogene Lieberman DA, Hoffman B, Reed JC (1994) Tumor suppressor 32(37):4448–4456. https ://doi.org/10.1038/onc.2012.443 p53 is a regulator of Bcl-2 and Bax gene expression in vitro and 74. Panier S, Boulton SJ (2014) Double-strand break repair: 53BP1 in vivo. Oncogene 9:1799–1805 comes into focus. Nat Rev Mol Cell Biol 15(1):7–18. https://doi. 93. Menendez D, Inga A, Resnick MA (2009) The expanding uni- org/10.1038/nrm37 19 verse of p53 targets. Nat Rev Cancer 9(10):724–737. https: //doi. 75. Levine AJ (1997) p53, the cellular gatekeeper for growth and org/10.1038/nrc27 30 division. Cell 88(3):323–331 94. Lazo PA (2017) Reverting p53 activation after recovery of cel- 76. Selivanova G, Wiman KG (1995) p53: a cell cycle regulator acti- lular stress to resume with cell cycle progression. Cell Signal vated by DNA damage. Adv Cancer Res 66:143–180 33:49–58. https ://doi.org/10.1016/j.cells ig.2017.02.005 77. Oren M (2003) Decision making by p53: life, death and can- 95. Piya S, Kim JY, Bae J, Seol DW, Moon AR, Kim TH (2012) cer. Cell Death Differ 10(4):431–442. https ://doi.org/10.1038/ DUSP6 is a novel transcriptional target of p53 and regulates sj.cdd.44011 83 p53-mediated apoptosis by modulating expression levels of 78. Toledo F, Wahl GM (2006) Regulating the p53 pathway: in vitro Bcl-2 family proteins. FEBS Lett 586(23):4233–4240. https :// hypotheses, in vivo veritas. Nat Rev Cancer 6(12):909–923. https doi.org/10.1016/j.febsl et.2012.10.031 ://doi.org/10.1038/nrc20 12 96. Yamaguchi H, Durell SR, Chatterjee DK, Anderson CW, Appella 79. Meek DW, Anderson CW (2009) Posttranslational modification E (2007) The Wip1 phosphatase PPM1D dephosphorylates SQ/ of p53: cooperative integrators of function. Cold Spring Harb TQ motifs in checkpoint substrates phosphorylated by PI3K- Perspect Biol 1:a000950. https ://doi.or g/10.1101/cshpe rspec like kinases. Biochemistry 46(44):12594–12603. https ://doi. t.a0009 50org/10.1021/bi701 096s 80. Meek DW (2009) Tumour suppression by p53: a role for the 97. Shreeram S, Demidov ON, Hee WK, Yamaguchi H, Onishi N, DNA damage response? Nat Rev Cancer 9(10):714–723. https Kek C, Timofeev ON, Dudgeon C, Fornace AJ, Anderson CW, ://doi.org/10.1038/nrc27 16 Minami Y, Appella E, Bulavin DV (2006) Wip1 phosphatase 81. Lopez-Sanchez I, Valbuena A, Vazquez-Cedeira M, Khadake modulates ATM-dependent signaling pathways. Mol Cell J, Sanz-Garcia M, Carrillo-Jimenez A, Lazo PA (2014) VRK1 23(5):757–764. https ://doi.org/10.1016/j.molce l.2006.07.010 interacts with p53 forming a basal complex that is activated by 98. Shen WH, Wang J, Wu J, Zhurkin VB, Yin Y (2006) Mitogen- UV-induced DNA damage. FEBS Lett 588(5):692–700. https :// activated protein kinase phosphatase 2: a novel transcription doi.org/10.1016/j.febsl et.2014.01.040 target of p53 in apoptosis. Cancer Res 66(12):6033–6039. https 82. Levine AJ (2017) The p53 protein plays a central role in the ://doi.org/10.1158/0008-5472.CAN-05-3878 mechanism of action of epigenetic drugs that alter the methyla- 99. Jeong MW, Kang TH, Kim W, Choi YH, Kim KT (2013) Mito- tion of cytosine residues in DNA. Oncotarget 8(5):7228–7230. gen-activated protein kinase phosphatase 2 regulates histone https ://doi.org/10.18632 /oncot arget .14805 H3 phosphorylation via interaction with vaccinia-related kinase 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2387 1. Mol Biol Cell 24(3):373–384. https ://doi.org/10.1091/mbc. lung cell lineage and mitotic networks in lung adenocarcinomas. E12-06-0456 Nat Commun 4:1701. https ://doi.org/10.1038/ncomm s2660 100. Valbuena A, Castro-Obregon S, Lazo PA (2011) Downregula- 116. Fournier MV, Martin KJ, Kenny PA, Xhaja K, Bosch I, Yas- tion of VRK1 by p53 in response to DNA damage is mediated wen P, Bissell MJ (2006) Gene expression signature in organ- by the autophagic pathway. PLoS One 6(2):e17320. https ://doi. ized and growth-arrested mammary acini predicts good outcome org/10.1371/journ al.pone.00173 20 in breast cancer. Cancer Res 66(14):7095–7102. https ://doi. 101. Valbuena A, Blanco S, Vega FM, Lazo PA (2008) The C/H3 org/10.1158/0008-5472.CAN-06-0515 domain of p300 is required to protect VRK1 and VRK2 from 117. Martin KJ, Patrick DR, Bissell MJ, Fournier MV (2008) their downregulation induced by p53. PLoS One 3(7):e2649. Prognostic breast cancer signature identified from 3D culture https ://doi.org/10.1371/journ al.pone.00026 49 model accurately predicts clinical outcome across independent 102. Baehrecke EH (2005) Autophagy: dual roles in life and death? datasets. PLoS One 3(8):e2994. https ://doi.org/10.1371/journ Nat Rev Mol Cell Biol 6(6):505–510. https ://doi.org/10.1038/al.pone.00029 94 nrm16 66 118. Huang W, Cui X, Chen Y, Shao M, Shao X, Shen Y, Liu Q, Wu 103. Cecconi F, Levine B (2008) The role of autophagy in mamma- M, Liu J, Ni W, Lu C, Wan C (2016) High VRK1 expression lian development: cell makeover rather than cell death. Dev Cell contributes to cell proliferation and survival in hepatocellu- 15(3):344–357. https ://doi.org/10.1016/j.devce l.2008.08.012 lar carcinoma. Pathol Res Pract 212(3):171–178. https ://doi. 104. Mizushima N (2007) Autophagy: process and function. Genes org/10.1016/j.prp.2015.11.015 Dev 21(22):2861–2873. https ://doi.org/10.1101/gad.15992 07 119. Varghese RT, Liang Y, Guan T, Franck CT, Kelly DF, Sheng 105. Maiuri MC, Zalckvar E, Kimchi A, Kroemer G (2007) Self-eat- Z (2016) Survival kinase genes present prognostic signifi- ing and self-killing: crosstalk between autophagy and apoptosis. cance in glioblastoma. Oncotarget 7:20140–20151. https :// Nat Rev Mol Cell Biol 8(9):741–752. https ://doi.org/10.1038/doi.org/10.18632 /oncot arget .7917 nrm22 39 120. Li J, Wang T, Pei L, Jing J, Hu W, Sun T, Liu H (2017) Expres- 106. Tasdemir E, Chiara Maiuri M, Morselli E, Criollo A, D’Amelio sion of VRK1 and the downstream gene BANF1 in esopha- M, Djavaheri-Mergny M, Cecconi F, Tavernarakis N, Kroemer G geal cancer. Biomed Pharmacother 89:1086–1091. https://doi. (2008) A dual role of p53 in the control of autophagy. Autophagy org/10.1016/j.bioph a.2017.02.095 4(6):810–814. https ://doi.org/10.4161/auto.6486 121. Valbuena A, Sanz-Garcia M, Lopez-Sanchez I, Vega FM, 107. Crighton D, Wilkinson S, O’Prey J, Syed N, Smith P, Harrison Lazo PA (2011) Roles of VRK1 as a new player in the con- PR, Gasco M, Garrone O, Crook T, Ryan KM (2006) DRAM, trol of biological processes required for cell division. Cell a p53-induced modulator of autophagy, is critical for apoptosis. Signal 23(8):1267–1272. https ://doi.or g/10.1016/j.cells Cell 126(1):121–134. https://doi.or g/10.1016/j.cell.2006.05.034 ig.2011.04.002 108. Mah LY, O’Prey J, Baudot AD, Hoekstra A, Ryan KM (2012) 122. Moura DS, Campillo-Marcos I, Vazquez-Cedeira M, Lazo PA DRAM-1 encodes multiple isoforms that regulate autophagy. (2018) VRK1 and AURKB form a complex that cross inhibit Autophagy 8(1):18–28. https ://doi.org/10.4161/auto.8.1.18077 their kinase activity and the phosphorylation of histone H3 109. Valbuena A, Suarez-Gauthier A, Lopez-Rios F, Lopez-Encuen- in the progression of mitosis. Cell Mol Life Sci. https ://doi. tra A, Blanco S, Fernandez PL, Sanchez-Cespedes M, Lazo org/10.1007/s0001 8-018-2746-7 PA (2007) Alteration of the VRK1-p53 autoregulatory loop in 123. Wiebe MS, Nichols RJ, Molitor TP, Lindgren JK, Traktman human lung carcinomas. Lung Cancer 58(3):303–309. https :// P (2010) Mice deficient in the serine/threonine protein kinase doi.org/10.1016/j.lungc an.2007.06.023 VRK1 are infertile due to a progressive loss of spermatogonia. 110. Santos CR, Rodriguez-Pinilla M, Vega FM, Rodriguez-Peralto Biol Reprod 82(1):182–193. https ://doi.org/10.1095/biolr eprod JL, Blanco S, Sevilla A, Valbuena A, Hernandez T, van Wijnen .109.07909 5 AJ, Li F, de Alava E, Sanchez-Cespedes M, Lazo PA (2006) 124. Schober CS, Aydiner F, Booth CJ, Seli E, Reinke V (2011) VRK1 signaling pathway in the context of the proliferation The kinase VRK1 is required for normal meiotic progression phenotype in head and neck squamous cell carcinoma. Mol in mammalian oogenesis. Mech Dev 128(3–4):178–190. https:// Cancer Res 4(3):177–185. https ://doi.org/10.1158/1541-7786. doi.org/10.1016/j.mod.2011.01.004 MCR-05-0212 125. Kim J, Choi YH, Chang S, Kim KT, Je JH (2012) Defective fol- 111. Wang S, Zhao Y, Aguilar A, Bernard D, Yang CY (2017) Target- liculogenesis in female mice lacking vaccinia-related kinase 1. ing the MDM2-p53 protein–protein interaction for new cancer Sci Rep 2:468. https ://doi.org/10.1038/srep0 0468 therapy: progress and challenges. Cold Spring Harb Perspect 126. Nichols RJ, Wiebe MS, Traktman P (2006) The vaccinia-related Med 7(5):a026245. https://doi.or g/10.1101/cshperspec t.a0262 45 kinases phosphorylate the N’ terminus of BAF, regulating its 112. Vega FM, Gonzalo P, Gaspar ML, Lazo PA (2003) Expression of interaction with DNA and its retention in the nucleus. Mol Biol the VRK (vaccinia-related kinase) gene family of p53 regulators Cell 17(5):2451–2464. https://doi.or g/10.1091/mbc.E05-12-1179 in murine hematopoietic development. FEBS Lett 544(1–3):176– 127. Jamin A, Wiebe MS (2015) Barrier to Autointegration Factor 180. https ://doi.org/10.1016/S0014 -5793(03)00501 -5 (BANF1): interwoven roles in nuclear structure, genome integ- 113. Valbuena A, Lopez-Sanchez I, Lazo PA (2008) Human VRK1 rity, innate immunity, stress responses and progeria. Curr Opin is an early response gene and its loss causes a block in cell cycle Cell Biol 34:61–68. https ://doi.org/10.1016/j.ceb.2015.05.006 progression. PLoS One 3(2):e1642. https://doi.or g/10.1371/journ 128. Molitor TP, Traktman P (2013) Molecular genetic analysis of al.pone.00016 42 VRK1 in mammary epithelial cells: depletion slows proliferation 114. Kiessling MK, Schuierer S, Stertz S, Beibel M, Bergling S, in vitro and tumor growth and metastasis in vivo. Oncogenesis Knehr J, Carbone W, de Valliere C, Tchinda J, Bouwmeester 2:e48. https ://doi.org/10.1038/oncsi s.2013.11 T, Seuwen K, Rogler G, Roma G (2016) Identification of onco- 129. McDonald ER, 3rd, de Weck A, Schlabach MR, Billy E, Mavra- genic driver mutations by genome-wide CRISPR-Cas9 dropout kis KJ, Hoffman GR, Belur D, Castelletti D, Frias E, Gampa K, screening. BMC Genom 17(1):723. https ://doi.or g/10.1186/ Golji J, Kao I, Li L, Megel P, Perkins TA, Ramadan N, Ruddy s1286 4-016-3042-2 DA, Silver SJ, Sovath S, Stump M, Weber O, Widmer R, Yu J, 115. Kim IJ, Quigley D, To MD, Pham P, Lin K, Jo B, Jen KY, Raz D, Yu K, Yue Y, Abramowski D, Ackley E, Barrett R, Berger J, Ber- Kim J, Mao JH, Jablons D, Balmain A (2013) Rewiring of human nard JL, Billig R, Brachmann SM, Buxton F, Caothien R, Caushi JX, Chung FS, Cortes-Cros M, deBeaumont RS, Delaunay C, 1 3 2388 I. Campillo-Marcos, P. A. Lazo Desplat A, Duong W, Dwoske DA, Eldridge RS, Farsidjani A, 131. Fedorov O, Marsden B, Pogacic V, Rellos P, Muller S, Bullock Feng F, Feng J, Flemming D, Forrester W, Galli GG, Gao Z, AN, Schwaller J, Sundstrom M, Knapp S (2007) A systematic Gauter F, Gibaja V, Haas K, Hattenberger M, Hood T, Hurov KE, interaction map of validated kinase inhibitors with Ser/Thr Jagani Z, Jenal M, Johnson JA, Jones MD, Kapoor A, Korn J, Liu kinases. Proc Natl Acad Sci USA 104(51):20523–20528. https J, Liu Q, Liu S, Liu Y, Loo AT, Macchi KJ, Martin T, McAllister ://doi.org/10.1073/pnas.07088 00104 G, Meyer A, Molle S, Pagliarini RA, Phadke T, Repko B, Schou- 132. Fedorov O, Sundstrom M, Marsden B, Knapp S (2007) Insights wey T, Shanahan F, Shen Q, Stamm C, Stephan C, Stucke VM, for the development of specific kinase inhibitors by targeted Tiedt R, Varadarajan M, Venkatesan K, Vitari AC, Wallroth M, structural genomics. Drug Discov Today 12(9–10):365–372. Weiler J, Zhang J, Mickanin C, Myer VE, Porter JA, Lai A, Bit-https ://doi.org/10.1016/j.drudi s.2007.03.006 ter H, Lees E, Keen N, Kauffmann A, Stegmeier F, Hofmann F, 133. Nebot-Bral L, Brandao D, Verlingue L, Rouleau E, Caron O, Schmelzle T, Sellers WR (2017) Project DRIVE: a compendium Despras E, El-Dakdouki Y, Champiat S, Aoufouchi S, Leary A, of cancer dependencies and synthetic lethal relationships uncov- Marabelle A, Malka D, Chaput N, Kannouche PL (2017) Hyper- ered by large-scale, deep RNAi screening. Cell 170(3):577–592 mutated tumours in the era of immunotherapy: the paradigm of e510. https ://doi.org/10.1016/j.cell.2017.07.005 personalised medicine. Eur J Cancer 84:290–303. https ://doi. 130. Knight ZA, Lin H, Shokat KM (2010) Targeting the cancer org/10.1016/j.ejca.2017.07.026 kinome through polypharmacology. Nat Rev Cancer 10(2):130– 137. https ://doi.org/10.1038/nrc27 87 1 3 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Cellular and Molecular Life Sciences Springer Journals

Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic target?

Free
14 pages

Loading next page...
 
/lp/springer_journal/implication-of-the-vrk1-chromatin-kinase-in-the-signaling-responses-to-Owy0fraeI4
Publisher
Springer Journals
Copyright
Copyright © 2018 by The Author(s)
Subject
Life Sciences; Cell Biology; Biomedicine, general; Life Sciences, general; Biochemistry, general
ISSN
1420-682X
eISSN
1420-9071
D.O.I.
10.1007/s00018-018-2811-2
Publisher site
See Article on Publisher Site

Abstract

DNA damage causes a local distortion of chromatin that triggers the sequential processes that participate in specific DNA repair mechanisms. This initiation of the repair response requires the involvement of a protein whose activity can be regulated by histones. Kinases are candidates to regulate and coordinate the connection between a locally altered chromatin and the response initiating signals that lead to identification of the type of lesion and the sequential steps required in specific DNA damage responses (DDR). This initiating kinase must be located in chromatin, and be activated independently of the type of DNA damage. We review the contribution of the Ser-Thr vaccinia-related kinase 1 (VRK1) chromatin kinase as a new player in the signaling of DNA damage responses, at chromatin and cellular levels, and its potential as a new therapeutic target in oncology. VRK1 is involved in the regulation of histone modifications, such as histone phosphorylation and acetylation, and in the formation of γH2AX, NBS1 and 53BP1 foci induced in DDR. Induction of DNA damage by chemotherapy or radia- tion is a mainstay of cancer treatment. Therefore, novel treatments can be targeted to proteins implicated in the regulation of DDR, rather than by directly causing DNA damage. Keywords VRK1 · H2AX · NBS1 · 53BP1 · p53 · Phosphorylation · DNA damage response · Ionizing radiation Abbreviations Introduction VRK1 Vaccinia-related kinase 1 DSB DNA double-strand break Genome stability DDR DNA damage response NBS1 Nijmegen breakage syndrome 1 (nibrin) Genome stability is essential for the maintenance of spe- NHEJ Non-homologous end-joining cies, but, at the same time, genetic variation is necessary for 53BP1 Tumor protein P53 binding protein 1 their evolution. Therefore, in all species, there are several ATM Ataxia-telangiectasia-mutated Ser/Thr kinase mechanisms aiming to protect DNA from genetic damage of endogenous or exogenous origin. Endogenous DNA damage is a consequence of the biological properties of cells, and includes oxidative stress, replication errors, transcriptional errors, or metabolism of DNA, to which cells are continu- ously exposed [1]. Alternatively, exogenous factors such as ultraviolet light, ionizing radiation, or chemicals also cause DNA damage to which exposure is frequently transient. The DNA damage has many different forms, single- or double- * Pedro A. Lazo strand breaks, nucleotide, or base modification [ 1]. To cope pedro.lazo@csic.es with all of them, cells have developed several specific DNA repair mechanisms, which increase their complexity in Experimental Therapeutics and Translational Oncology higher organisms because of the chromatin organization. Program, Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, 37007 Salamanca, Double-strand breaks constitute the most serious form of Spain DNA damage that has two alternative repair mechanisms Instituto de Investigación Biomédica de Salamanca (IBSAL), depending of the situation of the cell cycle. During repli- Hospital Universitario de Salamanca, 37007 Salamanca, cation, DNA double-strand breaks (DSBs) are repaired by Spain Vol.:(0123456789) 1 3 2376 I. Campillo-Marcos, P. A. Lazo homologous recombination (HR) using as template the other in the local chromatin organization. Chromatin can function chromatid. In non-dividing-cells or in G0/G1 phases, DSBs as a signaling platform that has effects not only on its remod- are repaired by non-homologous end-joining (NHEJ) [2]. eling, but can also send signals to other processes involved in Independently of the origin of DNA lesions, these lesions nuclear dynamics [14]. When cells encounter a stress such as have to be detected rapidly and efficiently before cells DNA damage, the activation of complex signaling networks divide, to avoid transmitting the damage to their progeny. triggers the detection and repair of the damage in a specific Because nuclear kinases are capable of rapidly and revers- and sequential process, before returning to the homeostatic ibly responding to changes in the cell and its environment, equilibrium. These networks integrate a wide variety of sig- and of integrating diverse stimuli, they are likely to be nals from inside the cell, transduced through protein kinases involved in sensing, triggering, regulating, and organizing [10–12], to ultimately control cell cycle arrest or progression the sequential steps that are needed for a correct and specific in the case of dividing cells [15]. Moreover, the chromatin- DNA damage response. signaling platform regulates DDR, cell cycle checkpoints, Cells are continuously exposed to DNA damage and it cell death, and senescence, among others. All these pro- can occur at any time during the cellular lifetime. The num- cesses are associated with the maintenance of genetic sta- ber of normal cell division is limited to approximately 40 bility and the transmission of a mutation-free genome to because of telomere shortening, which implies that, in the daughter cells. The major pathological consequence of DNA life of the organism, most cells are not dividing at the time of damage is the potential transmission of mutations to their exposure to DNA damage [3, 4]. Furthermore, cells are most progeny [16], which are implicated in aging and cancer [17]. of their lifetime in the G0/G1 phases, in which homologous In addition to the role of DNA damage in cancer, alterations recombination is not functional [5], but are exposed to DNA in DNA repair genes are also associated with neurodegenera- damage. Furthermore, stem cells have an enhanced response tive diseases [18], since neurons are not dividing in most of to DNA damage mediated by the NHEJ pathway [6]. There- the individual lifetime and have to repair these DNA lesions. fore, most of the DNA lesions will occur and have to be Most research into DNA damage responses has been studied repaired in the absence of replication. Very often, there is a in the context of replication and cell division [16]. large time interval between the moment in which DNA dam- In the highly organized eukaryotic chromatin, the most age occurs and the time when an individual cell replicates, vulnerable DNA is the fraction that is transcriptionally active in which most cells are non-dividing, and are thus able to at the time of exposure to damaging agents, particularly in pass the mutation to their daughter cells. Consequently, each resting or non-dividing cells, such as stem cells or neurons. cell has to deal individually with this problem and to respond In these locations, DNA has to relax and open to allow the independently of its particular situation, which is very vari- access of RNA polymerase and permit gene transcription. In able within a tissue. Cells are either resting or dividing, and these transcriptionally active regions, DNA is more exposed their individual position within a tissue implies that cellular and vulnerable, particularly in non-dividing or cells in G0/ interactions are heterogeneous depending on its location. G1. Therefore, in an individual resting cell, the response to DNA repair mechanisms have to function in all these dif- DNA damage does not have to be linked to cell division, ferent cellular contexts. In the particular case of neurons, differentiation state, or the cell location and its interactions by their exposition to oxidative stress, the accumulation of within a tissue. Even in dividing cells, the G1 phase last DNA damage might be a pathogenic mechanism for dete- several hours before entering replication. DNA damage has rioration of neurological functions associated with aging. to be detected, identified, and repaired immediately in all Recent evidence indicates that a significant proportion of the different types of situations. DNA damage is of endogenous origin [7, 8]. Francis Crick predicted that several redundant mechanisms must exist to repair damaged DNA and maintain genome integrity [9]. Cellular response to DNA damage Since then, several pathways have been identified [10– 13]. Induction of DNA damage is a mainstay of cancer treatment, The cellular reaction to DNA damage involves two major aims; one is to protect the DNA, and the other to protect and the specific targeting of regulatory proteins implicated in DDR can lead to the development of new drugs. cells and the organisms from the consequences of unre- paired DNA damage. The cellular protection against DNA Chromatin and DNA damage damage is mediated by arresting cell cycle in proliferating cells, so that damage can be repaired before its transmission The cellular response to DNA damage has to be initiated and to daughter cells. However, if DNA damage is excessive and cannot be repaired, the alternative response is medi- triggered at the site of the DNA lesion, independent of its type. DNA damage causes a local distortion of the double ated by the induction of cell death, and in that way, there is no progeny of mutated cells. These two types of responses helix, and of its associated nucleosomes, which is reflected 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2377 are associated with p53 and activated by different types of Chromatin DNA damage. DNA repair requires a sequential reorganization of chro- Transcription factors matin to allow for the different and consecutive steps in each DNA Damage Response repair pathway, which includes protection of damaged DNA, ac recognition of the type of lesion, recruitment of specific H2A H3 p53 repair mechanisms, ligation of DNA ends, and restoration P KAT5 to its normal chromatin organization. After DNA damage, in Sox2 P addition to the DNA lesion, the initial effect is a local distor - ac ATF2 P ATM tion of chromatin, which is the initiating event to trigger the P VRK1 cascade of DNA repair processes. As organisms increased P CREB NBS1 in their complexity, new regulatory elements are necessary P P Jun not only to coordinate different functions in DDR, but also γH2AX to adjust to their much more complex and dynamic structure FXR of chromatin. Therefore, new regulatory mechanisms that integrate and coordinate basic processes are necessary. In Fig. 1 VRK1 relation with transcription factors and DNA damage this context, new regulatory elements have evolved from pre- response proteins in chromatin existing proteins. A candidate for this role must be a chroma- tin protein with a reversible enzymatic activity. Among the which are organized in nucleosomes and in direct contact 518 kinase of the human kinome, vaccinia-related kinase-1 (VRK1) is a potential candidate for this role because of its with DNA, contributing to chromatin spatial organization. VRK1 is detected in the chromatin fraction forming a stable association to chromatin and its targets, with the exception of chromosomes condensed in mitosis [19, 20]. complex with histone H3 [29]. Moreover, VRK1 phospho- rylates histones H3 [27, 29, 30], H2A [31, 32] and H2AX [29]. Therefore, it is very likely that nucleosome organi- zation can be modified by covalent modifications because VRK1 roles in chromatin of histone phosphorylations by VRK1. This regulation of histone covalent modifications is essential for different func- The VRK1 chromatin kinase tions, normal or pathological, requiring a dynamic chroma- tin reorganization [33, 34]. VRK1 is a Ser-Thr kinase that belongs to the VRK family that diverged early from branch of the human kinome that An additional role of VRK1 as a chromatin kinase is its association with transcriptional complexes, where it inter- led the casein kinase family [21]. Bacteria and yeast have no VRK or p53 members, invertebrates such as D. mela- acts and phosphorylates several transcription factors that include p53 [28], CREB [35], ATF2 [36], c-Jun [37], Sox2 nogaster or C. elegans have one member, and mammals have three members in their respective families. The complex- [38], and the farnesoid X receptor (FXR) [39]. ity of VRK family [22] parallels that of p53 [23] and the autophagic DRAM (death-related autophagic modulator) VRK1 as a sensor of chromatin alterations [24]. This increased complexity during evolution is likely to reflect the need for additional regulatory or coordinating Chromatin in interphase has a very large size and DNA lesions can occur at any place, heterochromatin and euchro- roles as organisms and their functions became more com- plex. In mammals and C. elegans, it is known as Vrk-1 [25], matin, which are likely to have a different sensitivity to DNA damage. Alterations of DNA by strand breaks or chemical and in D. melanogaster as nucleosomal histone kinase 1 (NHK-1) [26]. modifications, such as oxidation, alkylation, or intercalation among others, will alter the chromatin organization by intro- VRK1 is a Ser-Thr kinase in nuclei [19] that is located on chromatin in resting cells and in all phases of the cell cycle ducing a local distortion [40, 41], which is a likely initiating event for triggering the complex processes of DNA repair covering all DNA, except when chromosomes are already condensed in mitosis [27, 28], in which VRK1 is ejected [42–44]. However, responding to DNA damage requires the coupling of chromatin distortion to a signal transduction from mitotic chromosomes. When chromosomes segregate, VRK1 returns to chromatin in daughter cells. VRK1 forms system, probably mediated by a nuclear chromatin kinase. A requirement for a sensor kinase is that its activation stable complexes with several different types of chromatin proteins, ranging from histones, transcription factors, and is independent of the type of DNA damage and, therefore, is not associated to any particular type of DNA damage. proteins involved in DNA repair processes (Fig. 1). The pro- teins more closely associated with DNA are histones [29], In this latter case, the kinase involved will participate in 1 3 2378 I. Campillo-Marcos, P. A. Lazo specific steps of a particular DNA damage, as is the case for [29]. ATM-null cells, such as the HT144 cell line, has a high ATM, ATR, or DNA-PK in the response to double-strand endogenous level of H4K16ac that is also lost by depletion +/+ DNA breaks [45]. In the particular case of VRK1, its kinase of VRK1 [29]. In ATM cells, this acetylation induced activity increases tenfold after induction of DNA damage by IR does not occur in the absence of VRK1 [29]. These independently of its type, which includes pyrimidine dimers results indicate that VRK1 is a good candidate to regulate caused by ultraviolet light, single-strand DNA breaks caused the enzymes involved in epigenetic modifications of chroma- by hydroxyurea treatment, or double-strand DNA breaks tin. DNA damage causes a local distortion of chromatin that induced by either doxorubicin or ionizing radiation [46]. can affect its different covalent modifications. Consequently, Early sensor mechanism of DNA damage must fulfill the regulation and coordination of histone modifiers such some basic requirements, be a nuclear enzyme that inter- as acetylases, deacetylases, methylases, and demethylases acts with basic chromatin components in nucleosomes, and is very poorly understood. Moreover, VRK1 also directly be a capable of an immediate signaling reaction that is also phosphorylates histone H2A in T120 [32], which is next to reversible. In this context, a kinase, such as VRK1, is a very K119 ubiquitinated, and both modifications are functional suitable candidate for this role [29, 46, 47]. alternatives, being T120 phosphorylation an activator of Other important early proteins at the site of specific types chromatin. Thus, two histones in nucleosomes, H3 and H2A, of DNA damage are Ku70/Ku80 (XRCC6/XRCC5), which are directly regulated by VRK1. Furthermore, histone H4 have to re-localize and interact with free DNA ends at the is not a phosphorylation target of VRK1, but its covalent breakpoints, mainly in double-strand breaks [48], a subtype modification by acetylation is sensitive to VRK1 in an ATM- of DNA damage, or in telomeres [48, 49]. It is unknown independent manner, since it is detected in ATM-null cells whether these proteins are targets of VRK1, but it is a real [29]. possibility. Ku70 and Artemis have multiple phosphoryla- It is important to remark that the sensor kinase activity tion sites, but the kinases involved in their specific phospho- has to be regulated by protein–protein interactions. In this rylation and their regulation are unknown. Telomeres are context, the C-terminal region of VRK1 has a low complex- naturally occurring DNA ends in chromosomes and there ity structure, which is very flexible and can adopt different is evidence for a role of VRK1 in their maintenance [50]. conformations [58]. This C-terminal region can fold and Moreover, VRK1 phosphorylates hnRNP A1 (heterogeneous block the active site of the kinase [58] and proteins inter- nuclear ribonucleoprotein A1) and facilitates its binding to acting with this region can modulate the activity of VRK1. telomeric ssDNA and telomeric RNA [50]. Two proteins that inhibit the VRK1 kinase activity have been identified, macrohistone H2A1.2 in interphase [ 59], VRK1, chromatin relaxation, and histone acetylation and Ran-GDP, but not Ran-GTP [60], which have an asym- metric nuclear distribution [61]. DNA damage and local disruption of chromatin are associ- ated with an increase in histone acetylation, which is medi- ated by KAT (lysine acetyl transferase) proteins. Histone VRK1 in DNA damage responses acetylation extends over an area of several hundred kilobases flanking the damaged DNA site [51, 52], which requires the VRK1 and histone H2AX local activation of KATs by a not yet identified mechanism. Defects in histone acetylation are associated with an increase VRK1 directly and stably interacts with histones H2AX in cellular sensitivity to DNA damage as a consequence of a and H3 in basal conditions, and is able to phosphoryl- defective DNA repair [53, 54]. Furthermore, acetylation of ate them in  vitro with purified proteins in Ser139 and histone H4 in Lys16 disrupts the interaction between H4 and Thr3, respectively [29]. The early response to DNA dam- H2A–H2B, and facilitates the relaxation of chromatin [55, age requires the phosphorylation of H2AX in Ser139 56]. Consistently, the inactivation of KAT5/Tip60 blocks (γH2AX). γH2AX covers large areas of DNA surround- the opening of chromatin at DSBs (double-strand breaks) ing the site of DNA damage [62] and protects DNA from that are required to facilitate the repair process [52]. Induc- exonuclease attack. This γH2AX organization can also tion of DNA damage by UV light or radiation causes an function as a platform for the recruitment of proteins increase in histone acetylation [52, 57]. Depletion of VRK1, that participate in sequential DDR steps, such as NBS1, a nucleosomal chromatin kinase, causes a loss of histones 53BP1, or BRCA1, among others [40, 63]. Phosphoryla- H3 and H4 acetylation, which are necessary for chromatin tion of histone H2AX in Ser139 (γH2AX) is a mark of relaxation, either in basal conditions or after DNA damage, an early reaction to DNA damage that can be detected by independently of ATM and p53 [29]. VRK1 knockdown formation of γH2AX foci [62, 64]. The phosphorylation also causes a loss of specific histone acetylations, including of H2AX and the formation of γH2AX foci induced by H4K16 acetylation (H4K16ac), induced by DNA damage ionizing radiation (IR) are lost by depletion of VRK1 and 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2379 can be rescued by kinase-active, but not by kinase-dead, VRK1 and NBS1 in early DDR VRK1 [29]. This effect of VRK1 is also independent of ATM, suggesting that VRK1 is an upstream participant. Cellular responses to DNA damage require the formation of VRK1 is also necessary for the activation of ATM and protein complexes in a highly organized fashion. In resting CHK2 in response to IR [46]. However, in the absence cells, VRK1 plays an important role in the formation of ion- of ATM, the γH2AX foci induced by IR have a smaller izing radiation-induced foci formed by γH2AX, NBS1, and size, which indicates that both kinases cooperate either in 53BP1 during DDR. The MRE11 complex holds together the formation or stabilization of the foci [29]. This latter the two free ends of the broken DNA. This complex, formed possibility might be a consequence of the effect of VRK1 NBS1–Mre11–Rad50, is highly dynamic and has a very on the stability of NBS1 [47]. In this context, VRK1 is a complex organization [66]. Phosphorylation of NBS1/nibrin novel chromatin component that reacts to its alterations is necessary for the recruitment of ATM to damaged sites and participates very early in DDR by itself and in coop- and for the stabilization of the repair complex [73]. VRK1 is eration with ATM [29]. activated by DNA double-strand breaks induced by ionizing radiation (IR) or doxorubicin, and specifically phosphoryl- ates NBS1 in Ser343 [47] and 53BP1 in serum-starved cells VRK1 and specific DNA damage response proteins and ATM-null and p53-null cells [46], indicating that they are independent of both p53 and ATM activation [47], and Because of the physical association of VRK1 with chroma- consistent with VRK1 role as an early step in the response tin, VRK1 has also been implicated in the regulation of DDR to DNA damage. Depletion of VRK1 causes a loss of NBS1 proteins. The VRK1 kinase has also been directly associated stability that is prevented by treatment with the MG132 pro- with different components in DDR pathways, which have teasome inhibitor [47]. This phosphorylation mediated by been studied in the context of the response to DSBs, in both VRK1 protects the NBS1 protein of RNF8-mediated ubiqui- resting and cycling cells as well as in ATM-null and p53- tination [47]. Therefore, it is likely that NBS1 phosphoryla- null cells. VRK1 physically interacts and directly phospho- tion by VRK1 contributes to the stabilization of foci, and rylates specific proteins participating at different sequential facilitates the recruitment of additional participants in the stages of DDR, which include H2AX [29], NBS1 [47], and specific DNA repair process, such as kinases of the PI3K 53BP1 [46, 65] in NHEJ [66, 67]; and all of these activating family, ATM, ATR, or DNA-PK, for specific signaling steps phosphorylations are lost by VRK1 depletion. Intermediate or pathways in DDR [45]. steps in DDR signal transmission are well known. The most common pathways in DNA damage response (DDR) impli- VRK1 and 53BP1 in NHEJ cate protein phosphorylation by different kinases such as ATM [10], ATR [11], and DNA-PK [12]; all members of the Double-strand breaks are the most serious form of DNA PI-3K family, which have been mostly studied in the context damage, particularly in cells that are resting or in the early of cell division and cell cycle checkpoints [15]. In response phases of the cell cycle, which includes differentiated rest- to double-strand breaks induced by ionizing radiation (IR), ing cells, as neurons, and stem cells. Under these conditions, the 53BP1 scaffold protein is recruited to IR-induced foci these DSBs are repaired by non-homologous end-joining (IRIF), and is an important marker for monitoring cellular (NHEJ); and one of its main components is 53BP1, a scaf- DDR by NHEJ. 53BP1 foci induced by ionizing radiation or fold protein that forms foci induced by DNA damage [74]. doxorubicin are intermediate steps in DDR activation [68, VRK1 stably interacts with 53BP1 in the region comprised 69] and are known to be regulated by ATM in response to between residues 955-1354, which is implicated in the DSBs [70], and by ATR in response to replication stress interaction with H2AX, but its phosphorylation site is in [71]. However, it is also known that DNA damage response Ser25/29 within the 53BP1N-terminal region and occurs can be ATM-independent [72]. The effect of VRK1 in DDR even in the absence of ATM (null cells) [46]. VRK1 deple- is insensitive to inhibitors of PI3KK proteins that target tion causes a defective formation of 53BP1 foci induced by ATM and DNA-PK [46]. This suggests that there are alterna- ionizing radiation or doxorubicin, both in number and size, tive kinases participating in DDR induced by ionizing radia- which requires a kinase-active VRK1 protein for their rescue tion. The complete molecular components that sequentially [46]. Moreover, this effect of VRK1 on 53BP1 foci is insen- participate in DDR, particularly regulatory proteins, remain sitive to ATM and DNA-PK inhibitors and is functional in unknown. In this context, VRK1 knockdown also prevents p53-null and ATM-null cells. All these data indicate that the the activating phosphorylations of ATM in Ser1981, CHK2 effect of VRK1 is independent of both ATM and p53 [46], in Thr68, and DNA-PK in Ser2056, all induced in response and that VRK1 activation in response to DNA damage is a to IR [46], suggesting that VRK1 is an early and upstream novel participant in the NHEJ mechanism of mammalian component in this DDR process. DNA damage responses [29, 46, 47]. 1 3 2380 I. Campillo-Marcos, P. A. Lazo stress or DNA damage, the basal intracellular level of the Cellular protection mediated by VRK1 and its p53 protein is very low, but it is always present. This basal target p53 low level of p53 is necessary to initiate a fast response to cellular stress by its immediate phosphorylation. The VRK1 forms a complex and phosphorylates p53 p53 phosphorylation in several residues within its TAD1 region (residues 1–46) is the main determinants of the The p53-mediated responses induced by DNA damage stress response [79]. To trigger an immediate reaction to have two major roles in the context of cellular protection DNA damage, the response will be greatly facilitated by (Fig.  2). The first one is preventing the transmission of the formation of a stable and inactive complex between damaged DNA to daughter cells during cell proliferation. p53 and one of its regulatory kinases that are activated by This p53 action is mediated by the induction of a cell cycle DNA damage. In non-damaged cells, the basal low p53 arrest, and forms part of cell cycle checkpoints [75, 76]. level is partially forming a stable complex with VRK1, The other role is the protection of the organism from the which are detected by reciprocal immunoprecipitations, consequences of accumulating cells with damaged DNA, and are detected in resting and cycling cells [81]. This which is mediated by induction of cell death [77]. The basal VRK1-p53 complex forms a basic early warning p53 transcription factor mediates these two main protec- system for detection of cellular stress and its activation is tive responses that are regulated by p53 immediate phos- induced by DNA damage caused by ultraviolet light, ion- phorylation in response to DNA damage. These cellular izing radiation, or doxorubicin treatments. All these types responses have a different temporal order because of the of DNA damage activate the kinase activity of VRK1, a covalent modifications, which are immediate as the stabi- previous step required for the specific phosphorylation of lization of p53, or require hours, such as the induction of p53 at Thr18 [28, 81]. Therefore, the subpopulation of specific gene expression. basal p53 that is forming a complex with VRK1 facili- The stabilization and activation of p53 is performed by tates a readiness state of p53 to initiate an immediate acti- several Ser-Thr kinases that target different residues within vating response in different cellular stress situations [28, the p53N-terminal transactivation domain (Fig.  2), and 81]. Furthermore, the p53 protein also indirectly plays an have different sequential roles [78– 80]. In the absence of important role in epigenetic regulation of chromatin [82]. Fig. 2 Kinase activation DNA damage induced by DNA damage and the regulation of p53 in G0/G1 cells. An enzyme (X) activated by VRK1, and that has not yet Local chromatin been identified, mediates the alteration AT M activation of ATM CHK2 Ub VRK1 Ub Ub Ub P P Ub Ub Ub Ub p53 p53 p53 p53 p53 mdm2 Target genes Proteasomal degradaon BAX CDKN1A MDM2 BBC3 (PUMA) (p21) NOXA Cell cycle Apoptosis arrest 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2381 autophagic proteins [94]. The reversion of activated p53 Phosphorylation of p53 by VRK1 prevents the interaction with MDM2 and regulates the switch also requires downregulation of p53 activating kinases, including VRK1 and ATM, so that dephosphorylated between ubiquitination and transcription p53 is not re-phosphorylated and becomes accessible to MDM2. In this context, p53 induces of the expression of Non-phosphorylated p53 binds to the human MDM2 (HDM2) ubiquitin ligase [83]. VRK1 uniquely and specifi- DUSP6 and WIP1 phosphatases targeting ATM [95–97], and that of the DUSP4 phosphatase targeting VRK1 [98, cally phosphorylates p53 in Thr-18 [28, 84, 85]. This Thr18 residue is critical to maintain the folding of the p53 α-helix 99]. However, downregulation of p53 activation is more complex and also requires additional deactivation of other required for its binding to a hydrophobic pocket in MDM2 [86]. The phosphorylation of p53 in Thr18 alters the align- kinases, which are mediated by phosphatases, and deacety- lation of p53 [94]. ment of hydrophobic residues in this α-helix, and this altered conformation permits the p53 binding to transcriptional The stabilization and accumulation of p53 by VRK1 in response to DNA damage is reverted by a novel p53-depend- cofactors. Moreover, this phosphorylation of Thr18 deter- mines the change in binding mode from ubiquitin ligases to ent activation of autophagy that removes its activating VRK1 [100], a p53 stabilizer, and thus permits p53 dephos- transcription factors, and additional p53 phosphorylation in Ser15 or Ser20 [87] contributes to the selection of specific phorylation and its downregulation by MDM2 [85, 100, 101]. Among the degradation processes regulated by p53 is transcriptional cofactors [88]. The specific phosphorylation of p53 in Thr18 places VRK1 upstream of additional phos- autophagy. In normal cells, autophagy contributes to regu- late basal levels of cytosolic and particulate proteins [102], a phorylation in Ser15 and Ser20 mediated by other kinases [79]. The activated ATM-CHK2, ATR-CHK1, or DNA-PK process that is further activated in response to several types of stress, including DNA damage. Autophagy is required pathways mediate the phosphorylation p53 in Ser15 or Ser20 [78, 79], and all of them are necessary to achieve the full for recycling of proteins implicated in negative cell cycle regulation, and can provide a survival strategy to tumor cells transcriptional activation of p53 [88]. These additional p53 phosphorylations, and their combination, select transcrip- [103]. By this process, regulated by p53, cells remove and digest endogenous proteins, particularly those that are very tional cofactors and activate p53-dependent genes such as CDKN1A (p21) expression [89], which induces a cell cycle stable, functioning as an important mechanism for tissue remodeling [103] and maintenance of cellular homeostasis arrest and senescence [90], and BAX that facilitates apopto- sis [91, 92], among others. The role of p53 in transcription [104], but it can also result in a form of cell death, thus hav- ing a dual role [105, 106]. in these processes has been extensively reviewed [93]. The kinase activity of all these p53 kinases, VRK1, ATM, The downregulation of VRK1 is a late response that is also mediated by the p53-dependent transcription of DRAM ATR, and DNA-PK, are inducible by DNA damage, but their spatial organization, coordination, and sequential activation (death-related autophagic modulator) [107]. DRAM is a small hydrophobic protein located in the membrane of require further studies for its complete understanding. In this context, because of its interactions with histones, VRK1 is a autophagosomes [108]. Expression of DRAM facilitates degradation of VRK1 in the lysosome, and the elimination of new component that participates very early in the response mechanisms to DNA damage, as well as in specific steps DRAM or Beclin1 prevents the downregulation of VRK1 by proteolytic degradation [85, 100] (Fig. 3). This degradation of DDR. of VRK1 takes place in the cytosol and is sensitive to the inhibition of nuclear export with leptomycin B and to lysoso- Activated p53 induces the downregulation of VRK1 mal inhibitors [100]. DRAM expression induced by p53 reg- ulates the degradation of stable proteins. DRAM is a novel Once DNA damage has been repaired, the cell cycle arrest induced by activated p53 has to be reverted. Otherwise, component of the cell autophagic response [107]. Autophagy is partly regulated by p53-induced DRAM expression [107], p53 will maintain the cell cycle arrest or even induce apop- tosis. This reversal requires the deactivation of p53, which and p53-induced VRK1 degradation requires entry in the endosomal–lysosomal pathway [85]. In this way, DRAM is mediated by its dephosphorylation and subsequent inter- action with MDM2. However, the phosphorylation of p53 downregulates VRK1 forming an autoregulatory loop [101] (Fig. 3). Moreover, this autophagic downregulation of VRK1 in Thr18 by VRK1 blocks its interaction with MDM2 and other phosphorylations, in Ser15 and Ser20 further is altered in tumors with p53 mutations that affect its DNA- binding domain, including all the most frequent mutations interfere with the interaction [88]. All these phospho- rylations have to be removed, to revert the p53-mediated detected in human cancer [85, 109], because they disrupt this autoregulatory loop. Consequently, tumors harboring responses, such as a cell cycle arrest, in viable cells. This is accomplished by the regulation by p53 of different target p53 mutations also have very high levels of VRK1, as it has been shown in head and neck squamous cell carcinomas genes that range from ubiquitin ligases, phosphatases, to 1 3 2382 I. Campillo-Marcos, P. A. Lazo Fig. 3 Downregulation of ATM VRK1 by DRAM1 in the DNA damage autophagic pathway induced DRAM1 by p53 and deactivation of p53 by phosphatases and ubiquitin WIP1 ligases the proteasome in DNA damage response. Solid black VRK1 lines represent the activation route. Dashed lines represent ATM the downregulatory routes and each color represents a MDM2 different route. Kinases: VRK1 and ATM. Phosphatases: p53 WIP1 (wild-type P53-induced VRK1 DRAM1 phosphatase 1) and DUSP4 (dual specificity phosphatase endosome DUSP4 4). DRAM1: damage-regulated autophagy modulator 1 Beclin1 p53 Ub-p53 lysosome proteasome [110] and lung cancer [109], which can also facilitate cell proliferation and cell cycle progression, where it plays sev- proliferation. eral roles [121]. VRK1 is required for G0 exit, behaving like In conclusion, the main mechanism of downregulation of an early gene such as MYC and FOS, which facilitate the p53 is mediated MDM2, but for this to occur, it is necessary progression in G1 and passing the restriction point [113]. to previously dephosphorylate p53 and its activating kinases, In this context, depletion of VRK1 prevents the expression all of which are regulated by p53 [94]. Once p53 is dephos- of CCND1 (cyclin D1), since VRK1 directly binds to the phorylated, it becomes available for its ubiquitination by human CCND1 promoter [32], and consequently, retinoblas- MDM2 and degradation in the proteasome, which has been toma cannot be phosphorylated [110]. Later, in cell cycle extensively reviewed and has become a target for therapeutic progression, VRK1 is also required for the phosphorylation intervention with drugs that interfere with the p53-MDM2 of histone H3 that facilitates the initiation of chromatin com- interaction, such as nutlins [111]. paction in G2/M [27] and cooperates with AURKB in the sequential remodeling of chromatin in the progression of mitosis [122]. Implications of VRK1 in cancer biology However, based on the biological actions of VRK1, either in cell proliferation or DNA damage responses indicates that The functions of VRK1 suggest that it is likely to actively depending on the cellular context, VRK1 might function as participate in tumor biology. Knockdown experiments indi- an oncogene or a tumor suppressor or predisposition gene. cate that VRK1 plays a major role in cell cycle progression VRK1 might behave an oncogene because of its roles in and proliferation [27, 112, 113]. Moreover, VRK1 elimina- the promotion of cell cycle progression and proliferation. tion by CRISPR/Cas9 identifies wild-type VRK1 as an over - However, in other contexts, VRK1 might behave as a tumor expressed oncogenic driver gene [114], consistent with its suppressor or a tumor susceptibility gene represented by the role in lung adenocarcinomas [115]. In most cell types, the effects mediated by p53 and those associated with genome human VRK1 gene is expressed at different levels and is not stability. These properties, in the context of cancer, can mutated in cancer, and it is overexpressed in many cancer contribute to a poorer prognosis of tumors overexpressing types of different origins correlating with a poorer prognosis VRK1 because of its contribution to the promotion of cell in breast [116, 117], lung [115], liver [118], glioblastoma proliferation and resistance to treatments based on DNA [119], head and neck [110], and esophageal cancer [120]. damage. Some driver genes are oncogenic in situations in which they Due to the essential role played by VRK1, attempts to are overexpressed by different mechanisms, as it occurs with generate knock-out mice have been unsuccessful. However, members of the MYC and EGFR families that promote cell the consequences of VRK1 deficiency in animal models proliferation. In the context of tumor growth, the human have been studied in gene-trap mice with a fifteen percent VRK1 protein has been implicated in the regulation of residual level of VRK1 [123–125]. In this model, deficient 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2383 animals were sterile, both male and female [123–125], pre- high probability of high toxicity and side effects. The elimi- venting additional studies. The role that VRK1 plays in nation of VRK1 causes a defective DDR that facilitates and response to DNA damage in this model was not studied. increases the sensitivity to DNA damaging agents, such as In one of the studies, the problem was identified as lagging ionizing radiation or doxorubicin [65]. Depletion of VRK1 chromosomes during meiosis leading to sterility [124], an sensitizes cells to these treatments because of defective DNA observation consistent with the role of VRK1 in dynamic repair, and thus permits the use of lower doses of toxic drugs chromatin reorganization. In addition, VRK1 regulates the to achieve the same result. This is important, because this attachment of chromatin to the nuclear envelop that is medi- sensitization also occurs in non-dividing cells, and might be ated by the phosphorylation of BANF1 [126]. The disrup- useful for targeting non-dividing cells within a tumor that tion of this process can also lead to alterations of chromatin later might cause a relapse. Moreover, the treatment with a reorganization in mitosis and affect cell viability [127]. lower dose of commonly used cancer drugs can contribute to a reduction of the toxicity associated with them. Facilitating some degree of DNA damage in tumor cells VRK1 potential as therapeutic target can contribute to the generation of new antigens and facili- in oncology tate the response to new therapies based on manipulation of the immune system, as supported by the evidence that Protein kinases, because of their structural characteristics, tumors with an intrinsic higher genome instability are better are candidates for development of inhibitors. Knockdown responders to these new therapies [133]. screening is a useful approach to identify potential thera- In conclusion, the pharmacological targeting of VRK1 peutic targets. Knockdown of VRK1 sensitizes cells to other will impair p53-mediated responses, prevent cell cycle pro- cancer treatments based on DNA damage such as ionizing gression and proliferation, and sensitize cells to treatments radiation or doxorubicin by impairing the DNA damage based on DNA damage, such as ionizing radiation and some response [46, 65]. Moreover, depletion of VRK1 inhibits chemotherapeutic drugs. The consequence of therapeutically cell proliferation [113, 128]. VRK1 has been identified as exploiting this target will be a better control of the tumor a potential target in a screening of synthetic lethal relation- if the new drugs are selective regarding both its molecular ships in a massive siRNA screening [129]. These observa- target and the specific tumor cell. tions suggests that inhibitors of VRK1 can be of potential Acknowledgements I.C-M was supported by FPI-MINECO-Fondo use in cancer treatments, by themselves or in combinations, Social Europeo predoctoral contract (BES-2014-06772). The labora- by facilitating inhibition of proliferation and at the same tory was supported by grants from Agencia Estatal de Investigación- time sensitizing cells to treatments based on DNA damage. MINECO (SAF2016-75744-R) and Consejería de Educación de la In cancer treatment, many drugs are directed to the main Junta de Castilla y León (CSI001U16, UIC-017) to P.A.L. driver as targets. However, cancer cells can be derailed if alternative pathways that impinge on basic processes of the Compliance with ethical standards tumor phenotype are targeted. These alternative targets will Conflict of interest The authors declare no conflict of interests. open a wide range of possibilities, as well as provide with alternatives to manage individual cases. Open Access This article is distributed under the terms of the Creative Kinases share a common structure in their catalytic Commons Attribution 4.0 International License (http://creativecom- kinase domain and are druggable proteins [130]. Therefore, mons.org/licenses/by/4.0/), which permits unrestricted use, distribu- the likelihood of cross inhibition with other kinases is very tion, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the high and makes many kinase inhibitors promiscuous. In the Creative Commons license, and indicate if changes were made. human kinome, there are kinases that are isolated from other major branches, among which is VRK1. The VRK family has some structural differences, which makes its members susceptible of highly specific inhibition with no promis- References cuity as detected in kinase assays or by structural thermal shift upon binding to inhibitors [131, 132]. However, at this 1. Friedberg EC, McDaniel LD, Schultz RA (2004) The role of time, there is no specific inhibitor for VRK1. Testing kinases endogenous and exogenous DNA damage and mutagenesis. Curr Opin Genet Dev 14(1):5–10. https ://doi.or g/10.1016/j. inhibitors that target the main kinome families did not detect gde.2003.11.001 any that has an effect in assays of VRK1 autophosphoryla- 2. Ciccia A, Elledge SJ (2010) The DNA damage response: making tion and VRK1 phosphorylation of p53 or H3 [30]. This is it safe to play with knives. Mol Cell 40(2):179–204. https ://doi. due to the very high inhibitor concentrations needed because org/10.1016/j.molce l.2010.09.019 of their low ani ffi ty, which required doses in the micromolar range that have a very high risk of cross inhibition and of the 1 3 2384 I. Campillo-Marcos, P. A. Lazo 3. Flores I, Blasco MA (2010) The role of telomeres and telomerase VRK1 (vaccinia-related kinase 1). Encyclopedia of sign- in stem cell aging. FEBS Lett 584(17):3826–3830. https ://doi. aling molecules, 2nd edn. Springer Science. https ://doi. org/10.1016/j.febsl et.2010.07.042 org/10.1007/978-1-4614-6438-9_561-2 4. Henriques CM, Ferreira MG (2012) Consequences of telomere 21. Manning G, Whyte DB, Martinez R, Hunter T, Sudarsanam S shortening during lifespan. Curr Opin Cell Biol 24(6):804–808. (2002) The protein kinase complement of the human genome. https ://doi.org/10.1016/j.ceb.2012.09.007 Science 298(5600):1912–1934. h t t p s : / / d o i . o r g / 1 0 . 1 1 2 6 / s c i e n 5. Orthwein A, Noordermeer SM, Wilson MD, Landry S, Enchev ce.10757 62 RI, Sherker A, Munro M, Pinder J, Salsman J, Dellaire G, Xia B, 22. Nichols RJ, Traktman P (2004) Characterization of three paralo- Peter M, Durocher D (2015) A mechanism for the suppression of gous members of the mammalian vaccinia related kinase fam- homologous recombination in G1 cells. Nature 528(7582):422– ily. J Biol Chem 279(9):7934–7946. https://doi.or g/10.1074/jbc. 426. https ://doi.org/10.1038/natur e1614 2M3108 13200 6. Soteriou D, Fuchs Y (2018) A matter of life and death: stem cell 23. Belyi VA, Ak P, Markert E, Wang H, Hu W, Puzio-Kuter A, survival in tissue regeneration and tumour formation. Nat Rev Levine AJ (2010) The origins and evolution of the p53 family Cancer 18(3):187–201. https ://doi.org/10.1038/nrc.2017.122 of genes. Cold Spring Harb Perspect Biol 2(6):a001198. https :// 7. Tomasetti C, Vogelstein B (2015) Cancer etiology. Variation doi.org/10.1101/cshpe rspec t.a0011 98 in cancer risk among tissues can be explained by the number 24. Mrschtik M, Ryan KM (2016) Another DRAM involved in of stem cell divisions. Science 347(6217):78–81. https ://doi. autophagy and cell death. Autophagy 12(3):603–605. https :// org/10.1126/scien ce.12608 25doi.org/10.1080/15548 627.2015.11374 12 8. Tomasetti C, Li L, Vogelstein B (2017) Stem cell divisions, 25. Gorjanacz M, Klerkx EP, Galy V, Santarella R, Lopez-Igle- somatic mutations, cancer etiology, and cancer prevention. sias C, Askjaer P, Mattaj IW (2008) Caenorhabditis elegans Science 355(6331):1330–1334. h t t p s : / / d o i . o r g / 1 0 . 1 1 2 6 / s c i e n BAF-1 and its kinase VRK-1 participate directly in post-mitotic ce.aaf90 11 nuclear envelope assembly. EMBO J 26(1):132–143. https://doi. 9. Crick F (1974) The double helix: a personal view. Nature org/10.1038/sj.emboj .76014 70 248(5451):766–769 26. Cullen CF, Brittle AL, Ito T, Ohkura H (2005) The conserved 10. Savitsky K, Bar-Shira A, Gilad S, Rotman G, Ziv Y, Vanagaite kinase NHK-1 is essential for mitotic progression and unifying L, Tagle DA, Smith S, Uziel T, Sfez S, Ashkenazi M, Pecker I, acentrosomal meiotic spindles in Drosophila melanogaster. J Frydman M, Harnik R, Patanjali SR, Simmons A, Clines GA, Cell Biol 171(4):593–602. https ://doi.or g/10.1083/jcb.20070 Sartiel A, Gatti RA, Chessa L, Sanal O, Lavin MF, Jaspers NG, 6067 Taylor AM, Arlett CF, Miki T, Weissman SM, Lovett M, Collins 27. Kang TH, Park DY, Choi YH, Kim KJ, Yoon HS, Kim KT (2007) FS, Shiloh Y (1995) A single ataxia telangiectasia gene with a Mitotic histone H3 phosphorylation by vaccinia-related kinase product similar to PI-3 kinase. Science 268(5218):1749–1753. 1 in mammalian cells. Mol Cell Biol 27(24):8533–8546. https:// https ://doi.org/10.1126/scien ce.77926 00doi.org/10.1128/MCB.00018 -07 11. Lakin ND, Hann BC, Jackson SP (1999) The ataxia-telangi- 28. Vega FM, Sevilla A, Lazo PA (2004) p53 Stabilization and ectasia related protein ATR mediates DNA-dependent phos- accumulation induced by human vaccinia-related kinase 1. phorylation of p53. Oncogene 18(27):3989–3995. https ://doi. Mol Cell Biol 24(23):10366–10380. https ://doi.or g/10.1128/ org/10.1038/sj.onc.12029 73MCB.24.23.10366 -10380 .2004 12. Lee SE, Mitchell RA, Cheng A, Hendrickson EA (1997) Evi- 29. Salzano M, Sanz-Garcia M, Monsalve DM, Moura DS, Lazo PA dence for DNA-PK-dependent and -independent DNA double- (2015) VRK1 chromatin kinase phosphorylates H2AX and is strand break repair pathways in mammalian cells as a function required for foci formation induced by DNA damage. Epigenetics of the cell cycle. Mol Cell Biol 17(3):1425–1433. https ://doi. 10(5):373–383. https://doi.or g/10.1080/15592294.2015.10287 08 org/10.1128/MCB.17.3.1425 30. Vazquez-Cedeira M, Barcia-Sanjurjo I, Sanz-Garcia M, Barcia R, 13. Soria G, Polo SE, Almouzni G (2012) Prime, repair, restore: the Lazo PA (2011) Differential inhibitor sensitivity between human active role of chromatin in the DNA damage response. Mol Cell kinases VRK1 and VRK2. PLoS One 6(8):e23235. https ://doi. 46(6):722–734. https ://doi.org/10.1016/j.molce l.2012.06.002org/10.1371/journ al.pone.00232 35 14. Bustin M, Misteli T (2016) Nongenetic functions of the genome. 31. Aihara H, Nakagawa T, Yasui K, Ohta T, Hirose S, Dhomae Science 352(6286):aad6933. https ://doi.or g/10.1126/scien N, Takio K, Kaneko M, Takeshima Y, Muramatsu M, Ito T ce.aad69 33 (2004) Nucleosomal histone kinase-1 phosphorylates H2A Thr 15. Abraham RT (2001) Cell cycle checkpoint signaling through the 119 during mitosis in the early Drosophila embryo. Genes Dev ATM and ATR kinases. Genes Dev 15(17):2177–2196. https :// 18(8):877–888. https ://doi.org/10.1101/gad.11846 04 doi.org/10.1101/gad.91440 1 32. Aihara H, Nakagawa T, Mizusaki H, Yoneda M, Kato M, Doi- 16. Jackson SP, Bartek J (2009) The DNA-damage response in guchi M, Imamura Y, Higashi M, Ikura T, Hayashi T, Kodama human biology and disease. Nature 461(7267):1071–1078. https Y, Oki M, Nakayama T, Cheung E, Aburatani H, Takayama KI, ://doi.org/10.1038/natur e0846 7 Koseki H, Inoue S, Takeshima Y, Ito T (2016) Histone H2A 17. Hoeijmakers JH (2009) DNA damage, aging, and cancer. N Engl T120 phosphorylation promotes oncogenic transformation via J Med 361(15):1475–1485. https://doi. org/10.1056/NEJMra0804 upregulation of cyclin D1. Mol Cell 64(1):176–188. https ://doi. 615org/10.1016/j.molce l.2016.09.012 18. Rass U, Ahel I, West SC (2007) Defective DNA repair and 33. Tessarz P, Kouzarides T (2014) Histone core modifications regu- neurodegenerative disease. Cell 130(6):991–1004. https ://doi. lating nucleosome structure and dynamics. Nat Rev Mol Cell org/10.1016/j.cell.2007.08.043 Biol 15(11):703–708. https ://doi.org/10.1038/nrm38 90 19. Varjosalo M, Sacco R, Stukalov A, van Drogen A, Planyavsky 34. Bannister AJ, Kouzarides T (2011) Regulation of chromatin M, Hauri S, Aebersold R, Bennett KL, Colinge J, Gstaiger M, by histone modifications. Cell Res 21(3):381–395. https ://doi. Superti-Furga G (2013) Interlaboratory reproducibility of large- org/10.1038/cr.2011.22 scale human protein-complex analysis by standardized AP-MS. 35. Kang TH, Park DY, Kim W, Kim KT (2008) VRK1 phosphoryl- Nat Methods 10(4):307–314. https://doi.or g/10.1038/nmeth.2400 ates CREB and mediates CCND1 expression. J Cell Sci 121(Pt 18):3035–3041. https ://doi.org/10.1242/jcs.02675 7 20. Cantarero L, Moura DS, Salzano M, Monsalve DM, Campillo-Marcos I, Martín-Doncel E, Lazo PA (2017) 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2385 36. Sevilla A, Santos CR, Vega FM, Lazo PA (2004) Human vac- of repair proteins and repair of DNA double-strand breaks. Nat cinia-related kinase 1 (VRK1) activates the ATF2 transcriptional Cell Biol 8(1):91–99. https ://doi.org/10.1038/ncb13 43 activity by novel phosphorylation on Thr-73 and Ser-62 and 53. Bird AW, Yu DY, Pray-Grant MG, Qiu Q, Harmon KE, Megee cooperates with JNK. J Biol Chem 279(26):27458–27465. https PC, Grant PA, Smith MM, Christman MF (2002) Acetylation ://doi.org/10.1074/jbc.M4010 09200 of histone H4 by Esa1 is required for DNA double-strand break 37. Sevilla A, Santos CR, Barcia R, Vega FM, Lazo PA (2004) repair. Nature 419(6905):411–415. https://doi.or g/10.1038/natur c-Jun phosphorylation by the human vaccinia-related kinase 1 e0103 5 (VRK1) and its cooperation with the N-terminal kinase of c-Jun 54. Ikura T, Tashiro S, Kakino A, Shima H, Jacob N, Amunugama (JNK). Oncogene 23(55):8950–8958. https ://doi.org/10.1038/ R, Yoder K, Izumi S, Kuraoka I, Tanaka K, Kimura H, Ikura sj.onc.12080 15 M, Nishikubo S, Ito T, Muto A, Miyagawa K, Takeda S, Fishel 38. Moura DS, Fernandez IF, Marin-Royo G, Lopez-Sanchez I, R, Igarashi K, Kamiya K (2007) DNA damage-dependent Martin-Doncel E, Vega FM, Lazo PA (2016) Oncogenic Sox2 acetylation and ubiquitination of H2AX enhances chroma- regulates and cooperates with VRK1 in cell cycle progression tin dynamics. Mol Cell Biol 27(20):7028–7040. https ://doi. and differentiation. Sci Rep 6:28532. https ://doi.org/10.1038/org/10.1128/MCB.00579 -07 srep2 8532 55. Robinson PJ, An W, Routh A, Martino F, Chapman L, Roeder 39. Hashiguchi T, Arakawa S, Takahashi S, Gonzalez FJ, Sueyoshi RG, Rhodes D (2008) 30 nm chromatin fibre decompaction T, Negishi M (2016) Phosphorylation of Farnesoid X receptor at requires both H4-K16 acetylation and linker histone evic- serine 154 links ligand activation with degradation. Mol Endo- tion. J Mol Biol 381(4):816–825. https ://doi.or g/10.1016/j. crinol 30(10):1070–1080. https://doi.or g/10.1210/me.2016-1105 jmb.2008.04.050 40. Shi L, Oberdoerffer P (2012) Chromatin dynamics in DNA dou- 56. Shogren-Knaak M, Ishii H, Sun JM, Pazin MJ, Davie JR, Peter- ble-strand break repair. Biochim Biophys Acta 7:811–819. https son CL (2006) Histone H4-K16 acetylation controls chromatin ://doi.org/10.1016/j.bbagr m.2012.01.002 structure and protein interactions. Science 311(5762):844–847. 41. Deem AK, Li X, Tyler JK (2012) Epigenetic regulation of https ://doi.org/10.1126/scien ce.11240 00 genomic integrity. Chromosoma 121(2):131–151. https ://doi. 57. Li X, Corsa CA, Pan PW, Wu L, Ferguson D, Yu X, Min J, Dou org/10.1007/s0041 2-011-0358-1 Y (2010) MOF and H4 K16 acetylation play important roles 42. Raschella G, Melino G, Malewicz M (2017) New factors in in DNA damage repair by modulating recruitment of DNA mammalian DNA repair—the chromatin connection. Oncogene damage repair protein Mdc1. Mol Cell Biol 30(22):5335–5347. 36(33):4673–4681. https ://doi.org/10.1038/onc.2017.60https ://doi.org/10.1128/MCB.00350 -10 43. Ceccaldi R, Rondinelli B, D’Andrea AD (2016) Repair pathway 58. Shin J, Chakraborty G, Bharatham N, Kang C, Tochio N, choices and consequences at the double-strand break. Trends Cell Koshiba S, Kigawa T, Kim W, Kim KT, Yoon HS (2011) NMR Biol 26(1):52–64. https ://doi.org/10.1016/j.tcb.2015.07.009 solution structure of human vaccinia-related kinase 1 (VRK1) 44. Polo SE, Jackson SP (2011) Dynamics of DNA damage response reveals the C-terminal tail essential for its structural stability proteins at DNA breaks: a focus on protein modifications. Genes and autocatalytic activity. J Biol Chem 286(25):22131–22138. Dev 25(5):409–433. https ://doi.org/10.1101/gad.20213 11https ://doi.org/10.1074/jbc.M110.20016 2 45. Falck J, Coates J, Jackson SP (2005) Conserved modes of recruit- 59. Kim W, Chakraborty G, Kim S, Shin J, Park CH, Jeong MW, ment of ATM, ATR and DNA-PKcs to sites of DNA damage. Bharatham N, Yoon HS, Kim KT (2012) Macro histone Nature 434(7033):605–611. https: //doi.org/10.1038/nature 03442 H2A1.2 (MacroH2A1) protein suppresses mitotic kinase 46. Sanz-Garcia M, Monsalve DM, Sevilla A, Lazo PA (2012) VRK1 during interphase. J Biol Chem 287(8):5278–5289. Vaccinia-related Kinase 1 (VRK1) is an upstream nucleoso-https ://doi.org/10.1074/jbc.M111.28170 9 mal kinase required for the assembly of 53BP1 foci in response 60. Sanz-Garcia M, Lopez-Sanchez I, Lazo PA (2008) Proteom- to ionizing radiation-induced DNA damage. J Biol Chem ics identification of nuclear Ran GTPase as an inhibitor of 287(28):23757–23768. https://doi.or g/10.1074/jbc.M112.353102 human VRK1 and VRK2 (vaccinia-related kinase) activities. 47. Monsalve DM, Campillo-Marcos I, Salzano M, Sanz-Garcia M, Mol Cell Proteom 7(11):2199–2214. https ://doi.org/10.1074/ Cantarero L, Lazo PA (2016) VRK1 phosphorylates and pro-mcp.M7005 86-MCP20 0 tects NBS1 from ubiquitination and proteasomal degradation in 61. Kalab P, Pralle A, Isacoff EY, Heald R, Weis K (2006) Analy - response to DNA damage. BBA Mol Cell Res 4:760–769. https sis of a RanGTP-regulated gradient in mitotic somatic cells. ://doi.org/10.1016/j.bbamc r.2016.02.005 Nature 440(7084):697–701. h t t p s : / / d o i . o r g / 1 0 . 1 0 3 8 / n a t u r 48. Fell VL, Schild-Poulter C (2015) The Ku heterodimer: function e0458 9 in DNA repair and beyond. Mutat Res Rev Mutat Res 763:15–29. 62. Rogakou EP, Boon C, Redon C, Bonner WM (1999) Megabase https ://doi.org/10.1016/j.mrrev .2014.06.002 chromatin domains involved in DNA double-strand breaks 49. Celli GB, Denchi EL, de Lange T (2006) Ku70 stimulates fusion in vivo. J Cell Biol 146(5):905–916. https ://doi.org/10.1083/ of dysfunctional telomeres yet protects chromosome ends from jcb.146.5.905 homologous recombination. Nat Cell Biol 8(8):885–890. https 63. Nakamura AJ, Rao VA, Pommier Y, Bonner WM (2010) The ://doi.org/10.1038/ncb14 44 complexity of phosphorylated H2AX foci formation and DNA 50. Choi YH, Lim JK, Jeong MW, Kim KT (2012) HnRNP A1 phos- repair assembly at DNA double-strand breaks. Cell Cycle phorylated by VRK1 stimulates telomerase and its binding to 9(2):389–397. https ://doi.org/10.4161/cc.9.2.10475 telomeric DNA sequence. Nucleic Acids Res 40(17):8499–8518. 64. Paull TT, Rogakou EP, Yamazaki V, Kirchgessner CU, Gel- https ://doi.org/10.1093/nar/gks63 4 lert M, Bonner WM (2000) A critical role for histone H2AX 51. Downs JA, Allard S, Jobin-Robitaille O, Javaheri A, Auger A, in recruitment of repair factors to nuclear foci after DNA dam- Bouchard N, Kron SJ, Jackson SP, Cote J (2004) Binding of age. Curr Biol 10(15):886–895. https ://doi.org/10.1016/S0960 chromatin-modifying activities to phosphorylated histone H2A -9822(00)00610 -2 at DNA damage sites. Mol Cell 16(6):979–990. https ://doi. 65. Salzano M, Vazquez-Cedeira M, Sanz-Garcia M, Valbuena A, org/10.1016/j.molce l.2004.12.003 Blanco S, Fernandez IF, Lazo PA (2014) Vaccinia-related kinase 52. Murr R, Loizou JI, Yang YG, Cuenin C, Li H, Wang ZQ, Herceg 1 (VRK1) confers resistance to DNA-damaging agents in human Z (2006) Histone acetylation by Trrap-Tip60 modulates loading breast cancer by affecting DNA damage response. Oncotarget 5(N7):1770–1778. https ://doi.org/10.18632 /oncot arget .1678 1 3 2386 I. Campillo-Marcos, P. A. Lazo 66. Williams GJ, Lees-Miller SP, Tainer JA (2010) Mre11–Rad50– 83. Moll UM, Petrenko O (2003) The MDM2–p53 interaction. Mol Nbs1 conformations and the control of sensing, signaling, and Cancer Res 1(14):1001–1008 effector responses at DNA double-strand breaks. DNA Repair 84. Lopez-Borges S, Lazo PA (2000) The human vaccinia-related (Amst) 9(12):1299–1306. https ://doi.or g/10.1016/j.dnar e kinase 1 (VRK1) phosphorylates threonine-18 within the mdm-2 p.2010.10.001 binding site of the p53 tumour suppressor protein. Oncogene 67. Williams GJ, Hammel M, Radhakrishnan SK, Ramsden D, 19(32):3656–3664. https ://doi.org/10.1038/sj.onc.12037 09 Lees-Miller SP, Tainer JA (2014) Structural insights into NHEJ: 85. Valbuena A, Vega FM, Blanco S, Lazo PA (2006) p53 down- building up an integrated picture of the dynamic DSB repair regulates its activating vaccinia-related kinase 1, forming a new super complex, one component and interaction at a time. DNA autoregulatory loop. Mol Cell Biol 26(13):4782–4793. https :// Repair (Amst) 17:110–120. https ://doi.or g/10.1016/j.dnar e doi.org/10.1128/MCB.00069 -06 p.2014.02.009 86. Kussie PH, Gorina S, Marechal V, Elenbaas B, Moreau J, Lev- 68. Schultz LB, Chehab NH, Malikzay A, Halazonetis TD (2000) ine AJ, Pavletich NP (1996) Structure of the MDM2 oncopro- p53 binding protein 1 (53BP1) is an early participant in the tein bound to the p53 tumor suppressor transactivation domain. cellular response to DNA double-strand breaks. J Cell Biol Science 274(5289):948–953. https ://doi.or g/10.1126/scien 151(7):1381–1390. https ://doi.org/10.1083/jcb.151.7.1381 ce.274.5289.948 69. Wang B, Matsuoka S, Carpenter PB, Elledge SJ (2002) 87. Teufel DP, Freund SM, Bycroft M, Fersht AR (2007) Four 53BP1, a mediator of the DNA damage checkpoint. Science domains of p300 each bind tightly to a sequence spanning both 298(5597):1435–1438. https://doi.or g/10.1126/science.10761 82 transactivation subdomains of p53. Proc Natl Acad Sci USA 70. Mochan TA, Venere M, DiTullio RA Jr, Halazonetis TD (2003) 104(17):7009–7014. https ://doi.org/10.1073/pnas.07020 10104 53BP1 and NFBD1/MDC1-Nbs1 function in parallel interact- 88. Teufel DP, Bycroft M, Fersht AR (2009) Regulation by phos- ing pathways activating ataxia-telangiectasia mutated (ATM) in phorylation of the relative affinities of the N-terminal transacti- response to DNA damage. Cancer Res 63(24):8586–8591 vation domains of p53 for p300 domains and Mdm2. Oncogene 71. Ward IM, Chen J (2001) Histone H2AX is phosphorylated in an 28(20):2112–2118. https ://doi.org/10.1038/onc.2009.71 ATR-dependent manner in response to replicational stress. J Biol 89. Del Sal G, Murphy M, Ruaro E, Lazarevic D, Levine AJ, Schnei- Chem 276(51):47759–47762. https://doi.or g/10.1074/jbc.C1005 der C (1996) Cyclin D1 and p21/waf1 are both involved in p53 69200 growth suppression. Oncogene 12(1):177–185 72. Riballo E, Kuhne M, Rief N, Doherty A, Smith GC, Recio MJ, 90. Ferbeyre G, de Stanchina E, Lin AW, Querido E, McCurrach ME, Reis C, Dahm K, Fricke A, Krempler A, Parker AR, Jackson SP, Hannon GJ, Lowe SW (2002) Oncogenic ras and p53 cooperate Gennery A, Jeggo PA, Lobrich M (2004) A pathway of double- to induce cellular senescence. Mol Cell Biol 22(10):3497–3508. strand break rejoining dependent upon ATM, Artemis, and pro-https ://doi.org/10.1128/MCB.22.10.3497-3508.2002 teins locating to gamma-H2AX foci. Mol Cell 16(5):715–724. 91. Miyashita T, Reed JC (1995) Tumor suppressor p53 is a direct https ://doi.org/10.1016/j.molce l.2004.10.029 transcriptional activator of the human bax gene. Cell 80(2):293– 73. Wen J, Cerosaletti K, Schultz KJ, Wright JA, Concannon P 299. https ://doi.org/10.1016/0092-8674(95)90412 -3 (2013) NBN phosphorylation regulates the accumulation of 92. Miyashita T, Krajewski S, Krajewski M, Wang HG, Lin HK, MRN and ATM at sites of DNA double-strand breaks. Oncogene Lieberman DA, Hoffman B, Reed JC (1994) Tumor suppressor 32(37):4448–4456. https ://doi.org/10.1038/onc.2012.443 p53 is a regulator of Bcl-2 and Bax gene expression in vitro and 74. Panier S, Boulton SJ (2014) Double-strand break repair: 53BP1 in vivo. Oncogene 9:1799–1805 comes into focus. Nat Rev Mol Cell Biol 15(1):7–18. https://doi. 93. Menendez D, Inga A, Resnick MA (2009) The expanding uni- org/10.1038/nrm37 19 verse of p53 targets. Nat Rev Cancer 9(10):724–737. https: //doi. 75. Levine AJ (1997) p53, the cellular gatekeeper for growth and org/10.1038/nrc27 30 division. Cell 88(3):323–331 94. Lazo PA (2017) Reverting p53 activation after recovery of cel- 76. Selivanova G, Wiman KG (1995) p53: a cell cycle regulator acti- lular stress to resume with cell cycle progression. Cell Signal vated by DNA damage. Adv Cancer Res 66:143–180 33:49–58. https ://doi.org/10.1016/j.cells ig.2017.02.005 77. Oren M (2003) Decision making by p53: life, death and can- 95. Piya S, Kim JY, Bae J, Seol DW, Moon AR, Kim TH (2012) cer. Cell Death Differ 10(4):431–442. https ://doi.org/10.1038/ DUSP6 is a novel transcriptional target of p53 and regulates sj.cdd.44011 83 p53-mediated apoptosis by modulating expression levels of 78. Toledo F, Wahl GM (2006) Regulating the p53 pathway: in vitro Bcl-2 family proteins. FEBS Lett 586(23):4233–4240. https :// hypotheses, in vivo veritas. Nat Rev Cancer 6(12):909–923. https doi.org/10.1016/j.febsl et.2012.10.031 ://doi.org/10.1038/nrc20 12 96. Yamaguchi H, Durell SR, Chatterjee DK, Anderson CW, Appella 79. Meek DW, Anderson CW (2009) Posttranslational modification E (2007) The Wip1 phosphatase PPM1D dephosphorylates SQ/ of p53: cooperative integrators of function. Cold Spring Harb TQ motifs in checkpoint substrates phosphorylated by PI3K- Perspect Biol 1:a000950. https ://doi.or g/10.1101/cshpe rspec like kinases. Biochemistry 46(44):12594–12603. https ://doi. t.a0009 50org/10.1021/bi701 096s 80. Meek DW (2009) Tumour suppression by p53: a role for the 97. Shreeram S, Demidov ON, Hee WK, Yamaguchi H, Onishi N, DNA damage response? Nat Rev Cancer 9(10):714–723. https Kek C, Timofeev ON, Dudgeon C, Fornace AJ, Anderson CW, ://doi.org/10.1038/nrc27 16 Minami Y, Appella E, Bulavin DV (2006) Wip1 phosphatase 81. Lopez-Sanchez I, Valbuena A, Vazquez-Cedeira M, Khadake modulates ATM-dependent signaling pathways. Mol Cell J, Sanz-Garcia M, Carrillo-Jimenez A, Lazo PA (2014) VRK1 23(5):757–764. https ://doi.org/10.1016/j.molce l.2006.07.010 interacts with p53 forming a basal complex that is activated by 98. Shen WH, Wang J, Wu J, Zhurkin VB, Yin Y (2006) Mitogen- UV-induced DNA damage. FEBS Lett 588(5):692–700. https :// activated protein kinase phosphatase 2: a novel transcription doi.org/10.1016/j.febsl et.2014.01.040 target of p53 in apoptosis. Cancer Res 66(12):6033–6039. https 82. Levine AJ (2017) The p53 protein plays a central role in the ://doi.org/10.1158/0008-5472.CAN-05-3878 mechanism of action of epigenetic drugs that alter the methyla- 99. Jeong MW, Kang TH, Kim W, Choi YH, Kim KT (2013) Mito- tion of cytosine residues in DNA. Oncotarget 8(5):7228–7230. gen-activated protein kinase phosphatase 2 regulates histone https ://doi.org/10.18632 /oncot arget .14805 H3 phosphorylation via interaction with vaccinia-related kinase 1 3 Implication of the VRK1 chromatin kinase in the signaling responses to DNA damage: a therapeutic… 2387 1. Mol Biol Cell 24(3):373–384. https ://doi.org/10.1091/mbc. lung cell lineage and mitotic networks in lung adenocarcinomas. E12-06-0456 Nat Commun 4:1701. https ://doi.org/10.1038/ncomm s2660 100. Valbuena A, Castro-Obregon S, Lazo PA (2011) Downregula- 116. Fournier MV, Martin KJ, Kenny PA, Xhaja K, Bosch I, Yas- tion of VRK1 by p53 in response to DNA damage is mediated wen P, Bissell MJ (2006) Gene expression signature in organ- by the autophagic pathway. PLoS One 6(2):e17320. https ://doi. ized and growth-arrested mammary acini predicts good outcome org/10.1371/journ al.pone.00173 20 in breast cancer. Cancer Res 66(14):7095–7102. https ://doi. 101. Valbuena A, Blanco S, Vega FM, Lazo PA (2008) The C/H3 org/10.1158/0008-5472.CAN-06-0515 domain of p300 is required to protect VRK1 and VRK2 from 117. Martin KJ, Patrick DR, Bissell MJ, Fournier MV (2008) their downregulation induced by p53. PLoS One 3(7):e2649. Prognostic breast cancer signature identified from 3D culture https ://doi.org/10.1371/journ al.pone.00026 49 model accurately predicts clinical outcome across independent 102. Baehrecke EH (2005) Autophagy: dual roles in life and death? datasets. PLoS One 3(8):e2994. https ://doi.org/10.1371/journ Nat Rev Mol Cell Biol 6(6):505–510. https ://doi.org/10.1038/al.pone.00029 94 nrm16 66 118. Huang W, Cui X, Chen Y, Shao M, Shao X, Shen Y, Liu Q, Wu 103. Cecconi F, Levine B (2008) The role of autophagy in mamma- M, Liu J, Ni W, Lu C, Wan C (2016) High VRK1 expression lian development: cell makeover rather than cell death. Dev Cell contributes to cell proliferation and survival in hepatocellu- 15(3):344–357. https ://doi.org/10.1016/j.devce l.2008.08.012 lar carcinoma. Pathol Res Pract 212(3):171–178. https ://doi. 104. Mizushima N (2007) Autophagy: process and function. Genes org/10.1016/j.prp.2015.11.015 Dev 21(22):2861–2873. https ://doi.org/10.1101/gad.15992 07 119. Varghese RT, Liang Y, Guan T, Franck CT, Kelly DF, Sheng 105. Maiuri MC, Zalckvar E, Kimchi A, Kroemer G (2007) Self-eat- Z (2016) Survival kinase genes present prognostic signifi- ing and self-killing: crosstalk between autophagy and apoptosis. cance in glioblastoma. Oncotarget 7:20140–20151. https :// Nat Rev Mol Cell Biol 8(9):741–752. https ://doi.org/10.1038/doi.org/10.18632 /oncot arget .7917 nrm22 39 120. Li J, Wang T, Pei L, Jing J, Hu W, Sun T, Liu H (2017) Expres- 106. Tasdemir E, Chiara Maiuri M, Morselli E, Criollo A, D’Amelio sion of VRK1 and the downstream gene BANF1 in esopha- M, Djavaheri-Mergny M, Cecconi F, Tavernarakis N, Kroemer G geal cancer. Biomed Pharmacother 89:1086–1091. https://doi. (2008) A dual role of p53 in the control of autophagy. Autophagy org/10.1016/j.bioph a.2017.02.095 4(6):810–814. https ://doi.org/10.4161/auto.6486 121. Valbuena A, Sanz-Garcia M, Lopez-Sanchez I, Vega FM, 107. Crighton D, Wilkinson S, O’Prey J, Syed N, Smith P, Harrison Lazo PA (2011) Roles of VRK1 as a new player in the con- PR, Gasco M, Garrone O, Crook T, Ryan KM (2006) DRAM, trol of biological processes required for cell division. Cell a p53-induced modulator of autophagy, is critical for apoptosis. Signal 23(8):1267–1272. https ://doi.or g/10.1016/j.cells Cell 126(1):121–134. https://doi.or g/10.1016/j.cell.2006.05.034 ig.2011.04.002 108. Mah LY, O’Prey J, Baudot AD, Hoekstra A, Ryan KM (2012) 122. Moura DS, Campillo-Marcos I, Vazquez-Cedeira M, Lazo PA DRAM-1 encodes multiple isoforms that regulate autophagy. (2018) VRK1 and AURKB form a complex that cross inhibit Autophagy 8(1):18–28. https ://doi.org/10.4161/auto.8.1.18077 their kinase activity and the phosphorylation of histone H3 109. Valbuena A, Suarez-Gauthier A, Lopez-Rios F, Lopez-Encuen- in the progression of mitosis. Cell Mol Life Sci. https ://doi. tra A, Blanco S, Fernandez PL, Sanchez-Cespedes M, Lazo org/10.1007/s0001 8-018-2746-7 PA (2007) Alteration of the VRK1-p53 autoregulatory loop in 123. Wiebe MS, Nichols RJ, Molitor TP, Lindgren JK, Traktman human lung carcinomas. Lung Cancer 58(3):303–309. https :// P (2010) Mice deficient in the serine/threonine protein kinase doi.org/10.1016/j.lungc an.2007.06.023 VRK1 are infertile due to a progressive loss of spermatogonia. 110. Santos CR, Rodriguez-Pinilla M, Vega FM, Rodriguez-Peralto Biol Reprod 82(1):182–193. https ://doi.org/10.1095/biolr eprod JL, Blanco S, Sevilla A, Valbuena A, Hernandez T, van Wijnen .109.07909 5 AJ, Li F, de Alava E, Sanchez-Cespedes M, Lazo PA (2006) 124. Schober CS, Aydiner F, Booth CJ, Seli E, Reinke V (2011) VRK1 signaling pathway in the context of the proliferation The kinase VRK1 is required for normal meiotic progression phenotype in head and neck squamous cell carcinoma. Mol in mammalian oogenesis. Mech Dev 128(3–4):178–190. https:// Cancer Res 4(3):177–185. https ://doi.org/10.1158/1541-7786. doi.org/10.1016/j.mod.2011.01.004 MCR-05-0212 125. Kim J, Choi YH, Chang S, Kim KT, Je JH (2012) Defective fol- 111. Wang S, Zhao Y, Aguilar A, Bernard D, Yang CY (2017) Target- liculogenesis in female mice lacking vaccinia-related kinase 1. ing the MDM2-p53 protein–protein interaction for new cancer Sci Rep 2:468. https ://doi.org/10.1038/srep0 0468 therapy: progress and challenges. Cold Spring Harb Perspect 126. Nichols RJ, Wiebe MS, Traktman P (2006) The vaccinia-related Med 7(5):a026245. https://doi.or g/10.1101/cshperspec t.a0262 45 kinases phosphorylate the N’ terminus of BAF, regulating its 112. Vega FM, Gonzalo P, Gaspar ML, Lazo PA (2003) Expression of interaction with DNA and its retention in the nucleus. Mol Biol the VRK (vaccinia-related kinase) gene family of p53 regulators Cell 17(5):2451–2464. https://doi.or g/10.1091/mbc.E05-12-1179 in murine hematopoietic development. FEBS Lett 544(1–3):176– 127. Jamin A, Wiebe MS (2015) Barrier to Autointegration Factor 180. https ://doi.org/10.1016/S0014 -5793(03)00501 -5 (BANF1): interwoven roles in nuclear structure, genome integ- 113. Valbuena A, Lopez-Sanchez I, Lazo PA (2008) Human VRK1 rity, innate immunity, stress responses and progeria. Curr Opin is an early response gene and its loss causes a block in cell cycle Cell Biol 34:61–68. https ://doi.org/10.1016/j.ceb.2015.05.006 progression. PLoS One 3(2):e1642. https://doi.or g/10.1371/journ 128. Molitor TP, Traktman P (2013) Molecular genetic analysis of al.pone.00016 42 VRK1 in mammary epithelial cells: depletion slows proliferation 114. Kiessling MK, Schuierer S, Stertz S, Beibel M, Bergling S, in vitro and tumor growth and metastasis in vivo. Oncogenesis Knehr J, Carbone W, de Valliere C, Tchinda J, Bouwmeester 2:e48. https ://doi.org/10.1038/oncsi s.2013.11 T, Seuwen K, Rogler G, Roma G (2016) Identification of onco- 129. McDonald ER, 3rd, de Weck A, Schlabach MR, Billy E, Mavra- genic driver mutations by genome-wide CRISPR-Cas9 dropout kis KJ, Hoffman GR, Belur D, Castelletti D, Frias E, Gampa K, screening. BMC Genom 17(1):723. https ://doi.or g/10.1186/ Golji J, Kao I, Li L, Megel P, Perkins TA, Ramadan N, Ruddy s1286 4-016-3042-2 DA, Silver SJ, Sovath S, Stump M, Weber O, Widmer R, Yu J, 115. Kim IJ, Quigley D, To MD, Pham P, Lin K, Jo B, Jen KY, Raz D, Yu K, Yue Y, Abramowski D, Ackley E, Barrett R, Berger J, Ber- Kim J, Mao JH, Jablons D, Balmain A (2013) Rewiring of human nard JL, Billig R, Brachmann SM, Buxton F, Caothien R, Caushi JX, Chung FS, Cortes-Cros M, deBeaumont RS, Delaunay C, 1 3 2388 I. Campillo-Marcos, P. A. Lazo Desplat A, Duong W, Dwoske DA, Eldridge RS, Farsidjani A, 131. Fedorov O, Marsden B, Pogacic V, Rellos P, Muller S, Bullock Feng F, Feng J, Flemming D, Forrester W, Galli GG, Gao Z, AN, Schwaller J, Sundstrom M, Knapp S (2007) A systematic Gauter F, Gibaja V, Haas K, Hattenberger M, Hood T, Hurov KE, interaction map of validated kinase inhibitors with Ser/Thr Jagani Z, Jenal M, Johnson JA, Jones MD, Kapoor A, Korn J, Liu kinases. Proc Natl Acad Sci USA 104(51):20523–20528. https J, Liu Q, Liu S, Liu Y, Loo AT, Macchi KJ, Martin T, McAllister ://doi.org/10.1073/pnas.07088 00104 G, Meyer A, Molle S, Pagliarini RA, Phadke T, Repko B, Schou- 132. Fedorov O, Sundstrom M, Marsden B, Knapp S (2007) Insights wey T, Shanahan F, Shen Q, Stamm C, Stephan C, Stucke VM, for the development of specific kinase inhibitors by targeted Tiedt R, Varadarajan M, Venkatesan K, Vitari AC, Wallroth M, structural genomics. Drug Discov Today 12(9–10):365–372. Weiler J, Zhang J, Mickanin C, Myer VE, Porter JA, Lai A, Bit-https ://doi.org/10.1016/j.drudi s.2007.03.006 ter H, Lees E, Keen N, Kauffmann A, Stegmeier F, Hofmann F, 133. Nebot-Bral L, Brandao D, Verlingue L, Rouleau E, Caron O, Schmelzle T, Sellers WR (2017) Project DRIVE: a compendium Despras E, El-Dakdouki Y, Champiat S, Aoufouchi S, Leary A, of cancer dependencies and synthetic lethal relationships uncov- Marabelle A, Malka D, Chaput N, Kannouche PL (2017) Hyper- ered by large-scale, deep RNAi screening. Cell 170(3):577–592 mutated tumours in the era of immunotherapy: the paradigm of e510. https ://doi.org/10.1016/j.cell.2017.07.005 personalised medicine. Eur J Cancer 84:290–303. https ://doi. 130. Knight ZA, Lin H, Shokat KM (2010) Targeting the cancer org/10.1016/j.ejca.2017.07.026 kinome through polypharmacology. Nat Rev Cancer 10(2):130– 137. https ://doi.org/10.1038/nrc27 87 1 3

Journal

Cellular and Molecular Life SciencesSpringer Journals

Published: Apr 20, 2018

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off