Plant Molecular Biology 52: 273–284, 2003.
© 2003 Kluwer Academic Publishers. Printed in the Netherlands.
Arabidopsis RecQsim, a plant-speciﬁc member of the RecQ helicase
family, can suppress the MMS hypersensitivity of the yeast sgs1 mutant
Mohammad B. Bagherieh-Najjar
, Onno M.H. de Vries
, Johan T.M. Kroon
, Emma L.
, Kieran M. Elborough
, Jacques Hille
and Paul P. Dijkwel
Molecular Biology of Plants, Groningen Biomolecular Sciences and Biotechnology Institute, Univer-
sity of Groningen, Kerklaan 30, 9751 NN Haren, Netherlands (
author for correspondence; e-mail
School of Biological and Biomedical Sciences, University of Durham, Science Lab-
oratories, South Road, Durham, DH1 3LE, UK;
ViaLactia Biosciences, PO Box 109-185, Auckland, New
Received 23 August 2002; accepted in revised form 22 November 2002
Key words: Arabidopsis, DNA helicase, DNA repair, MMS, RecQ
The Arabidopsis genome contains seven genes that belong to the RecQ family of ATP- dependent DNA helicases.
RecQ members in Saccharomyces cerevisiae (SGS1)andman(WRN, BLM and RecQL4) are involved in DNA
recombination, repair and genome stability maintenance, but little is known about the function of their plant
counterparts. The Arabidopsis thaliana RecQsim gene is remarkably different from the other RecQ-like genes due
to an insertion in its helicase domain. We isolated the AtRecQsim orthologues from rice and rape and established
the presence of a similar insertion in their helicase domain, which suggests a plant speciﬁc function for the insert.
The expression pattern of the AtRecQsim gene was compared with the other Arabidopsis RecQ-like members in
different tissues and in response to stress. The transcripts of the AtRecQsim gene were found in all plant organs
and its accumulation was higher in roots and seedlings, as compared to the other AtRecQ-like members. In contrast
to most AtRecQ-like genes, the examined environmental cues did not have a detectable effect on the accumulation
of the AtRecQsim transcripts. The budding yeast sgs1 mutant, which is known to be hypersensitive to the DNA-
damaging drug MMS, was transformed with the AtRecQsim cDNA. The AtRecQsim gene suppressed the MMS
hypersensitivity phenotype of the sgs1 cells. We propose that the Arabidopsis RecQsim gene, despite its unusual
structure, exhibits an evolutionary conserved function.
Abbreviations: aa, amino acids; ABA, abscisic acid; HU, hydroxyurea; MMS, methyl methanesulfonate
The genetic content of living cells persistently suffers
from damage caused by external and internal factors
and is maintained by various DNA repair mechanisms.
These repair pathways, commonly, require the in-
volvement of DNA helicases. Most DNA helicases
share a highly conserved helicase domain with seven
signature motifs (Gorbalenya et al., 1989; Ellis et al.,
1995) and utilize the energy derived from hydrolysis
of ATP to perform essential roles in DNA repair, tran-
scription and replication (reviewed in Matson et al.,
1994; Villani and Tanguy, 2000). According to the
amino acid sequences of these motifs, the super family
of DNA helicases can be divided into several sub fam-
ilies, one of which is the RecQ family of ATP depen-
dent DNA helicases (DEXH box DNA helicases). The
RecQ protein was originally described in Escherichia
coli, as a component of the RecF recombination path-
way (Nakayama et al., 1985). Thereafter, proteins
with high homology to the E. coli RecQ protein have
been grouped and, until now, more than 60 members
of this sub family have been reported from different
organisms, including bacteria (E. coli), fungi (Sac-