1022-7954/01/3709- $25.00 © 2001
Russian Journal of Genetics, Vol. 37, No. 9, 2001, pp. 1014–1024. Translated from Genetika, Vol. 37, No. 9, 2001, pp. 1213–1224.
Original Russian Text Copyright © 2001 by Koltovaya, Mayorova, Rzyanina, Guerasimova, Devin.
Haploid cells of
to maintain, in addition to the components of the hered-
itary apparatus essential to viability (chromosomes),
the facultative genetic structures (FGSs): natural extra
chromosomes, the mitochondrial genome, and recom-
binant plasmids. The ﬁdelity of the mitotic transmis-
sion (mitotic stability) of chromosomes of an euploid
sells is high (the frequency of spontaneous loss of a
chromosome is usually 10
and lower). FGSs exhibit
much lower mitotic stability than chromosomes indis-
pensable for viability. Between different FGSs, signiﬁcant
variations of their mitotic stability were also found.
In recent years, we obtained data suggesting that the
mechanisms responsible for the mitotic stability of dif-
ferent FGSs overlap or are under coordinated regula-
tion. In particular, a mutation in the
gene, which is known to play a key role in the cell cycle
a regulation, was found to change the mitotic stability
of both nuclear and mitochondrial FGSs [1, 2]. More-
over, we detected that the same
mutation is accompanied by an increase in yeast cell
sensitivity to the lethal effect of ionizing radiation .
Thus, FGS maintenance, cell cycle control, and the
cells were found to be
interconnected at the genetical level.
We used a genetic approach to the study of this rela-
tionship. UV mutagenesis and selection of mutants
with changed mitotic stability of both the mitochon-
drial genome and a natural extra chromosome were
employed for selecting, in addition to
mutants for other nuclear genes (designated as
. In this work, the effects of novel
the maintenance of genetic structures and on yeast cell
sensitivity to ionizing radiation were studied.
MATERIALS AND METHODS
Strains of microorganisms.
The yeast strains used in
this study are listed in Table 1. The DH5 strain of
served as a host for plasmid DNA
manipulation, the strain XL-1Blue (Stratagene)  was
a recipient of a phagemid.
Plasmids and a library of yeast genomic DNA.
DNA library designated as 2J351  was
created after partial hydrolysis of genomic DNA by
3A followed by fragment liga-
tion at the
HI site of plasmid YEp351  carrying
marker and the 2
Work we also used standard plasmids YCp50 ,
YEp13 , and YRp12 . Sequence analysis of the
DNA fragment was conducted with the use of pTZ19U
phagemid  and the helper phage M13KO7.
Media and reagents.
We used the standard complete
nutrient medium YEPD  and media CM, MM, and
LCD described in , restriction endonucleases and
other enzymes (Fermentas, Vilnius), ethidium bromide
(Sigma), and cycloheximide (Serva).
Transformation of yeast cells with plasmid DNA
was conducted by a routine technique .
An approximately 3 kb
fragment was cloned in the pTZ19U phagemid trans-
formed into a double-stranded form with the use of the
helper phage M13KO7. The XL1-Blue strain was used
as a recipient. Single-stranded DNA was isolated
according to a conventional procedure . Plasmid
New Mutations of
and Certain Characteristics of Their Phenotypic Effects
N. A. Koltovaya
, E. S. Mayorova
, A. V. Rzyanina
, A. S. Guerasimova
, and A. B. Devin
Joint Institute for Nuclear Research, Moscow oblast, Dubna, 141980 Russia
fax: 007 09621 65948; e-mail: firstname.lastname@example.org
Max Planck Institute of Molecular Genetics, Berlin (Dahlem), Germany
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, 123182 Russia
Received September 22, 2000; in ﬁnal form, February 28, 2001
—The effects of the previously identiﬁed mutations in nuclear genes
SRM8, SRM12, SRM15
on the maintenance of chromosomes and recombinant plasmids in
on cell sensitivity to ionizing radiation were studied. The
mutation caused an increase in spontaneous
chromosome loss in diploid cells. In yeast cells with the intact mitochondrial genome, all examined
tions decreased the mitotic stability of a centromeric recombinant plasmid with the chromosomal ARS element.
also decreased the mitotic stability of a centromereless plasmid containing
the same ARS element, whereas the
mutation did not markedly affect the maintenance of this plasmid.
were shown to increase cell sensitivity to
mapped, cloned, and found to correspond to the open reading frame YJLO76w in chromosome X.