Stationary-phase mutations in proofreading exonuclease-deficient strains of the yeast Saccharomyces cerevisiae
- PDF / 91,205 Bytes
- 5 Pages / 595 x 785 pts Page_size
- 90 Downloads / 157 Views
O R I GI N A L P A P E R
N. Babudri á Y. I. Pavlov á N. Matmati C. Ludovisi á A. Achilli
Stationary-phase mutations in proofreading exonuclease-de®cient strains of the yeas t Saccharomyces cerevisiae Received: 16 August 2000 / Accepted: 13 November 2000 / Published online: 21 February 2001 Ó Springer-Verlag 2001
Abstract In order to understand the role of yeast polymerases in spontaneous mutagenesis in non-growing cells we have studied the eects of mutations that impair the 3¢ ® 5¢ exonuclease function of polymerases delta (pol3-01) and epsilon (pol2-4 ) on the spontaneous reversion frequency of the frameshift mutation his7-2 in cells starved for histidine. We showed that for each exonuclease-de®cient mutant the rate of reversion per viable cell per day observed in stationary-phase cells remained constant up to the 9th day of starvation (while the number of viable cells dropped), and was very similar to that observed in the same mutants during the growth phase. These data suggest that both DNA polymerases are involved in the control of mutability in non-growing cells. Key words Saccharomyces cerevisiae á Stationaryphase mutations á pol2-4 á pol3-01 á Exonucleolytic proofreading
Introduction During the last few years the debate on adaptive mutations in micro-organisms has revived interest in mutations that arise during starvation. Adaptive mutations (directed mutations) were originally de®ned as mutations that arise only in the presence of selection for such muCommunicated by R. Devoret N. Babudri (&) á N. Matmati á C. Ludovisi á A. Achilli Department of Cellular and Molecular Biology, University of Perugia, Via Pascoli, 06100 Perugia, Italy E-mail: [email protected] Fax: +39-75-5855719 Y. I. Pavlov1 Department of Genetics, St. Petersburg University, 199034 St. Petersburg, Russia Present address: 1 Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
tations in non-dividing or slowly growing stationaryphase cells. However, in Escherichia coli it was found that non-selected mutations may also arise at an unexpectedly high rate during the stationary phase. Several mechanisms have been discovered which may be contribute to stationary-phase mutagenesis; however, there is as yet no unifying model for the process (Rosenberg 1994; Rosenberg et al. 1998; Foster 1999; Lombardo et al. 1999). In Saccharomyces cerevisiae, Hall (1992) and Steele and Jinks-Robertson (1992) reported the occurrence of mutations during starvation and concluded that these are true adaptive mutations. In contrast, a paper by Marini et al. (1999) showed that starvation increases the mutation frequency for both selected and non-selected markers. Actually, little is known about the genetic control of this phenomenon; as far as we know, only one paper has reported an in¯uence of the cdc2 (pol3) gene on mutagenesis in non-growing yeast cells (Baranowska et al. 1995). DNA polymerases delta (polymerase III) and epsilon (polymerase II), encoded by the cdc2 (pol3) and pol2 genes, respe
Data Loading...
