RESUMO
The effects of the previously identified mutations in nuclear genes SRM8, SRM12, SRM15, and SRM17 on the maintenance of chromosomes and recombinant plasmids in Saccharomyces cerevisiae cells and on cell sensitivity to ionizing radiation were studied. The srm8 mutation caused instability of chromosome maintenance in diploid cells. In yeast cells with the intact mitochondrial genome, all examined srm mutations decreased the mitotic stability of a centromeric recombinant plasmid with the chromosomal ARS element. Mutations srm12, srm15, and srm17 also decreased the mitotic stability of a centromereless plasmid containing the same ARS element, whereas the srm8 mutation did not markedly affect the maintenance of this plasmid. Mutations srm8, srm12, and srm17 were shown to increase cell sensitivity to gamma-ray irradiation. The SRM8 gene was mapped, cloned, and found to correspond to the open reading frame YJLO76w in chromosome X.
Assuntos
Genes Fúngicos , Mutação , Saccharomyces cerevisiae/genética , Etídio/farmacologia , Raios gama , Fenótipo , Tolerância a Radiação/genética , Saccharomyces cerevisiae/efeitos da radiaçãoRESUMO
The presence in the cell genotype of srm1 and srm5 (cdc28-srm) mutations decreasing the spontaneous rho- mutability was shown to have no effect on the rates of spontaneous nuclear gene mutations and gamma-ray-induced mitotic recombination. Mutation cdc28-srm exerts a marked effect on cell sensitivity to the lethal action of ionizing radiation and on the appearance of homoplasmic segregants generated from heteroplasmic diploids. Additive interactions between mutations cdc28-srm and each of the rad6 and rad52 mutations were revealed by an analysis of double mutants with respect to their sensitivity to radiation. Mutation rad9 was epistatic with mutation cdc28-srm. These data agree with the idea that the p34CDC28 gene product is a target for the RAD9-dependent feedback control operating at the cell cycle checkpoints (checkpoint control) and ensuring an additional amount of time for premitotic repair of chromosomal DNA damage.
Assuntos
Proteínas de Ligação a DNA/genética , Proteínas Fúngicas/genética , Mutação , Proteínas Nucleares/genética , Tolerância a Radiação/genética , Proteínas de Saccharomyces cerevisiae , Saccharomyces/efeitos da radiação , Alelos , Proteína Quinase CDC28 de Saccharomyces cerevisiae/genética , Fatores de Troca do Nucleotídeo Guanina , Ligases/genética , Mitose , Proteína Rad52 de Recombinação e Reparo de DNA , Recombinação Genética , Saccharomyces/genética , Enzimas de Conjugação de UbiquitinaRESUMO
The appearance dynamics of spontaneous revertants in adenine- or leucine-auxotrophic haploid Saccharomyces cerevisiae strains has been studied using mathematical simulation methods. In the case of adenine auxotrophs an increase in the number of revertants with decreasing metabolite content is found to result mainly from increasing the rate of intragenic suppressor mutations. In the case of leucine auxotrophs revertants result from increasing the appearance of mutants formed at similar rates under different cultivation conditions. In the latter case the appearance of mutant colonies increases with decreasing size of colonies of the initial auxotrophic cells. The last can simulate so-called adaptive mutagenesis. The heterogeneity of revertants appearing in different time periods is described.
