RADIOSENSITIVITY OF THE YEAST SACCHAROMYCES AND SRM GENES - EFFECTS OF SRM1 AND SRM5 MUTATIONS

The presence in the cell genotype of srm1 and srm5 (cdc28-srm) mutatio ns decreasing the spontaneous rho(-) mutability was shown to have no e ffect on the rates of spontaneous nuclear gene mutations and gamma-ray -induced mitotic recombination. Mutation cdc28-srm exerts a marked eff ect on cell sensitivity to the lethal action of ionizing radiation and on the appearance of homoplasmic segregants generated from heteroplas mic diploids. Additive interactions between mutations cdc28-srm and ea ch of the rad6 and rad52 mutations were revealed by an analysis of dou ble mutants with respect to their sensitivity to radiation. Mutation, rad9 was epistatic with mutation cdc28-srm. These data agree with the idea that the p34(CDC28) gene product is a target for the RAD9-depende nt feedback control operating at the cell cycle checkpoints (checkpoin t control) and ensuring an additional amount of time for premitotic re pair of chromosomal DNA damage.