THE SACCHAROMYCES-CEREVISIAE YEAST-STRAIN FOR TESTING ENVIRONMENTAL MUTAGENS BASED ON THE INTERACTION BETWEEN RAD2 AND HIM1 MUTATIONS

The interaction between mutations at the RAD2 and HIM1 genes was studi ed. The RAD2 gene encodes endonuclease involved in nucleotide excision repair. Mutants at this gene are highly sensitive to the lethal effec t of a variety of mutagens. The product of the HIM1 gene is needed for correction of mismatched bases and repair of premutational DNA damage . Mutations in this gene lead to the formation of the mutator phenotyp e and high sensitivity to induced mutagenesis. The double rad2 him1 mu tant manifested the synergic type of interaction. The level of W-induc ed mutagenesis in the double mutant was five times higher than in sing le mutants, and the absolute yield of forward mutations in five genes controlling adenine biosynthesis was 1 to 2%. UV-induced mutagenesis w as increased, at low doses, by several orders of magnitude in the doub le mutant, compared to the wild-type strain. The high level of mutagen esis in this mutant was caused by ethyl and methyl methanesulfonate. T hese properties of the stock with the double rad2 him1 mutation makes it promising as a tester in analysis of the gene toxicity of different substances.