Isolation and characterization of additional genes influencing resistance to various mutagens in the yeast Saccharomyces cerevisiae.

Screening of a multi-copy vector-based yeast genomic library in haploid cells of wild-type Saccharomyces cerevisiae yielded transformants hyper-resistant to various chemical mutagens. Genetical analysis of the yeast insert DNAs revealed three genes SNG1, SNQ2, and SNQ3 that confer the phenotype hyper-resistance to MNNG, to 4-NQO and triaziquone, and to mutagens 4-NQO, MNNG, and triaziquone, respectively. Integration of the gene disruption-constructs into the haploid yeast genome yielded viable null-mutants with a mutagen-sensitive phenotype. Thus, copy number of these non-essential yeast genes determines the relative resistance to certain chemical mutagens, with zero copies yielding a phenotype of mutagen sensitivity and multiple copies one of mutagen hyper-resistance, respectively.