UV-induced mutability in repair-deficient rad6-1 strains of Saccharomyces cerevisiae is caused by a suppressor gene.

The RAD6 gene is a multifunctional gene required for DNA repair, induced mutagenesis and sporulation. The survival and revertibility of two loci in four rad6-1 mutant strains of different origin after UV irradiation were followed. As expected, all the rad6-1 strains tested were more sensitive to UV radiation in comparison with RAD6 strains. The reversion frequency per survivor in trp1-289 and arg4-17 alleles was significantly higher in all four rad6-1 mutant strains than in wild-type strains after equal doses of UV radiation. On the basis of genetic analysis we suggest that the phenomenon of increased frequency of induced mutagenesis is caused by a suppressor gene.