Analysis of the effect of radiation repair mutations on the DEL1 mutator region of Saccharomyces cerevisiae.

In DEL1 strains of the yeast, Saccharomyces cerevisiae, the iso-1-cytochrome c (CYC1) region is flanked on either side by Tyl elements in direct orientation which promote cyc1 deletions of the bracketed DNA in the haploid cell. In this study, we asked which genes might control this event by testing the possibility that the DEL1 mutation mechanism requires an enzyme (or enzymes) that is also utilized in the repair of damaged DNA. To this end, we independently coupled eight repair mutations, rad3-2, rad4-4, rad6-1, rad6-3, rad9-1, rev3-1, rad50-1, and rad51-1, toDEL1 and asked whether DEL1 was still functional. We found that none of these rad mutations significantly affects the mutation frequency of 10(-6)-10(-5) established in DEL1 strains for the CYC1 locus. Furthermore, we determined that ste7, a temperature-sensitive sterile allele known to alter gene regulation in Ty-mediated mutations, is not required for DEL1 function. Finally, DEL1 is not temperature-sensitive at 23° or 37 °C.