A ROLE FOR REV3 IN MUTAGENESIS DURING DOUBLE-STRAND BREAK REPAIR IN SACCHAROMYCES-CEREVISIAE

Recombinational repair of double-strand breaks (DSBs), traditionally b elieved to be an error-free DNA repair pathway, was recently shown to increase the frequency of mutations in a nearby interval. The reversio n rate of trp1 alleles (either nonsense or frameshift mutations) near an HO-endonuclease cleavage site is increased at least 100-fold among cells that have experienced an HO-mediated DSB. We report here that in strains deleted for rev3 this DSB-associated reversion of a nonsense mutation was greatly decreased. Thus REV3, which encodes a subunit of the translesion DNA polymerase zeta, was responsible for the majority of these base substitution errors near a DSB. However, rev3 strains sh owed no decrease in HO-stimulated recombination, implying that another DNA polymerase also functioned in recombinational repair of a DSB. Re version of trp1 frameshift alleles near a DSB was not reduced in rev3 strains, indicating that another polymerase could act during DSB repai r to make these frameshift errors. Analysis of spontaneous reversion i n haploid strains suggested that Rev3p had a greater role in making po int mutations than in frameshift mutations.