POL32, a subunit of the Saccharomyces cerevisiae DNA polymerase δ, defines a link between DNA replication and the mutagenic bypass repair pathway

Po132 is a subunit of Saccharomyces cerevisine DNA polymerase delta required in DNA replication and repair. To gain insight into the function of Po132 and to determine in which repair pathway POL32 may be involved, we extended the analysis of the pol32 Delta mutant with respect to UV and methylation sensitivity, UV-induced mutagenesis: and we performed an epistasis analysis of UV sensitivity by combining the pol32 Delta with mutations in several genes for postreplication repair (RAD6 group), nucleotide excision repair (RAD3 group) and recombinational repair (RAD52 group). These studies showed that pol32 Delta is deficient in UV-induced mutagenesis and place POL32 in the error-prone RAD61 REV3 pathway. We also found that the increase in the CAN1 spontaneous forward mutation of different rad mutators relies entirely or partially on a functional POL32 gene. Moreover, in a two-hybrid screen, we observed that Po132 interacts with Srs2 a DNA helicase required for DNA replication and mutagenesis. Simultaneous deletion of POL32 and SRS2 dramatically decreases cellular viability at 15 degreesC and greatly increases cellular sensitivity to hydroxyurea at the permissive temperature. Based on these findings, we propose that POL32 defines a link between the DNA polymerase and helicase activities. and plays a role in the mutagenic bypass repair pathway.