The absence of the catalytic domains of Saccharomyces cerevisiae DNA polymerase epsilon strongly reduces DNA replication fidelity

摘要

w The four B-family DNA polymerases alpha, delta, epsilon and zeta c-ooperate to accurately replicate the eukaryotic nuclear genome. Here, we report that a Saccharomyces cere-visiae strain encoding the pol2-16 mutation that lacks Pol epsilon's polymerase and exonuclease activities has increased dNTP concentrations and an increased mutation rate at the CAN1 locus compared to wild type yeast. About half of this mutagenesis disappears upon deleting the REV3 gene encoding the catalytic subunit of Pol zeta. The remaining, still strong, mutator phenotype is synergistically elevated in an msh6 Delta strain and has a mutation spectrum characteristic of mistakes made by Pol delta. The results support a model wherein slow-moving replication forks caused by the lack of Pol epsilon's catalytic domains result in greater involvement of mutagenic DNA synthesis by Pol zeta as well as diminished proofreading by Pol delta during replication.