title: The 3'-->5' exonucleases of both DNA polymerases delta and epsilon participate in correcting errors of DNA replication in Saccharomyces cerevisiae.
abstract: DNA polymerases II (epsilon) and III (delta) are the only nuclear DNA polymerases known to possess an intrinsic 3'-->5' exonuclease in Saccharomyces cerevisiae. We have investigated the spontaneous mutator phenotypes of DNA polymerase delta and epsilon 3'-->5' exonuclease-deficient mutants, pol3-01 and pol2-4, respectively. pol3-01 and pol2-4 increased spontaneous mutation rates by factors of the order of 10(2) and 10(1), respectively, measured as URA3 forward mutation and his7-2 reversion. Surprisingly, a double mutant pol2-4 pol3-01 haploid was inviable. This was probably due to accumulation of unedited errors, since a pol2-4/pol2-4 pol3-01/pol3-01 diploid was viable, with the spontaneous his7-2 reversion rate increased by about 2 x 10(3)-fold. Analysis of mutation rates of double mutants indicated that the 3'-->5' exonucleases of DNA polymerases delta and epsilon can act competitively and that, like the 3'-->5' exonuclease of DNA polymerase delta, the 3'-->5' exonuclease of DNA polymerase epsilon acts in series with the PMS1 mismatch correction system. Mutational spectra at a URA3 gene placed in both orientations near to a defined replication origin provided evidence that the 3'-->5' exonucleases of DNA polymerases delta and epsilon act on opposite DNA strands, but were in sufficient to distinguish conclusively between different models of DNA replication.
authors.affiliation: Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
authors.forename: A
authors.initials: A
authors.lastname: Morrison
authors.forename: A
authors.initials: A
authors.lastname: Sugino
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004257:DNA Polymerase II; D004258:DNA Polymerase III; D004260:DNA Repair; D004261:DNA Replication; D004271:DNA, Fungal; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D006238:Haploidy; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics*
chemical_list: D004271:DNA, Fungal; D004257:DNA Polymerase II; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase