The 3'-->5' exonucleases of both DNA polymerases delta and epsilon participate in correcting errors of DNA replication in Saccharomyces cerevisiae

Mol Gen Genet. 1994 Feb;242(3):289-96. doi: 10.1007/BF00280418.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • DNA Polymerase II
  • DNA Polymerase III
  • DNA Repair*
  • DNA Replication*
  • DNA, Fungal
  • DNA-Directed DNA Polymerase / metabolism*
  • Haploidy
  • Humans
  • Molecular Sequence Data
  • Mutation
  • Saccharomyces cerevisiae / genetics*

Substances

  • DNA, Fungal
  • DNA Polymerase II
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase