Proofreading-defective DNA polymerase II increases adaptive mutation in Escherichia coli

Proc Natl Acad Sci U S A. 1995 Aug 15;92(17):7951-5. doi: 10.1073/pnas.92.17.7951.


The role of Escherichia coli DNA polymerase (Pol) II in producing or avoiding mutations was investigated by replacing the chromosomal Pol II gene (polB+) by a gene encoding an exonuclease-deficient mutant Pol II (polBex1). The polBex1 allele increased adaptive mutations on an episome in nondividing cells under lactose selection. The presence of a Pol III antimutator allele (dnaE915) reduced adaptive mutations in both polB+ cells and cells deleted for polB (polB delta 1) to below the wild-type level, suggesting that both Pol II and Pol III are synthesizing episomal DNA in nondividing cells but that in wild-type cells Pol III generates the adaptive mutations. The adaptive mutations were mainly -1 frame-shifts occurring in short homopolymeric runs and were similar in wild-type, polB delta 1, and polBex1 strains. Mutations produced by both Pol III and Pol II ex1 were corrected by the mutHLS mismatch repair system.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acclimatization
  • Alleles
  • Base Sequence
  • Chromosomes, Bacterial
  • DNA Polymerase II / metabolism*
  • DNA Polymerase III / metabolism
  • DNA Primers
  • Escherichia coli / enzymology*
  • Escherichia coli / genetics*
  • Exodeoxyribonuclease V
  • Exodeoxyribonucleases / genetics
  • Genes, Bacterial
  • Genotype
  • Kinetics
  • Molecular Sequence Data
  • Mutagenesis
  • Mutation*
  • Polymerase Chain Reaction


  • DNA Primers
  • DNA Polymerase II
  • DNA Polymerase III
  • Exodeoxyribonucleases
  • Exodeoxyribonuclease V