Overproduction of the epsilon subunit of DNA polymerase III counteracts the SOS mutagenic response of Escherichia coli

Proc Natl Acad Sci U S A. 1988 Dec;85(23):9124-7. doi: 10.1073/pnas.85.23.9124.


It has been found that the mutator phenotype of the recA441 and recA730 strains that express the SOS response constitutively is suppressed by pIP1, a high-copy plasmid carrying the dnaQ gene encoding the 3'----5' exonuclease subunit (epsilon) of DNA polymerase III. We have constructed plasmid pIP11, in which the dnaQ gene is fused to the strong tac (trp-lac) promoter. Enhanced synthesis of the epsilon subunit stimulated by isopropyl beta-D-thiogalactopyranoside, the inducer of tac, prevents expression of the mutator phenotype of recA441 and markedly decreases the frequency of UV-induced mutations. These results strongly suggest that a loss of editing capacity by the epsilon subunit of DNA polymerase III holoenzyme plays a crucial role in generation of mutations during the SOS response.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA Polymerase III / biosynthesis
  • DNA Polymerase III / genetics*
  • DNA Repair*
  • DNA-Directed DNA Polymerase / genetics*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Escherichia coli / radiation effects
  • Genotype
  • Macromolecular Substances
  • Mutation*
  • Plasmids
  • SOS Response, Genetics*
  • Ultraviolet Rays


  • Macromolecular Substances
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase