Mutagenic DNA repair in Escherichia coli. XIII. Proofreading exonuclease of DNA polymerase III holoenzyme is not operational during UV mutagenesis

Mutat Res. 1987 Jan;183(1):31-7. doi: 10.1016/0167-8817(87)90042-3.


We have introduced a mutD5 mutation (which results in defective 3'-5'-exonuclease activity of the epsilon proofreading subunit of DNA polymerase III holoenzyme) into excision-defective Escherichia coli strains with varying SOS responses to UV light. MutD5 increased the spontaneous mutation frequency in all strains tested, including recA430, umuC122::Tn5, and umuC36 derivatives. It had no effect on UV mutability or immutability in any strain or on misincorporation revealed by delayed photoreversal in UV-irradiated umuC36, umuC122::Tn5, or recA430 bacteria. It is concluded that the epsilon proofreading subunit of DNA polymerase III holoenzyme is excluded, inhibited, or inoperative during misincorporation and mutagenesis after UV.

MeSH terms

  • Arginine / metabolism
  • DNA Polymerase III / metabolism*
  • DNA Repair*
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics*
  • Escherichia coli / radiation effects
  • Exonucleases / metabolism*
  • Genes, Bacterial
  • Histidine / metabolism
  • Mutation*
  • Ultraviolet Rays*


  • Histidine
  • Arginine
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase
  • Exonucleases