Mutagenic DNA repair in Escherichia coli. XIII. Proofreading exonuclease of DNA polymerase III holoenzyme is not operational during UV mutagenesis.
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.
D001120:Arginine / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism*; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D005092:Exonucleases / Q000378:metabolism*; D005798:Genes, Bacterial; D006639:Histidine / Q000378:metabolism; D009154:Mutation; D014466:Ultraviolet Rays
D006639:Histidine; D001120:Arginine; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases