title: Characterization of long patch excision repair of DNA in ultraviolet-irradiated Escherichia coli: an inducible function under rec-lex control.
abstract: Excision repair in ultraviolet-irradiated wild-type Escherichia coli produces a bimodal distribution of repair patch sizes in the DNA. Approximately 99% of the repair events result in short patches of 20-30 nucleotides produced by a constitutive repair system. The remaining 1% result in patches which are at least 1,500 nucleotides in length. This long patch repair is shown to be a damage-inducible process under control of the rec-lex regulatory circuit. The kinetics of the two processes differ; short patch synthesis begins immediately after irradiation and is virtually completed prior to synthesis of the majority of the long patches. Long patch repair synthesis is a linear function of UV dose up to a plateau at 60 J/m2, and hence each long patch event is the consequence of a single UV-induced lesion. Long patch repair does not appear to be necessarily error-prone, since no alteration in repair synthesis occurs as a result of a mutation umuC- which renders cells nonmutable by UV. Evidence is presented suggesting that DNA polymerase I is responsible for both long and short patch synthesis in wild type cells under inducing conditions. In the absence of polymerase I the constitutive patch size averages 80-90 nucleotides, and this distribution is unchanged by induction.
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology; D002701:Chloramphenicol / Q000494:pharmacology; D004256:DNA Polymerase I / Q000378:metabolism; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics / Q000528:radiation effects*; D004926:Escherichia coli; D005798:Genes, Bacterial; D008970:Molecular Weight; D011938:Rec A Recombinases; D012697:Serine Endopeptidases; D014466:Ultraviolet Rays; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D002701:Chloramphenicol; D004256:DNA Polymerase I; D004269:DNA, Bacterial; D011938:Rec A Recombinases; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein