title: Role of DNA polymerase I in postreplication repair: a reexamination with Escherichia coli delta polA.
abstract: Using strains of Escherichia coli K-12 that are deleted for the polA gene, we have reexamined the role of DNA polymerase I (encoded by polA) in postreplication repair after UV irradiation. The polA deletion (in contrast to the polA1 mutation) made uvrA cells very sensitive to UV radiation; the UV radiation sensitivity of a uvrA delta polA strain was about the same as that of a uvrA recF strain, a strain known to be grossly deficient in postreplication repair. The delta polA mutation interacted synergistically with a recF mutation in UV radiation sensitization, suggesting that the polA gene functions in pathways of postreplication repair that are largely independent of the recF gene. When compared to a uvrA strain, a uvrA delta polA strain was deficient in the repair of DNA daughter strand gaps, but not as deficient as a uvrA recF strain. Introduction of the delta polA mutation into uvrA recF cells made them deficient in the repair of DNA double-strand breaks after UV irradiation. The UV radiation sensitivity of a uvrA polA546(Ts) strain (defective in the 5'----3' exonuclease of DNA polymerase I) determined at the restrictive temperature was very close to that of a uvrA delta polA strain. These results suggest a major role for the 5'----3' exonuclease activity of DNA polymerase I in postreplication repair, in the repair of both DNA daughter strand gaps and double-strand breaks.
authors.affiliation: Department of Therapeutic Radiology, Stanford University School of Medicine, California 94305.
authors.forename: R C
authors.initials: RC
authors.lastname: Sharma
authors.forename: K C
authors.initials: KC
authors.lastname: Smith
mesh_terms: D002701:Chloramphenicol / Q000494:pharmacology; D004256:DNA Polymerase I / Q000378:metabolism*; D004260:DNA Repair; D004261:DNA Replication; D004269:DNA, Bacterial / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics* / Q000528:radiation effects; D005798:Genes, Bacterial; D009154:Mutation; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D002701:Chloramphenicol; D004256:DNA Polymerase I