title: Influence of mutations at the rep gene on survival of Escherichia coli following ultraviolet light irradiation or 8-methoxypsoralen photosensitization: evidence for a recA+ rep+-dependent pathway for repair of DNA crosslinks.
abstract: Bacteria mutant at the rep gene (specifying a DNA-unwinding enzyme) were slightly more sensitive than rep+ bacteria to far ultraviolet light (ca. 254 nm; (FUV) and to monofunctional psoralen photoproducts produced with near ultraviolet light (ca. 360 nm; NUV). The enhanced sensitivity was shown in uvrA excision-deficient bacteria but not in those carrying the recA mutation. It is concluded that the rep unwinding enzyme has a small promoting effect on post-replication recombination repair. Rep- bacteria were rather more sensitive to the DNA cross-linking action f 8-methoxypsoralen (8-MOP) and NUV. This effect also was found in uvrA but not in recA bacteria. A cross-link repair pathway, dependent on both the recA+ and rep+ genes, therefore exists in addition to the pathway which depends upon the uvrAB endonuclease. Various lines of evidence suggest that the pathway operates at or after DNA replication. Exposure of rep+ bacteria to 8-MOP plus NUV did not induce any activity capable of repairing psoralen cross-links in infecting lambda phage. A possible model involving removal of the cross-link by glycosylase action at the replication fork is proposed.
mesh_terms: D004265:DNA Helicases / Q000235:genetics*; D004260:DNA Repair; D004269:DNA, Bacterial / Q000528:radiation effects*; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects; D009154:Mutation; D011701:PUVA Therapy; D010641:Phenotype; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D004265:DNA Helicases