title: A new pathway for repair of cross-linkable 8-methoxypsoralen mono-adducts in Uvr strains of Escherichia coli.
abstract: UvrA-deficient Escherichia coli bacteria possess a DNA repair pathway for certain photoinduced mono-adducts of 8-methoxypsoralen. Such adducts can be converted to highly lethal cross-links by a second exposure to near-UV light in the absence of 8-methoxypsoralen. If a period of incubation is allowed to intervene between the primary and cross-linking exposure, the lethal effect is considerably diminished, indicating that some of the mono-adducts become unavailable for cross-linking. A repair pathway is postulated which is pre-replicative, unaffected by chloramphenicol, acriflavine or caffeine, and inhibited at 0 degrees C. It is unaffected by a rep mutation but is blocked by a polA mutation, suggesting that it involves DNA strand breakage and at least some exonuclease action.
mesh_terms: D004260:DNA Repair; D004269:DNA, Bacterial / Q000528:radiation effects; D004926:Escherichia coli / Q000235:genetics*; D008730:Methoxsalen / Q000494:pharmacology*; D009153:Mutagens; D010641:Phenotype; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D009153:Mutagens; D008730:Methoxsalen