title: The relative cytotoxicity and mutagenicity of cyclobutane pyrimidine dimers and (6-4) photoproducts in Escherichia coli cells.
abstract: In order to calculate the relative cytotoxicity and mutagenicity of (5-6) cyclobutane pyrimidine dimers and (6-4) photoproducts, we have measured survival and mutation induction in UV-irradiated excision-deficient E. coli uvrA cells, with or without complete photoreactivation of the (5-6) dimers. Radioimmunoassays with specificity for (5-6) dimers or (6-4) photoproducts have shown that maximum photoreactivation eliminates all of the (5-6) dimers produced up to 10 Jm-2 254-nm light, while it has no effect on (6-4) photoproducts. These results were confirmed by measuring the frequency of T4 endonuclease V-sensitive sites. Based on the best fit equations for survival and mutation induction, we have found that the calculated cytotoxicity of (6-4) photoproducts is similar to that of (5-6) dimers; however, the former is much more mutagenic than the latter.
mesh_terms: D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects* / Q000528:radiation effects; D007700:Kinetics; D009152:Mutagenicity Tests / Q000379:methods; D009153:Mutagens / Q000494:pharmacology*; D009154:Mutation; D011740:Pyrimidine Dimers / Q000494:pharmacology*; D014466:Ultraviolet Rays
chemical_list: D009153:Mutagens; D011740:Pyrimidine Dimers