title: Repair capability and the cellular age response for killing and mutation induction after UV.
abstract: The cell-cycle response for killing and mutation induction by ultraviolet irradiation was measured in synchronous Chinese hamster ovary cells (CHO wild-type) and in a UV-hypersensitive mutant (43-3B) derived from this line. The CHO 43-3B line shows a greatly enhanced sensitivity to killing (D0 of 0.3 as compared to 3.2 J/m2 for the wild-type), is hypermutable, and deficient in DNA repair. For the wild-type, a characteristic age response is seen for killing by UV, with maximum sensitivity in early-S and resistance increasing through the S-phase. There is also a life-cycle specificity for induction of diphtheria-toxin resistance in late-G1 and early-S. Relatively little variation is seen through the cell cycle for induced 6-thioguanine and ouabain resistance. In contrast, the 43-3B cell line shows a relatively 'flat' response to UV throughout the cell cycle, for both killing and mutation induction. Therefore it appears that the characteristic age responses seen in the wild-type CHO are associated with the function of an essentially error-free repair process. A variation in the ability of this repair process to act in eliminating potentially lethal and mutagenic lesions (either due to a variation in repair enzyme activities through the cell cycle, or in the time available for repair) would account for most of the age response which is seen in the wild-type for killing and mutation induction by ultraviolet light.
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000528:radiation effects*; D004260:DNA Repair; D005260:Female; D009154:Mutation; D010053:Ovary; D014466:Ultraviolet Rays
chemical_list: D004247:DNA