title: Induction and repair of closely opposed pyrimidine dimers in Saccharomyces cerevisiae.
abstract: Pyrimidine dimer-DNA glycosylase activity prepared from Micrococcus luteus has been used to develop an enzyme-sensitive site assay for the detection and quantification of closely opposed pyrimidine dimers in the nuclear DNA of UV-irradiated yeast. With this assay, closely opposed dimers were found to be induced as a linear function of dose from 0 to 200 J/m2 (254 nm). Closely opposed dimer frequencies decreased during the incubation of UV-irradiated, excision repair-proficient cells under liquid-holding conditions in the dark and during post-irradiation exposure of excision-deficient cells to photoreactivating light. Incubation of excision-deficient cells in the dark had no effect on the frequency of closely opposed dimers for up to 16 h. These results indicate that closely opposed dimers in UV-irradiated yeast are subject to repair by enzymatic photoreactivation and/or by dark-repair processes dependent, at least in part, upon functions necessary for normal excision repair. The genetic and biochemical implications of these results are discussed.
mesh_terms: D004249:DNA Damage; D045647:DNA Glycosylases; D004260:DNA Repair / Q000528:radiation effects; D004271:DNA, Fungal / Q000235:genetics / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D011740:Pyrimidine Dimers / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D004271:DNA, Fungal; D011740:Pyrimidine Dimers; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C036401:deoxyribopyrimidine endonucleosidase