title: Repair of pyrimidine dimer damage induced in yeast by ultraviolet light.
abstract: Crude extracts from ultraviolet (UV)-irradiated yeast cells compete with UV-irradiated transforming deoxyribonucleic acid (DNA) for photoreactivating enzyme. The amount of competition is taken as a measure of the level of cyclobutyl pyrimidine dimers in the yeast DNA. A calibration of the competition using UV-irradiated calf thymus DNA indicates that an incident UV dose (1,500 ergs/mm(2)) yielding 1% survivors of wild-type cells produces between 2.5 x 10(4) to 5 x 10(4) dimers per cell. Wild-type cells irradiated in the exponential phase of growth remove or alter more than 90% of the dimers within 220 min after irradiation. Pyrimidine dimers induced in stationary-phase wild-type cells appear to remain in the DNA; however, with incubation, they become less photoreactivable in vivo, although remaining photoreactivable in vitro. In contrast, exponentially growing or stationary-phase UV-sensitive cells (rad2-17) show almost no detectable alteration of dimers. We conclude that the UV-sensitive cells lack an early step in the repair of UV-induced pyrimidine dimers.
mesh_terms: D000818:Animals; D002417:Cattle; D002470:Cell Survival; D002850:Chromatography, Gel; D004247:DNA / Q000032:analysis* / Q000528:radiation effects; D004260:DNA Repair; D004269:DNA, Bacterial / Q000528:radiation effects; D004798:Enzymes / Q000378:metabolism; D006193:Haemophilus influenzae / Q000032:analysis; D008027:Light; D008970:Molecular Weight; D010936:Plant Extracts; D011743:Pyrimidines / Q000032:analysis*; D011830:Radiation Effects; D012440:Saccharomyces / Q000528:radiation effects*; D012441:Saccharomyces cerevisiae / Q000032:analysis / Q000201:enzymology / Q000528:radiation effects; D013950:Thymus Gland; D014170:Transformation, Genetic; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D004798:Enzymes; D010936:Plant Extracts; D011743:Pyrimidines; D004247:DNA