Resnick M A, Setlow J K
J Bacteriol. 1972 Mar;109(3):979-86. doi: 10.1128/jb.109.3.979-986.1972.
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.
紫外线（UV）照射的酵母细胞粗提物与UV照射的转化脱氧核糖核酸（DNA）竞争光复活酶。竞争量被用作酵母DNA中环丁基嘧啶二聚体水平的衡量指标。使用UV照射的小牛胸腺DNA对竞争进行校准表明，产生1%野生型细胞存活者的入射UV剂量（1500尔格/平方毫米）导致每个细胞产生2.5×10⁴至5×10⁴个二聚体。在生长指数期照射的野生型细胞在照射后220分钟内去除或改变了超过90%的二聚体。在静止期野生型细胞中诱导产生的嘧啶二聚体似乎保留在DNA中；然而，随着孵育，它们在体内的光复活能力降低，尽管在体外仍具有光复活能力。相比之下，指数生长期或静止期的UV敏感细胞（rad2 - 17）几乎没有可检测到的二聚体改变。我们得出结论，UV敏感细胞在修复UV诱导的嘧啶二聚体过程中缺乏早期步骤。
