Moore P D
Mutat Res. 1975 Jun;28(3):367-80. doi: 10.1016/0027-5107(75)90231-6.
Two mutants at the pyr I locus have been used to study the radiation sensitivity of pyrimidine auxotrophs of U. maydis. The mutant pry I-I has a reduced level of thymidine nucleotides, and this is a likely basis of the sensitivity. This strain is able to excise pyrimidine dimers from its DNA and is cross-sensitive to gamma-rays and nitrosoguanidine (NG) as well as to UV. A diploid heteroallelic at the pyr I locus was UV-sensitive but not deficient in UV-induced mitotic recombination. The results suggest that the UV sensitivity may be due to the failure of a repair DNA polymerase to fill post-excision single-strand gaps in the DNA. The mutant pyr I-I exhibits the property of UV recovery, and this is shown to be dependent on the presence of dimers in the DNA. A mechanism for UV recovery is proposed in which a repair system, possibly involving recombination, is induced by the UV irradiation.
已使用玉米黑粉菌嘧啶营养缺陷型pyr I位点的两个突变体来研究其辐射敏感性。突变体pry I-I的胸腺嘧啶核苷酸水平降低，这可能是其敏感性的基础。该菌株能够从其DNA中切除嘧啶二聚体，并且对γ射线、亚硝基胍（NG）以及紫外线具有交叉敏感性。在pyr I位点的二倍体杂合等位基因对紫外线敏感，但在紫外线诱导的有丝分裂重组方面并不缺陷。结果表明，紫外线敏感性可能是由于修复DNA聚合酶未能填补DNA切除后单链缺口所致。突变体pyr I-I表现出紫外线恢复特性，且这被证明依赖于DNA中二聚体的存在。提出了一种紫外线恢复机制，其中紫外线照射诱导了一个可能涉及重组的修复系统。
