Sekiguchi M, Shimizu K, Sato K, Yasuda S, Oshima S
Basic Life Sci. 1975;5A:135-42. doi: 10.1007/978-1-4684-2895-7_17.
Excision of pyrimidine dimers from ultraviolet-irradiated DNA in a cell-free system of Escherichia coli infected with bacteriophage T4 consists of two different steps, one to induce a single-strand break at a point close to a pyrimidine dimer and the other to release dimer-containing nucleotide from the DNA. The enzymes responsible for these steps were isolated and the reactions were characterized; T4 endonuclease V introduces a break at the 5' side of a dimer and 5' in equilibrium 3' exonucleases, which are also induced by T4, act at the break to excise dimer-containing nucleotides. We isolated temperature-dependent v mutants, which exhibit increased sensitivity to UV at 42 degrees C but not at 30 degrees C, and found that the mutants induce temperature-sensitive T4 endonuclease V, indicating that the v gene of T4 is indeed the structural gene for T4 endonuclease V and that the enzyme is responsible for the first step of excision-repair. A possible mechanism of excision-repair in T4-infected cells is discussed.
在感染了噬菌体T4的大肠杆菌无细胞体系中，从紫外线照射的DNA上切除嘧啶二聚体包括两个不同步骤，一个是在靠近嘧啶二聚体的位点诱导单链断裂，另一个是从DNA上释放含二聚体的核苷酸。负责这些步骤的酶被分离出来，并且对反应进行了表征；T4内切核酸酶V在二聚体的5'侧引入断裂，而同样由T4诱导的5'→3'平衡外切核酸酶在断裂处起作用，切除含二聚体的核苷酸。我们分离出温度依赖性v突变体，它们在42℃时对紫外线的敏感性增加，但在30℃时不增加，并且发现这些突变体诱导温度敏感型T4内切核酸酶V，这表明T4的v基因确实是T4内切核酸酶V的结构基因，并且该酶负责切除修复的第一步。讨论了T4感染细胞中切除修复的一种可能机制。
