Khanbekian L M, Savel'eva G E, Korol'ko O F, Zhestianikov V D
Tsitologiia. 1980 Apr;22(4):454-61.
The survival of cells and yield of DNA single-strand breaks after the completion of DNA repair in growth medium M9 and in the buffer at 30 degrees and 43 degrees C has been investigated in four strains of alpha-irradiated Escherichia coli: PC3 dnaGts, NY73 dnaGts polA1, W3110 pol+, P3478 polA1. The survival of the dnaGts mutant at 43 degrees in M9 and the buffer is lower and the yield of single-strand breaks is higher than at 30 degrees. In the polA1 mutant, the yield of single-strand breaks in M9 and in the buffer at both the temperatures is significantly higher, and the survival is significantly lower than in pol+- and dnaGts strains. These data indicate that dnaG gene product (primase, rifampicin-resistant RNA polymerase) and DNA polymerase I are involved in different pathways of DNA single-strand break repair. DNA polymerase I is the key enzyme for the fast, growth medium-independent repair of DNA single-strand breaks. Thus, the dnaG gene product is involved in the slow, growth medium-dependent polA-independent DNA single-strand break repair. The yield of breaks in double mutant polA1 dnaGts in M9 and in the buffer does not differ from that in single mutant polA1. Thus, DNA polymerase I in fast repair of DNA single strand breaks is not changed by the dnaG gene product. It has been demonstrated that the dnaG gene product does not participate in the UV-induced mutagenesis.
在生长培养基M9和缓冲液中，于30℃和43℃完成DNA修复后，对四株α射线辐照的大肠杆菌（PC3 dnaGts、NY73 dnaGts polA1、W3110 pol +、P3478 polA1）的细胞存活率和DNA单链断裂产量进行了研究。dnaGts突变体在43℃的M9和缓冲液中的存活率较低，单链断裂产量高于30℃时。在polA1突变体中，M9和缓冲液在两个温度下的单链断裂产量均显著更高，存活率显著低于pol +和dnaGts菌株。这些数据表明，dnaG基因产物（引发酶、利福平抗性RNA聚合酶）和DNA聚合酶I参与了DNA单链断裂修复的不同途径。DNA聚合酶I是DNA单链断裂快速、不依赖生长培养基修复的关键酶。因此，dnaG基因产物参与了缓慢、依赖生长培养基且不依赖polA的DNA单链断裂修复。M9和缓冲液中双突变体polA1 dnaGts的断裂产量与单突变体polA1的断裂产量无差异。因此，DNA聚合酶I在DNA单链断裂的快速修复中不受dnaG基因产物的影响。已证明dnaG基因产物不参与紫外线诱导的诱变。
