Hagensee M E, Bryan S K, Moses R E
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030.
J Bacteriol. 1987 Oct;169(10):4608-13. doi: 10.1128/jb.169.10.4608-4613.1987.
The pcbA1 mutation allows DNA replication dependent on DNA polymerase I at the restrictive temperature in polC(Ts) strains. Cells which carry pcbA1, a functional DNA polymerase I, and a temperature-sensitive DNA polymerase III gene were used to study the role of DNA polymerase III in DNA repair. At the restrictive temperature for DNA polymerase III, these strains were more sensitive to the alkylating agent methyl methanesulfonate (MMS) and hydrogen peroxide than normal cells. The same strains showed no increase in sensitivity to bleomycin, UV light, or psoralen at the restrictive temperature. The sensitivity of these strains to MMS and hydrogen peroxide was not due to the pcbAl allele, and normal sensitivity was restored by the introduction of a chromosomal or cloned DNA polymerase III gene, verifying that the sensitivity was due to loss of DNA polymerase III alpha-subunit activity. A functional DNA polymerase III is required for the reformation of high-molecular-weight DNA after treatment of cells with MMS or hydrogen peroxide, as demonstrated by alkaline sucrose sedimentation results. Thus, it appears that a functional DNA polymerase III is required for the optimal repair of DNA damage by MMS or hydrogen peroxide.
pcbA1突变使得在polC（温度敏感型）菌株的限制温度下，DNA复制依赖于DNA聚合酶I。携带pcbA1（一种功能性DNA聚合酶I）和温度敏感型DNA聚合酶III基因的细胞被用于研究DNA聚合酶III在DNA修复中的作用。在DNA聚合酶III的限制温度下，这些菌株对烷化剂甲磺酸甲酯（MMS）和过氧化氢比正常细胞更敏感。相同的菌株在限制温度下对博来霉素、紫外线或补骨脂素的敏感性没有增加。这些菌株对MMS和过氧化氢的敏感性并非由于pcbA1等位基因，通过引入染色体或克隆的DNA聚合酶III基因可恢复正常敏感性，这证实了敏感性是由于DNA聚合酶IIIα亚基活性丧失所致。如碱性蔗糖沉降结果所示，在用MMS或过氧化氢处理细胞后，形成高分子量DNA需要功能性DNA聚合酶III。因此，似乎功能性DNA聚合酶III是MMS或过氧化氢对DNA损伤进行最佳修复所必需的。
