Dzhataev S A, Tanirbergenov T B, Tarasov V A
Genetika. 1980 Apr;16(4):602-8.
There are at least 4 endonucleolytic activities in Escherichia coli cells specific to apurinic and apyrimidinic sites in DNA. The main enzyme in the case of this type of DNA damage is believed to be an endonuclease VI responsible for 90% of total cell activity. Endonuclease VI is associated with exonuclease III which degrades DNA in 3'--5' direction. Our data indicate the absolute necessity of exonuclease III activity in repair of DNA containing apyrimidinic sites. It is possible that in the absence of endonuclease VI this type of DNA damage may be recognized by other endonucleases of E. coli--endonucleases III, V and especially endonuclease IV. During the postincubation of xthA mutant cells the normal molecular weight of DNA was not restored but even further DNA degradation was observed. DNA polymerase I takes part in DNA repair both in case of apyrimidinic sites and UV-induced pyrimidine dimers. Repair kinetics study showed partial molecular weight restoration in polA1 mutant. It is likely that in the absence of this enzyme some of its functions can be taken by other cell DNA polymerases.
在大肠杆菌细胞中，至少有4种核酸内切酶活性作用于DNA中的脱嘌呤和脱嘧啶位点。对于这类DNA损伤，主要的酶被认为是核酸内切酶VI，它占细胞总活性的90%。核酸内切酶VI与核酸外切酶III相关联，核酸外切酶III沿3'→5'方向降解DNA。我们的数据表明，核酸外切酶III活性对于含有脱嘧啶位点的DNA修复是绝对必需的。在缺乏核酸内切酶VI的情况下，这类DNA损伤有可能被大肠杆菌的其他核酸内切酶识别，即核酸内切酶III、V，尤其是核酸内切酶IV。在xthA突变细胞的孵育后，DNA的正常分子量没有恢复，反而观察到进一步的DNA降解。在脱嘧啶位点和紫外线诱导的嘧啶二聚体的情况下，DNA聚合酶I都参与DNA修复。修复动力学研究表明polA1突变体中分子量有部分恢复。在缺乏这种酶的情况下，其一些功能可能由其他细胞DNA聚合酶承担。
