Zavil'gel'skii G B, Khodkova E M
Mol Biol (Mosk). 1979 Nov-Dec;13(6):1262-76.
Comparative analysis of UV-sensitivity was carried out on plasmids of various molecular weight. Recombinant plasmids containing fragments of prokaryotic DNA (E. coli, phage lambda) are repaired in E. coli cells more effectively than those containing eukaryotic DNA fragments. It was also shown that UV-sensitivity of recombinant plasmids is independent of their molecular weight provided that the active repair process in fact occurs. UV-sensitivity was strongly proporational to DNA size only when E. coli double mutant strain was used as host. The survival of plasmids strongly increased after M. luteus UV-endonuclease treatment when E. coli mutant strain uvr- was used as host, but remained practically constant in case of wild type strain. Agarose gel electrophoresis data provide evidence that DNA double-stranded breaks appear un UV-irradiated as well as in UV-endonuclease treated plasmids. One can suggest that UV-inactivation of plasmids results from DNA breaking as a consequence of repair gaps overlap when wild type strain is used as host. Mathematical analysis was carried out assuming this possibility. Experimental data are shown to fit theoretical values calculated assuming that the repair gap size in one DNA strand is equal to 2000-3000 bases.
对不同分子量的质粒进行了紫外线敏感性的比较分析。含有原核DNA片段（大肠杆菌、噬菌体λ）的重组质粒在大肠杆菌细胞中的修复效率高于含有真核DNA片段的重组质粒。研究还表明，只要确实发生了活跃的修复过程，重组质粒的紫外线敏感性与其分子量无关。只有当使用大肠杆菌双突变菌株作为宿主时，紫外线敏感性才与DNA大小密切相关。当使用大肠杆菌uvr-突变菌株作为宿主时，经藤黄微球菌紫外线内切酶处理后，质粒的存活率大幅提高，但在野生型菌株的情况下，存活率几乎保持不变。琼脂糖凝胶电泳数据表明，在未紫外线照射以及经紫外线内切酶处理的质粒中均出现了DNA双链断裂。可以推测，当使用野生型菌株作为宿主时，质粒的紫外线失活是由于修复缺口重叠导致DNA断裂的结果。基于这种可能性进行了数学分析。实验数据显示与假设一条DNA链中修复缺口大小等于2000 - 3000个碱基计算出的理论值相符。
