Boiteux S, Yeung A T, Sage E
LA147 CNRS, U140 INSERM Groupe Réparation des Lésions Radio et Chimioinduites, Institut Gustave Roussy, Villejuif, France.
Mutat Res. 1993 Jun;294(1):43-50. doi: 10.1016/0921-8777(93)90056-m.
The specific recognition of DNA modifications by repair endonucleases was used to characterize damage induced by 3-carbethoxypsoralen (3-CPs) plus UvA in M13mp8 replicative form I (RF-I) DNA. Under the conditions used, 3-CPs plus UVA generates DNA base modifications which are recognized by the UvrABC complex and the Fpg protein of E. coli. The rate of formation of UvrABC sensitive sites is 3-4-fold higher than that of Fpg sensitive sites. In addition a small number of sites of base loss (sensitive to Nfo protein) were observed. M13mp8 RF-I DNA treated with 3-CPs plus UVA was tested for transfection efficiency in E. coli mutants defective in either Fpg protein and/or UvrABC complex. The survival of 3-CPs plus UVA damaged M13mp8 RF-I DNA was significantly reduced when transfected into uvrA mutants compared to that in the wild-type strain. On the other hand, the survival of 3-CPs plus UVA damaged RF-I DNA was not altered in fpg-1 mutants. These results show that nucleotide excision repair mediated by the UvrABC complex is the major repair pathway involved in the elimination of lethal lesions induced in DNA by 3-CPs plus UVA. Our data suggest that in vitro exposure of M13mp8 RF-I DNA to 3-CPs plus UVA produces predominantly thymine photoaddition and to a lesser extent guanine photooxidation partially due to singlet oxygen generated during photoreaction. The photoaddition products are primarly responsible for the observed lethal effect.
利用修复核酸内切酶对DNA修饰的特异性识别来表征3 - 乙氧羰基补骨脂素（3 - CPs）加紫外线A（UvA）在M13mp8复制型I（RF - I）DNA中诱导的损伤。在所使用的条件下，3 - CPs加UVA会产生DNA碱基修饰，这些修饰可被大肠杆菌的UvrABC复合物和Fpg蛋白识别。UvrABC敏感位点的形成速率比Fpg敏感位点高3 - 4倍。此外，还观察到少量碱基缺失位点（对Nfo蛋白敏感）。用3 - CPs加UVA处理的M13mp8 RF - I DNA在Fpg蛋白和/或UvrABC复合物缺陷的大肠杆菌突变体中进行转染效率测试。与野生型菌株相比，将3 - CPs加UVA损伤的M13mp8 RF - I DNA转染到uvrA突变体中时，其存活率显著降低。另一方面，3 - CPs加UVA损伤的RF - I DNA在fpg - 1突变体中的存活率没有改变。这些结果表明，由UvrABC复合物介导的核苷酸切除修复是参与消除3 - CPs加UVA在DNA中诱导的致死性损伤的主要修复途径。我们的数据表明，M13mp8 RF - I DNA在体外暴露于3 - CPs加UVA主要产生胸腺嘧啶光加成产物，在较小程度上产生鸟嘌呤光氧化产物，部分原因是光反应过程中产生的单线态氧。光加成产物是观察到的致死效应的主要原因。
