Repair of O6-G-alkyl-O6-G interstrand cross-links by human O6-alkylguanine-DNA alkyltransferase
Repair of O6-G-alkyl-O6-G interstrand cross-links by human O6-alkylguanine-DNA alkyltransferase
复制标题
DOI：
10.1021/bi8008664
复制
发表时间：
2008-10-14
期刊：
影响因子：
2.9
通讯作者：
Pegg, Anthony E.
中科院分区：
文献类型：
--
作者：
Fang, Qingming;Noronha, Anne M.;Pegg, Anthony E.
O-6-烷基鸟嘌呤-DNA烷基转移酶(AGT)在保护细胞免受烷基化剂侵害方面发挥着重要作用。这降低了由这类药物引发的致癌和突变的频率，但AGT也提供了一些化疗药物的主要耐药机制。为了提高我们对AGT介导的修复反应的理解和对可修复损伤的光谱的理解，我们研究了AGT修复链间交联DNA损伤的能力，其中两条DNA链通过每条链上的鸟嘌呤-O-6连接在一起。含有庚烷交联物的寡聚脱氧核糖核苷酸被修复，最初形成AGT-寡聚物络合物，第二个AGT分子进一步反应产生HAGT二聚体和游离寡聚。然而，带有丁烷交联物的寡核苷酸是AGT介导的修复的非常差的底物，并且只能检测到形成AGT-寡核苷酸复合体的第一反应。这些底物在AGT活性部位的反应模型表明，DNA双链在局部被迫分离，以修复第一个鸟嘌呤。丁烷交联剂的引入大大阻碍了该反应的进行，丁烷交联剂主要埋在活性中心的口袋中，限制了构象的灵活性。这一限制也阻止了采用第二反应的构象来修复AGT-寡核苷酸复合体。这些结果与AGT修复涉及DNA结合和底物核苷酸翻转的假设机制一致，表明HAGT可以修复某些类型的链间交联损伤。
O-6-Alkylguanine-DNA alkyltransferase (AGT) plays an important role by protecting cells from alkylating agents. This reduces the frequency of carcinogenesis and mutagenesis initiated by such agents, but AGT also provides a major resistance mechanism to some chemotherapeutic drugs. To improve our understanding of the AGT-mediated repair reaction and our understanding of the spectrum of repairable damage, we have studied the ability of AGT to repair interstrand cross-link DNA damage where the two DNA strands are joined via the guanine-O-6 in each strand. An oligodeoxyribonucleotide containing a heptane cross-link was repaired with initial formation of an AGT-oligo complex and further reaction of a second AGT molecule yielding a hAGT dimer and free oligo. However, an oligodeoxyribonucleotide with a butane cross-link was a very poor substrate for AGT-mediated repair, and only the first reaction that forms an AGT-oligo complex could be detected. Models of the reaction of these substrates in the AGT active site show that the DNA duplex is forced apart locally to repair the first guanine. This reaction is greatly hindered with the butane cross-link, which is mostly buried in the active site pocket and limited in conformational flexibility. This limitation also prevents the adoption of a conformation for the second reaction to repair the AGT-oligo complex. These results are consistent with the postulated mechanism of AGT repair that involves DNA binding and flipping of the substrate nucleotide and indicate that hAGT can repair some types of interstrand cross-link damage.