Evidence for a recombination-independent pathway for the repair of DNA interstrand cross-links based on a site-specific study with nitrogen mustard
Evidence for a recombination-independent pathway for the repair of DNA interstrand cross-links based on a site-specific study with nitrogen mustard
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DOI：
10.1021/bi962778w
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发表时间：
1997-03-25
期刊：
影响因子：
2.9
通讯作者：
Loechler, EL
中科院分区：
文献类型：
--
作者：
Berardini, M;Mackay, W;Loechler, EL
DNA-DNA链间交联被认为是许多化疗药物细胞毒性的重要因素。为了更明确地研究这一点，我们使用加合物位点特异性的方法构建了一个带有单个氮芥链间交联物(interHN2-pTZSV28)的质粒。在转化到大肠杆菌后，复制效率(RE=[(interhn2-pTZSV28)/(无交联物对照)])类似于0.3，这意味着交联物被修复。通常接受的包括核苷酸切除修复(NER)和重组的交链修复途径被排除，因为RE类似于DrecA株的0.3。非RecA导向的重组，如复制选择，也不太可能。然而，在缺乏NER的菌株中，由于RE与0.02相似，因此NER参与了该基因的表达。碱基切除修复并不重要，因为在缺乏3-甲基腺嘌呤DNA糖基酶I和II、Fapy DNA糖基酶或DNA脱氧核糖核酸二酯酶的菌株中，RE类似于0.3。另一种假想的修复途径不太可能依赖于5‘-->；3’外切酶活性，因为在缺乏DNA聚合酶I、外切酶VII或RecJ的5‘-->；3’外切酶活性的细胞中，RE类似于0.3。因此，除了NER之外，目前尚不清楚NER还参与了这种重组非依赖的修复途径，尽管目前的工作假说是涉及NER的途径，随后是病变的复制旁路。补骨脂素链间交联物似乎不能通过第二条途径修复，这可能与不同试剂的链间交联物的相对细胞毒性有关。
DNA-DNA interstrand cross-links are thought to be important for the cytotoxicity of many chemotherapeutic agents. To study this more definitively, adduct site-specific methods are used to construct a plasmid with a single nitrogen mustard interstrand cross-link (inter-HN2-pTZSV28). Replication efficiency (RE = [colonies from (inter-HN2-pTZSV28)/(control with no cross-link)]) is similar to 0.3 following transformation into Escherichia coli, implying that the cross-link is repaired. The commonly accepted pathway for cross-link repair, which involves both nucleotide excision repair (NER) and recombination, is ruled out since RE is similar to 0.3 in a drecA strain. Non-RecA-directed recombination such as copy-choice is also unlikely. However, NER is involved since RE was similar to 0.02 in strains deficient in NER. Base excision repair is not important since RE is similar to 0.3 in strains deficient in 3-methyladenine DNA glycosylases I and II, FAPY DNA glycosylase, both known apurinic/apyrimidinic endonucleases, or DNA deoxyribophosphodiesterase. Another hypothetical repair pathway hinging on a 5' --> 3' exonuclease activity is unlikely since RE is similar to 0.3 in cells deficient in either the 5' --> 3' exonuclease activities of DNA polymerase I, exonuclease VII, or RecJ. Thus, aside from NER, it is unclear what else participates in this recombination-independent repair pathway, although a pathway involing NER followed by replicative bypass of the lesion is the current working hypothesis. Psoralen interstrand cross-links appear not to be repairable by this second pathway, which may have implications for the relative cytotoxicity of interstrand cross-links from different agents.