In vivo repair of ENU-induced oxygen alkylation damage by the nucleotide excision repair mechanism in Drosophila melanogaster
In vivo repair of ENU-induced oxygen alkylation damage by the nucleotide excision repair mechanism in Drosophila melanogaster
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DOI：
10.1007/s004380000419
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发表时间：
2001-04
影响因子：
3.1
通讯作者：
L. Tosal;M. A. Comendador;L. Sierra
中科院分区：
文献类型：
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作者：
L. Tosal;M. A. Comendador;L. Sierra
碱氧烷基化引起的DNA损伤(主要是DNA中的O6-G、O4-T和O2-T位)与单官能性烷基化试剂的致突变和致癌作用有关。在所有生物中，O6-烷基G的修复主要由O6-甲基鸟嘌呤-DNA甲基转移酶(MGMT)进行。然而，关于O-烷基T加合物的修复或核苷酸切除修复(NER)在这一过程中的作用，尤其是在高等真核生物中，人们知之甚少。为了研究NER系统对O-烷基化损伤修复的影响，获得了N-乙基-N-亚硝脲(ENU)对NER缺乏、在201位点携带突变的果蝇的分子突变谱，并与以前发表的NER熟练条件下的分子突变谱进行了比较。这一比较显示碱基对变化的频率明显增加，包括GC→AT和AT→GC转换以及AT→TA颠倒。此外，在NER缺乏的突变体中分离到了一个缺失突变和两个移码突变，这些突变在NER熟练的条件下没有发现。结果表明：(1)在NER缺乏的条件下，N-烷基化损伤对ENU的诱变活性有相当大的贡献(超过20%)，证实了NER系统修复了这种损伤；(2)在果蝇体内的生殖细胞中，NER似乎修复了O6-乙基鸟嘌呤和/或O2-乙基胞嘧啶、O4-乙基胸腺胺，也可能修复了O2-乙基胸腺嘧啶。
DNA damage caused by oxygen alkylation of bases (mainly at O6-G, O4-T and O2-T positions in DNA) has been correlated with the mutagenic and carcinogenic potency of monofunctional alkylating agents. In all kinds of organisms, repair of O6-alkylG is carried out mainly by the enzyme O6-methyl guanine-DNA methyltransferase (MGMT). However, little is known about the repair of the O-alkylT adducts or about the contribution of nucleotide excision repair (NER) to this process, especially in higher eukaryotes. To study the influence of the NER system on the repair of O-alkylation damage, the molecular mutation spectrum induced by N-ethyl-N-nitrosourea (ENU) in an NER-deficientDrosophilastrain, carrying a mutation at themus201locus, was obtained and compared with a previously published spectrum for NER-proficient conditions. This comparison reveals a clear increase in the frequency of base pair changes, including GC→AT and AT→GC transitions and AT→TA transversions. In addition, one deletion and two frameshift mutations, not found under NER-proficient conditions, were isolated in the NER-deficient mutant. The results demonstrate that: (1) N-alkylation damage contributes considerably (more than 20%) to the mutagenic activity of ENU under NER-deficient conditions, confirming that the NER system repairs this kind of damage; and (2) that in germ cells ofDrosophilain vivo, NER seems to repair O6-ethylguanine and/or O2-ethylcytosine, O4-ethylthymine, and possibly also O2-ethylthymine.