O6-methylguanine induces intrachromosomal homologous recombination in human cells.
O6-methylguanine induces intrachromosomal homologous recombination in human cells.
复制标题
O6-甲基鸟嘌呤在人类细胞中诱导染色体内同源重组。
DOI：
10.1093/carcin/17.10.2229
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发表时间：
1996
期刊：
影响因子：
4.7
通讯作者：
McCormick,JJ
中科院分区：
文献类型：
--
作者：
Zhang,H;Tsujimura,T;Bhattacharyya,NP;Maher,VM;McCormick,JJ
N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), which alkylates many positions in DNA including theO6position of guanine, efficiently induces intrachromosomal homologous recombination in mouse L-cells. To investigate the role ofO6-methylguanine in the induction of homologous recombination in human cells, three cell strains containing duplicated copies of the Herpes simplex virus I thymidine kinase (Htk) gene and three cell strains containing duplicated copies of the gene coding for hygromycin phosphotransfer-ase (hyg) were treated with MNNG. Neither theHtkgenes nor thehyggenes code for a functional enzyme because each contains an insertion mutation at a unique site, i.e. 8-bpXhoIlinker insertions in theHtkgenes and 10-bpHindIIIlinker insertions in the hyg genes. These cell strains differ in their level ofO6-alkylguanine-DNA alkyltrans-ferase (AGT), which specifically removes the methyl group from theO6position of guanine. Generation of a functionalHtkorhyggene has been shown to require intrachromo-somal homologous recombination between the two mutantHtkgenes or the two mutanthyggenes. In all six cell strains, MNNG induced a dose-dependent increase in the frequency of homologous recombination. In each set, there was an inverse correlation between the frequency of MNNG-induced recombination and the level of AGT activity. To further study the role ofO6-methylguanine in the induction of homologous recombination, we usedO6-benzylguanine to inactivate AGT in two additional human cell strains containing thehygrecombination substrate. After depletion of AGT activity byO6-benzylguanine, both cell strains showed a significantly elevated level of MNNG-induced homologous recombination. These results indicate thatO6-methylguanine is the principal lesion responsible for the induction of homologous recombination in these human cells by this methylating agent.
