MutS inhibits RecA-mediated strand transfer with methylated DNA substrates.
MutS inhibits RecA-mediated strand transfer with methylated DNA substrates.
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DOI：
10.1093/nar/gki673
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发表时间：
2005
影响因子：
14.9
通讯作者：
Marinus MG
中科院分区：
文献类型：
--
作者：
Calmann MA;Evans JE;Marinus MG
DNA错配修复(MMR)使人和大肠杆菌DAM细胞对N-甲基-N‘-硝基-N-亚硝基(MNNG)的细胞毒作用增敏，而这种修复的取消会导致耐药。在被MNNG甲基化的DNA中，MMR作用是MutS识别O6-甲基鸟嘌呤碱基对的结果。MutS和Ada甲基转移酶竞争MNNG诱导的O6-甲基鸟嘌呤残基，当Ada浓度高于正常浓度时，MMR诱导的细胞毒性被取消。为了验证MMR致敏是由于重组修复减少的假设，我们使用了RecA介导的同源phiX174底物分子之间的链交换分析，其中一个分子与MNNG甲基化。MutS以浓度依赖的方式抑制这些底物上的链转移，MutL可增强其抑制作用。在未甲基化的底物上，这些蛋白质对RecA活性没有影响。我们用HPLC-MS/MS对甲基化DNA中O6-甲基鸟嘌呤残基的数量进行了定量，在phiX174 DNA(5386个碱基)中有5-10个残基足以阻止MutS和MutL存在的RecA反应。这些结果与一个模型一致，在该模型中，甲基化的DNA被细胞认为是同源的，并通过MMR系统防止与同源DNA重新结合。
DNA mismatch repair (MMR) sensitizes human and Escherichia coli dam cells to the cytotoxic action of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) while abrogation of such repair results in drug resistance. In DNA methylated by MNNG, MMR action is the result of MutS recognition of O6-methylguanine base pairs. MutS and Ada methyltransferase compete for the MNNG-induced O6-methylguanine residues, and MMR-induced cytotoxicity is abrogated when Ada is present at higher concentrations than normal. To test the hypothesis that MMR sensitization is due to decreased recombinational repair, we used a RecA-mediated strand exchange assay between homologous phiX174 substrate molecules, one of which was methylated with MNNG. MutS inhibited strand transfer on such substrates in a concentration-dependent manner and its inhibitory effect was enhanced by MutL. There was no effect of these proteins on RecA activity with unmethylated substrates. We quantified the number of O6-methylguanine residues in methylated DNA by HPLC-MS/MS and 5–10 of these residues in phiX174 DNA (5386 bp) were sufficient to block the RecA reaction in the presence of MutS and MutL. These results are consistent with a model in which methylated DNA is perceived by the cell as homeologous and prevented from recombining with homologous DNA by the MMR system.
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DOI：
10.1073/pnas.82.9.2688
发表时间：
1985-01-01
影响因子：
11.1
作者：
DEMPLE, B;SEDGWICK, B;LINDAHL, T
通讯作者：
LINDAHL, T
影响因子：
3.8
作者：
Nowosielska, A;Calmann, MA;Marinus, MG
通讯作者：
Marinus, MG
影响因子：
3.8
作者：
Massey, A;Offman, J;Karran, P
通讯作者：
Karran, P
DOI：
10.1016/s1383-5742(00)00016-8
发表时间：
2000-04-01
影响因子：
5.3
作者：
Bignami, M;O'Driscoll, M;Karran, P
通讯作者：
Karran, P
影响因子：
64.8
作者：
KARRAN, P;MARINUS, MG
通讯作者：
MARINUS, MG