The Vsr endonuclease of Escherichia coli: an efficient DNA repair enzyme and a potent mutagen
The Vsr endonuclease of Escherichia coli: an efficient DNA repair enzyme and a potent mutagen
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DOI：
10.1128/jb.179.19.6048-6052.1997
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发表时间：
1997-10-01
影响因子：
3.2
通讯作者：
Cupples, CG
中科院分区：
文献类型：
--
作者：
Macintyre, G;Doiron, KMJ;Cupples, CG
大肠杆菌的Vsr核酸内切酶启动修复由5-甲基胞嘧啶脱氨为胸腺嘧啶引起的T/G错配。在本文中，我们研究了Vsr在细胞中防止胞嘧啶甲基化酶基因（dcm）转录增加的CG至TA突变的能力。我们发现，足够的VSR是由一个单一的染色体拷贝的VSR，以防止诱变。我们还研究了过度产生Vsr的细胞中的转换和移码突变的原因，dcm甲基化酶的缺乏或其过度产生都不影响Vsr刺激的诱变，然而，在多拷贝质粒上添加mutS、mutL或mutH具有显著的影响：mutL或mutH减少突变的数量，而mutS刺激诱变。含突变体的质粒在用2-氨基嘌呤处理的细胞和DNA校对缺陷的细胞中具有相同的效果，这两种实验情况已知通过饱和错配修复引起转换和移码突变。
The Vsr endonuclease of Escherichia coli initiates the repair of T/G mismatches caused by deamination of 5-methylcytosine to thymine, In this paper, we examine the capacity of Vsr to prevent CG-to-TA mutations in cells with increased transcription of the cytosine methylase gene (dcm). We find that sufficient Vsr is produced by a single chromosomal copy of vsr to prevent mutagenesis. We also investigate the cause of the transition and frameshift mutations in cells overproducing Vsr, Neither the absence of the dcm methylase nor its overproduction affects Vsr-stimulated mutagenesis, However, addition of mutS, mutL, or mutH on multicopy plasmids has a significant effect: mutL or mutH decreases the number of mutations, while mutS stimulates mutagenesis. The mut-containing plasmids have the same effect in cells treated with 2-aminopurine and in cells made defective in DNA proofreading, two experimental situations known to cause transition and frameshift mutations by saturating mismatch repair.