EVIDENCE THAT MUTY AND MUTM COMBINE TO PREVENT MUTATIONS BY AN OXIDATIVELY DAMAGED FORM OF GUANINE IN DNA
EVIDENCE THAT MUTY AND MUTM COMBINE TO PREVENT MUTATIONS BY AN OXIDATIVELY DAMAGED FORM OF GUANINE IN DNA
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DOI：
10.1073/pnas.89.15.7022
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发表时间：
1992-08-01
影响因子：
11.1
通讯作者：
MILLER, JH
中科院分区：
文献类型：
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作者：
MICHAELS, ML;CRUZ, C;MILLER, JH
先前已经在体内和体外显示，经过鸟嘌呤的氧化损伤形式7，8-二氢-8-氧代鸟嘌呤（8-oxoG）的DNA合成可以导致与8-oxodG相对的腺嘌呤（A）的错误掺入。在这项研究中，我们表明，MutY糖基化酶是活性的位点特异性，氧化损伤的A/8-oxoG错配对，它删除未受损的腺嘌呤从这个错配对。缺乏活性MutY蛋白的菌株具有升高的G. C-> T. A颠换率。我们发现，mutY菌株的增变表型可以通过从质粒克隆中过表达MutM蛋白（Fpg蛋白）来完全互补。MutM蛋白从DNA中去除8-oxoG损伤。此外，我们已经分离出一个菌株的染色体突变，抑制mutY表型，并发现这种抑制剂也过表达MutM。最后，mutY mutM双突变体的突变率比单独的任何一个增变因子高25至75倍。这些数据强烈表明MutY是针对核酸中8-oxoG损伤的复杂修复系统的一部分，并且MutY在体内的主要功能是去除在DNA合成过程中与8-oxoG损伤相反的错误掺入的腺嘌呤。
It has been previously shown both in vivo and in vitro that DNA synthesis past an oxidatively damaged form of guanine, 7,8-dihydro-8-oxoguanine (8-oxoG), can result in the misincorporation of adenine (A) opposite the 8-oxodG. In this study we show that MutY glycosylase is active on a site-specific, oxidatively damaged A/8-oxoG mispair and that it removes the undamaged adenine from this mispair. Strains that lack active MutY protein have elevated rates of G.C --> T.A transversions. We find that the mutator phenotype of a mutY strain can be fully complemented by overexpressing MutM protein (Fpg protein) from a plasmid clone. The MutM protein removes 8-oxoG lesions from DNA. In addition, we have isolated a strain with a chromosomal mutation that suppresses the mutY phenotype and found that this suppressor also overexpresses MutM. Finally, a mutY mutM double mutant has a 25- to 75-fold higher mutation rate than either mutator alone. The data strongly suggest that MutY is part of an intricate repair system directed against 8-oxoG lesions in nucleic acids and that the primary function of MutY in vivo is the removal of adenines that are misincorporated opposite 8-oxoG lesions during DNA synthesis.