Novel nuclear and mitochondrial glycosylases revealed by disruption of the mouse Nth1 gene encoding an endonuclease III homolog for repair of thymine glycols
Novel nuclear and mitochondrial glycosylases revealed by disruption of the mouse Nth1 gene encoding an endonuclease III homolog for repair of thymine glycols
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DOI：
10.1093/emboj/cdf350
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发表时间：
2002-07-01
期刊：
影响因子：
11.4
通讯作者：
Yasui, A
中科院分区：
文献类型：
--
作者：
Takao, M;Kanno, S;Yasui, A
内切酶III由大肠杆菌中的第N TH编码，它能去除胸腺嘧啶二醇(TG)，这是一种有毒的氧化性DNA损伤。为了确定这种修复在哺乳动物中的生物学意义，我们通过基因打靶建立了突变的mNth1小鼠模型，mNth1是nth的同源物。纯合子mNth1突变小鼠未表现出明显的表型异常。有或没有野生型mNth1的胚胎细胞对甲萘二酮或过氧化氢的敏感性没有差异。X射线照射突变小鼠肝脏DNA产生的甘油三酯随着时间的推移而消失，尽管比野生型小鼠慢。在突变小鼠肝脏的提取物中，我们发现至少有两种新的DNA糖基酶活性对甘油三酯具有抑制作用，而不是mNTH1活性。在线粒体中，突变体的一种活性显著高于野生型小鼠，而另一种活性则是甘油三酯的另一种核糖基酶。这些结果强调了哺乳动物细胞核和线粒体中TG碱基切除修复的重要性。
Endonuclease III, encoded by nth in Escherichia coli, removes thymine glycols (Tg), a toxic oxidative DNA lesion. To determine the biological significance of this repair in mammals, we established a mouse model with mutated mNth1, a homolog of nth, by gene targeting. The homozygous mNth1 mutant mice showed no detectable phenotypical abnormality. Embryonic cells with or without wild-type mNth1 showed no difference in sensitivity to menadione or hydrogen peroxide. Tg produced in the mutant mouse liver DNA by X-ray irradiation disappeared with time, though more slowly than in the wild-type mouse. In extracts from mutant mouse liver, we found, instead of mNTH1 activity, at least two novel DNA glycosylase activities against Tg. One activity is significantly higher in the mutant than in wild-type mouse in mitochondria, while the other is another nuclear glycosylase for Tg. These results underscore the importance of base excision repair of Tg both in the nuclei and mitochondria in mammals.