Identification of high excision capacity for 5-hydroxymethyluracil mispaired with guanine in DNA of Escherichia coli MutM, Nei and Nth DNA glycosylases
Identification of high excision capacity for 5-hydroxymethyluracil mispaired with guanine in DNA of Escherichia coli MutM, Nei and Nth DNA glycosylases
复制标题
DOI：
10.1093/nar/gkg223
复制
发表时间：
2003-02-15
影响因子：
14.9
通讯作者：
Zhang, QM
中科院分区：
文献类型：
--
作者：
Hori, M;Yonei, S;Zhang, QM
DNA中5-甲基胞嘧啶（5 mC）的氧化和脱氨作用在5-羟甲基尿嘧啶（5 hmU）和鸟嘌呤之间产生碱基对。5 hmU通常与腺嘌呤形成碱基对。因此，5 mC到5 hmU的转化是产生5 mC到T转换的潜在途径。哺乳动物细胞具有高水平的5 hmU-DNA糖基化酶活性，其从DNA切除5 hmU。然而，类似地切除5 hmU的糖基化酶尚未在酵母或大肠杆菌中观察到。最近，我们发现大肠杆菌MutM、Nei和Nth对5-甲酰尿嘧啶具有DNA糖基化酶活性，5-甲酰尿嘧啶是胸腺嘧啶甲基的另一种类型的氧化产物。在这项研究中，我们检查了大肠杆菌MutM、Nei和Nth是否也具有在体外作用于5 hmU的DNA糖基化酶活性。当与含有5 hmU：G或5 hmU：A的合成双链体寡核苷酸一起孵育时，纯化的MutM、Nei和Nth分别比5 hmU：A寡核苷酸更有效地切割5 hmU：G寡核苷酸58、5和37倍。在大肠杆菌中，MutM、Nei和Nth的5 hmU-DNA糖基化酶活性可能在修复5 hmU：G错配以避免5 mC到T转换中起关键作用。
The oxidation and deamination of 5-methylcytosine (5mC) in DNA generates a base-pair between 5-hydroxymethyluracil (5hmU) and guanine. 5hmU normally forms a base-pair with adenine. Therefore, the conversion of 5mC to 5hmU is a potential pathway for the generation of 5mC to T transitions. Mammalian cells have high levels of activity of 5hmU-DNA glycosylase, which excises 5hmU from DNA. However, glycosylases that similarly excise 5hmU have not been observed in yeast or Escherichia coli. Recently, we found that E.coli MutM, Nei and Nth have DNA glycosylase activity for 5-formyluracil, which is another type of oxidation product of the thymine methyl group. In this study, we examined whether or not E.coli MutM, Nei and Nth have also DNA glycosylase activity that acts on 5hmU in vitro. When incubated with synthetic duplex oligonucleotides containing 5hmU:G or 5hmU:A, purified MutM, Nei and Nth cleaved the 5hmU:G oligonucleotide 58, 5 and 37 times, respectively, more efficiently than the 5hmU:A oligonucleotide. In E.coli, the 5hmU-DNA glycosylase activities of MutM, Nei and Nth may play critical roles in the repair of 5hmU:G mispairs to avoid 5mC to T transitions.