Identification and characterization of a human DNA glycosylase for repair of modified bases in oxidatively damaged DNA
Identification and characterization of a human DNA glycosylase for repair of modified bases in oxidatively damaged DNA
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DOI：
10.1073/pnas.062053799
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发表时间：
2002-03-19
影响因子：
11.1
通讯作者：
Mitra, S
中科院分区：
文献类型：
--
作者：
Hazra, TK;Izumi, T;Mitra, S
8-氧代鸟嘌呤（8-oxoG）、开环嘌呤（甲酰氨基嘧啶或Fapys）和其它由活性氧物质产生的氧化DNA碱基损伤通常是致突变的和有毒的，并且与许多疾病（包括癌症）和衰老的病因学有关。在所有生物体中，这些损伤的修复主要通过DNA碱基切除修复途径发生，由DNA糖基化酶/AP裂解酶切除它们开始，这是两类。一类利用内部Lys残基作为活性位点亲核试剂，包括大肠杆菌Nth和两种已知的哺乳动物DNA糖基化酶/AP裂解酶，即OGG 1和NTH 1。E.大肠杆菌MutM和它的副产物Nei是第二类，它们的N-末端是Pro。在这里，我们报告了两个人类直系同源的E。coli mutM nei基因的克隆，并对其产物进行了鉴定。基于底物偏好性，我们将其命名为NEH 1（Nei homolog）。从E.从受损的DNA中切除Fapys，并从寡脱氧核苷酸中切除氧化的嘧啶和8-oxoG。由于N-末端Pro的缺失或N末端的Histag融合而导致的酶失活支持N-末端Pro作为其活性位点的作用。NEW和OGG 1 mRNA的组织特异性水平是不同的，NEH 1在RNA和蛋白质水平上的S期特异性增加表明NEW参与了氧化碱基的复制相关修复。
8-oxoguanine (8-oxoG), ring-opened purines (formamidopyrimidines or Fapys), and other oxidized DNA base lesions generated by reactive oxygen species are often mutagenic and toxic, and have been implicated in the etiology of many diseases, including cancer, and in aging. Repair of these lesions in all organisms occurs primarily via the DNA base excision repair pathway, initiated with their excision by DNA glycosylase/AP lyases, which are of two classes. One class utilizes an internal Lys residue as the active site nucleophile, and includes Escherichia coli Nth and both known mammalian DNA glycosylase/AP lyases, namely, OGG1 and NTH1. E. coli MutM and its paralog Nei, which comprise the second class, use N-terminal Pro as the active site. Here, we report the presence of two human orthologs of E. coli mutM nei genes in the human genome database, and characterize one of their products. Based on the substrate preference, we have named it NEH1 (Nei homolog). The 44-kDa, wild-type recombinant NEH1, purified to homogeneity from E. coli, excises Fapys from damaged DNA, and oxidized pyrimidines and 8-oxoG from oligodeoxynucleotides. Inactivation of the enzyme because of either deletion of N-terminal Pro or Histag fusion at the N terminus supports the role of N-terminal Pro as its active site. The tissue-specific levels of NEW and OGG1 mRNAs are distinct and S phase-specific increase in NEH1 at both RNA and protein levels suggests that NEW is involved in replication-associated repair of oxidized bases.