AID mutates E-coli suggesting a DNA deamination mechanism for antibody diversification
AID mutates E-coli suggesting a DNA deamination mechanism for antibody diversification
复制标题
DOI：
10.1038/nature00862
复制
发表时间：
2002-07-04
期刊：
影响因子：
64.8
通讯作者：
Neuberger, MS
中科院分区：
文献类型：
--
作者：
Petersen-Mahrt, SK;Harris, RS;Neuberger, MS
在基因重排后，免疫球蛋白可变基因通过体细胞超突变或基因转换而多样化，而恒定区则通过类切换重组而改变。所有这三个过程都依赖于激活诱导的胞苷脱氨酶(AID)(1-7)，这是一种B细胞特异性蛋白质，已被提出(由于序列同源性1)通过RNA编辑发挥功能。但有迹象表明，这三个基因多样化过程可能是由一种常见的DNA损伤(8-11)启动的，加上存在针对DC/DG(12)的第一阶段超突变的建议，向我们暗示AID可能直接在DC/DG对发挥作用。在这里，我们证明了AID在大肠杆菌中的表达给出了一个突变子表型，它以一种上下文相关的方式在DC/DG产生核苷酸转换。AID引发的突变是由于尿嘧啶-DNA糖基酶的缺乏而增强的，这表明AID是通过脱氨DNA中的DC残基发挥作用的。我们认为，免疫球蛋白功能基因的多样化是由AID介导的免疫球蛋白基因座DC残基的脱氨基引发的，结果-即高突变阶段1和2，基因转换或开关重组-取决于启动的DU/DG损伤的解决方式。
After gene rearrangement, immunoglobulin variable genes are diversified by somatic hypermutation or gene conversion, whereas the constant region is altered by class-switch recombination. All three processes depend on activation-induced cytidine deaminase (AID)(1-7), a B-cell-specific protein that has been proposed (because of sequence homology 1) to function by RNA editing. But indications that the three gene diversification processes might be initiated by a common type of DNA lesion(8-11), together with the proposal that there is a first phase of hypermutation that targets dC/dG(12), suggested to us that AID may function directly at dC/dG pairs. Here we show that expression of AID in Escherichia coli gives a mutator phenotype that yields nucleotide transitions at dC/dG in a context-dependent manner. Mutation triggered by AID is enhanced by a deficiency of uracil-DNA glycosylase, which indicates that AID functions by deaminating dC residues in DNA. We propose that diversification of functional immunoglobulin genes is triggered by AID-mediated deamination of dC residues in the immunoglobulin locus with the outcome-that is, hypermutation phases 1 and 2, gene conversion or switch recombination-dependent on the way in which the initiating dU/dG lesion is resolved.