Biochemical analysis of hypermutational targeting by wild type and mutant activation-induced cytidine deaminase
Biochemical analysis of hypermutational targeting by wild type and mutant activation-induced cytidine deaminase
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DOI：
10.1074/jbc.m408135200
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发表时间：
2004-12-03
影响因子：
4.8
通讯作者：
Goodman, MF
中科院分区：
文献类型：
--
作者：
Bransteitter, R;Pham, P;Goodman, MF
高亲和力抗体的合成需要激活诱导的胞苷脱氨酶（AID）来启动体细胞超突变和类别转换重组。在这里，我们研究了艾滋病催化的单链DNA和活性转录的闭合环状双链DNA上的C -> U脱氨基作用。突变最初在典型WRC（W = A或T，R = A或G）体细胞超突变热点基序处受到青睐，但随着时间的推移，相邻非热点位点处的突变增加，以看似进行性的方式产生突变区域的随机簇。与野生型AID相比，N-末端AID突变体R35 E和R35 E/R36 D表现出较低的进行性并且具有改变的突变特异性。相反，体内CSR缺陷的C-末端缺失突变体与野生型AID非常相似。封闭的环状双链DNA的转录过程中产生的突变谱表明，野生型艾滋病保留其特异性的WRC热点图案的范围内的移动转录气泡，同时引入集群的多个脱氨主要在非转录链。
The synthesis of high affinity antibodies requires activation-induced cytidine deaminase ( AID) to initiate somatic hypermutation and class-switch recombination. Here we investigate AID-catalyzed deamination of C --> U on single-stranded DNA and on actively transcribed closed circular double-stranded DNA. Mutations are initially favored at canonical WRC ( W = A or T, R = A or G) somatic hypermutation hot spot motifs, but over time mutations at neighboring non-hot spot sites increase creating random clusters of mutated regions in a seemingly processive manner. N-terminal AID mutants R35E and R35E/R36D appear less processive and have altered mutational specificity compared with wild type AID. In contrast, a C-terminal deletion mutant defective in CSR in vivo closely resembles wild type AID. A mutational spectrum generated during transcription of closed circular double-stranded DNA indicates that wild type AID retains its specificity for WRC hot spot motifs within the confines of a moving transcription bubble while introducing clusters of multiple deaminations predominantly on the nontranscribed strand.