Activation-induced cytidine deaminase acts on double-strand breaks in vitro.
Activation-induced cytidine deaminase acts on double-strand breaks in vitro.
复制标题
激活诱导的胞苷脱氨酶在体外作用于双链断裂。
DOI：
10.1016/j.molimm.2006.03.015
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发表时间：
2007
影响因子：
3.6
通讯作者：
Shen,HongMing
中科院分区：
文献类型：
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作者：
Shen,HongMing
激活诱导胞苷脱氨酶（AID）可能负责DNA胞苷脱氨，尽管它也可能作为RNA脱氨酶。在转录过程中，它作用于单链DNA，双链DNA中的非模板链，或超螺旋DNA中的两条链。为了了解AID是否能够在DNA断裂处脱氨胞苷，我们生成了含有SnaBI位点（TAC↓GTA）的质粒，该质粒在被SnaBI消化后形成钝端。如果AID在上游钝端脱胺胞苷，则在没有udg的大肠杆菌细胞中，两个耐药基因中任何一个的ATG起始密码子在结扎和复制后都会再生。这项研究表明，AID在断裂处靶向胞苷。断裂带以外的脱氨活性程度与断裂带内的碱基组成有关。如果断裂区域富含A、T，则C、T跃迁广泛。然而，当断裂区域不富含A， t时，突变主要局限于断裂，与体内研究结果相似。结果表明，AID对双链断裂（DSBs）具有活性。基于以往和目前的研究结果，提出了一个体细胞超突变（SHM）模型，其中转录装置和复制叉之间的碰撞产生dsb。在AID作用于断裂末端后，容易出错的DNA修复机制进行修复并产生突变。
Activation-induced cytidine deaminase (AID) is likely responsible for DNA cytidine deamination, although it may also act as an RNA deaminase. It functions on single-stranded DNA, the non-template strand in double-stranded DNA during transcription, or both strands in supercoiled DNA. To ask whether AID is able to deaminate cytidine at DNA breaks, plasmids, containing a SnaBI site (TAC↓GTA) that forms blunt ends after digestion with SnaBI, were generated. If AID deaminates cytidine at the upstream blunt end, the ATG start codon in either of two drug resistance genes will be regenerated after ligation and replication in UDG-null E. coli cells. This study shows that AID targets cytidine at the break. The extent of deamination activity beyond the break is correlated with the base composition in the break region. If the break region is A, T-rich, C>T transitions are extensive. However, when the break region is not A, T-rich, mutations are mainly restricted to the break, similar to findings in vivo. The results indicate that AID has activity on double strand breaks (DSBs). Based on previous and current findings, a somatic hypermutation (SHM) model is proposed, in which collision between the transcription apparatus and the replication fork generates DSBs. After AID acts on break ends, the error-prone DNA repair machinery fixes and creates mutations.