Inducible DNA breaks in Ig S regions are dependent on AID and UNG

被引:138
作者
Schrader, CE [1 ]
Linehan, EK [1 ]
Mochegova, SN [1 ]
Woodland, RT [1 ]
Stavnezer, J [1 ]
机构
[1] Univ Massachusetts, Sch Med, Program Immunol & Virol, Dept Mol Genet & Microbiol, Worcester, MA 01655 USA
关键词
D O I
10.1084/jem.20050872
中图分类号
R392 [医学免疫学]; Q939.91 [免疫学];
学科分类号
100102 ;
摘要
Class switch recombination (CSR) occurs by an intrachromosomal deletion whereby the IgM constant region gene (C mu) is replaced by a downstream constant region gene. This unique recombination event involves formation of double-strand breaks (DSBs) in immunoglobulin switch ( S) regions, and requires activation-induced cytidine deaminase (AID), which converts cytosines to uracils. Repair of the uracils is proposed to lead to DNA breaks required for recombination. Uracil DNA glycosylase (UNG) is required for most CSR activity although its role is disputed. Here we use ligation-mediated PCR to detect DSBs in S regions in splenic B cells undergoing CSR. We find that the kinetics of DSB induction corresponds with AID expression, and that DSBs are AID- and UNG-dependent and occur preferentially at G: C basepairs in WRC/GYW AID hotspots. Our results indicate that AID attacks cytosines on both DNA strands, and staggered breaks are processed to blunt DSBs at the initiating ss break sites. We propose a model to explain the types of end-processing events observed.
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页码:561 / 568
页数:8
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