标题：The C-terminal region of activation-induced cytidine deaminase is responsible for a recombination function other than DNA cleavage in class switch recombination
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2009
卷号：106
期号：8
页码：2758-2763
DOI：10.1073/pnas.0813253106
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Activation-induced cytidine deaminase (AID) is an essential factor for the class switch recombination (CSR) and somatic hypermutation (SHM) of Ig genes. CSR and SHM are initiated by AID-induced DNA breaks in the S and V regions, respectively. Because truncation or frame-shift mutations at the carboxyl (C)-terminus of AID abolishes CSR but not SHM, the C-terminal region of AID likely is required for the targeting of DNA breaks in the S region. To test this hypothesis, we determined the precise location and relative amounts of AID-induced DNA cleavage using an in situ DNA end-labeling method. We established CH12F3-2 cell transfectants expressing the estrogen receptor (ER) fused with wild-type (WT) AID or a deletion mutant lacking the C-terminal 16 aa, JP8Bdel. We found that AID-ER, but not JP8Bdel-ER, caused a CSR to IgA from the addition of 4-hydroxy tamoxifen. In contrast, both WT AID and JP8Bdel induced DNA breaks in both the V and S regions. In addition, JP8Bdel enhanced c-myc/IgH translocations. Our findings indicate that the C-terminal domain of AID is not required for S-region DNA breaks but is required for S-region recombination after DNA cleavage. Therefore, AID does not distinguish between the V and S regions for cleavage, but carries another function specific to CSR.
