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AID Recognizes Structured DNA for Class Switch Recombination
Molecular Cell ( IF 16.0 ) Pub Date : 2017-07-27 , DOI: 10.1016/j.molcel.2017.06.034
Qi Qiao , Li Wang , Fei-Long Meng , Joyce K. Hwang , Frederick W. Alt , Hao Wu

Activation-induced cytidine deaminase (AID) initiates both class switch recombination (CSR) and somatic hypermutation (SHM) in antibody diversification. Mechanisms of AID targeting and catalysis remain elusive despite its critical immunological roles and off-target effects in tumorigenesis. Here, we produced active human AID and revealed its preferred recognition and deamination of structured substrates. G-quadruplex (G4)-containing substrates mimicking the mammalian immunoglobulin switch regions are particularly good AID substrates in vitro. By solving crystal structures of maltose binding protein (MBP)-fused AID alone and in complex with deoxycytidine monophosphate, we surprisingly identify a bifurcated substrate-binding surface that explains structured substrate recognition by capturing two adjacent single-stranded overhangs simultaneously. Moreover, G4 substrates induce cooperative AID oligomerization. Structure-based mutations that disrupt bifurcated substrate recognition or oligomerization both compromise CSR in splenic B cells. Collectively, our data implicate intrinsic preference of AID for structured substrates and uncover the importance of G4 recognition and oligomerization of AID in CSR.



中文翻译:

AID识别用于类开关重组的结构化DNA

激活诱导的胞苷脱氨酶(AID)在抗体多样化中同时引发类开关重组(CSR)和体细胞超突变(SHM)。尽管其在免疫发生中起关键的免疫学作用和脱靶作用,但AID靶向和催化的机制仍然难以捉摸。在这里,我们生产了活性人AID,并揭示了其对结构化底物的首选识别和脱氨基作用。模仿哺乳动物免疫球蛋白转换区的含G-四链体(G4)的底物在体外特别好。通过单独和与脱氧胞苷单磷酸复合解决麦芽糖结合蛋白(MBP)融合的AID的晶体结构,我们出乎意料地确定了分叉的底物结合表面,该表面通过同时捕获两个相邻的单链突出端来解释结构化的底物识别。此外,G4底物诱导协同AID寡聚。破坏分叉的底物识别或寡聚的基于结构的突变均会损害脾脏B细胞中的CSR。总的来说,我们的数据暗示了AID对结构化底物的固有偏好,并揭示了G4识别和AID的低聚在企业社会责任中的重要性。

更新日期:2017-07-27
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