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：2020
卷号：117
期号：21
页码：11624-11635
DOI：10.1073/pnas.1921115117
出版社：The National Academy of Sciences of the United States of America
摘要：Activation-induced cytidine deaminase (AID) is the key enzyme for class switch recombination (CSR) and somatic hypermutation (SHM) to generate antibody memory. Previously, heterogeneous nuclear ribonucleoprotein K (hnRNP K) was shown to be required for AID-dependent DNA breaks. Here, we defined the function of major RNA-binding motifs of hnRNP K, GXXGs and RGGs in the K-homology (KH) and the K-protein-interaction (KI) domains, respectively. Mutation of GXXG, RGG, or both impaired CSR, SHM, and cMyc/IgH translocation equally, showing that these motifs were necessary for AID-dependent DNA breaks. AID–hnRNP K interaction is dependent on RNA; hence, mutation of these RNA-binding motifs abolished the interaction with AID, as expected. Some of the polypyrimidine sequence-carrying prototypical hnRNP K-binding RNAs, which participate in DNA breaks or repair bound to hnRNP K in a GXXG and RGG motif-dependent manner. Mutation of the GXXG and RGG motifs decreased nuclear retention of hnRNP K. Together with the previous finding that nuclear localization of AID is necessary for its function, lower nuclear retention of these mutants may worsen their functional deficiency, which is also caused by their decreased RNA-binding capacity. In summary, hnRNP K contributed to AID-dependent DNA breaks with all of its major RNA-binding motifs.
关键词：activation-induced cytidine deaminase ; heterogeneous nuclear ribonucleoprotein K ; RNA-binding motifs ; DNA breaks ; IgH
