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标题：Role of RAG1 autoubiquitination in V(D)J recombination
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作者：Samarendra K. Singh ; Martin Gellert
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：2015
卷号：112
期号：28
页码：8579-8583
DOI：10.1073/pnas.1510464112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceThe immune system of vertebrates has to respond to a great variety of infectious agents. Its power to meet these challenges relies on the assembly of a diverse set of genes for antibodies and T-cell receptors from large arrays of gene segments. This genomic reshuffling, known as V(D)J recombination, is initiated by the RAG1 and RAG2 proteins working together to cut DNA at specific sites. In addition to its role in DNA cleavage, RAG1 is known to contain a ubiquitin ligase activity that attaches ubiquitin to itself, as well as other proteins. Here we show that ubiquitination of RAG1, which can be promoted by RAG1's own ubiquitin ligase activity, is a powerful activator of the DNA cutting and recombination activity of RAG1/RAG2. The variable domains of Ig and T-cell receptor genes in vertebrates are assembled from gene fragments by the V(D)J recombination process. The RAG1-RAG2 recombinase (RAG1/2) initiates this recombination by cutting DNA at the borders of recombination signal sequences (RSS) and their neighboring gene segments. The RAG1 protein is also known to contain a ubiquitin E3 ligase activity, located in an N-terminal region that is not strictly required for the basic recombination reaction but helps to regulate recombination. The isolated E3 ligase domain was earlier shown to ubiquitinate one site in a neighboring RAG1 sequence. Here we show that autoubiquitination of full-length RAG1 at this specific residue (K233) results in a large increase of DNA cleavage by RAG1/2. A mutational block of the ubiquitination site abolishes this effect and inhibits recombination of a test substrate in mouse cells. Thus, ubiquitination of RAG1, which can be promoted by RAG1's own ubiquitin ligase activity, plays a significant role in governing the level of V(D)J recombination activity.
关键词：ubiquitin ; immunoglobulin ; diversification