Chromosomal Loop Domains Direct the Recombination of Antigen Receptor Genes.
Chromosomal Loop Domains Direct the Recombination of Antigen Receptor Genes.
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DOI：
10.1016/j.cell.2015.10.016
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发表时间：
2015-11-05
期刊：
影响因子：
64.5
通讯作者：
Alt FW
中科院分区：
文献类型：
--
作者：
Hu J;Zhang Y;Zhao L;Frock RL;Du Z;Meyers RM;Meng FL;Schatz DG;Alt FW
RAG通过在匹配的真正重组信号序列（RSS）对处产生“靶向”DNA断裂来启动抗体V（D）J在发育中的淋巴细胞中的重组。我们采用诱饵RAG产生的内源性或异位插入的RSS对的休息，以确定大量的RAG“脱靶”休息。这种断裂发生在简单的CAC基序，定义了RSS切割位点，并在很大程度上被限制在收敛的CTCF结合元件（CBE）侧翼环域含有诱饵RSS对。RAG脱靶活性在跨越高达2兆碱基的环内的显著方向依赖性意味着涉及线性跟踪。在这方面，染色体易位中的主要RAG脱靶在环内的增强子处作为会聚的RSS对发生。最后，基于CBE的IgH基因座元件的缺失破坏了V（D）J重组结构域，并且相应地改变了IgH内的RAG在靶和脱靶分布。我们的研究结果揭示了RAG活动是如何发展的重点和牵连的机制，染色质结构域利用生物过程中。
RAG initiates antibody V(D)J recombination in developing lymphocytes by generating “on-target” DNA breaks at matched pairs of bona fide recombination signal sequences (RSSs). We employ bait RAG-generated breaks in endogenous or ectopically-inserted RSS pairs to identify huge numbers of RAG “off-target” breaks. Such breaks occur at the simple CAC motif that defines the RSS cleavage-site and are largely confined within convergent CTCF-binding element (CBE)-flanked loop domains containing bait RSS pairs. Marked orientation-dependence of RAG off-target activity within loops spanning up to 2 megabases implies involvement of linear tracking. In this regard, major RAG off-targets in chromosomal translocations occur as convergent RSS pairs at enhancers within a loop. Finally, deletion of a CBE-based IgH locus element disrupts V(D)J recombination domains and, correspondingly, alters RAG on- and off-target distributions within IgH. Our findings reveal how RAG activity is developmentally focused and implicate mechanisms by which chromatin domains harness biological processes within them.