Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, USA.
J Exp Med. 2010 Dec 20;207(13):2809-16. doi: 10.1084/jem.20101136. Epub 2010 Nov 29.
V(D)J recombination assembles antigen receptor genes in a well-defined order during lymphocyte development. This sequential process has long been understood in the context of the accessibility model, which states that V(D)J recombination is regulated by controlling the ability of the recombination machinery to gain access to its chromosomal substrates. Indeed, many features of "open" chromatin correlate with V(D)J recombination, and promoters and enhancers have been strongly implicated in creating a recombinase-accessible configuration in neighboring chromatin. An important prediction of the accessibility model is that cis-elements and transcription control binding of the recombination-activating gene 1 (RAG1) and RAG2 proteins to their DNA targets. However, this prediction has not been tested directly. In this study, we use mutant Tcra and Tcrb alleles to demonstrate that enhancers control RAG1 binding globally at Jα or Dβ/Jβ gene segments, that promoters and transcription direct RAG1 binding locally, and that RAG1 binding can be targeted in the absence of RAG2. These findings reveal important features of the genetic mechanisms that regulate RAG binding and provide a direct confirmation of the accessibility model.
V(D)J 重组在淋巴细胞发育过程中以确定的顺序组装抗原受体基因。在可及性模型的背景下，人们长期以来一直理解这个顺序过程，该模型指出 V(D)J 重组受控制重组机制获得其染色体底物的能力的调节。事实上，许多“开放”染色质的特征与 V(D)J 重组相关，并且启动子和增强子强烈暗示在相邻染色质中创建一个可重组酶进入的构象。可及性模型的一个重要预测是顺式元件和转录控制重组激活基因 1 (RAG1) 和 RAG2 蛋白与其 DNA 靶标的结合。然而，这一预测尚未得到直接验证。在这项研究中，我们使用突变的 Tcra 和 Tcrb 等位基因来证明增强子全局控制 Jα 或 Dβ/Jβ 基因片段上的 RAG1 结合，启动子和转录指导局部的 RAG1 结合，并且在没有 RAG2 的情况下可以靶向 RAG1 结合。这些发现揭示了调节 RAG 结合的遗传机制的重要特征，并直接证实了可及性模型。
