The Mouse Immunoglobulin Heavy Chain V-D Intergenic Sequence Contains Insulators That May Regulate Ordered V(D)J Recombination
The Mouse Immunoglobulin Heavy Chain V-D Intergenic Sequence Contains Insulators That May Regulate Ordered V(D)J Recombination
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DOI：
10.1074/jbc.m109.098251
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发表时间：
2010-03-26
影响因子：
4.8
通讯作者：
Corcoran, Anne E.
中科院分区：
文献类型：
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作者：
Featherstone, Karen;Wood, Andrew L.;Corcoran, Anne E.
在免疫球蛋白重链（Igh）V（D）J重组期间，D至J以有序方式先于V至DJ重组，由V和DJ区的不同染色质可及性控制，并且对于正确的抗体组装至关重要。然而，除了内含子增强子E μ，它调节D到J重组，顺式作用的调控元件尚未确定。我们已经组装了一个战略性地位于96-kb的V-D基因间区在小鼠免疫球蛋白的序列，并分析其在淋巴细胞发育过程中的活性。我们表明，E μ依赖的D反义转录，提出打开染色质之前，D到J重组，延伸到V-D区域超过30 kb的B细胞之前，期间和之后V（D）J重组和T细胞，但终止40 kb的第一个V基因。因此，在V到DJ重组之前，随后的V反义转录被积极地阻止，并且必须被独立地激活。为了找到调节这种差异染色质开放的顺式作用元件，我们在V-D区域确定了六个DNase I超敏感位点（HS）。第一个D基因上游的一个保守的HS局部调节D基因。D区附近的两个进一步保守的HS标志着反义转录的急剧下降，并且这两个HS在体内结合CTCF。此外，它们都具有体内增强子阻断活性。因此，我们建议，他们是增强子阻断绝缘体，防止E μ依赖的染色质开口延伸到V区。因此，它们是第一个被鉴定的元件，可以控制有序的V（D）J重组和抗体基因的正确组装。
During immunoglobulin heavy chain (Igh) V(D)J recombination, D to J precedes V to DJ recombination in an ordered manner, controlled by differential chromatin accessibility of the V and DJ regions and essential for correct antibody assembly. However, with the exception of the intronic enhancer E mu, which regulates D to J recombination, cis-acting regulatory elements have not been identified. We have assembled the sequence of a strategically located 96-kb V-D intergenic region in the mouse Igh and analyzed its activity during lymphocyte development. We show that E mu-dependent D antisense transcription, proposed to open chromatin before D to J recombination, extends into the V-D region for more than 30 kb in B cells before, during, and after V(D) J recombination and in T cells but terminates 40 kb from the first V gene. Thus, subsequent V antisense transcription before V to DJ recombination is actively prevented and must be independently activated. To find cis-acting elements that regulate this differential chromatin opening, we identified six DNase I-hypersensitive sites (HSs) in the V-D region. One conserved HS upstream of the first D gene locally regulates D genes. Two further conserved HSs near the D region mark a sharp decrease in antisense transcription, and both HSs bind CTCF in vivo. Further, they both possess enhancer-blocking activity in vivo. Thus, we propose that they are enhancer-blocking insulators preventing E mu-dependent chromatin opening extending into the V region. Thus, they are the first elements identified that may control ordered V(D) J recombination and correct assembly of antibody genes.