Department of Molecular Biology and Genetics and Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Laboratory of Molecular Biology and Immunology, National Institute on Aging, Baltimore, Maryland, USA.
Mol Cell Biol. 2018 Jul 16;38(15). doi: 10.1128/MCB.00159-18. Print 2018 Aug 1.
Accessibility of antigen receptor loci to RAG is correlated with the presence of H3K4me3, which binds to a plant homeodomain (PHD) in the RAG-2 subunit and promotes V(D)J recombination. A point mutation in the PHD, W453A, eliminates binding of H3K4me3 and impairs recombination. The debilitating effect of the W453A mutation is ameliorated by second-site mutations that locate an inhibitory domain in the interval from residues 352 through 405 of RAG-2. Disruption of the inhibitory domain stimulates V(D)J recombination within extrachromosomal substrates and at endogenous antigen receptor loci. Association of RAG-1 and RAG-2 with chromatin at the locus in B cell progenitors is dependent on recognition of H3K4me3 by the PHD. Strikingly, disruption of the inhibitory domain permits association of RAG with the locus in the absence of H3K4me3 binding. Thus, the inhibitory domain acts as a gate that prohibits RAG from accessing the locus unless RAG-2 is engaged by H3K4me3.
抗原受体基因座对 RAG 的可及性与 H3K4me3 的存在相关，H3K4me3 与 RAG-2 亚基中的植物同源域 (PHD) 结合，促进 V(D)J 重组。PHD 中的一个点突变 W453A 消除了 H3K4me3 的结合，并损害了重组。W453A 突变的削弱作用可以通过第二点突变得到改善，第二点突变将抑制域定位在 RAG-2 的残基 352 到 405 之间的区间内。抑制域的破坏刺激了染色体外底物和内源性抗原受体基因座中的 V(D)J 重组。B 细胞祖细胞中 RAG-1 和 RAG-2 与 基因座染色质的关联取决于 PHD 对 H3K4me3 的识别。引人注目的是，抑制域的破坏允许 RAG 在没有 H3K4me3 结合的情况下与 基因座关联。因此，抑制域充当一个门，除非 RAG-2 被 H3K4me3 结合，否则阻止 RAG 进入 基因座。
