V(D)J recombination is initiated by the recombination-activating gene protein (RAG) recombinase, consisting of RAG-1 and RAG-2 subunits. The susceptibility of gene segments to cleavage by RAG is associated with gene transcription and with epigenetic marks characteristic of active chromatin, including histone H3 trimethylated at lysine 4 (H3K4me3). Binding of H3K4me3 by a plant homeodomain (PHD) in RAG-2 induces conformational changes in RAG-1, allosterically stimulating substrate binding and catalysis. To better understand the path of allostery from the RAG-2 PHD finger to RAG-1, here we employed phylogenetic substitution. We observed that a chimeric RAG-2 protein in which the mouse PHD finger is replaced by the corresponding domain from the shark Chiloscyllium punctatum binds H3K4me3 but fails to transmit an allosteric signal, indicating that binding of H3K4me3 by RAG-2 is insufficient to support recombination. By substituting residues in the C. punctatum PHD with the corresponding residues in the mouse PHD and testing for rescue of allostery, we demonstrate that H3K4me3 binding and transmission of an allosteric signal to RAG-1 are separable functions of the RAG-2 PHD finger.

中文翻译：

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组蛋白 H3 Lys-4 三甲基化与重组酶 RAG-1 的结合和变构传递是 RAG-2 植物同源域指的可分离功能。


V(D)J 重组由重组激活基因蛋白 (RAG) 重组酶启动，该重组酶由 RAG-1 和 RAG-2 亚基组成。基因片段对 RAG 切割的敏感性与基因转录和活性染色质的表观遗传标记特征相关，包括在赖氨酸 4 处三甲基化的组蛋白 H3 (H3K4me3)。 RAG-2 中的植物同源结构域 (PHD) 与 H3K4me3 的结合会诱导 RAG-1 的构象变化，从而以变构方式刺激底物结合和催化。为了更好地理解从 RAG-2 PHD 指到 RAG-1 的变构路径，我们在这里采用了系统发育替换。我们观察到，小鼠 PHD 指被鲨鱼 Chiloscyllium punctatum 的相应结构域取代的嵌合 RAG-2 蛋白结合 H3K4me3，但无法传递变构信号，表明 RAG-2 与 H3K4me3 的结合不足以支持重组。通过用小鼠 PHD 中的相应残基替换 C. punctatum PHD 中的残基并测试变构的拯救，我们证明 H3K4me3 结合和变构信号向 RAG-1 的传递是 RAG-2 PHD 指的可分离功能。