Phase separation directs ubiquitination of gene-body nucleosomes
Phase separation directs ubiquitination of gene-body nucleosomes
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DOI：
10.1038/s41586-020-2097-z
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发表时间：
2020-03-11
期刊：
影响因子：
64.8
通讯作者：
Koehler, Alwin
中科院分区：
文献类型：
--
作者：
Gallego, Laura D.;Schneider, Maren;Koehler, Alwin
酵母 E3 连接酶 Bre1 与支架蛋白 Lge1 形成核壳缩合物，表明液-液相分离是组蛋白 H2B 沿基因体泛素化的机制。保守的酵母 E3 泛素连接酶 Bre1 及其伴侣 E2 泛素结合酶 Rad6，跨基因单泛素化组蛋白 H2B 转录周期中的身体(1)。尽管原则上进行性泛素化可能是由随 RNA 聚合酶 II2 移动的 Bre1 和 Rad6 产生的，但跨基因核小体的 H2B 泛素化机制仍不清楚。在这里，我们将液-液相分离（3）作为基本机制。生化重建显示 Bre1 结合支架蛋白 Lge1，该蛋白具有本质上无序的区域，通过多价相互作用进行相分离。所得的缩合物包含被 Bre1 催化外壳包裹的 Lge1 核心。这种分层液体吸收 Rad6 和核小体底物，加速 H2B 的泛素化。在体内，Lge1 的缩合物形成区域需要泛素化 +1 核小体以外的基因体中的 H2B。我们的数据表明，组蛋白修饰酶的层状缩合物会产生染色质相关的“反应室”，并增强基因体的催化活性。人体细胞中也可能发生类似的过程，当受损时会导致神经系统疾病。
The yeast E3 ligase Bre1 forms a core-shell condensate with the scaffold protein Lge1, implicating liquid-liquid phase separation as a mechanism in the ubiquitination of histone H2B along gene bodies.The conserved yeast E3 ubiquitin ligase Bre1 and its partner, the E2 ubiquitin-conjugating enzyme Rad6, monoubiquitinate histone H2B across gene bodies during the transcription cycle(1). Although processive ubiquitination might-in principle-arise from Bre1 and Rad6 travelling with RNA polymerase II2, the mechanism of H2B ubiquitination across genic nucleosomes remains unclear. Here we implicate liquid-liquid phase separation(3) as the underlying mechanism. Biochemical reconstitution shows that Bre1 binds the scaffold protein Lge1, which possesses an intrinsically disordered region that phase-separates via multivalent interactions. The resulting condensates comprise a core of Lge1 encapsulated by an outer catalytic shell of Bre1. This layered liquid recruits Rad6 and the nucleosomal substrate, which accelerates the ubiquitination of H2B. In vivo, the condensate-forming region of Lge1 is required to ubiquitinate H2B in gene bodies beyond the +1 nucleosome. Our data suggest that layered condensates of histone-modifying enzymes generate chromatin-associated 'reaction chambers', with augmented catalytic activity along gene bodies. Equivalent processes may occur in human cells, and cause neurological disease when impaired.