Functional compartmentalization has emerged as an important factor modulating the kinetics and specificity of biochemical reactions in the nucleus, including those involved in transcriptional regulation. The glucocorticoid receptor (GR) is a ligand-activated transcription factor that translocates to the nucleus upon hormone stimulation and distributes between the nucleoplasm and membraneless compartments named nuclear foci. While a liquid-liquid phase separation process has been recently proposed to drive the formation of many nuclear compartments, the mechanisms governing the heterogeneous organization of GR in the nucleus and the functional relevance of foci formation remain elusive. We dissected some of the molecular interactions involved in the formation of GR condensates and analyzed the GR structural determinants relevant to this process. We show that GR foci present properties consistent with those expected for biomolecular condensates formed by a liquid-liquid phase separation process in living human cells. Their formation requires an initial interaction of GR with certain chromatin regions at specific locations within the nucleus. Surprisingly, the intrinsically disordered region of GR is not essential for condensate formation, in contrast to many nuclear proteins that require disordered regions to phase separate, while the ligand-binding domain seems essential for that process. We finally show that GR condensates include Mediator, a protein complex involved in transcription regulation. We show that GR foci have properties of liquid condensates and propose that active GR molecules interact with chromatin and recruit multivalent cofactors whose interactions with additional molecules lead to the formation of a focus. The biological relevance of the interactions occurring in GR condensates supports their involvement in transcription regulation.

中文翻译：

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揭示糖皮质激素受体相分离中涉及的分子相互作用。


功能区室化已成为调节细胞核内生化反应动力学和特异性的重要因素，包括那些涉及转录调控的生化反应。糖皮质激素受体（GR）是一种配体激活的转录因子，在激素刺激下易位到细胞核，并分布在核质和称为核灶的无膜区室之间。虽然最近提出了液-液相分离过程来驱动许多核区室的形成，但控制细胞核中 GR 异质组织的机制以及焦点形成的功能相关性仍然难以捉摸。我们剖析了 GR 凝聚物形成中涉及的一些分子相互作用，并分析了与该过程相关的 GR 结构决定因素。我们表明，GR 焦点表现出的特性与人类活细胞中液-液相分离过程形成的生物分子凝聚物的预期特性一致。它们的形成需要 GR 与细胞核内特定位置的某些染色质区域进行初始相互作用。令人惊讶的是，与许多需要无序区域进行相分离的核蛋白相比，GR 本质上无序的区域对于凝聚态形成并不是必需的，而配体结合域似乎对该过程至关重要。我们最终证明 GR 凝聚物包含介体，一种参与转录调控的蛋白质复合物。我们证明GR焦点具有液体凝聚物的特性，并提出活性GR分子与染色质相互作用并招募多价辅因子，这些多价辅因子与其他分子的相互作用导致焦点的形成。 GR 凝聚物中发生的相互作用的生物学相关性支持它们参与转录调控。