Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, USA.
Department of Biochemistry and Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN, USA
Life Sci Alliance. 2022 Jul 19;5(12):e202201536. doi: 10.26508/lsa.202201536.
Mounting evidence implicates liquid-liquid phase separation (LLPS), the condensation of biomolecules into liquid-like droplets in the formation and dissolution of membraneless intracellular organelles (MLOs). Cells use MLOs or condensates for various biological processes, including emergency signaling and spatiotemporal control over steady-state biochemical reactions and heterochromatin formation. Insulator proteins are architectural elements involved in establishing independent domains of transcriptional activity within eukaryotic genomes. In <i>Drosophila</i>, insulator proteins form nuclear foci known as insulator bodies in response to osmotic stress. However, the mechanism through which insulator proteins assemble into bodies is yet to be investigated. Here, we identify signatures of LLPS by insulator bodies, including high disorder tendency in insulator proteins, scaffold-client-dependent assembly, extensive fusion behavior, sphericity, and sensitivity to 1,6-hexanediol. We also show that the cohesin subunit Rad21 is a component of insulator bodies, adding to the known insulator protein constituents and γH2Av. Our data suggest a concerted role of cohesin and insulator proteins in insulator body formation and under physiological conditions. We propose a mechanism whereby these architectural proteins modulate 3D genome organization through LLPS.
越来越多的证据表明，液-液相分离（LLPS），即生物分子在无膜细胞内细胞器（MLOs）的形成和溶解过程中凝聚成类似液体的液滴，与 MLOs 或液滴的形成有关。细胞利用 MLOs 或液滴进行各种生物学过程，包括紧急信号传递以及对稳态生化反应和异染色质形成的时空控制。绝缘子蛋白是参与建立真核基因组中独立转录活性区域的结构元件。在<i>果蝇</i>中，绝缘子蛋白在响应渗透胁迫时形成称为绝缘子体的核焦点。然而，绝缘子蛋白组装成体的机制仍有待研究。在这里，我们通过绝缘子体鉴定出液-液相分离的特征，包括绝缘子蛋白的高无序倾向、支架-客户依赖性组装、广泛的融合行为、球形和对 1,6-己二醇的敏感性。我们还表明，黏连蛋白亚基 Rad21 是绝缘子体的一个组成部分，增加了已知的绝缘子蛋白成分和 γH2Av。我们的数据表明黏连蛋白和绝缘子蛋白在绝缘子体形成中具有协同作用，并且在生理条件下具有协同作用。我们提出了一种机制，即这些结构蛋白通过液-液相分离来调节 3D 基因组组织。
