Phase separation of Ki-67 during mitotic exit

划分成功能单位是细胞生命的关键原则。除了膜结合的细胞器，真核细胞利用无膜生物分子凝聚物局部浓缩蛋白质和核酸。虽然我们开始了解无膜冷凝物组装和拆卸的基本原理，但我们对在这种冷凝物表面发生的生物过程知之甚少。有丝分裂染色体是最大的无膜细胞集合体，其表面被内在无序的蛋白质Ki-67所覆盖。我们以前的研究表明Ki-67具有双重功能。在早期有丝分裂中，Ki-67作为表面活性剂发挥作用，以防止染色体塌陷成单个染色质团，而在退出有丝分裂期间，Ki-67积极促进染色体聚类。Ki-67如何在这两种相反的活动-染色体扩散和染色体聚类-之间切换仍然未知。在这里，我概述了一个跨学科的研究计划，结合细胞生物学和蛋白质组学的方法与新的体外重建系统，以深入了解的物理化学性质，Ki-67的开关从染色体排斥染色体引诱。该项目的结果不仅有可能揭示有丝分裂染色体的生物物理性质的新见解，而且有可能揭示发生在无膜组件表面的细胞组织的新的一般原则。

Compartmentalization into functional units is a key principle of cellular life. In addition to membrane-bound organelles, eukaryotic cells utilize membrane-less biomolecular condensates to locally concentrate proteins and nucleic acids. While we are beginning to understand the principles that underlie membrane-less condensate assembly and disassembly, we know very little about the biological processes that take place at the surface of such condensates. The surface of the largest membrane-less cellular assembly, the mitotic chromosome, is covered by the intrinsically disordered protein Ki-67. Our previous studies have revealed that Ki-67 has dual functionality. In early mitosis, Ki-67 functions as a surfactant to prevent chromosomes from collapsing into a single chromatin mass, whereas it actively promotes chromosome clustering during exit from mitosis. How Ki-67 switches between these two opposing activities – chromosome dispersal and chromosome clustering – has remained unknown. Here, I outline an interdisciplinary research program that combines cell biological and proteomics approaches with novel in-vitro reconstitution systems to gain insight into the physicochemical properties that underlie the switch of Ki-67 from chromosome repellent to chromosome attractant. The results from this project have the potential to not only reveal new insights into the biophysical nature of mitotic chromosomes but have the potential to reveal new general principles of cellular organization that occur on the surface of membrane-less assemblies.