Cytoplasmic organization by phase separation

项目总结/摘要（PI Gladfelter，AS） 细胞必须在时间和空间上划分生物化学。一种新的组织机制 是生物分子凝聚。在许多情况下，凝聚物通过弱的多价相互作用形成， 无序的蛋白质和核酸。这些相互作用决定了凝聚物的物质状态， 如粘度、表面张力和孔隙度，这些又会影响浓度、反应和传输速率 在关键成分的浓缩物中。在理解细胞如何控制 冷凝物在哪里形成，哪些分子共同组装，以及冷凝物物质状态如何有助于 功能我们发现了凝聚物在控制核分裂和细胞分裂中的生理功能， 极性的丝状真菌，阿舒囊菌gossypii。这些浓缩物可以控制翻译， 通过一种名为Whi 3的RNA结合蛋白与对核分裂（细胞周期蛋白）和细胞增殖重要的靶RNA结合， 极性（formins）。这个细胞系统的强大之处在于，我们可以将细胞的物理性质和位置联系起来， 浓缩成蛋白质翻译、细胞形状和核分裂的功能输出。的目标 建议的工作是确定蛋白质，RNA和细胞膜中的结构元件如何控制细胞膜的功能。 细胞内冷凝物的物质状态、位置和功能。我们将确定纳米尺度 蛋白质和RNA序列的特征促进了凝聚物的中尺度物理状态在空间上的模式化 蛋白质翻译我们使用先进的成像，遗传，生物物理和建模的跨学科套件 解决这些基本的开放性问题的方法， 系统具体来说，我们将：目标1：确定蛋白质的隐藏结构域的作用。我们 假设瞬时有序状态促进特定的蛋白质-蛋白质相互作用和凝聚 材料性能目标二。建立基于RNA的支架的结构和功能。我们假设 mRNA通过碱基配对形成了一个更高级的网络，决定了凝聚物的性质。目标3： 描述膜平台如何控制冷凝组件。我们假设内膜 提供装配地点，以指明冷凝物的位置。这项工作将定义蛋白质如何 结构，RNA支架和细胞膜被利用来控制性质，功能和位置 细胞中的冷凝物。大量的发现强调了冷凝物的重要性， 冷凝物的形成导致多种人类疾病，包括癌症和神经退行性疾病。 虽然很明显，冷凝物对生物化学的影响是显而易见的，但我们还不知道冷凝物是如何影响生物化学的。 实际上有助于正常的细胞功能，这对于了解它们的功能障碍如何导致人类 病理学

Project Summary/Abstract (PI Gladfelter, AS) Cells must compartmentalize biochemistry in time and space. A newly appreciated mechanism of organization is biomolecular condensation. In many cases, condensates form via weak, multivalent interactions among disordered proteins and nucleic acids. These interactions determine the material states of condensates such as viscosity, surface tension and porosity, which in turn impact the concentrations, reaction and transport rates in, out and within condensates of key constituents. There are major gaps in understanding how cells control where condensates form, which molecules coassemble, and how condensate material state contributes to function. We discovered a physiological function for condensates in controlling nuclear division and cell polarity in the filamentous fungus, Ashbya gossypii. These condensates can control translation and are formed by an RNA-binding protein called Whi3 binding to target RNAs important for nuclear division (cyclins) and cell polarity (formins). The power of this cell system is that we can link physical properties and locations of condensates to functional outputs of protein translation, cell shape and nuclear division. The goals of the proposed work are to determine how structured elements in proteins, RNAs and cell membranes control the material state, location and function of condensates in the cell. We will determine how nanometer scale features of protein and RNA sequences promote mesoscale physical states of condensates to spatially pattern protein translation. We use an interdisciplinary suite of advanced imaging, genetic, biophysical and modeling approaches to tackle these fundamental open problems that not yet understood for any phase-separating system. Specifically, we will: Aim 1: Determine roles of hidden structured domains of proteins. We hypothesize that transiently ordered states promote specific protein-protein interactions and condensate material properties. Aim 2. Establish the architecture and function of RNA-based scaffolds. We hypothesize that mRNA forms a higher-order network using base-pairing that determines condensate properties. Aim 3: Delineate how membrane platforms control condensate assemblies. We hypothesize that endomembranes provide sites of assembly to specify the location of condensates. The proposed work will define how protein structure, RNA scaffolds and cell membranes are harnessed to control the properties, functions and locations of condensates in cells. The importance of condesates is underscored by numerous findings that link aberrant formation of condensates to multiple human diseases, including cancer and neurodegenerative diseases. While it is clear condensates undoubtably impact biochemistry, we do not yet understand how condensates actually contribute to normal cell function which is critical to understand how their malfunction leads to human pathologies.