NSF/MCB-BSF: Mechanism of liquid-liquid phase separation in pathway-specific transcription regulation

这项研究的目的是确定人类细胞如何对给定的激素或生长因子产生特定的生物结果。在动物中，细胞暴露在各种调节激素和生长因子中，这些激素和生长因子充当信号，导致细胞采取不同的命运，包括生长、存活、获得特定功能(如产生胰岛素)，或成为一种特殊的细胞类型，如神经元。这些激素或生长因子不能进入细胞，因此依赖细胞内的一系列蛋白质将信号传递到细胞核，并协调基因表达的变化，导致特定的生物结果。一个关键的悬而未决的问题是，这些信号蛋白如何激活高度特定的基因集，以回应一种激素。这种信号特异性对于正常发育和细胞功能是必不可少的。这种特异性的破坏会导致发育缺陷和其他疾病。这项研究项目由加州大学伯克利分校的Luo实验室和特拉维夫大学的Henis实验室共同努力，将剖析一条重要信号通路的分子基础，以了解单一信号如何产生不同的细胞结果，这是信号转导中的一个长期难题。该项目还将有助于对博士后研究员、本科生和研究生进行跨学科教育和培训，包括代表人数不足的少数族裔研究生。最后，预计该项目将通过发布主要发现和共享试剂，为更广泛的科学界做出贡献。河马信号通路将被用作该项目的模型系统。河马信号通过两个同源转录效应因子TAZ和YAP调节多种生物学过程。虽然它们在很大程度上执行非冗余功能，但这种功能特异性是如何实现的尚不清楚。最近，一种被称为液-液相分离(LLP)的过程被发现，它允许细胞内的蛋白质在细胞内形成无膜凝聚体。我们的初步研究表明，TAZ，而不是YAP，与其重要的功能伙伴一起，通过LLP形成核凝聚。我们建议TAZ可以使用LLP来分隔其伙伴蛋白，这些蛋白在物理上不同的结构域中执行类似的功能，从而实现有效的基因表达和途径隔离来产生特异性。将进行生化和生物物理研究，以确定TAZ LLPs的分子基础，并确定TAZ LLPs的组装机制。如果成功，这项研究将提供一种新的范式来解决多个细胞内途径的信号特异性的广泛问题，并对基础细胞生物学有许多影响。该项目由生物科学管理局分子和细胞生物科学部门的细胞动力学和功能计划和遗传机制计划联合资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The objective of this research is to determine how a human cell generates specific biological outcomes in response to a given hormone or growth factor. In animals, cells are exposed to a variety of regulatory hormones and growth factors that act as a signal to cause the cells to adopt different fates, including growth, survival, acquisition of specific functions such as producing insulin, or becoming a special cell type such as a neuron. These hormones or growth factors cannot enter cells and thus rely on a series of proteins inside the cell to transmit the signals into the cell nucleus and orchestrate the changes in gene expression, leading to specific biological outcomes. A key unanswered question is how these signaling proteins activate highly specific sets of genes in response to a hormone. This signaling specificity is essential for normal development and cell function. Disruption of this specificity results in defects in development and other diseases. This research project, a collaborative effort of the Luo lab at UC Berkeley and the Henis lab at Tel Aviv University, will dissect the molecular basis of an important signaling pathway to understand how a single signal can create different cellular outcomes, a long-standing puzzle in signal transduction. The project will also contribute to interdisciplinary education and training of postdoctoral fellows, undergraduate and graduate students, including an underrepresented minority graduate student. Finally, the project is expected to contribute to the broader scientific community through publication of the major findings and sharing of reagents.The Hippo signaling pathway will be used as a model system for this project. Hippo signaling regulates multiple biological processes via two homologous transcription effectors, TAZ and YAP. Although they perform largely non-redundant functions, how this functional specificity is achieved is unknown. Recently a process called liquid-liquid phase separation (LLPS) has been discovered that allows intracellular proteins to form membraneless condensates inside the cells. Our preliminary study has shown that TAZ, but not YAP, forms nuclear condensates via LLPS together with its important functional partners. We propose that TAZ may employ LLPS to compartmenta¬lize its partner proteins that perform similar functions within a physically distinct domain, enabling efficient gene expression and pathway insulation to generate specificity. Biochemical and biophysical studies will be performed to define the molecular basis of TAZ LLPS and to determine the mechanisms of TAZ LLPS assembly. If successful, this research will provide a new paradigm to address the broad question of signaling specificity for multiple intracellular pathways and has many implications for fundamental cell biology.This project is jointly funded by the Cellular Dynamics and Function program and the Genetic Mechanisms program of the Molecular and Cellular Biosciences Division in the Biological Sciences Directorate.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.