Organization of transcriptional machinery by weak multivalent interactions

项目摘要 蛋白质内在无序区（IDR）介导的弱多价相互作用已经被提出 在空间上将转录机制组织成多组分簇，但我们对如何组织知之甚少。 这些内部发展报告与具体伙伴互动，以实现功能成果。由于这些相互作用是高度 动态的和依赖于簇的它们被识别蛋白质-蛋白质的传统策略所忽视 交互.我们的初步数据支持我们的总体假设，即在高阶集群的背景下， 弱的多价相互作用能够产生高度特异性的异型相互作用， 核心的组织。我们的长期目标是了解弱多价相互作用是如何组织的 转录机器的特定组件，以使基因激活。的目的 本研究旨在探讨MED 1的IDR簇介导的相互作用的机制和功能， 介体辅激活因子复合物的最大亚基。介体是一种连接DNA结合的巨道尔顿复合物 转录因子与激活过程的下游步骤，需要它动态地参与 监管机构的许多组成部分。虽然最近的结构研究揭示了 在这种复合物中，负责多价相互作用的结构域是动态IDR，并且仍然未得到解决。在 特别地，MED 1亚基含有>600个氨基酸的C-末端IDR（MED 1-IDR），其先前公开 研究暗示了集群的形成。我们的初步数据表明，MED 1-IDR集群选择性分区 转录的正调控因子，排除负调控因子或功能无关但丰富的核 proteins.这些数据使我们假设IDR介导的选择性区室化是一种机制， 来调节转录。为了验证这一假设，我们将确认和验证这些集群的特异性- 介导的相互作用（目的1），表征这些相互作用特异性的分子特征 (Aim 2），并研究这些相互作用在各种基因激活模型中的功能（目的3）。后 完成这些拟议的研究，我们将了解弱多价相互作用介导的作用， MED 1-IDR在组织转录机器的特定组件中的作用。这一贡献意义重大 因为它将导致对基因激活中普遍但经常被忽视的IDR功能的新认识。 虽然我们在这里专注于MED 1-IDR，但开发的工具和方法以及在这里学到的原理可以 适用于其他弱多价相互作用涉及基因调控或越来越多的生化 由调节器动态聚集调节的过程。

Project Summary Weak multivalent interactions mediated by intrinsically disordered regions (IDRs) of proteins have been proposed to spatially organize the transcriptional machinery into multi-component clusters, yet we know little about how these IDRs interact with specific partners to enable functional outcomes. As these interactions are highly dynamic and cluster-dependent they have been overlooked by conventional strategies to identify protein-protein interactions. Our preliminary data support our overarching hypothesis that in the context of higher-order clusters weak multivalent interactions are capable of highly specific hetero-typic interactions leading to functional organization of the nucleus. Our long-term objective is to understand how weak multivalent interactions organize specific components of the transcriptional machinery in order to enable gene activation. The objective of this grant is to investigate the mechanism and function of cluster-mediated interactions of the IDR of MED1, the largest subunit of the mediator coactivator complex. Mediator is a megadalton complex that bridges DNA-binding transcription factors with downstream steps of the activation process requiring it to engage dynamically with many components of the regulatory machinery. While recent structural studies have revealed the architecture of this complex, the domains responsible for multivalent interactions are dynamic IDRs and remain unresolved. In particular the MED1 subunit contains a >600 amino acid c-terminal IDR (MED1-IDR) which previously published studies implicate in cluster formation. Our preliminary data show that MED1-IDR clusters selectively partition positive regulators of transcription and exclude negative regulators or functionally unrelated yet abundant nuclear proteins. These data lead us to hypothesize that IDR-mediated selective compartmentalization is a mechanism to regulate transcription. To test this hypothesis we will confirm and validate the specificity of these cluster- mediated interactions (Aim 1), characterize the molecular features underlying specificity of these interactions (Aim 2), and investigate the function of these interactions in various models of gene activation (Aim 3). Upon completion of these proposed studies, we will understand the role of weak multivalent interactions mediated by MED1-IDR in organization of specific components of the transcriptional machinery. This contribution is significant as it will lead to a new appreciation for the function of the prevalent yet often overlooked IDRs in gene activation. While we focus here on MED1-IDR, the tools and methods developed and the principles learned here can be applied to other weak multivalent interactions involved in gene regulation or the growing list of biochemical process regulated by dynamic clustering of regulators.