Transcription Control by the Ubiquitin-Proteasome System

描述(由申请人提供)：转录调节和泛素介导的蛋白分解是控制细胞生长和发育的两个重要过程。与它们在维持细胞动态平衡方面的关键作用一致，转录和泛素介导的蛋白质破坏的解除调控是包括癌症在内的各种人类疾病的核心。乍一看，这两个过程显然没有什么共同之处--转录是任何蛋白质生命的第一步，蛋白质分解是最后一步。然而，尽管这些过程的性质不同，但越来越多的证据表明，泛素-蛋白酶体系统的组件直接参与了基因表达的调节。这些过程的联系揭示了我们急于探索的转录控制的以前没有预料到的水平。这项提议定义了一种研究策略，以调查泛素依赖的过程如何调节转录调控中的三个关键角色-转录激活因子、RNA聚合酶和组蛋白的活性。这些研究将与对蛋白酶体成分在基因激活中的作用的高度整合的分析相补充。为了实现这一目标，我们将使用遗传和生化方法相结合的模式生物酿酒酵母。我们将研究典型酵母激活剂Gal4的泛素化如何将转录激活与共转录前信使RNA处理所需的事件联系起来。我们将研究RNA聚合酶II最大亚基的泛素化如何调节聚合酶活性和亚基组成，以及组蛋白H2B的泛素化如何调节组蛋白动态以及染色质与核环境的相互作用。最后，我们将研究蛋白酶体亚基是如何被招募到染色质中的，以及它们在基因激活和转录沉默中的功能。这些研究的结果将为转录和泛素-蛋白酶体系统如何相交提供有价值的见解，并将为我们理解转录调控的这一新维度提供一个范例。重要的是，我们的工作还将为理解这些过程如何导致人类疾病提供一个智力框架，并提供通过调节泛素系统的活性来确定调节异常转录的方法的可能性；这一策略很可能形成改进的癌症治疗的基础。

DESCRIPTION (provided by applicant): Transcriptional regulation and ubiquitin-mediated proteolysis are two processes that feature prominently in the control of cell growth and development. Consistent with their pivotal roles in maintaining cellular homeostasis, deregulation of both transcription and ubiquitin-mediated protein destruction lies at the heart of a variety of human diseases, including cancer. At first blush, these two processes have apparently very little in common-transcription is the first step in the life of any protein; proteolysis is the last. Despite the disparate nature of these processes, however, a growing body of evidence suggests that components of the ubiquitin-proteasome system are directly involved in the regulation of gene expression. The connection of these processes reveals a previously unanticipated level of transcriptional control that we are anxious to explore. This proposal defines a research strategy to investigate how ubiquitin-dependent processes regulate the activity of three key players in transcriptional regulation-transcriptional activators, RNA polymerase, and histones. These studies will be complemented with a highly-integrated analysis of the role of proteasome components in gene activation. To achieve this objective, we will employ a combination of genetic and biochemical approaches using the model organism Saccharomyces cerevisiae. We will study how ubiquitylation of the prototypical yeast activator Gal4 connects transcriptional activation to events required for co-transcriptional pre-messenger RNA processing. We will investigate how ubiquitylation of the largest subunit of RNA polymerase II regulates polymerase activity and subunit composition, and how ubiquitylation of histone H2B modulates histone dynamics and interaction of chromatin with the nuclear environment. And, finally, we will study how proteasome subunits are recruited to chromatin and their function in both gene activation and transcriptional silencing. Results of these studies will provide valuable insight into how transcription and the ubiquitin-proteasome systems intersect, and will serve as a paradigm for our understanding of this new dimension in transcriptional control. Importantly, our work will also provide an intellectual framework for understanding how these processes contribute to human disease, and offers the potential to identify ways to regulate aberrant transcription by modulating the activity of the ubiquitin system; a strategy that could very-well form the basis of improved cancer therapies.