Regulation by Proteolysis-Independent Ubiquitination

描述（由申请人提供）：泛素化，小蛋白泛素与其他蛋白的共价连接，调节许多细胞过程。蛋白质泛素化已经成为蛋白质降解的代名词。然而，我们开始认识到，许多蛋白质是由泛素化以一种不依赖于蛋白质水解的方式调节的。目前的研究大多集中在泛素在26S蛋白酶体靶向蛋白降解中的作用。然而，蛋白质组范围内的方法表明，许多蛋白质受蛋白质水解-不依赖泛素化的调节，对这些过程的详细了解显然对生物医学研究很重要。一些关键的问题是：为什么一些泛素化的蛋白质会被降解，而另一些则不会？泛素化如何直接影响蛋白质活性？由泛素以不依赖于蛋白质水解的方式调节的蛋白质是否共享序列结构域？本研究以酵母转录因子Met4为模型，研究非蛋白水解泛素化（aim1）调控蛋白活性的机制；泛素结合结构域在保护泛素化蛋白免受26S蛋白酶体降解中的作用以及泛素结合结构域在调节泛素链长度中的作用（目的2）；以及通过泛素化而不降解来调节蛋白质活性的生理益处（目的3）。在目标4中，我们使用蛋白质组范围的方法来鉴定受蛋白质水解不依赖泛素化调节的蛋白质，并应用生物信息学策略来鉴定共享的蛋白质结构域。泛素化影响许多重要的细胞过程，并与许多人类疾病有关，包括癌症、神经变性和逆转录病毒感染。不依赖蛋白水解的泛素化在这些疾病中的作用正在出现，理解这种调节背后的机制对设计诊断工具和治疗策略将是重要的。本研究旨在深入了解泛素对蛋白水解不依赖的调控机制，并定义这种泛素化调控途径的一些特征。

DESCRIPTION (provided by applicant): Ubiquitination, the covalent attachment of the small protein ubiquitin to other proteins, regulates a host of cellular processes. Protein ubiquitination has become a synonym for protein degradation. However, we are beginning to appreciate that a number of proteins are regulated by ubiquitination in a proteolysis-independent manner. Most of the current research is focused on the role of ubiquitin in targeting proteins for degradation by the 26S proteasome. However, proteome-wide approaches indicate that many proteins are regulated by proteolysis- independent ubiquitination and a detailed understanding of these processes is clearly important for biomedical research. Some of the key questions are: Why are some ubiquitinated proteins degraded and others are not? How can ubiquitination directly affect protein activity? Do proteins that are regulated in a proteolysis-independent manner by ubiquitin share sequence domains? In this proposal we use the yeast transcription factor Met4 as a model to study the mechanism of regulation of protein activity by proteolysis-independent ubiquitination (aim1); the role of ubiquitin-binding domains in protecting ubiquitinated proteins from degradation by the 26S proteasome and the role of ubiquitin-binding domains in regulating ubiquitin chain length (aim 2); and the physiological benefit of regulating protein activity by ubiquitination without degradation (aim 3). In aim 4 we use a proteome-wide approach to identify proteins that are regulated by proteolysis-independent ubiquitination and apply a bioinformatics strategy to identify shared protein domains. Ubiquitination affects many important cellular processes and has been linked to a number of human diseases including cancer, neurodegeneration, and retroviral infection. A contribution of proteolysis-independent ubiquitination in these diseases is emerging and it will be important to understand the mechanism behind this regulation to design diagnostic tools and treatment strategies. This proposal aims to achieve detailed mechanistic insight into proteolysis- independent regulation by ubiquitin and to define some of the characteristics of this regulatory ubiquitination pathway.