Regulation by Proteolysis-Independent Ubiquitination

描述(申请人提供)：泛素化，即小蛋白泛素与其他蛋白质的共价结合，调节一系列细胞过程。蛋白质泛素化已成为蛋白质降解的代名词。然而，我们开始认识到，一些蛋白质是由泛素化以一种不依赖于蛋白质降解的方式调节的。目前的研究大多集中在泛素在26S蛋白酶体降解靶向蛋白中的作用。然而，蛋白质组的方法表明，许多蛋白质受蛋白质降解-非依赖泛素化的调控，对这些过程的详细了解对于生物医学研究显然是重要的。其中一些关键问题是：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的活性？泛素以不依赖蛋白分解的方式调节的蛋白质是否共享序列结构域？在这项建议中，我们使用酵母转录因子Met4作为模型来研究蛋白降解非依赖性泛素化(AIM1)调节蛋白质活性的机制；泛素结合结构域在保护泛素蛋白免受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中的作用(目标2)；以及通过泛素化而不降解调节蛋白质活性的生理益处(目标3)。在目标4中，我们使用蛋白质组范围的方法来识别受蛋白质降解非依赖泛素化调控的蛋白质，并应用生物信息学策略来识别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、神经退行性变和逆转录病毒感染。在这些疾病中，蛋白分解非依赖泛素化的作用正在显现，了解这一调节背后的机制以设计诊断工具和治疗策略将是重要的。这项建议旨在实现对泛素对蛋白质降解非依赖性调节的详细机制洞察，并定义这一调节泛素化途径的一些特征。

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.