Ubiquitin-Dependent Proteolysis: Specificity & Mechanism

描述：这项研究的长期目标是了解泛素结构域是如何被识别为靶向信号的。泛素结构域是一种广泛使用的多种多样的靶向信号，翻译后与多种细胞蛋白结合。泛素途径与生长控制(癌症和细胞凋亡)、信号转导(炎症和转录控制)和应激反应(蛋白质质量控制、神经退化和基因组完整性)有关。结构域的结合用于修饰目标蛋白的定位或活性。单个泛素与组蛋白的结合参与染色质和DMA交易，并在内体分选途径中作为分选信号。NEDD8连接调控泛素E3连接，而SUMO-1(小泛素样修饰物)连接广泛参与核蛋白代谢。目标蛋白的多泛素化(或SUMO化)是通过赖氨酸残基将一个泛素连接到另一个泛素上而实现的。K48连接的多聚泛素是一种将目标蛋白运送到蛋白酶体进行蛋白降解的信号，而K63连接的链参与了NFkB途径中信号复合体的组装，并在DNA修复中发挥了一些未知的作用。还观察到通过赖氨酸6、11、29和33的连接，尽管这些链以及PolySUMO-2/3链的功能完全未知。统一的假设是，存在特定的受体或适配器，它们特异性地识别不同的泛素结构域和上下文，并随后将结合的蛋白质导向适当的细胞命运。这项研究建议通过研究多聚泛素的识别和定义区分不同版本泛素结构域的受体和结合蛋白来定义不同链连接的一些潜在作用。这里使用了两种方法。首先，定向方法使用脱泛素化酶作为多泛素的特异性识别模型，通过直接识别(USP5/异肽酶T，AIM 1)或通过适配器辅助识别特定底物(BAP1，AIM 2)。第二，现代系统生物学方法利用我们合成的多泛素链类似物来鉴定具有不同泛素结构域和不同结构的特异性的泛素结合蛋白(目标3)。

DESCRIPTION: The long-term goal of this research is to understand how the ubiquitin domain is recognized as a targeting signal. The ubiquitin domain is a diverse and widely used targeting signal that is post- translationally attached to a variety of cellular proteins. The ubiquitin pathway is implicated in growth control (cancer and apoptosis), signal transduction (inflammation and transcriptional control), and the stress response (protein quality control, neurodegeneration, and genome integrity). Conjugation of the domain serves to modify the localization or activities of the target protein. Conjugation of a single ubiquitin to histones is involved in chromatin and DMA transactions and as a sorting signal in endosomal sorting pathways. NEDD8 conjugation regulated ubiquitin E3 liganses while SUMO-1 (small ubiquitin-like modifier) conjugation is widely involved in nuclear protein metaboslism. Poly ubiquitination (or SUMOylation) of target proteins is achieved by attachment of one ubiquitin to another through lysine residues. K48-Iinked polyubiquitin is a signal for delivery of the target protein to the proteasome for proteolysis while K63-linked chains are involved in assembling signaling complexes in the NFkB pathway and play some undetermined role in DNA repair. Linkages through lysines 6,11, 29, and 33 are also observed, although the function of these chains, as well as that of polySUMO-2/3 chains is completely unknown. The unifying hypothesis is that there are specific receptors or adapters that specifically recognize the different ubiquitin domains and contexts and that subsequently direct the conjugated protein to the appropriate cellular fate. This study proposes to define some of the potential roles of the different chain linkages by studying polyubiquitin recognition and defining the receptors and binding proteins that distinguish among different version of the ubiquitin domain. Two approaches are used here. First, a directed approach uses deubiquitinating enzymes as a model for specific recognition of polyubiquitin, either by direct recognition (USP5/isopeptidase T, Aim 1) or by adapter-assisted recognition of specific substrates (BAP1, Aim 2). Second, a modern systems biology approach takes advantage of our synthesis of polyubiquitin chain analogs to identify ubiquitin-binding proteins with specificity for different ubiquitin domains and different architectures (Aim 3).