Proteolytic signaling by polyubiquitin chains

超出提供的空间。泛素化是多种生物过程中的信号，包括内吞作用、细胞内蛋白运输、DNA修复、激酶激活和蛋白酶体蛋白分解。泛素(Ub)标记的这些多重结果表明，存在区分不同Ub结合蛋白的机制。本研究要检验的一个中心假设是，不同的结果可能在一定程度上取决于Ub组装成不同类型的多聚Ub链(涉及Ub的不同Lys残基)，然后这些多聚Ub链受到不同因素的识别。拟议的研究通过分析蛋白酶体对含有两种不同类型的PolyUb链(通过Lys-48或Lys-29连接)的底物的识别和处理来验证这一假说，因为我们的初步结果表明，这两种类型的链可能被蛋白酶体有效地识别，但有差异地识别。我们还将比较多泛素化底物的蛋白酶体降解，差异仅在于存在或不存在与底物线性融合的泛素部分，以解决a)解开泛素的需要如何影响依赖于蛋白酶体的降解速度和途径，以及b)含有CDC48/VCP的蛋白酶体外伴侣复合体如何在泛素融合底物的降解中发挥作用。蛋白酶体抑制剂目前正处于治疗某些癌症的晚期临床试验阶段。从我们的研究结果中，我们将对26S蛋白酶体的基本功能有更好的理解，并最终发现改进抑制剂设计策略的可能性。最后，我们将研究在单个Hect结构域Ub连接酶(E3)催化的不同多聚Ub链组装中催化和特异性的分子决定因素。如果这些研究成功，他们将提供重要的新信息，关于亚基突变被翻译成特定下游事件的分子机制。这项研究的结果也将为揭示26S蛋白酶体的机制提供新的线索，它是真核细胞中调节蛋白降解的主要实体。表演网站========================================Section End===========================================

EXCEED THE SPACE PROVIDED. Ubiquitination is a signal in diverse biological processes, including endocytosis, intracellular protein trafficking, DNA repair, kinase activation, and proteasomal proteolysis. These multiple consequences of ubiquitin (Ub) tagging indicate that there are mechanisms to discriminate among different Ub-conjugated proteins. A central hypothesis to be tested in this research is that differential outcomes can rely, in part, on the assembly of Ub into different types of polyUb chains (involving different Lys residues of Ub), which are then subject to recognition by distinct factors. The proposed research tests this hypothesis through analyses of the proteasomal recognition and processing of substrates carrying two different types of polyUb chains (linked through Lys-48 or Lys-29) because our preliminary results suggest that these two types of chains may be productively, but differentially, recognized by proteasomes. We will also compare the proteasomal degradation of polyubiquitinated substrates that differ only in the presence or absence of a ubiquitin moiety that is linearly fused to the substrate, in order to address a) how the need to unfold ubiquitin influences the rate and pathway of proteasome-dependent degradation and b) how an extraproteasomal chaperone complex containing Cdc48/VCP functions in the degradation of ubiquitin-fused substrates. Proteasome inhibitors are currently in late-stage clinical trials for the treatment of certain cancers. From the results of our research will come an improved understanding of the basic functioning of 26S proteasomes, and ultimately, the possiblity of improved strategies for inhibitor design. Finally, we will study the molecular determinants of catalysis and specificity in the assembly of different polyUb chains as catalyzed by a single HECT domain Ub ligase (E3). If these studies are successful, they will provide important new information about the molecular mechanisms by which ubqiutination is translated into specific downstream events. The results of this research will also shed new light on the mechanism of the 26S proteasome, which is the major entity for regulatory proteolysis in eukaryotic cells. PERFORMANCE SITE ========================================Section End===========================================