Erkennung proteolytischer Substrate durch Cdc20 und Hct1, Rezeptoren der Ubiquitin-Ligase APC (Recognition of proteolytic substrates by Cdc20 and Hct1, receptors of the ubiquitin-ligase APC)

泛素-蛋白酶体系统的蛋白质水解在真核细胞分裂周期中发挥重要作用。一种称为后期促进复合物（APC）的多亚基泛素连接酶控制染色体分离和退出有丝分裂。APC与两种相关的WD蛋白（在芽殖酵母中称为Cdc 20和Hct 1）合作，在有丝分裂和G1期间泛素化后期抑制剂、各种B型细胞周期蛋白和其他蛋白质底物。该建议的目的是定义APC招募其底物的分子步骤。我们最近观察到，Hct 1可以结合APC底物的特定子集，这表明WD蛋白可能作为底物受体发挥作用。为了遵循这个想法，我们将研究Cdc 20的结合模式。此外，我们将确定底物，WD蛋白和APC的相互作用域，并进一步研究Cdc 20和Hct 1的细胞周期调控。通过这些和进一步的研究，我们希望建立一个底物识别过程的详细图片。

Proteolysis by the ubiquitin-proteasome-system serves essential functions in the eukaryotic cell division cycle. A multi-subunit ubiquitin ligase termed anaphase promoting complex (APC) controls chromosome separation and exit from mitosis. The APC cooperates with two related WD proteins, called Cdc20 and Hct1 in budding yeast, to ubiquitinate an anaphase inhibitor, various B-type cyclins and other protein substrates during mitosis and G1. The objective of this proposal is to define the molecular steps by which the APC recruits its substrates. We most recently observed that Hct1 can bind a specific subset of APC substrates suggesting that WD proteins may function as substrate receptors. To follow this idea we will study the binding pattern of Cdc20. We will moreover determine interaction domains in substrates, WD proteins and the APC, and further investigate the cell cycle regulation of Cdc20 and Hct1. By these and further studies we wish to build a detailed picture of the substrate recognition process.