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分解作用在真核细胞分裂周期中起着至关重要的作用。一种称为后期促进复合体(APC)的多亚基泛素连接酶控制着染色体的分离和退出有丝分裂。APC与两个相关的WD蛋白合作，在萌芽酵母中称为CDc20和Hct1，在有丝分裂和G1期泛素化后期抑制物、各种B型周期蛋白和其他蛋白质底物。这项提案的目的是定义APC招募底物的分子步骤。我们最近观察到Hct1可以与特定的APC底物结合，这表明WD蛋白可能作为底物受体发挥作用。为了遵循这一想法，我们将研究Cdc20的结合模式。此外，我们还将确定底物、WD蛋白和APC中的相互作用结构域，并进一步研究CDc20和Hct1对细胞周期的调控。通过这些和进一步的研究，我们希望对底物识别过程有一个详细的了解。

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.