Exosome-Ski-Complex · Structural and functional studies on how the Ski complex activates the exosome to degrade RNA

Regulation of RNA stability is recognized as a widely used strategy to regulate protein abundance in time and space in all eukaryotes. RNA degradation regulates gene expression in various processes during development and differentiation and in changing physiological conditions. Many elements of the RNA decay machinery have been identified, but details of their function remain elusive.The exosome is a multi-subunit exonuclease complex that functions in turnover, quality control and processing of many RNA species. Depending on its subcellular localization it requires different accessory protein complexes that specifically target RNAs towards the exosome and stimulate the degradation process. In the yeast cytosol the Ski complex is the major accessory factor of the exosome. It is required for nearly all exosome-mediated mRNA degradation processes. The core Ski complex is formed by Ski2, an RNA helicase, the large TPR protein Ski3 and two copies of Ski8. This core complex interacts genetically and physically with the exosome via the GTPase Ski7.In the proposed project, I will study how the activities of the Ski238 complex, Ski7p and the exosome are concerted. For this I will recombinantly express, purify and crystallize the Ski2387 complex alone and together with the exosome to learn about their interaction on atomic level. This approach structural approach will be complemented by electron microscopic studies of the complexes. The results of the structural analysis will guide the design of subsequent functional biochemical and in vivo studies.The study will be exemplary for the understanding of the functioning of an important cellular machinery in atomic detail.