Function and structure of the RNA-processing exosome in the hyperthermophilic archaeon Sulfolobus solfataricus

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While different aspects of RNA processing and degradation are well studied in Eubacteria and Eukarya, little is known about these essential processes in Archaea, the third domain of life. We have isolated a protein complex from the hyperthermophilic archaeon Sulfolobus solfataricus which is a simplified version of the eukaryotic exosome. The eukaryotic exosome is involved in maturation and degradation of RNA, its subunits are essential for cell viability. This project aims to unravel the physiological function of the S. solfataricus exosome and to identify its natural RNA substrates. The in vivo function of the exosome subunits will be studied by gene silencing in S. solfataricus and by complementation of conditional yeast mutants. In addition the biochemical activity of the subunits will be determined in vitro. The exact structure of the eukaryotic exosome could not be solved to date. We like to take advantage of the simpler organization of the archaeal exosome for structural analyses. We will study protein-protein interaction between the individual subunits and reconstitute complexes of different composition for electron microscopic and crystallographic analyses. Our results will build the fundament for future investigations of gene regulation at post-transcriptional level in Archaea, will contribute to our understanding of protein-protein and RNA-protein interactions at high temperatures and will provide interesting aspects on the evolution of RNA processing protein complexes.