Characterization of native and reconstituted exosome complexes from the hyperthermophilic archaeon Sulfolobus solfataricus

• Published in: Molecular microbiology 2006-11, Vol.62 (4), p.1076-1089
• Main Authors: Walter, Pamela, Klein, Franziska, Lorentzen, Esben, Ilchmann, Anne, Klug, Gabriele, Evguenieva‐Hackenberg, Elena
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases; Archaea; Archaeal Proteins - chemistry; Archaeal Proteins - metabolism; Bacteriology; Biological and medical sciences; Cell Cycle Proteins - chemistry; DNA Primase - chemistry; DNA Primase - metabolism; Eukaryotes; Exoribonucleases - chemistry; Exoribonucleases - metabolism; Fundamental and applied biological sciences. Psychology; Marine; Microbiology; Miscellaneous; Molecular structure; Multiprotein Complexes - chemistry; Multiprotein Complexes - metabolism; Proteins; Ribonucleic acid; RNA; RNA - metabolism; RNA Stability; Studies; Sulfolobus solfataricus; Sulfolobus solfataricus - chemistry; Sulfolobus solfataricus - cytology; Sulfolobus solfataricus - enzymology; Valosin Containing Protein
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/j.1365-2958.2006.05393.x

Summary The eukaryotic exosome is a protein complex with essential functions in processing and degradation of RNA. Exosome‐like complexes were recently found in Archaea. Here we characterize the exosome of Sulfolobus solfataricus. Two exosome fractions can be discriminated by density gradient centrifugation. We show that the Cdc48 protein is associated with the exosome from the 30S−50S fraction but not with the exosome of the 11.3S fraction. While only some complexes contain Cdc48, the archaeal DnaG‐like protein was found to be a core exosome subunit in addition to Rrp4, Rrp41, Rrp42 and Csl4. Assays with depleted extracts revealed that the exosome is responsible for major ribonucleolytic activity in S. solfataricus. Various complexes consisting of the Rrp41‐Rrp42 hexameric ring and Rrp4, Csl4 and DnaG were reconstituted. Dependent on their composition, different complexes showed variations in RNase activity indicating functional interdependence of the subunits. The catalytic activity of these complexes and of the native exosome can be ascribed to the Rrp41‐Rrp42 ring, which degrades RNA phosphorolytically. Rrp4 and Csl4 do not exhibit any hydrolytic RNase activity, either when assayed alone or in context of the complex, but influence the activity of the archaeal exosome.