About EXOSC / Exosome Component:
EXOSC genes encode a multiple protein intracellular complex and mediate the degradation of several types of RNA molecules. EXOSCs are found in archaea and eukaryotic cells and mainly mediate 3' to 5'mRNA degradation. A simpler complex known as the degradosome performs similar functions in bacteria.
Exosome Component Function
The proteins CD9, CD63, CD81, and CD82 (tetraspanins) participate in cell invasion, fusion, and penetration events. Also, heat shock EXOSC proteins HSP70 and HSP90 are integral to the stress response process and are involved in binding and presenting antigens. Additionally, TSG101 and Alix are MVB formation proteins that participate in the exosome release process. Annexins and Rab are also responsible for membrane fusion and transport. Finally, among these EXOSC proteins, certain types like ALinx, TSG101, and flotillin partake in exosome biogenesis. Others enriched in exosomes, like TSG101, CD81, CD63, and HSP70, are mainly used as exosomal marker proteins.
Exosome component 2 is known to interact with Exosome components 4 and 8. Exosome component 6 is also known to interact with Exosome component 1, Exosome component 7, and Exosome component 8. Finally, Exosome component 1 is known to interact with Exosome component 5, Exosome component 6, and Exosome component 7.
Exosome Component Structure
The RNA exosome includes ten conserved subunits that make a ring-like structure. This subunit core exosome contains a central, inert, six-subunit ring, a three-subunit cap, and an active ribonuclease associated with the base’s subunit ring. The eukaryotic RNA exosome has an eleventh RNA exonuclease sub-unit associated with the cap within the nucleus.