An exosome is a piece of cell machinery which degrades RNA.
Structure of the exosome
The exosome is a complex protein, specific to eukaryotes and archeae, and consists of a central core (formed from six proteins with ribonuclease activity) and annexed proteins (containing an RNA binding domain).
Function of the exosome
The purpose of the exosome is to degrade RNA molecules; large (messenger RNA) or small (ribosomal RNA, etc.), in order to remove those which are not correct. Degradation occurs progressively from the terminal end (called 3') of the RNA.
The exosome is a circular protein complex. © Reinoutr, Wikimedia, CC by-sa 3.0