Abstract
The eukaryotic 26S proteasome is a large multi-subunit complex that degrades the majority of proteins in the cell under normal conditions. The 26S proteasome can be divided into two subcomplexes: the 19S regulatory particle (RP) and the 20S core particle (CP). Most substrates are first covalently modified by ubiquitin, which then directs them to the proteasome. The function of the RP is to recognize, unfold, deubiquitylate and translocate substrates into the CP, which contains the proteolytic sites of the proteasome. Given the abundance and subunit complexity of the proteasome, the assembly of this ~2.5 MDa complex must be carefully orchestrated to ensure its correct formation. In recent years, significant advances have been made in the understanding of proteasome assembly, structure and function. Technical advances in cryo-electron microscopy have resulted in a series of atomic cryo-EM structures of both human and yeast 26S proteasomes. These structures have illuminated new intricacies and dynamics of the proteasome. In this review, we focus on the mechanisms of proteasome assembly, particularly in light of recent structural information.
