[Non-canonical activities of the proteasomes]

Abstract

26S proteasome is a highly specialized evolutionarily conserved ribonucleoprotein machine to instantly restore order in the intracellular proteome. It is composed of the 20S core particle and attached there to regulatory complexes. In addition to a comprehensively studied ubiquitin-proteasome pathway of protein degradation, proteasomes are involved (directly or indirectly) in most stages of the regulation of gene expression (at the levels of transcription, splicing, mRNA stability control, etc.). In the present review an attempt to systematize the recent literature on proteasomes' role in the regulation of transcription at all stages, including the modulation of the activity and stability of transcription factors, chromatin remodulation, elongation and termination of RNA synthesis is made. In addition, very interesting but controversial feature of the proteasome: their ability to bind and hydrolyze certain types of RNA, is observed. Obviously, universal role of proteasomes in gene regulation is determined by complicated composition of these protein complexes possessing a unique set of different enzymatic activities: ATPase/helicase, proteolytic and ribonuclease, which, depending on the case, can be used together or separately.