Stress- and ubiquitylation-dependent phase separation of the proteasome

Yasuda, Sayaka; Tsuchiya, Hikaru; Kaiho, Ai; Guo, Qiang; Ikeuchi, Ken; Endo, Akinori; Arai, Naoko; Ohtake, Fumiaki; Murata, Shigeo; Inada, Toshifumi; Baumeister, Wolfgang; Fernandez-Busnadiego, Ruben; Tanaka, Keiji und Saeki, Yasushi (2020): Stress- and ubiquitylation-dependent phase separation of the proteasome. In: Nature, Bd. 578, Nr. 7794: S. 296-300

Abstract

The proteasome is a major proteolytic machine that regulates cellular proteostasis through selective degradation of ubiquitylated proteins(1,2). A number of ubiquitin-related molecules have recently been found to be involved in the regulation of biomolecular condensates or membraneless organelles, which arise by liquid-liquid phase separation of specific biomolecules, including stress granules, nuclear speckles and autophagosomes(3-8), but it remains unclear whether the proteasome also participates in such regulation. Here we reveal that proteasome-containing nuclear foci form under acute hyperosmotic stress. These foci are transient structures that contain ubiquitylated proteins, p97 (also known as valosin-containing protein (VCP)) and multiple proteasome-interacting proteins, which collectively constitute a proteolytic centre. The major substrates for degradation by these foci were ribosomal proteins that failed to properly assemble. Notably, the proteasome foci exhibited properties of liquid droplets. RAD23B, a substrate-shuttling factor for the proteasome, and ubiquitylated proteins were necessary for formation of proteasome foci. In mechanistic terms, a liquid-liquid phase separation was triggered by multivalent interactions of two ubiquitin-associated domains of RAD23B and ubiquitin chains consisting of four or more ubiquitin molecules. Collectively, our results suggest that ubiquitin-chain-dependent phase separation induces the formation of a nuclear proteolytic compartment that promotes proteasomal degradation. Hyperosmotic stress leads to a phase separation of the proteasome, triggered by interactions between RAD23B and ubiquitylated proteins, which bring together p97 and proteasome-associated proteins into nuclear proteolytic foci.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Chemie und Pharmazie > Department Biochemie
• Fakultätsübergreifende Einrichtungen: Center for Integrated Protein Science Munich (CIPSM)
• Themengebiete: 500 Naturwissenschaften und Mathematik > 540 Chemie
• ISSN: 0028-0836
• Sprache: Englisch