2017/08/02 by Zhu Chao Gu, Edwin S. C. Wu, Edwin Wu +14
Biochemistry, Genetics and Molecular Biology · Medicine · #Autophagy in Disease and Therapy #Endoplasmic Reticulum Stress and Disease #Ubiquitin and proteasome pathways
paper · doi:10.1091/mbc.e17-03-0162
openalex publication_date 2017/08/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Proteasomes are essential for protein degradation in proliferating cells. Little is known about proteasome functions in quiescent cells. In nondividing yeast, a eukaryotic model of quiescence, proteasomes are depleted from the nucleus and accumulate in motile cytosolic granules termed proteasome storage granules (PSGs). PSGs enhance resistance to genotoxic stress and confer fitness during aging. Upon exit from quiescence PSGs dissolve, and proteasomes are rapidly delivered into the nucleus. To identify key players in PSG organization, we performed high-throughput imaging of green fluorescent protein (GFP)-labeled proteasomes in the yeast null-mutant collection. Mutants with reduced levels of ubiquitin are impaired in PSG formation. Colocalization studies of PSGs with proteins of the yeast GFP collection, mass spectrometry, and direct stochastic optical reconstitution microscopy of cross-linked PSGs revealed that PSGs are densely packed with proteasomes and contain ubiquitin but no polyubiquitin chains. Our results provide insight into proteasome dynamics between proliferating and quiescent yeast in response to cellular requirements for ubiquitin-dependent degradation.