title: Reversible cytoplasmic localization of the proteasome in quiescent yeast cells.
abstract: The 26S proteasome is responsible for the controlled proteolysis of a vast number of proteins, including crucial cell cycle regulators. Accordingly, in Saccharomyces cerevisiae, 26S proteasome function is mandatory for cell cycle progression. In budding yeast, the 26S proteasome is assembled in the nucleus, where it is localized throughout the cell cycle. We report that upon cell entry into quiescence, proteasome subunits massively relocalize from the nucleus into motile cytoplasmic structures. We further demonstrate that these structures are proteasome cytoplasmic reservoirs that are rapidly mobilized upon exit from quiescence. Therefore, we have named these previously unknown structures proteasome storage granules (PSGs). Finally, we observe conserved formation and mobilization of these PSGs in the evolutionary distant yeast Schizosaccharomyces pombe. This conservation implies a broad significance for these proteasome reserves.
authors.affiliation: Institut de Biochimie et Génétique Cellulaires, Université Victor Segalen Bordeaux II, 33077 Bordeaux, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Laporte
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Salin
authors.forename: Bertrand
authors.initials: B
authors.lastname: Daignan-Fornier
authors.forename: Isabelle
authors.initials: I
authors.lastname: Sagot
mesh_terms: D000199:Actins / Q000378:metabolism; D002453:Cell Cycle; D003593:Cytoplasm / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000378:metabolism; D008954:Models, Biological; D046988:Proteasome Endopeptidase Complex / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000378:metabolism*; D013696:Temperature
chemical_list: D000199:Actins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease