title: Ump1p is required for proper maturation of the 20S proteasome and becomes its substrate upon completion of the assembly.
abstract: We report the discovery of a short-lived chaperone that is required for the correct maturation of the eukaryotic 20S proteasome and is destroyed at a specific stage of the assembly process. The S. cerevisiae Ump1p protein is a component of proteasome precursor complexes containing unprocessed beta subunits but is not detected in the mature 20S proteasome. Upon the association of two precursor complexes, Ump1p is encased and is rapidly degraded after the proteolytic sites in the interior of the nascent proteasome are activated. Cells lacking Ump1p exhibit a lack of coordination between the processing of beta subunits and proteasome assembly, resulting in functionally impaired proteasomes. We also show that the propeptide of the Pre2p/Doa3p beta subunit is required for Ump1p's function in proteasome maturation.
authors.affiliation: Biotechnologisches Zentrallabor, Institut für Mikrobiologie, Heinrich-Heine-Universität Düsseldorf, Germany.
authors.forename: P C
authors.initials: PC
authors.lastname: Ramos
authors.forename: J
authors.initials: J
authors.lastname: Höckendorff
authors.forename: E S
authors.initials: ES
authors.lastname: Johnson
authors.forename: A
authors.initials: A
authors.lastname: Varshavsky
authors.forename: R J
authors.initials: RJ
authors.lastname: Dohmen
mesh_terms: D003546:Cysteine Endopeptidases; D010450:Endopeptidases / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D018832:Molecular Chaperones / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D046988:Proteasome Endopeptidase Complex; D011498:Protein Precursors / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D013172:Spores, Fungal / Q000502:physiology; D013379:Substrate Specificity; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D018832:Molecular Chaperones; D011498:Protein Precursors; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; C110856:proteasome maturation protein; D010450:Endopeptidases; D003546:Cysteine Endopeptidases; C080044:PRE2 protein, S cerevisiae; D046988:Proteasome Endopeptidase Complex