title: A cryptic protease couples deubiquitination and degradation by the proteasome.
abstract: The 26S proteasome is responsible for most intracellular proteolysis in eukaryotes. Efficient substrate recognition relies on conjugation of substrates with multiple ubiquitin molecules and recognition of the polyubiquitin moiety by the 19S regulatory complex--a multisubunit assembly that is bound to either end of the cylindrical 20S proteasome core. Only unfolded proteins can pass through narrow axial channels into the central proteolytic chamber of the 20S core, so the attached polyubiquitin chain must be released to allow full translocation of the substrate polypeptide. Whereas unfolding is rate-limiting for the degradation of some substrates and appears to involve chaperone-like activities associated with the proteasome, the importance and mechanism of degradation-associated deubiquitination has remained unclear. Here we report that the POH1 (also known as Rpn11 in yeast) subunit of the 19S complex is responsible for substrate deubiquitination during proteasomal degradation. The inability to remove ubiquitin can be rate-limiting for degradation in vitro and is lethal to yeast. Unlike all other known deubiquitinating enzymes (DUBs) that are cysteine proteases, POH1 appears to be a Zn(2+)-dependent protease.
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018432:Drug Resistance, Multiple; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal / Q000235:genetics; D005804:Genes, Lethal; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010059:Ovomucin / Q000737:chemistry / Q000378:metabolism; D010447:Peptide Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011489:Protein Denaturation; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; C109285:PSMD14 protein, human; D021122:Protein Subunits; C115451:RPN11 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014452:Ubiquitins; D010059:Ovomucin; D010450:Endopeptidases; D010447:Peptide Hydrolases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; C119011:26S proteasome non-ATPase regulatory subunit 13; D000251:Adenosine Triphosphatases; D015032:Zinc