Sem1p is a novel subunit of the 26 S proteasome from Saccharomyces cerevisiae

J Biol Chem. 2004 Jul 2;279(27):28807-16. doi: 10.1074/jbc.M403165200. Epub 2004 Apr 26.

Abstract

The 26 S proteasome, which catalyzes degradation of polyubiquitinated proteins, is composed of the 20 S proteasome and the 19 S regulatory particle (RP). The RP is composed of the lid and base subcomplexes and regulates the catalytic activity of the 20 S proteasome. In this study, we carried out affinity purification of the lid and base subcomplexes from the tagged strains of Saccharomyces cerevisiae, and we found that the lid contains a small molecular mass protein, Sem1. The Sem1 protein binds with the 26 S proteasome isolated from a mutant with deletion of SEM1 but not with the 26 S proteasome from the wild type. The lid lacking Sem1 is unstable at a high salt concentration. The 19 S RP was immunoprecipitated together with Sem1 by immunoprecipitation using hemagglutinin epitope-tagged Sem1 as bait. Degradation of polyubiquitinated proteins in vivo or in vitro is impaired in the Sem1-deficient 26 S proteasome. In addition, genetic interaction between SEM1 and RPN10 was detected. The human Sem1 homologue hDSS1 was found to be a functional homologue of Sem1 and capable of interacting with the human 26 S proteasome. The results suggest that Sem1, possibly hDSS1, is a novel subunit of the 26 S proteasome and plays a role in ubiquitin-dependent proteolysis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Catalysis
  • Cell Line
  • Cysteine Endopeptidases / metabolism
  • Electrophoresis, Polyacrylamide Gel
  • Epitopes / chemistry
  • Gene Deletion
  • Genetic Complementation Test
  • Glutathione Transferase / metabolism
  • Hemagglutinins / chemistry
  • Humans
  • Multienzyme Complexes / metabolism
  • Mutation
  • Peptide Hydrolases / chemistry
  • Peptide Hydrolases / metabolism*
  • Peptides / chemistry
  • Phenotype
  • Precipitin Tests
  • Proteasome Endopeptidase Complex
  • Protein Conformation
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / metabolism
  • Salts / pharmacology
  • Temperature
  • Time Factors
  • Transfection
  • Ubiquitin / chemistry

Substances

  • Epitopes
  • Hemagglutinins
  • Multienzyme Complexes
  • Peptides
  • SEM1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Salts
  • Ubiquitin
  • Glutathione Transferase
  • Peptide Hydrolases
  • Cysteine Endopeptidases
  • Proteasome Endopeptidase Complex
  • ATP dependent 26S protease