Identification of the gal4 suppressor Sug1 as a subunit of the yeast 26S proteasome

Nature. 1996 Feb 15;379(6566):655-7. doi: 10.1038/379655a0.

Abstract

The SUG1 gene of Saccharomyces cerevisiae encodes a putative ATPase. Mutations in SUG1 were isolated as suppressors of a mutation in the transcriptional activation domain of GAL4. Sug1 was recently proposed to be a subunit of the RNA polymerase II holoenzyme and to mediate the association of transcriptional activators with holoenzyme. We show here that Sug1 is not a subunit of the holoenzyme, at least in its purified form, but of the 26S proteasome, a large complex of relative molecular-mass 2,000K that catalyses the ATP-dependent degradation of ubiquitin-protein conjugates. Sug1 co-purifies with the proteasome in both conventional and nickel-chelate affinity chromatography. Our observations account for the reduced ubiquitin-dependent proteolysis in sug1 mutants and suggest that the effects of sug1 mutations on transcription are indirect results of defective proteolysis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases
  • Amino Acid Sequence
  • DNA-Binding Proteins
  • Fungal Proteins / analysis*
  • Fungal Proteins / genetics
  • Molecular Sequence Data
  • Peptide Hydrolases / chemistry*
  • Peptide Hydrolases / genetics
  • Proteasome Endopeptidase Complex*
  • Repressor Proteins / analysis*
  • Repressor Proteins / genetics
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae Proteins*
  • Transcription Factors*

Substances

  • DNA-Binding Proteins
  • Fungal Proteins
  • GAL4 protein, S cerevisiae
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • Peptide Hydrolases
  • Proteasome Endopeptidase Complex
  • ATP dependent 26S protease
  • Adenosine Triphosphatases
  • RPT6 protein, S cerevisiae