Identification of the gal4 suppressor Sug1 as a subunit of the yeast 26S proteasome.
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.
Mesh Terms:
Adenosine Triphosphatases, Amino Acid Sequence, DNA-Binding Proteins, Fungal Proteins, Molecular Sequence Data, Peptide Hydrolases, Proteasome Endopeptidase Complex, Repressor Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transcription Factors
Adenosine Triphosphatases, Amino Acid Sequence, DNA-Binding Proteins, Fungal Proteins, Molecular Sequence Data, Peptide Hydrolases, Proteasome Endopeptidase Complex, Repressor Proteins, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins, Transcription Factors
Nature
Date: Feb. 15, 1996
PubMed ID: 8628401
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