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

• Published in: Nature (London) Vol. 379; no. 6566; pp. 655 - 657
• Main Authors: Rubin, David M, Coux, Olivier, Wefes, Inge, Hengartner, Christoph, Young, Richard A, Goldberg, Alfred L, Daniel Finley, Daniel
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 15.02.1996; Nature Publishing Group
• Subjects: Adenosine Triphosphatases; Amino Acid Sequence; Biological and medical sciences; DNA-Binding Proteins; Fundamental and applied biological sciences. Psychology; Fungal Proteins - analysis; Fungal Proteins - genetics; Genes; Genetics; Growth, nutrition, metabolism, transports, enzymes. Molecular biology; Microbiology; Molecular Sequence Data; Mutation; Mycology; Nickel; Peptide Hydrolases - chemistry; Peptide Hydrolases - genetics; Proteasome Endopeptidase Complex; Repressor Proteins - analysis; Repressor Proteins - genetics; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae Proteins; Transcription Factors; Yeast; Yeasts; Fungi; Multicatalytic endopeptidase complex; Yeast; Multienzyme complex; Enzyme; Gene product; Hydrolases; Ascomycetes; Subunit; Proteinases; Saccharomyces cerevisiae; Thallophyta
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/379655a0

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.