Feedback‐regulated degradation of the transcriptional activator Met4 is triggered by the SCFMet30 complex

Astrid Rouillon, Régine Barbey, E.Elizabeth Patton, Mike Tyers, Dominique Thomas

Author Affiliations

  1. Astrid Rouillon1,
  2. Régine Barbey1,
  3. E.Elizabeth Patton2,3,
  4. Mike Tyers2 and
  5. Dominique Thomas*,1
  1. 1 Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91198, Gif‐sur‐Yvette, France
  2. 2 Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, M5G 1X5, Canada
  3. 3 Graduate Department of Molecular and Medical Genetics, University of Toronto, Toronto, Canada, M5S 1A8
  1. *Corresponding author. E-mail: thomas{at}
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Saccharomyces cerevisiae SCFMet30 ubiquitin–protein ligase controls cell cycle function and sulfur amino acid metabolism. We report here that the SCFMet30 complex mediates the transcriptional repression of the MET gene network by triggering degradation of the transcriptional activator Met4p when intracellular S‐adenosylmethionine (AdoMet) increases. This AdoMet‐induced Met4p degradation is dependent upon the 26S proteasome function. Unlike Met4p, the other components of the specific transcriptional activation complexes that are assembled upstream of the MET genes do not appear to be regulated at the protein level. We provide evidence that the interaction between Met4p and the F‐box protein Met30p occurs irrespective of the level of intracellular AdoMet, suggesting that the timing of Met4p degradation is not controlled by its interaction with the SCFMet30 complex. We also demonstrate that Met30p is a short‐lived protein, which localizes within the nucleus. Furthermore, transcription of the MET30 gene is regulated by intracellular AdoMet levels and is dependent upon the Met4p transcription activation function. Thus Met4p appears to control its own degradation by regulating the amount of assembled SCFMet30 ubiquitin ligase.

  • Received September 6, 1999.
  • Revision received November 8, 1999.
  • Accepted November 11, 1999.
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