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Mol Cell. 2002 Jul;10(1):69-80.

Dual regulation of the met4 transcription factor by ubiquitin-dependent degradation and inhibition of promoter recruitment.

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Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91198 Gif-sur-Yvettte, France.


The ubiquitin system has been recently implicated in various aspects of transcriptional regulation, including proteasome-dependent degradation of transcriptional activators. In yeast, the activator Met4 is inhibited by the SCF(Met30) ubiquitin ligase, which recognizes and oligo-ubiquitylates Met4. Here, we demonstrate that in minimal media, Met4 is ubiquitylated and rapidly degraded in response to methionine excess, whereas in rich media, Met4 is oligo-ubiquitylated but remains stable. In the latter growth condition, oligo-ubiquitylated Met4 is not recruited to MET gene promoters, but is recruited to the SAM genes, which are required for production of S-adenosylmethionine, an unstable metabolite that is not present in rich medium. Thus, ubiquitylation not only regulates Met4 by distinct degradation-dependent and -independent mechanisms, but also controls differential recruitment of a single transcription factor to distinct promoters, thereby diversifying transcriptional activator specificity.

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