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First published online 2 January 2007
doi: 10.1242/jcs.03346

Journal of Cell Science 120, 256-264 (2007)
Published by The Company of Biologists 2007
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Research Article

Regulation of the arsenic-responsive transcription factor Yap8p involves the ubiquitin-proteasome pathway

Yujun Di and Markus J. Tamás*

Department of Cell and Molecular Biology/Microbiology, Göteborg University, S-405 30 Göteborg, Sweden

* Author for correspondence (e-mail: markus.tamas{at}gmm.gu.se)

Accepted 8 November 2006

Toxic metals are ubiquitous in the environment and all organisms possess systems to evade toxicity and acquire tolerance. The Saccharomyces cerevisiae AP-1-like protein Yap8p (systematic name YPR199c; also known as Acr1p and Arr1p) confers arsenic tolerance by stimulating enhanced transcription of the arsenic-specific detoxification genes ACR2 and ACR3. Here, we report that Yap8p is regulated at the level of degradation. We show that Yap8p is stabilized in arsenite-exposed cells in a time- and dose-dependent manner. Yap8p degradation proceeds through the ubiquitin-proteasome pathway and is dependent on the ubiquitin-conjugating enzyme Ubc4p. Further, we show that mutants that are defective in the ubiquitin-proteasome pathway display increased Yap8p levels and elevated expression of the Yap8p gene-target ACR3. Yap8p forms homodimers in vivo but dimerization is not regulated by arsenite. Instead, arsenite-stimulated Yap8p stabilization and transcriptional activation of ACR3 requires critical cysteine residues within Yap8p. Collectively, our data is consistent with a model where Yap8p is degraded by the ubiquitin-proteasome pathway in untreated cells, whereas arsenite-exposure results in Yap8p stabilization and gene activation. In this way, regulated degradation contributes to Yap8p control.

Key words: Arsenite, Yap8p, Ubiquitin-proteasome pathway, Protein degradation, Yeast


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© The Company of Biologists Ltd 2007