title: Regulation of the arsenic-responsive transcription factor Yap8p involves the ubiquitin-proteasome pathway.
abstract: 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.
authors.affiliation: Department of Cell and Molecular Biology/Microbiology, Göteborg University, S-405 30 Göteborg, Sweden.
authors.forename: Yujun
authors.initials: Y
authors.lastname: Di
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Tamás
mesh_terms: D000409:Alanine / Q000378:metabolism; D019943:Amino Acid Substitution; D001151:Arsenic / Q000494:pharmacology*; D018053:Arsenites / Q000494:pharmacology; D050976:Basic-Leucine Zipper Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015153:Blotting, Western; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D010957:Plasmids; D011233:Precipitin Tests; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013997:Time Factors; D015533:Transcriptional Activation; D025801:Ubiquitin / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000235:genetics / Q000378:metabolism; D001616:beta-Galactosidase / Q000032:analysis / Q000378:metabolism
chemical_list: C494591:ARR1 protein, S cerevisiae; D018053:Arsenites; D050976:Basic-Leucine Zipper Transcription Factors; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; C501306:Ubc4 protein, S cerevisiae; D044763:Ubiquitin-Conjugating Enzymes; D001616:beta-Galactosidase; D046988:Proteasome Endopeptidase Complex; D003545:Cysteine; C015001:arsenite; D001151:Arsenic; D000409:Alanine