title: Functional dissection of the glucose signaling pathways that regulate the yeast glucose transporter gene (HXT) repressor Rgt1.
abstract: The yeast Rgt1 repressor is a bifunctional protein that acts as a transcriptional repressor and activator. Under glucose-limited conditions, Rgt1 induces transcriptional repression by forming a repressive complex with its corepressors Mth1 and Std1. Here, we show that Rgt1 is converted from a transcriptional repressor into an activator under high glucose conditions and this occurs through two independent but consecutive events mediated by two glucose signaling pathways: (1) disruption of the repressive complex by the Rgt2/Snf3 pathway; (2) phosphorylation of Rgt1 by the cAMP-dependent protein kinase (cAMP-PKA) pathway. Rgt1 is phosphorylated by PKA at four serine residues within its amino-terminal region, but this does not occur until the repressive complex is disrupted. While phosphorylation of any one of these sites is sufficient to enable Rgt1 to induce transcriptional activation, phosphorylation of all the sites results in the release of Rgt1 from DNA. We discuss how the bifunctional properties of Rgt1 are regulated through differential phosphorylation.
authors: Department of Biological Sciences, The University of Southern Mississippi, 118 College Dr., Hattiesburg, Mississippi 39406, USA.
authors: David
authors: D
authors: Jouandot
authors: Adhiraj
authors: A
authors: Roy
authors: Jeong-Ho
authors: JH
authors: Kim
mesh_terms: D055162:Biocatalysis; D015153:Blotting, Western; D047369:Chromatin Immunoprecipitation; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C102114:RGT1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D017868:Cyclic AMP-Dependent Protein Kinases; D005947:Glucose