title: Tpk3 and Snf1 protein kinases regulate Rgt1 association with Saccharomyces cerevisiae HXK2 promoter.
abstract: Hexokinase 2 is an essential factor for signalling repression through the Saccharomyces cerevisiae high-glucose sensing pathway. The main regulatory mechanism that controls the HXK2 gene expression in yeast is mediated by the Rgt1 and Med8 transcription factors, which repress HXK2 expression in low-glucose containing media. In this study, we show that the repression activity of Rgt1 is regulated by Snf1 and Tpk3 protein kinases. Binding of Rgt1 to the HXK2 promoter requires Rgt1 phosphorylation by Snf1 or by an Snf1-dependent protein kinase. Conversely, Rgt1 hyperphosphorylation by the Tpk3 or by a Tpk3-dependent protein kinase dissociates Rgt1 from the repressor complex. Two-hybrid and chromatin immunoprecipitation experiments indicate that an Snf1-dependent interaction between Rgt1 and Med8 in the repressor complex is also essential for Rgt1 repression. The repression of HXK2 transcription by Rgt1 likely occurs through the formation of a DNA loop in the HXK2 locus, spanning the promoter and coding regions. These results suggest that a novel silent-chromatin loop is responsible for Rgt1-dependent transcriptional regulation of the HXK2 gene.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Universidad de Oviedo, 33006-Oviedo, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Palomino
authors.forename: P
authors.initials: P
authors.lastname: Herrero
authors.forename: F
authors.initials: F
authors.lastname: Moreno
mesh_terms: D001665:Binding Sites; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology*; D004271:DNA, Fungal / Q000378:metabolism; D004268:DNA-Binding Proteins; D015966:Gene Expression Regulation, Fungal; D005947:Glucose / Q000494:pharmacology; D006593:Hexokinase / Q000235:genetics* / Q000378:metabolism; D056892:Mediator Complex; D008957:Models, Genetic; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D012097:Repressor Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C421882:MED8 protein, S cerevisiae; D056892:Mediator Complex; C102114:RGT1 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C071570:SNF1-related protein kinases; C490214:HXK2 protein, S cerevisiae; D006593:Hexokinase; D017346:Protein Serine-Threonine Kinases; D054751:Cyclic AMP-Dependent Protein Kinase Catalytic Subunits; D017868:Cyclic AMP-Dependent Protein Kinases; C509333:Tpk3 protein, S cerevisiae; D005947:Glucose