title: Biochemical evidence for glucose-independent induction of HXT expression in Saccharomyces cerevisiae.
abstract: The yeast glucose sensors Rgt2 and Snf3 generate a signal in response to glucose that leads to degradation of Mth1 and Std1, thereby relieving repression of Rgt1-repressed genes such as the glucose transporter genes (HXT). Mth1 and Std1 are degraded via the Yck1/2 kinase-SCF(Grr1)-26S proteasome pathway triggered by the glucose sensors. Here, we show that RGT2-1 promotes ubiquitination and subsequent degradation of Mth1 and Std1 regardless of the presence of glucose. Site-specific mutagenesis reveals that the conserved lysine residues of Mth1 and Std1 might serve as attachment sites for ubiquitin, and that the potential casein kinase (Yck1/2) sites of serine phosphorylation might control their ubiquitination. Finally, we show that active Snf1 protein kinase in high glucose prevents degradation of Mth1 and Std1.
authors.affiliation: Mississippi Functional Genomics Network, Department of Biological Sciences, The University of Southern Mississippi, Hattiesburg, MS 39406, USA.
authors.forename: Satish
authors.initials: S
authors.lastname: Pasula
authors.forename: David
authors.initials: D
authors.lastname: Jouandot
authors.forename: Jeong-Ho
authors.initials: JH
authors.lastname: Kim
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D001665:Binding Sites; D047389:Casein Kinase I / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D044783:F-Box Proteins; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D008239:Lysine / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology; D009004:Monosaccharide Transport Proteins / Q000235:genetics* / Q000502:physiology; D010766:Phosphorylation; D020033:Protein Isoforms / Q000502:physiology; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism / Q000502:physiology; D025801:Ubiquitin / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D044783:F-Box Proteins; D047908:Intracellular Signaling Peptides and Proteins; C118806:MTH1 protein, S cerevisiae; D008565:Membrane Proteins; D009004:Monosaccharide Transport Proteins; D020033:Protein Isoforms; C112512:RGT2 protein, S cerevisiae; C081335:STD1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; C071032:GRR1 protein, S cerevisiae; D044843:SKP Cullin F-Box Protein Ligases; D044767:Ubiquitin-Protein Ligases; C071570:SNF1-related protein kinases; D047389:Casein Kinase I; D017346:Protein Serine-Threonine Kinases; C479664:YCK1 protein, S cerevisiae; C479666:YCK2 protein, S cerevisiae; D005947:Glucose; D008239:Lysine