title: The Hsp70 homolog Ssb and the 14-3-3 protein Bmh1 jointly regulate transcription of glucose repressed genes in Saccharomyces cerevisiae.
abstract: Chaperones of the Hsp70 family interact with a multitude of newly synthesized polypeptides and prevent their aggregation. Saccharomyces cerevisiae cells lacking the Hsp70 homolog Ssb suffer from pleiotropic defects, among others a defect in glucose-repression. The highly conserved heterotrimeric kinase SNF1/AMPK (AMP-activated protein kinase) is required for the release from glucose-repression in yeast and is a key regulator of energy balance also in mammalian cells. When glucose is available the phosphatase Glc7 keeps SNF1 in its inactive, dephosphorylated state. Dephosphorylation depends on Reg1, which mediates targeting of Glc7 to its substrate SNF1. Here we show that the defect in glucose-repression in the absence of Ssb is due to the ability of the chaperone to bridge between the SNF1 and Glc7 complexes. Ssb performs this post-translational function in concert with the 14-3-3 protein Bmh, to which Ssb binds via its very C-terminus. Raising the intracellular concentration of Ssb or Bmh enabled Glc7 to dephosphorylate SNF1 even in the absence of Reg1. By that Ssb and Bmh efficiently suppressed transcriptional deregulation of Δreg1 cells. The findings reveal that Ssb and Bmh comprise a new chaperone module, which is involved in the fine tuning of a phosphorylation-dependent switch between respiration and fermentation.
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Hübscher
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Kaivalya
authors.initials: K
authors.lastname: Mudholkar
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, D-79104 Freiburg, Germany BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Chiabudini
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Edith
authors.initials: E
authors.lastname: Fitzke
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Tina
authors.initials: T
authors.lastname: Wölfle
authors.affiliation: Genomics Lab, Department of Hematology, Oncology and Stem Cell Transplantation, University Medical Center, University of Freiburg, D-79106 Freiburg, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Pfeifer
authors.affiliation: BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany Department of Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Friedel
authors.initials: F
authors.lastname: Drepper
authors.affiliation: BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany Department of Biochemistry and Functional Proteomics, Faculty of Biology, University of Freiburg, D-79104 Freiburg, Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Warscheid
authors.affiliation: Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg, D-79104 Freiburg, Germany BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany sabine.rospert@biochemie.uni-freiburg.de.
authors.forename: Sabine
authors.initials: S
authors.lastname: Rospert
mesh_terms: D048948:14-3-3 Proteins / Q000235:genetics / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000235:genetics*; D005285:Fermentation / Q000235:genetics; D005947:Glucose / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D012119:Respiration / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D048948:14-3-3 Proteins; C075852:BMH1 protein, S cerevisiae; D018840:HSP70 Heat-Shock Proteins; C095192:SSB1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C071570:SNF1-related protein kinases; D017346:Protein Serine-Threonine Kinases; C092048:GLC7 protein, S cerevisiae; D054645:Protein Phosphatase 1; C070829:REG1 protein, S cerevisiae; D000251:Adenosine Triphosphatases; C494470:SSB2 protein, S cerevisiae; D005947:Glucose