Mediator factor Med8p interacts with the hexokinase 2: implication in the glucose signalling pathway of Saccharomyces cerevisiae.
In the presence of glucose the protein hexokinase 2 (Hxk2p), normally resident in the cytosol, is translocated to the nucleus where it impairs the activation of transcription of the glucose-repressed genes HXK1, GLK1 and SUC2, and promotes the activation of transcription of the glucose-induced genes HXK2 and HXT1. Here, we demonstrate the involvement of an heptameric motif, named the MED8 site, in the direct binding of the mediator protein Med8p, either as a monomer or as a homodimer. Because this site was previously involved in the Hxk2p-dependent glucose-induced regulation of gene transcription, we tested whether Hxk2p interacts with Med8p. Our results show that Hxk2 and Med8 proteins are physically associated and that this Hxk2p-Med8p interaction is of physiological significance because both proteins have been found interacting together in a cluster with DNA fragments containing the MED8 site. We conclude that Hxk2p operates through the MED8 site, by interacting with Med8p, in the glucose signal transduction pathway of Saccharomyces cerevisiae.
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Departamento de Bioquímica y Biología Molecular, Inst. Univ. de Biotoecn. de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain
Herrero
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Moreno-Herrero
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Chaves
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Moreno
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D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D019281:Dimerization; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal / Q000187:drug effects; D005800:Genes, Fungal / Q000235:genetics; D005947:Glucose / Q000494:pharmacology*; D006593:Hexokinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D056892:Mediator Complex; D018625:Microscopy, Atomic Force; D011233:Precipitin Tests; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction / Q000187:drug effects*; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C421882:MED8 protein, S cerevisiae; D056892:Mediator Complex; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D006593:Hexokinase; D005947:Glucose