A distal region involving hepatocyte nuclear factor 4alpha and CAAT/enhancer binding protein markedly potentiates the protein kinase A stimulation of the glucose-6-phosphatase promoter.
Glucose-6-phosphatase (Glc6Pase) is the last enzyme of gluconeogenesis and is only expressed in the liver, kidney, and small intestine. In these tissues, the mRNA and its activity are increased when cAMP levels increased (e.g. in fasting or diabetes). We first report that a proximal region (within -200 bp relative to the transcription start site) and a distal region (-694/-500 bp) are both required for a potent cAMP and a protein kinase A (PKA) responsiveness of the Glc6Pase promoter. Using different molecular approaches, we demonstrate that hepatocyte nuclear factor (HNF4alpha), CAAT/enhancer-binding protein-alpha (C/EBPalpha), C/EBPbeta, and cAMP response element-binding protein (CREB) are involved in the potentiated PKA responsiveness: in the distal region, via one HNF4alpha- and one C/EBP-binding sites, and in the proximal region, via two HNF4alpha and two CREB-binding sites. We also show that HNF4alpha, C/EBPalpha, and C/EBPbeta are constitutively bound to the endogenous Glc6Pase gene, whereas CREB and CREB-binding protein (CBP) will be bound to the gene upon stimulation by cAMP. These data strongly suggest that the cAMP responsiveness of the Glc6Pase promoter requires a tight cooperation between a proximal and a distal region, which depends on the presence of several HNF4alpha-, C/EBP-, and CREB-binding sites, therefore involving an intricate association of hepatic and ubiquitous transcription factors.
Gautier-Stein
Amandine
A
Institut National de la Santé et de la Recherche Médicale, Unité 449/Institut National de la Recherche Agronomique 1235/Université Claude Bernard Lyon 1, Insitut Fédératif de Recherche Laennec, 69372 Lyon cedex 08, France. Amandine.Gautier@univ-lyon1.fr
Mithieux
Gilles
G
Rajas
Fabienne
F
D000818:Animals; D001665:Binding Sites; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D000242:Cyclic AMP / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005952:Glucose-6-Phosphatase / Q000235:genetics*; D051557:Hepatocyte Nuclear Factor 4; D006801:Humans; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011485:Protein Binding / Q000187:drug effects; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051381:Rats; D020218:Response Elements / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D022762:CCAAT-Enhancer-Binding Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C496592:HNF4A protein, human; D051557:Hepatocyte Nuclear Factor 4; C496594:Hnf4a protein, rat; D010750:Phosphoproteins; D020033:Protein Isoforms; D014157:Transcription Factors; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D005952:Glucose-6-Phosphatase