Two HNF-1 binding sites govern the glucose repression of the human sucrase-isomaltase promoter.
We have previously shown, using the Caco-2 clone PF11, that glucose represses transcription of the human sucrase-isomaltase (SI) gene and that the -370/+30 fragment of the SI gene conferred glucose-regulated expression on a heterologous gene. Different fragments beginning at the already characterized SI footprint (SIF) 1 (-53/-37), SIFR (-153/-129) or SIF3 (-176/-156) elements [Wu, Chen, Forslund and Traber (1994) J. Biol. Chem. 269, 17080-17085] were tested, in comparison with the -370/+30 fragment, for their capacity to inhibit reporter gene expression under high-glucose (25 mM) conditions. Unlike SIF1 and SIFR, the addition of the HNF (hepatocyte nuclear factor)-1-binding element SIF3 to the promoter fragment was required for repression under high-glucose conditions. This effect was enhanced when the SI promoter was extended to position -370, indicating that the -370/-176 region contains elements that may co-operate with SIF3 to increase the metabolic control of the SI promoter. We have characterized an additional HNF-1-binding site near to and upstream from SIF3; SIF4. By mutagenesis of the three HNF-1-binding elements we show that the two distal HNF-1-recognition sites are the most important for the glucose regulation of the SI gene. Moreover, this glucose regulation was abolished in PF11 cells overexpressing vHNF-1C (variant HNF, an isoform of the HNF-1 family). We thus propose that the differential binding of HNF-1-family proteins to their DNA targets on the SI promoter constitutes the molecular mechanism that controls the glucose regulation of the SI gene transcription.
Rodolosse
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INSERM U178, Unité de Recherches sur la Différenciation Cellulaire Intestinale, 16 avenue Paul-Vaillant-Couturier, 94807 Villejuif cedex, France.
Carriere
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V
Rousset
M
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Lacasa
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M
D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005947:Glucose / Q000494:pharmacology*; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D013394:Sucrase-Isomaltase Complex / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*
D017931:DNA Primers; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D009687:Nuclear Proteins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D013394:Sucrase-Isomaltase Complex; D005947:Glucose