C/EBP and Cdx family factors regulate liver fatty acid binding protein transgene expression in the small intestinal epithelium.
A transgene constructed from the rat liver fatty acid binding protein gene (Fabp1) promoter is active in all murine small intestinal crypt and villus epithelial cells. Coincident Cdx and C/EBP transcription factor binding sites were identified spanning Fabp1 nucleotides -90 to -78. CDX-1, CDX-2, C/EBPalpha, and C/EBPbeta activated the Fabp1 transgene in CaCo-2 cells, and mutagenizing the -78 site prevented activation by these factors. CDX but not C/EBP factors bound to the site in vitro, although C/EBP factors competed with CDX factors for transgene activation. The -78 site adjoins an HNF-1 site, and CDX and C/EBP family factors cooperated with HNF-1alpha but not HNF-1beta to activate the transgene. Furthermore, CDX-1, CDX-2, C/EBPalpha, and C/EBPbeta bound to HNF-1alpha and HNF-1beta. The transgene with a mutagenized -78 site was silenced in vivo specifically in small intestinal crypt epithelial cells but remained active in villus cells. These results demonstrate functional interactions between HNF-1, C/EBP, and CDX family factors and suggest that these interactions may contribute to differential transcriptional regulation in the small intestinal crypt and villus compartments.
Staloch
Lora J
LJ
Department of Pediatrics, Washington University School of Medicine, Campus Box 8208, St. Louis, MO 63110, USA.
Divine
Joyce K
JK
Witten
Joshua T
JT
Simon
Theodore C
TC
D000818:Animals; D001665:Binding Sites / Q000235:genetics; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018938:Caco-2 Cells; D050556:Fatty Acid-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D006367:HeLa Cells; D051537:Hepatocyte Nuclear Factor 1 / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D016296:Mutagenesis; D011401:Promoter Regions, Genetic; D051381:Rats; D014158:Transcription, Genetic; D019076:Transgenes / Q000235:genetics
D022762:CCAAT-Enhancer-Binding Proteins; C491273:CDX1 protein, human; C491271:Cdx1 protein, rat; C493321:Fabp1 protein, rat; D050556:Fatty Acid-Binding Proteins; D018398:Homeodomain Proteins; D051537:Hepatocyte Nuclear Factor 1