Novel interaction at the Cdx-2 binding sites of the lactase-phlorizin hydrolase promoter.
Cdx-2 is an intestine-specific homeodomain-containing transcription factor that activates the promoters of intestinal genes through specific interactions with the consensus, TTTAT/C. Here, we demonstrate that Cdx-2 interacts with the lactase-phlorizin hydrolase (LPH) promoter at cis-element (CE)-LPH1a (-54 to -40 bp) as well as the LPH TATA-box. Affinity comparisons between SIF-1, CE-LPH1a, and the LPH TATA-box revealed that the TATA-box has the lowest affinity for Cdx-2. Characterization of CE-LPH1a using EMSAs revealed binding of a novel, non-Cdx-2 complex in multiple cell lines that bind to sequence that is different from that of the Cdx-2 binding site. Heterologous promoter analysis in transient transfection assays revealed a repressor function for this protein, and thus, it was designated as nuclear factor-LPH1/repressor (NF-LPH1/R). These data are consistent with the hypothesis that NF-LPH1/R represses LPH gene expression in non-Cdx-2-producing cells, and that this repression is released in cells that synthesize Cdx-2, such as those in the intestinal epithelium.
van Wering
Herbert M
HM
Division of Gastroenterology and Nutrition, Department of Medicine, Harvard Medical School, Children's Hospital Boston, 300 Longwood Avenue, Boston, MA 02115, USA.
Moyer
Leah
L
Grand
Richard J
RJ
Krasinski
Stephen D
SD
D000818:Animals; D001665:Binding Sites; D000071616:CDX2 Transcription Factor; D002460:Cell Line; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D010694:Lactase-Phlorizin Hydrolase / Q000235:genetics*; D046911:Macromolecular Substances; D009841:Oligonucleotides / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*
D000071616:CDX2 Transcription Factor; D018398:Homeodomain Proteins; D046911:Macromolecular Substances; D009841:Oligonucleotides; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D010694:Lactase-Phlorizin Hydrolase