The HOXC11 homeodomain protein interacts with the lactase-phlorizin hydrolase promoter and stimulates HNF1alpha-dependent transcription.
The lactase-phlorizin hydrolase (LPH) gene is expressed specifically in the enterocytes of the small intestine. LPH levels are high in newborn mammals, but decrease after weaning. We have previously suggested that the promoter element CE-LPH1, located at -40 to -54, plays an important role in this down-regulation, because the DNA binding activity of a nuclear factor that binds to this site is present specifically in small intestinal extracts and is down-regulated after weaning. In an effort to clone CE-LPH1-binding factors, a yeast one-hybrid genetic selection was used, resulting in the isolation of a partial cDNA encoding the human homeodomain protein HOXC11. The full-length HOXC11 sequence was obtained by rapid amplification of cDNA ends. It was shown in a yeast assay and by electrophoretic mobility shift assay that HOXC11 binds to the CE-LPH1 element with similar specificity to the endogenous intestinal factor. Two HOXC11 transcript sizes were identified by Northern blot analysis. The larger transcript (2.1 kilobase pairs) is likely to contain a translational start site in good context and is present in HeLa cells. The shorter 1.7-kilobase pair transcript, present in HeLa and Caco-2 cells, probably encodes a protein lacking 114 amino acids at the N-terminal end. Both forms of HOXC11 potentiate transcriptional activation of the LPH promoter by HNF1alpha. The expression of HOXC11 mRNA in human fetal intestine suggests a role in early intestinal development.
Mitchelmore
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Department of Medical Biochemistry and Genetics, Biochemical Laboratory C, The Panum Institute, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen N, Denmark. mitch@biobase.dk
Troelsen
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JT
Sjöström
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Norén
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D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D010694:Lactase-Phlorizin Hydrolase / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D017931:DNA Primers; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; C496487:HNF1A protein, human; C496495:HNF1B protein, human; C484731:HOXC11 protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; D051537:Hepatocyte Nuclear Factor 1; D051539:Hepatocyte Nuclear Factor 1-beta; D010694:Lactase-Phlorizin Hydrolase