REGULATION OF LACTASE-PHLORHIZIN HYDROLASE GENE-EXPRESSION BY THE CAUDAL-RELATED HOMOEODOMAIN PROTEIN CDX-2

Lactase-phlorizin hydrolase is exclusively expressed in the small inte stine and is often used as a marker for the differentiation of enteroc ytes. The cis-element CE-LPH1 found in the lactase-phlorizin hydrolase promoter has previously been shown to bind an intestinal-specific nuc lear factor. By electrophoretic mobility-shift assay it was shown that the factor Cdx-2 (a homoeodomain-protein related to caudal) binds to a TTTAC sequence in the CE-LPH1. Furthermore it was demonstrated that Cdx-2 is able to activate reporter gene transcription by binding to CE -LPH1. A mutation in CE-LPH1, which does not affect Cdx-2 binding, res ults in a higher transcriptional activity, indicating that the CE-LPH1 site contains other binding site(s) in addition to the Cdx-2-binding site.