title: The homeodomain protein Cdx2 regulates lactase gene promoter activity during enterocyte differentiation.
abstract: OBJECTIVE
  Lactase is the intestinal disaccharidase responsible for digestion of lactose, the predominant carbohydrate in milk. Transcription of the lactase gene is activated during enterocyte differentiation. We have characterized the interaction between the lactase promoter and Cdx2, a homeodomain protein involved in regulating intestinal development and differentiation.
  
  
  METHODS
  Nuclear protein bound to the lactase gene cis element, CE-LPH1, was analyzed by electrophoretic mobility shift assays and supershifts with Cdx2 antibody. Lactase promoter activities were assayed in cells transfected with luciferase reporter constructs and a Cdx2 expression construct.
  
  
  RESULTS
  Electrophoretic mobility shift assay with CE-LPH1 yields a specific DNA/protein complex that requires the caudal-related protein binding site, TTTAC. The complex is recognized by Cdx2 antibody and is more abundant in differentiated enterocytes. A Cdx2 expression construct is able to activate transcription driven by the wild-type, but not a mutated, promoter and results in increased endogenous lactase messenger RNA.
  
  
  CONCLUSIONS
  The homeodomain protein Cdx2 interacts with the lactase promoter and is capable of activating transcription of the endogenous gene. In contrast to a previous report, Cdx2 interaction with the lactase promoter correlates with enterocyte differentiation. These conclusions are consistent with the role of Cdx2 in regulating intestinal cell differentiation.
authors.affiliation: Department of Pediatrics, Stanford University Medical Center, Stanford, California 94305, USA.
authors.forename: R
authors.initials: R
authors.lastname: Fang
authors.forename: N A
authors.initials: NA
authors.lastname: Santiago
authors.forename: L C
authors.initials: LC
authors.lastname: Olds
authors.forename: E
authors.initials: E
authors.lastname: Sibley
mesh_terms: D000818:Animals; D000071616:CDX2 Transcription Factor; D018938:Caco-2 Cells; D002454:Cell Differentiation; D002874:Chromosome Mapping; D020895:Enterocytes / Q000166:cytology / Q000378:metabolism*; D017353:Gene Deletion; D017930:Genes, Reporter; D018398:Homeodomain Proteins / Q000378:metabolism*; D006801:Humans; D043322:Lactase; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D015534:Trans-Activators; D014162:Transfection; D001616:beta-Galactosidase / Q000235:genetics*
chemical_list: D000071616:CDX2 Transcription Factor; D018398:Homeodomain Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D043322:Lactase; D001616:beta-Galactosidase