title: GATA-6 stimulates a cell line-specific activation element in the human lactase promoter.
abstract: Lactase-phlorizin hydrolase (LPH) synthesis is restricted to differentiated small intestinal enterocytes and is highly regulated during development. Analysis of expression of LPH promoter segments fused with luciferase transfected in Caco-2 cells, a line that uniquely expresses LPH mRNA, mapped an 18-base pair (bp) segment 100 bp upstream of the transcription start site that is required for transactivation. Remarkably, the LPH upstream element (LUE) has no stimulatory activity in both human intestinal and nonintestinal lines in which LPH mRNA is absent. Electrophoretic analysis of sequence-specific DNA-nuclear protein complexes demonstrated the presence of a Caco-2 cell-specific protein(s) (CCP), which is uniformly absent in LPH nonproducer cell lines. Mutational analysis of the LUE demonstrated that bases contained within a GATA consensus motif are critical for both CCP binding and transcription from the LPH promoter. Caco-2 cells express high levels of GATA-6 mRNA in a cell line-specific manner, suggesting that GATA-6 is a CCP that complexes with the LUE. When expressed by a plasmid, GATA-6 transactivated the LPH promoter. The stimulation was abrogated with mutations in the GATA consensus motif as well as mutations in a flanking downstream element. These studies are consistent with an important role of an intestinal GATA binding protein in cell type-specific transactivation of the LPH promoter.
authors.affiliation: Department of Pathology, Georgetown University School of Medicine, Washington, District of Columbia 20007, USA.
authors.forename: K
authors.initials: K
authors.lastname: Fitzgerald
authors.forename: L
authors.initials: L
authors.lastname: Bazar
authors.forename: M I
authors.initials: MI
authors.lastname: Avigan
mesh_terms: D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids / Q000378:metabolism; D050993:GATA6 Transcription Factor; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006801:Humans; D010694:Lactase-Phlorizin Hydrolase / Q000096:biosynthesis / Q000235:genetics*; D018996:Myelin P2 Protein / Q000378:metabolism; D009363:Neoplasm Proteins; D011401:Promoter Regions, Genetic; D017422:Sequence Analysis, DNA; D013394:Sucrase-Isomaltase Complex / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D016335:Zinc Fingers
chemical_list: D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C107608:FABP7 protein, human; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005227:Fatty Acids; D050993:GATA6 Transcription Factor; C494759:GATA6 protein, human; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D013394:Sucrase-Isomaltase Complex; D010694:Lactase-Phlorizin Hydrolase