Characterization of promoter elements required for cell-specific expression of the neurotensin/neuromedin N gene in a human endocrine cell line
AuthorsEvers, B. Mark
Townsend, Courtney M.
McNeil, Gerard P.
Dobner, Paul R.
UMass Chan AffiliationsDepartment of Molecular Genetics and Microbiology
Graduate School of Biomedical Sciences
KeywordsActivating Transcription Factor 1; Activating Transcription Factor 2; Adenocarcinoma; Animals; Base Sequence; Binding, Competitive; Cyclic AMP Response Element-Binding Protein; DNA Mutational Analysis; DNA-Binding Proteins; *Gene Expression Regulation, Neoplastic; Humans; Molecular Sequence Data; Neurotensin; Pancreatic Neoplasms; Peptide Fragments; Promoter Regions (Genetics); Protein Binding; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; Rats; Sequence Deletion; Tissue Distribution; Transcription Factors; Tumor Cells, Cultured
Medicine and Health Sciences
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AbstractExpression of the gene encoding neurotensin/neuromedin N (NT/N) is mostly limited to the brain and specialized enteroendocrine cells (N cells) of the distal small intestine. We have analyzed the NT/N DNA sequences upstream of the RNA start site that direct cell-specific expression using a novel human endocrine cell line, BON, that resembles intestinal N cells in several important aspects, including NT/N precursor protein processing, ratios of different NT/N mRNA forms, and high levels of constitutive expression of the NT/N gene. Transient transfection assays with plasmids with progressive 5' deletions of the rat NT/N promoter identified the proximal 216 bp of 5' flanking sequences as essential for high-level constitutive NT/N expression in BON cells. In addition, a detailed mutational analysis defined multiple regions within the proximal 216 bp that contribute to cell-specific NT/N expression. These elements include a proximal cyclic AMP response element (CRE)/AP-1-like motif (TGACATCA) that binds c-Jun, JunD, CRE-binding (CREB), and ATF proteins, a near-consensus glucocorticoid response element, and a distal consensus AP-1 site that binds c-Fos, Fra-1, and JunD. In addition, elements contained within two 21-bp imperfect direct repeats play an important role in NT/N expression in BON cells and may bind novel factors that act as positive regulators of NT/N expression. DNase I footprinting and gel shift analyses demonstrate that the sites identified by mutational analysis, and at least one additional site, specifically bind BON cell nuclear proteins in vitro. We speculate that a complex pattern of regulation requiring interaction between a proximal CRE/AP-1-like motif and other upstream control elements play an important role in the high-level constitutive expression of NT/N in the human endocrine cell line BON. In addition, the BON cell line provides a unique model to further characterize the factors regulating cell-specific NT/N expression and to better understand the mechanisms responsible for the terminal differentiation of the N-cell lineage in the gut.
Mol Cell Biol. 1995 Jul;15(7):3870-81.
Permanent Link to this Itemhttp://hdl.handle.net/20.500.14038/33601
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