title: Characterization of the promoter region of the human MDR3 P-glycoprotein gene.
abstract: The human MDR3 (or MDR2) P-glycoprotein is probably involved in the transport of phospholipids from liver hepatocytes into bile (Smit et al. (1993) Cell 75, 451-462). In accordance with this function, MDR3 is highly expressed in human liver, but lower mRNA levels were also found in adrenal, heart, muscle and cells of the B-cell compartment. We have cloned and analyzed the MDR3 promoter region. It is GC-rich, and contains neither a TATA nor a CAAT box, but it does contain multiple putative SP1 binding sites, features also found in so-called housekeeping genes. RNase protection and primer extension analyses indicate that the MDR3 gene has multiple transcription start sites in a GC-rich region with considerable homology to the putative mouse mdr2 promoter. A 3 kb genomic fragment containing the MDR3 start sites directs transcription of a chloramphenicol acetyltransferase (CAT) reporter gene upon transient transfection in the human hepatoma cell line HepG2. This transcription is orientation dependent, and stimulated by a SV40 enhancer, indicating that the 3 kb insert contains the core promoter elements of the MDR3 gene. The promoter region contains several consensus sequences where known or putative liver-specific (C/EBP, HNF5) or lymphoid specific (Pu.1, ets-1) transcription factors may bind.
authors.affiliation: The Netherlands Cancer Institute, Division of Molecular Biology, Amsterdam.
authors.forename: J J
authors.initials: JJ
authors.lastname: Smit
authors.forename: C A
authors.initials: CA
authors.lastname: Mol
authors.forename: L
authors.initials: L
authors.lastname: van Deemter
authors.forename: E
authors.initials: E
authors.lastname: Wagenaar
authors.forename: A H
authors.initials: AH
authors.lastname: Schinkel
authors.forename: P
authors.initials: P
authors.lastname: Borst
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D006528:Carcinoma, Hepatocellular / Q000473:pathology; D003001:Cloning, Molecular; D016384:Consensus Sequence; D018076:DNA, Complementary / Q000235:genetics; D004742:Enhancer Elements, Genetic; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation; D005796:Genes; D017930:Genes, Reporter; D006801:Humans; D008113:Liver Neoplasms / Q000473:pathology; D051379:Mice / Q000235:genetics; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D012326:RNA Splicing; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D018076:DNA, Complementary; D011993:Recombinant Fusion Proteins