title: Oct-1 transcription factor is a negative regulator of rat CYP1A1 expression via an octamer sequence in its negative regulatory element.
abstract: The rat CYP1A1 negative regulatory element (NRE) contains AP-1 and Oct-1 motifs at -808 to -788 bp. The CYP1A1 sequence from -813 to -779 bp and an identical sequence bearing a point mutation in the octamer motif were synthesized. Gel mobility shift assays showed the formation of two complexes with the wild-type CYP1A1 sequence and nuclear extracts from H4IIE and HepG2 hepatoma cells and from rat liver. The formation of the major complex was significantly reduced with the mutant octamer-containing oligomer and was specifically competed by an Oct-1 oligodeoxyribonucleotide. The addition of Oct-1 antibody caused a supershift of the major complex. The presence of the wild-type sequence, but not the mutant octamer sequence, caused a 3-fold decrease in SV40 enhancerless promoter activity in transfected HepG2 cells. Co-transfection of an Oct-1 expression vector with rat CYP1A1 NRE octamer-containing, promoter/reporter gene constructs specifically further decreased promoter activity of the wild-type octamer-containing constructs in HepG2 cells. The results indicate that Oct-1 binds to the rat CYP1A1 promoter NRE and is a negative regulator of rat CYP1A1 expression.
authors.affiliation: Department of Pharmacology and Molecular Toxicology, University of Massachusetts Medical Center, Worcester 01655, USA.
authors.forename: K
authors.initials: K
authors.lastname: Sterling
authors.forename: E
authors.initials: E
authors.lastname: Bresnick
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000235:genetics*; D004268:DNA-Binding Proteins; D015971:Gene Expression Regulation, Enzymologic; D018398:Homeodomain Proteins / Q000096:biosynthesis / Q000378:metabolism*; D051863:Host Cell Factor C1; D006801:Humans; D007700:Kinetics; D008113:Liver Neoplasms; D008156:Luciferases / Q000096:biosynthesis / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D050811:Octamer Transcription Factor-1; D009838:Oligodeoxyribonucleotides; D017354:Point Mutation; D011401:Promoter Regions, Genetic; D051381:Rats; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D014157:Transcription Factors / Q000096:biosynthesis / Q000378:metabolism*; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D018398:Homeodomain Proteins; D051863:Host Cell Factor C1; D050811:Octamer Transcription Factor-1; D009838:Oligodeoxyribonucleotides; C494165:POU2F1 protein, human; C494168:Pou2f1 protein, rat; D011994:Recombinant Proteins; D014157:Transcription Factors; D003577:Cytochrome P-450 Enzyme System; D008156:Luciferases