title: Transcriptional regulation of human oxysterol 7 alpha-hydroxylase gene (CYP7B1) by Sp1.
abstract: Oxysterol 7 alpha-hydroxylase catalyzes hydroxylation of oxysterols and neurosterols and plays a role in the alternative bile acid synthesis pathway. This gene is widely expressed in many organs and peripheral tissues and may protect tissues from the toxicity of oxysterols. Mutation in CYP7B1 caused neonatal cholestasis. To examine the regulatory mechanisms governing CYP7B1 expression, the 5' flanking sequence of the CYP7B1 was analyzed and revealed a CpG island of about 1.2 kb. Transient transfection assays of deletion mutants of the CYP7B1 promoter-luciferase reporter gene in human liver-derived HepG2, fibroblast NT1088, and human embryonic kidney 293 cell lines revealed that the region from -291 to +189 was critical for gene transcription. Three GC box sequences located between -25 and +10 were essential for basal transcription because mutations of these sequences markedly reduced promoter activity. Sp1 and Sp3 bound to these sequences as demonstrated by DNase I footprinting assays and electrophoretic mobility shift assay. Thus, regulation of CYP7B1 transcription by Sp1 may play a pivotal role in regulating oxysterol levels, which regulate cholesterol metabolism.
authors.affiliation: Department of Biochemistry and Molecular Pathology, Northeastern Ohio Universities College of Medicine, P.O. Box 95, Rootstown, OH 44272, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Wu
authors.forename: J Y
authors.initials: JY
authors.lastname: Chiang
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D002460:Cell Line; D018899:CpG Islands / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D000072474:Cytochrome P450 Family 7; D004247:DNA / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D017384:Sequence Deletion; D016329:Sp1 Transcription Factor / Q000378:metabolism / Q000502:physiology*; D013250:Steroid Hydroxylases / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D011993:Recombinant Fusion Proteins; D016329:Sp1 Transcription Factor; D004247:DNA; D003577:Cytochrome P-450 Enzyme System; D008156:Luciferases; D013250:Steroid Hydroxylases; C115867:oxysterol 7-alpha-hydroxylase; D000072474:Cytochrome P450 Family 7; C499571:CYP7B1 protein, human