A stable HepG2 cell line harboring a human cholesterol 7 alpha-hydroxylase (CYP7A) minigene/luciferase reporter gene construct was selected for studying transcriptional regulation of CYP7A gene promoter. Insulin and phorbol 12-myristate-13-acetate (PMA) strongly repressed the promoter activity as measured with luciferase activity expressed in the cells. The promoter activity of the 5' progressive deletion/luciferase reporter gene constructs was studied in a transient transfection assay in HepG2 cells. PMA represses the promoter activity and the response elements were localized in the -184/-151 and -134/-81 regions. Insulin also represses the promoter activity and response element was mapped in the -298/-81 region. Surprisingly, glucocorticoid receptor (GR) strongly inhibited promoter activity in the presence of dexamethasone, and response elements were localized in the -298/-151 and the -150/+24 regions. Thyroid hormone receptor also repressed promoter activity and response elements were localized in the -150/+24 and upstream regions. Cotransfection of CYP7A chimeric constructs with an expression vector carrying liver-enriched transcription factor HNF3 alpha stimulated the reporter gene activity, but cotransfection with GR plasmid interfered with the HNF3 alpha-stimulated activity possibly through competition for binding to overlapping GR/HNF3 binding sites. Thus, human cholesterol 7 alpha-hydroxylase gene promoter is strongly repressed by insulin, PMA, and steroid/thyroid hormones and results in the low level of cholesterol 7 alpha-hydroxylase expression in the human liver
Transcriptional regulation of the human cholesterol 7-hydroxylase gene (CYP7A) in HepG2 cells / D-P. Wang, D. Stroup, M. Marrapodi, M. Crestani, G. Galli, J.Y.L. Chiang. - In: JOURNAL OF LIPID RESEARCH. - ISSN 0022-2275. - 37:9(1996), pp. 1831-1841.
|Titolo:||Transcriptional regulation of the human cholesterol 7-hydroxylase gene (CYP7A) in HepG2 cells|
|Settore Scientifico Disciplinare:||Settore BIO/10 - Biochimica|
|Data di pubblicazione:||1996|
|Appare nelle tipologie:||01 - Articolo su periodico|