title: Dietary cholesterol fails to stimulate the human cholesterol 7alpha-hydroxylase gene (CYP7A1) in transgenic mice.
abstract: Dietary cholesterol has been shown to have a stimulatory effect on the murine cholesterol 7alpha-hydroxylase gene (Cyp7a1), but its effect on human cholesterol 7alpha-hydroxylase gene (CYP7A1) expression in vivo is not known. A transgenic mouse strain harboring the human CYP7A1 gene and homozygous for the disrupted murine Cyp7a1 gene was created. Cholesterol feeding increased the expression of the endogenous modified Cyp7a1 allele but failed to stimulate the human CYP7A1 transgene. In transfected hepatoma cells, 25-hydroxycholesterol increased murine Cyp7a1 gene promoter activity, whereas the human CYP7A1 gene promoter was unresponsive. Electrophoretic mobility shift assays demonstrated the interaction of the liver X receptor alpha (LXRalpha): retinoid X receptor (RXR) heterodimer, a transcription factor complex that is activated by oxysterols, with the murine Cyp7a1 gene promoter, whereas no binding to the human CYP7A1 gene promoter was detected. The results demonstrate that the human CYP7A1 gene is not stimulated by dietary cholesterol in the intact animal, and this is attributable to the inability of the CYP7A1 gene promoter to interact with LXRalpha:RXR.
authors.affiliation: Department of Biochemistry and Canadian Institutes of Health Research Group in Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta T6G 2S2, Canada. luis.agellon@ualberta.ca
authors.forename: Luis B
authors.initials: LB
authors.lastname: Agellon
authors.forename: Victor A B
authors.initials: VA
authors.lastname: Drover
authors.forename: Sukhinder K
authors.initials: SK
authors.lastname: Cheema
authors.forename: G Franck
authors.initials: GF
authors.lastname: Gbaguidi
authors.forename: Annemarie
authors.initials: A
authors.lastname: Walsh
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics*; D002791:Cholesterol, Dietary / Q000494:pharmacology*; D017931:DNA Primers; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D051379:Mice; D008822:Mice, Transgenic; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D002791:Cholesterol, Dietary; D017931:DNA Primers; D012333:RNA, Messenger; D002790:Cholesterol 7-alpha-Hydroxylase