The Murine and Human Cholesterol 7α-Hydroxylase Gene Promoters Are Differentially Responsive to Regulation by Fatty Acids Mediated via Peroxisome Proliferator-activated Receptor α*
- From the Medical Research Council Group on Molecular and Cell Biology of Lipids and the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2S2, Canada
Abstract
We determined if fatty acids can regulate the murine Cyp7a1 and human CYP7A1 gene promoters via peroxisome proliferator-activated receptor α (PPARα)/9-cis-retinoic acid receptor α (RXRα). In transfected cells, the murine Cyp7a1 gene promoter displayed markedly lower basal activity, but greater sensitivity to fatty acid- or WY 14,643-activated PPARα/RXRα when compared with the human CYP7A1 gene promoter. PPARα/RXRα can bind to a site (Site II) located within the region at nucleotides −158 to −132 of both promoters. Mutagenesis of the human CYP7A1Site II element abolished the response to activated PPARα/RXRα. The murine Cyp7a1 gene promoter contains an additional PPARα/RXRα-binding site (Site I) located within nucleotides −72 to −57. Replacement of a single residue in human CYP7A1 Site I with that found in the murine Cyp7a1 Site I sequence enabled PPARα/RXRα binding, and this mutation resulted in reduced basal activity, but substantially improved the response to activated PPARα/RXRα in transfected cells. We conclude that fatty acids can regulate the cyp7a gene promoter via PPARα/RXRα. The differential response of the murine Cyp7a1 and human CYP7A1gene promoters to PPARα activators is attributable to the additional PPARα/RXRα-binding site in the murine Cyp7a1 gene promoter.
Footnotes
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↵* This work was supported by Grant MT-14812 (to L. B. A.) from the Medical Research Council of Canada.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ Present address: Dept. of Biochemistry, BT 3012, Memorial University of Newfoundland, St. John's, NF A1B 3X9, Canada.
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↵§ Senior Medical Scholar of the Alberta Heritage Foundation for Medical Research. To whom correspondence should be addressed: 303 Heritage Medical Research Centre, Dept. of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada. Tel.: 780-492-5251; Fax: 780-492-3383; E-mail: luis.agellon@ualberta.ca.
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↵2 V. Drover and L. B. Agellon, unpublished results.
- Abbreviations:
- PPARs
-
peroxisome proliferator-activated receptors
- RXRα
-
9-cis-retinoic acid receptor α
- PPRE
-
peroxisome proliferator response element
- cyp7a
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cholesterol 7α-hydroxylase
- LXR
-
nuclear oxysterol receptor
- CAT
-
chloramphenicol acetyltransferase
- nt
-
nucleotides
- BSA
-
bovine serum albumin
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- Received February 8, 2000.
- The American Society for Biochemistry and Molecular Biology, Inc.
