Abstract
We discovered a nuclear receptor element in the FAS promoter consisting of an inverted repeat spaced by one nucleotide (IR-1) and located 21 bases downstream of a direct repeat sequenced by 4 nucleotides (DR-4) oxysterol liver X receptor response element. An IR-1 is present in promoters of several genes of bile acid and lipid homeostasis and binds farnesoid X receptor/retinoid X receptor (FXR/RXR) heterodimers to mediate bile acid-dependent transcription. We show that FXR/RXRα specifically binds to the FAS IR-1 and that the FAS promoter is activated ∼10-fold by the addition of a synthetic FXR agonist in transient transfection assays. We also demonstrate that endogenous FXR binds directly to the murine FAS promoter in the hepatic genome using a tissue-based chromatin immunoprecipitation procedure. Furthermore, we show that feeding wild-type mice a chow diet supplemented with the natural FXR agonist chenodeoxycholic acid results in a significant induction of FAS mRNA expression. Thus, we have identified a novel IR-1 in the FAS promoter and demonstrate that it mediates FXR/bile acid regulation of the FAS gene. These findings provide the first evidence for direct regulation of lipogenesis by bile acids and also provide a mechanistic rationale for previously unexplained observations regarding bile acid control of FAS expression.
Original language | English (US) |
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Pages (from-to) | 2754-2761 |
Number of pages | 8 |
Journal | Journal of Lipid Research |
Volume | 47 |
Issue number | 12 |
DOIs | |
State | Published - Dec 2006 |
Externally published | Yes |
Keywords
- Farnesoid X receptor
- Nuclear receptors
- Small heterodimer partner
ASJC Scopus subject areas
- Biochemistry
- Endocrinology
- Cell Biology