title: Unsaturated fatty acids inhibit transcription of the sterol regulatory element-binding protein-1c (SREBP-1c) gene by antagonizing ligand-dependent activation of the LXR.
abstract: Sterol regulatory element-binding protein-1c (SREBP-1c) enhances transcription of genes encoding enzymes of unsaturated fatty acid biosynthesis in liver. SREBP-1c mRNA is known to increase when cells are treated with agonists of liver X receptor (LXR), a nuclear hormone receptor, and to decrease when cells are treated with unsaturated fatty acids, the end products of SREBP-1c action. Here we show that unsaturated fatty acids lower SREBP-1c mRNA levels in part by antagonizing the actions of LXR. In cultured rat hepatoma cells, arachidonic acid and other fatty acids competitively inhibited activation of the endogenous SREBP-1c gene by an LXR ligand. Arachidonate also blocked the activation of a synthetic LXR-dependent promoter in transfected human embryonic kidney-293 cells. In vitro, arachidonate and other unsaturated fatty acids competitively blocked activation of LXR, as reflected by a fluorescence polarization assay that measures ligand-dependent binding of LXR to a peptide derived from a coactivator. These data offer a potential mechanism that partially explains the long-known ability of dietary unsaturated fatty acids to decrease the synthesis and secretion of fatty acids and triglycerides in livers of humans and other animals.
authors.affiliation: Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390-9046, USA.
authors.forename: J
authors.initials: J
authors.lastname: Ou
authors.forename: H
authors.initials: H
authors.lastname: Tu
authors.forename: B
authors.initials: B
authors.lastname: Shan
authors.forename: A
authors.initials: A
authors.lastname: Luk
authors.forename: R A
authors.initials: RA
authors.lastname: DeBose-Boyd
authors.forename: Y
authors.initials: Y
authors.lastname: Bashmakov
authors.forename: J L
authors.initials: JL
authors.lastname: Goldstein
authors.forename: M S
authors.initials: MS
authors.lastname: Brown
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism / Q000494:pharmacology; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics*; D002460:Cell Line; D002784:Cholesterol / Q000031:analogs & derivatives* / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics*; D005231:Fatty Acids, Unsaturated / Q000378:metabolism* / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D016350:Leucine Zippers; D008024:Ligands; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid / Q000037:antagonists & inhibitors*; D011988:Receptors, Thyroid Hormone / Q000037:antagonists & inhibitors*; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; D005231:Fatty Acids, Unsaturated; D008024:Ligands; D000071518:Liver X Receptors; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D018168:Receptors, Retinoic Acid; D011988:Receptors, Thyroid Hormone; C497387:SREBF1 protein, human; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1; D014157:Transcription Factors; D016718:Arachidonic Acid; C028358:24,25-epoxycholesterol; D002784:Cholesterol