title: A natural polymorphism in peroxisome proliferator-activated receptor-alpha hinge region attenuates transcription due to defective release of nuclear receptor corepressor from chromatin.
abstract: Peroxisome proliferator-activated receptor-alpha (PPARalpha) is a central regulator of lipid metabolism. Fibrate drugs act on PPARalpha to modulate dyslipidemias. A natural variant (V227A) affecting the PPARalpha hinge region was associated with perturbations in blood lipid levels in Asian populations. In this study, we investigated the functional significance of the V227A substitution. The variant significantly attenuated PPARalpha-mediated transactivation of the cytochrome P450 4A6 and mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMGCS2) genes in the presence of fibrate ligands. Screening of a panel of PPARalpha coregulators revealed that V227A enhanced recruitment of the nuclear corepressor NCoR. Transactivation activity of V227A could be restored by silencing NCoR or by inhibition of its histone deacetylase activity. Deletion studies indicated that PPARalpha interacted with NCoR receptor-interacting domain 1 (ID1) but not ID2 or ID3. These interactions were dependent on the intact consensus nonapeptide nuclear receptor interaction motif in NCoR ID1 and were enhanced by the adjacent 24 N-terminal residues. Novel corepressor interaction determinants involving PPARalpha helices 1 and 2 were identified. In hepatic cells, the V227A substitution stabilized PPARalpha/NCoR interactions and caused defective release of NCoR in the presence of agonists on the HMGCS2 promoter. These results provide the first indication that defective function of a natural PPARalpha variant was due, at least partially, to increased corepressor binding. Our data suggest that the PPARalpha/NCoR interaction is physiologically relevant and can produce a discernable phenotype when the magnitude of the interaction is altered by a naturally occurring variation.
authors.affiliation: Department of Obstetrics and Gynecology, National University Hospital, Yong Loo Lin School of Medicine, Republic of Singapore.
authors.forename: Mei Hui
authors.initials: MH
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Ping
authors.initials: P
authors.lastname: Shen
authors.forename: B
authors.initials: B
authors.lastname: Husna
authors.forename: E Shyong
authors.initials: ES
authors.lastname: Tai
authors.forename: E L
authors.initials: EL
authors.lastname: Yong
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002843:Chromatin / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006904:Hydroxymethylglutaryl-CoA Synthase / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism*; D056971:Nuclear Receptor Co-Repressor 1; D047493:PPAR alpha / Q000235:genetics* / Q000378:metabolism; D011110:Polymorphism, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic / Q000235:genetics*; D020798:Two-Hybrid System Techniques
chemical_list: D002843:Chromatin; C539127:NCOR1 protein, human; D009687:Nuclear Proteins; D056971:Nuclear Receptor Co-Repressor 1; D047493:PPAR alpha; D012097:Repressor Proteins; D003577:Cytochrome P-450 Enzyme System; C465479:cytochrome P-450 CYP4A6 (rabbit); D006904:Hydroxymethylglutaryl-CoA Synthase