title: The acyl-CoA thioesterase I is regulated by PPARalpha and HNF4alpha via a distal response element in the promoter.
abstract: The cytosolic acyl-coenzyme A thioesterase I (Acot1) is an enzyme that hydrolyzes long-chain acyl-CoAs of C(12)-C(20)-CoA in chain length to the free fatty acid and CoA. Acot1 was shown previously to be strongly upregulated at the mRNA and protein level in rodents by fibrates. In this study, we show that Acot1 mRNA levels were increased by 90-fold in liver by treatment with Wy-14,643 and that Acot1 mRNA was also increased by 15-fold in the liver of hepatocyte nuclear factor 4alpha (HNF4alpha) knockout animals. Our study identified a direct repeat 1 (DR1) located in the Acot1 gene promoter in mouse, which binds the peroxisome proliferator-activated receptor alpha (PPARalpha) and HNF4alpha. Chromatin immunoprecipitation (ChIP) assay showed that the identified DR1 bound PPARalpha/retinoid X receptor alpha (RXRalpha) and HNF4alpha, whereas the binding in ChIP was abrogated in the PPARalpha and HNF4alpha knockout mouse models. Reporter gene assays showed activation of the Acot1 promoter in cells by the PPARalpha agonist Wy-14,643 after cotransfection with PPARalpha/RXRalpha. However, transfection with a plasmid containing HNF4alpha also resulted in an increase in promoter activity. Together, these data show that Acot1 is under regulation by an interplay between HNF4alpha and PPARalpha.
authors.affiliation: Karolinska Institutet, Department of Laboratory Medicine, Division of Clinical Chemistry, Karolinska University Hospital at Huddinge, Stockholm, Sweden.
authors.forename: Bikesh
authors.initials: B
authors.lastname: Dongol
authors.forename: Yatrik
authors.initials: Y
authors.lastname: Shah
authors.forename: Insook
authors.initials: I
authors.lastname: Kim
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Gonzalez
authors.forename: Mary C
authors.initials: MC
authors.lastname: Hunt
mesh_terms: D000818:Animals; D001665:Binding Sites; D002995:Clofibric Acid / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D051557:Hepatocyte Nuclear Factor 4 / Q000378:metabolism*; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D047493:PPAR alpha / Q000378:metabolism*; D010170:Palmitoyl-CoA Hydrolase / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011743:Pyrimidines / Q000494:pharmacology; D020218:Response Elements; D047490:Retinoid X Receptor alpha / Q000378:metabolism; D013869:Thiolester Hydrolases / Q000235:genetics* / Q000378:metabolism; D024363:Transcription Initiation Site
chemical_list: D051557:Hepatocyte Nuclear Factor 4; C496593:Hnf4a protein, mouse; D047493:PPAR alpha; D011743:Pyrimidines; D047490:Retinoid X Receptor alpha; D002995:Clofibric Acid; C006253:pirinixic acid; D013869:Thiolester Hydrolases; C447830:Acot1 protein, mouse; D010170:Palmitoyl-CoA Hydrolase