The nuclear receptor corepressor (NCoR) was isolated as a peroxisome-proliferator-activated receptor (PPAR) δ interacting protein using the yeast two-hybrid system. NCoR interacted strongly with the ligand-binding domain of PPARδ, whereas interactions with the ligand-binding domains of PPARγ and PPARα were significantly weaker. PPAR—NCoR interactions were antagonized by ligands in the two-hybrid system, but were ligand-insensitive in in vitro pull-down assays. Interaction between PPARδ and NCoR was unaffected by coexpression of retinoid X receptor (RXR) α. The PPARδ—RXRα heterodimer bound to an acyl-CoA oxidase (ACO)-type peroxisome-proliferator response element recruited a glutathione S-transferase—NCoR fusion protein in a ligand-independent manner. Contrasting with most other nuclear receptors, PPARδ was found to interact equally well with interaction domains I and II of NCoR. In transient transfection experiments, NCoR and the related silencing mediator for retinoid and thyroid hormone receptor (SMRT) were shown to exert a marked dose-dependent repression of ligand-induced PPARδ-mediated transactivation; in addition, transactivation induced by the cAMP-elevating agent forskolin was efficiently reduced to basal levels by NCoR as well as SMRT coexpression. Our results suggest that the transactivation potential of liganded PPARδ can be fine-tuned by interaction with NCoR and SMRT in a manner determined by the expression levels of corepressors and coactivators.
Nuclear receptor corepressor-dependent repression of peroxisome-proliferator-activated receptor δ-mediated transactivation
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Anne-M. KROGSDAM, Curt A.F. NIELSEN, Søren NEVE, Dorte HOLST, Torben HELLEDIE, Bo THOMSEN, Christian BENDIXEN, Susanne MANDRUP, Karsten KRISTIANSEN; Nuclear receptor corepressor-dependent repression of peroxisome-proliferator-activated receptor δ-mediated transactivation. Biochem J 1 April 2002; 363 (1): 157–165. doi: https://doi.org/10.1042/bj3630157
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