PPARβ/δ can directly up-regulate target genes in response to ligand activation (A), interact with other transcription factors such as NF-κB and possibly others such as AP1 (B), or repress gene expression (C). CBP, CREB (cAMP-response-element-binding protein)-binding protein; HAT, histone acetylase; HDAC, histone deacetylase; NCoR, nuclear receptor co-repressor; RNA Pol II, RNA polymerase II; RXRα, retinoid X receptor α; SMRT, silencing mediator for retinoic acid receptor and thyroid-hormone receptor.