Orphan Nuclear Hormone Receptor RevErbα Modulates Expression from the Promoter of the Hydratase-dehydrogenase Gene by Inhibiting Peroxisome Proliferator-activated Receptor α-Dependent Transactivation*

Peroxisome proliferator-activated receptor alpha (PPARalpha) heterodimerizes with the 9-cis-retinoic acid receptor (RXRalpha) to bind to peroxisome proliferator-response elements (PPRE) present in the upstream regions of a number of genes involved in metabolic homeostasis. Among these genes are those encoding fatty acyl-CoA oxidase (AOx) and enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (HD), the first two enzymes of the peroxisomal beta-oxidation pathway. Here we demonstrate that the orphan nuclear hormone receptor, RevErbalpha, modulates PPARalpha/RXRalpha- dependent transactivation in a response element-specific manner. In vitro binding analysis showed that RevErbalpha bound the HD-PPRE but not the AOx-PPRE. Determinants within the HD-PPRE required for RevErbalpha binding were distinct from those required for PPARalpha/RXRalpha binding. In transient transfections, RevErbalpha antagonized transactivation by PPARalpha/RXRalpha from an HD-PPRE luciferase reporter construct, whereas no effects were observed with an AOx-PPRE reporter construct. These data identify the HD gene as a target for RevErbalpha and illustrate cross-talk between the RevErbalpha and PPARalpha signaling pathways on the HD-PPRE. Our results suggest a novel role for RevErbalpha in regulating peroxisomal beta-oxidation.