Peroxisome Proliferator-activated Receptor (PPAR)-2 controls adipocyte differentiation and adipose tissue function through the regulation of the activity of the retinoid X receptor/PPARγ heterodimer

The peroxisome proliferator-activated receptor-γ (PPARγ, NR1C3) in complex with the retinoid X receptor (RXR) plays a central role in white adipose tissue (WAT) differentiation and function, regulating the expression of key WAT proteins. In this report we show that poly(ADP-ribose) polymerase-2 (PARP-2), also known as an enzyme participating in the surveillance of the genome integrity, is a member of the PPARγ/RXR transcription machinery. PARP-2^-/- mice accumulate less WAT, characterized by smaller adipocytes. In the WAT of PARP-2^-/- mice the expression of a number of PPARγ target genes is reduced despite the fact that PPARγ1 and -γ2 are expressed at normal levels. Consistent with this, PARP-2 ^-/- mouse embryonic fibroblasts fail to differentiate to adipocytes. In transient transfection assays, PARP-2 small interference RNA decreases basal activity and ligand-dependent activation of PPARγ, whereas PARP-2 overexpression enhances the basal activity of PPARγ, although it does not change the maximal ligand-dependent activation. In addition, we show a DNA-dependent interaction of PARP-2 and PPARγ/RXR heterodimer by chromatin immunoprecipitation. In combination, our results suggest that PARP-2 is a novel cofactor of PPARγ activity.