The PPARg2 A/B-domain plays a gene specific role in transactivation and co-factor recruitment

We have previously shown that adenoviral expression of peroxisome proliferator-activated receptors (PPARs) leads to rapid establishment of transcriptionally active complexes and activation of target gene expression within 5-8 h following transduction. Here we have used the adenoviral delivery system combined with expression array analysis to identify novel putative PPARgamma target genes in murine fibroblasts and to determine the role of the A/B-domain in PPARgamma mediated transactivation of genomic target genes. Of the 257 genes found to be induced by PPARgamma2 expression, only 25 displayed A/B-domain dependency, i.e. significantly reduced induction in the cells expressing the truncated PPARgamma lacking the A/B-domain (PPARgammaCDE). Nine of the 25 A/B-domain dependent genes were involved in lipid storage and in line with this, triglyceride accumulation was considerably decreased in the cells expressing PPARgammaCDE compared to cells expressing full length PPARgamma2. Using chromatin immunoprecipitation (ChIP) we demonstrate that PPARgamma binding to genomic target sites and recruitment of the mediator component TRAP220/MED1/PBP/DRIP205 is not affected by the deletion of the A/B-domain. By contrast, the PPARgamma-mediated CBP and p300 recruitment to A/B-domain dependent target genes is abolished by deletion of the A/B-domain. These results indicate that the A/B-domain of PPARgamma2 is specifically involved in the recruitment or stabilization of CBP and p300 containing co-factor complexes to a subset of target genes.

9