Project description:Peroxisome proliferator-activated receptor γ (PPARγ) is the master regulator of adipocyte differentiation and is closely linked to the development of obesity. Despite a large progress on the transcriptional network of PPARγ, the epigenetic regulation associated with histone modification remains elusive. Here, we found that CDK2-associated cullin 1 (CACUL1), identified as a novel SIRT1 interacting protein, directly binds to PPARγ through the CoRNR box 2 and represses the transcription activity and adipogenic potential of PPARγ. Upon CACUL1 depletion, less SIRT1 and more LSD1 was recruited to the PPARγ-responsive gene promoter, leading to the increased histone H3K9 acetylation and decreased H3K9 methylation for PPARγ activation during adipogenesis of 3T3-L1 cells. These findings were reversed upon fasting or resveratrol treatment. Further, gene expression profiling using RNA-seq supported the repressive role of CACUL1 in PPARγ activation and fat accumulation. Finally, we confirmed the CACUL1 function in human adipose-derived stem cells. Overall, our data suggest that CACUL1 tightly regulates PPARγ signaling through the mutual opposition between SIRT1 and LSD1, providing additional insight into its use for anti-obesity treatment.
Project description:PPARγ promotes adipogenesis while Wnt proteins inhibit adipogenesis. However, the mechanisms that control expression of these positive and negative master regulators of adipogenesis remain incompletely understood. By genome-wide histone methylation profiling in preadipocytes, we find that among gene loci encoding adipogenesis regulators, histone methyltransferase (HMT) G9a-mediated repressive epigenetic mark H3K9me2 is enriched on the entire PPARγ locus. H3K9me2 and G9a levels decrease during adipogenesis, which correlates inversely with induction of PPARγ. Removal of H3K9me2 by G9a deletion enhances chromatin opening and binding of adipogenic transcription factor C/EBP-beta to PPARγ promoter, which promotes PPARγ expression. Interestingly, G9a represses PPARγ expression in an HMT activity-dependent manner but facilitates Wnt10a expression independent of its enzymatic activity. Consistently, deletion of G9a or inhibiting G9a HMT activity promotes adipogenesis. Finally, deletion of G9a in mouse adipose tissues increases adipogenic gene expression and tissue weight. Thus, by inhibiting PPARγ expression and facilitating Wnt10a expression, G9a represses adipogenesis. Examination of gene expression changes in G9a KO brown preadipocytes
