CACUL1 reciprocally regulates SIRT1 and LSD1 to repress PPARγ and inhibit adipogenesis.

Peroxisome proliferator-activated receptor γ (PPARγ) is the master regulator of adipocyte differentiation and is closely linked to the development of obesity. Despite great progress in elucidating the transcriptional network of PPARγ, epigenetic regulation of this pathway by histone modification remains elusive. Here, we found that CDK2-associated cullin 1 (CACUL1), identified as a novel SIRT1 interacting protein, directly bound to PPARγ through the co-repressor nuclear receptor (CoRNR) box 2 and repressed the transcriptional activity and adipogenic potential of PPARγ. Upon CACUL1 depletion, less SIRT1 and more LSD1 were recruited to the PPARγ-responsive gene promoter, leading to increased histone H3K9 acetylation, decreased H3K9 methylation, and PPARγ activation during adipogenesis in 3T3-L1 cells. These findings were reversed upon fasting or resveratrol treatment. Further, gene expression profiling using RNA sequencing supported the repressive role of CACUL1 in PPARγ activation and fat accumulation. Finally, we confirmed 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 insight into its potential use for anti-obesity treatment.