DDB1 Binds Histone Reader BRWD3 to Activate the Transcriptional Cascade in Adipogenesis and Promote Onset of Obesity (RNA-Seq)

DDB1 is typically recognized as a component of the Cullin4 (CUL4)-RING E3 ubiquitin ligase complex. Here, we show that DDB1 functions independently of CUL4 to promote adipogenesis and diet-induced obesity. In contrast to depletion of CUL4A or CUL4B that stimulates adipogenesis, lack of DDB1 dramatically suppresses the process. Re-introduction of a DDB1 mutant that lacks the binding ability to CUL4A or CUL4B fully restores adipogenesis in DDB1-deficient preadipocytes. Furthermore, while inducibly knocking out Cul4a or Cul4b in mice aggravates diet-induced obesity, Ddb1+/- mice are lean on high-fat diet. Mechanistically, by binding the bromodomain-containing histone reader BRWD3, DDB1 is recruited to acetylated histones in the proximal promoters of immediate-early response genes, where it facilitates the release of paused RNA polymerase II (Pol II) and activates the transcription of these genes. Our findings have thus uncovered a mechanism of activating the transcriptional cascade in adipogenesis by DDB1-mediated release of paused Pol II. Overall design: ChIP-seq performed in this study was designed to understand the molecular mechanisms underlying DDB1 in gene transcription regulation.