Dissecting The Molecular Mechanisms Underlying VEGF-stimulated Angiogenesis

Angiogenesis is an ubiquitous and essential biological activity,its abnormality leads to the onset and progression of various diseases.Release of promoter-proximally paused RNA polymerase ?(RNAP?)has been recently recognized as the transcriptional regulatory checkpoint.The biological roles of RNAP? pausing release and the mechanisms by which extracellular signals control it are incompletely understood.Here we show that VEGF stimulated RNAP? pausing release by inducing the acetylation of endothelial master regulator ETS1,which interacted with BRD4 to recruit the pausing release complex P-TEFb,which promoted RNAP? pausing release and gene expressions.Despite of it,at later time points,ETS1 increased the occupancy at promoters of transcribed genes and stimulated their expression.We further proved that the angiogenic responses both in vitro and in vivo required the ETS1-mediated transduction of VEGF signaling and RNAP? pausing release.Together,our results defined a novel angiogenic pathway in which VEGF enhances ETS1–BRD4 interaction to broadly promote RNAP? pausing release and drives angiogenesis.Bivalent domain(BD)is an unique epigenetic feature of processing both H3K4me3 and H3K27me3 marks at the same promoter region,which normally primes genes ready for activation.BD was first discovered in the embryonic stem cells,but its functions in well-differentiated cells remained elusive.Here we found that the primary endothelial cells harbored genomewide distribution of BDs,especially on VEGF-responsive genes.Early gene responsiveness to VEGF replies on EZH1-mediated RNAP? pausing release rather than the erasure of H3K27me3.The following suppression depended on the recruitment of KDM5 A and its interactions with Polycomb repressive complex 2(PRC2).VEGF promoted angiogenesis through BD-modulated EGR3 upregulation,while KDM5 A suppressed this process.Therefore,we unraveled an essential role of BD in regulating angiogenesis,and we also identified a distinct mechanism of BD in regulating gene expressions comparing to embryonic stem cells.To summarize,we first identified the importance of ETS1 acetylation and BD in angiogenesis,and the crucial role of RNAP? pausing in mediating of these processes.Second,different from the embryonic stem cells,we unveiled that BD executed a distinct function in HUVEC cells through an novel mechanism,which provided us a more diverse role of BD in gene regulations.Collectively,we filled the gap about the means by which intranuclear epigenetic and transcriptional molecules in endothelial cells response to the environmental stimulus.