Fig. 7.

ETS1–P-TEFb modulated in vitro angiogenesis. a Experimental design for the matrigel plug assay. ECFCs were transduced with lentivirus expressing indicated proteins or shRNA. Alternatively, ECFCs were cultured in JQ1 overnight, prior to matrigel implantation. Cells were then mixed with MSCs in matrigel, and injected subcutaneously into mice. b Matrigel plugs were sectioned and stained with fluorescently labeled UEA, which binds human ECs. Representative confocal images are shown. Bar = 100 µm. c Inhibition of ETS1 activity, BRD4 activity, or ETS1–BRD4 interaction impaired vessel formation in the matrigel plug assay. UEA-stained vascular area in matrigel plugs was quantified. Student’s t-test compared to GFP control: *p < 0.05; **p < 0.01; ***p < 0.001. n = 3–5. Bar plots show mean ± s.d. d Working model of ETS1-mediated transcriptional response to VEGF. VEGF activates ERK, which phosphorylates ETS1 (1). This recruits CBP to ETS1. CBP acetylates ETS1 at K8,18 in the NT domain, stimulating BRD4 binding and activation of P-TEFb. P-TEFb phosphorylates serine 2 within the C-terminal domain of RNAPII and releases RNAPII pausing, resulting in productive elongation. VEGF also stimulates ETS1 chromatin occupancy (2), enhancing its effect on both RNAPII initiation and pause release