Article Transcriptional synergy in human aortic endothelial cells is vulnerable to combination p300/CBP and BET bromodomain inhibition

Combinatorial signaling by proinflammatory cytokines synergizes to exacerbate toxicity to cells and tissue injury during acute infections. To explore synergism at the gene -regulatory level, we investigated the dynamics of transcription and chromatin signaling in response to dual cytokines by integrating nascent RNA imaging mass spectrometry, RNA sequencing, amplification -independent mRNA quantification, assay for transposase-accessible chromatin using sequencing (ATAC-seq), and transcription factor profiling. Costimulation with interferon -gamma (IFN g ) and tumor necrosis factor alpha (TNF a ) synergistically induced a small subset of genes, including the chemokines CXCL9 , - 10 , and - 11 . Gene induction coincided with increased chromatin accessibility at non -coding regions enriched for p65 and STAT1 binding sites. To discover coactivator dependencies, we conducted a targeted chemogenomic screen of transcriptional inhibitors followed by modeling of inhibitor dose -response curves. These results identified high efficacy of either p300/CREB-binding protein (CBP) or bromodomain and extra -terminal (BET) bromodomain inhibitors to disrupt induction of synergy genes. Combination p300/CBP and BET bromodomain inhibition at half -maximal inhibitory concentrations (subIC 50 ) synergistically abrogated IFN g /TNF a- in- duced chemokine gene and protein levels.