BET Bromodomain Epigenetic Control of Macrophage Inflammatory Activation - PROJECT SUMMARY Sixty percent of people worldwide die due to inflammatory diseases like cardiovascular disease, chronic obstructive pulmonary disease (COPD), and stroke. This highlights the need for an improved mechanistic understanding of the initiation and progression of inflammation. Macrophages are ubiquitous in all major tissues and play an essential role in inflammation, driving the development and progression of inflammatory disorders by secreting cytokines and other inflammatory mediators. Proinflammatory macrophage activation is initiated via NF-κB signaling, a master transcriptional regulator of inflammation. However, broad inhibition of the NF-κB pathway results in many unacceptable patient toxicities, including impaired tissue repair. Recent studies have shown that the bromodomain and extraterminal domain (BET) family of epigenetic reader proteins promote transcription of a subset of NF-κB-regulated inflammatory target genes in a cell- and context-specific manner. Small molecule inhibitors of the BET family (BETi) provide broad anti-inflammatory effects, significantly decrease macrophage-mediated inflammation, and exhibit beneficial anti-inflammatory effects in several inflammatory disease models by attenuating a subset of NF-κB target genes. However, the transcriptional mechanisms by which BETi modulate inflammatory gene transcription remain largely unknown. The BET family consists of four members (BRD2/3/4/T), each with two independent acetyl-lysine binding bromodomains (BD1 and BD2). Most studies of BET transcriptional regulation use non-selective BETi that block both BD1 and BD2 across the entire protein family (pan-BETi). In clinical trials, pan-BETi are associated with significant adverse effects and dose-limiting toxicities. Thus, BETi with improved selectivity for a subset of BET bromodomains are urgently required to improve inflammatory disease treatment options. We are determining the specific role of BET proteins and their individual bromodomains in macrophage activation and contrasting that activity to BET protein functions in non-immune cells. While our prior work has suggested that BRD4-BD1 is required for non-immune cell inflammatory transcription, our preliminary studies in macrophages suggest that both bromodomains of BRD2 promote inflammatory transcription. Here, we will elucidate the precise biochemical mechanisms and individual BET bromodomains regulating macrophage inflammatory activation and identify the exact protein interactions underlying that regulation. Aim 1 will identify the precise transcriptional role of each BET bromodomain in macrophage inflammatory activation with a focus on BRD2. Aim 2 will examine the BET bromodomain-based protein interactions that drive BET protein nuclear localization and activity. This fellowship addresses knowledge gaps in the biochemical mechanisms underlying BET bromodomain control of macrophage inflammation. Completing this fellowship will further develop precision medicine approaches for inflammatory disorders by identifying which BET bromodomains are the most attractive therapeutic targets to modulate inflammation with fewer off-target toxicities.
