Epigenetic dependencies of interferon gamma-induced gene expression [ChIP-Seq]

Interferon gamma (IFNy) is a pro-inflammatory cytokine that directly activates the JAK/STAT pathway. However, the temporal dynamics of chromatin remodeling and transcriptional activation initiated by IFN have not been systematically profiled in an unbiased manner. Herein, we integrated transcriptomic and epigenomic profiling to characterize the acute epigenetic changes induced by IFNy stimulation in a murine breast cancer model. We identified de novo activation of cis-regulatory elements bound by Irf1 that were characterized by increased chromatin accessibility, differential usage of pro-inflammatory enhancers, and downstream recruitment of BET proteins and RNA polymerase II. To functionally validate this hierarchical model of IFNy-driven transcription, we applied selective antagonists of histone acetyltransferases P300/CBP or acetyl-lysine readers of the BET family. This highlighted that histone acetylation is an antecedent event in IFNy-driven transcription, whereby targeting of P300/CBP but not BET inhibition, could curtail the epigenetic remodeling induced by IFNy through suppression of Irf1 transactivation. These data highlight the utility for epigenetic therapies to reprogram pro-inflammatory gene expression, which may have therapeutic implications for anti-tumor immunity and inflammatory diseases. Examination of changes in Histone H3 Lysine 27 acetylation (H3K27ac) and IRF1 genomic localization by ChIP-seq following stimulation of AT3 cells treatedwith interferon gamma (IFNy) alone and in combination with catalytic inhibition of P300/CBP for 3 hours.