GSE96775
Chromatin-associated protein interactions drive megadomain formation in NUT midline carcinoma
To investigate the mechanism that drives dramatic mistargeting of active chromatin in NUT-midline carcinoma, we have identified protein interactions unique to the BRD4-NUT fusion oncoprotein compared to wild type BRD4.  Using crosslinking, affinity purification, and mass spectrometry, we identify the p300 acetyltransferase as ectopically associated with BRD4 through the NUT fusion in both NMC and non-NMC cell types. We also identify ZNF532 among a number of candidates uniquely associated with BRD4-NUT in NMC patient cells but not present in 293T cells.  p300 and ZNF532 are both implicated in feed-forward regulatory loops leading to propagation of the oncogenic regulatory complex in BRD4-NUT patient cells.  Extending our biochemical findings, we independently identified a novel ZNF532-NUT translocation fusion in a newly diagnosed NMC patient. ChIP-seq of key players: NUT, ZNF532, BRD4, p300, and anti-H3K27ac, reveals the formation of ZNF532-NUT-associated hyperacetylated megadomains, distinctly localized, but otherwise analogous to those found in BRD4-NUT patient cells. Our results support a model in which NMC is caused by a cascade of misregulation that is initiated by ectopic protein-protein interactions on chromatin between NUT and several distinct, but interacting, components of BRD4 regulatory complexes. Overall design: ChIP-seq and nascent RNA sequencing of patient-derived cancer cell lines.