Project description:Discarded live tumor tissue from a metastatic focus in the patientM-bM-^@M-^Ys lung was collected under institutional review board approval through the NUT midline carcinoma registry (www.NMCRegistry.org). From this tissue the first known NUT-variant cell line, 1221, was established. To determine the putative partner gene to NUT, we performed comprehensive RNA-sequencing on RNA purified from 1221. We identified an in-frame transcript fusing the 5M-bM-^@M-^Y coding sequence of NSD3 (exons 1-7) to exons 2-7 of NUT. Expression of the NSD3-NUT fusion oncoprotein was verified by immunobloting with an antibody to NUT, revealing an approximately 200kDa band that is similar in size to BRD3-NUT, but smaller than BRD4-NUT Identification of a NUT fusion partner using RNA extracted from live cultured 1221 cell line derived from a lung metastasis from the index case of a 13 year old female with NUT-positive NMC.
Project description:Discarded live tumor tissue from a metastatic focus in the patient’s lung was collected under institutional review board approval through the NUT midline carcinoma registry (www.NMCRegistry.org). From this tissue the first known NUT-variant cell line, 1221, was established. To determine the putative partner gene to NUT, we performed comprehensive RNA-sequencing on RNA purified from 1221. We identified an in-frame transcript fusing the 5’ coding sequence of NSD3 (exons 1-7) to exons 2-7 of NUT. Expression of the NSD3-NUT fusion oncoprotein was verified by immunobloting with an antibody to NUT, revealing an approximately 200kDa band that is similar in size to BRD3-NUT, but smaller than BRD4-NUT
Project description: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 identified the EP300 acetyltransferase as uniquely associated with BRD4 through the NUT fusion in both NMC and non-NMC cell types. We also discovered ZNF532 among a small number of candidates associated with BRD4-NUT in NMC patient cells but not present in 293T cells.
Project description: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.
2017-08-22 | GSE96775 | GEO
Project description:Novel NUT Fusion Oncogen in NUT Midline Carcinoma identified in 24335 patient-derived cell line by RNA-seq
Project description:NUT midline carcinoma (NMC) is a rare, aggressive subtype of squamous carcinoma that is driven by the BRD4-NUT fusion oncoprotein. BRD4, a BET protein, binds to chromatin through its two bromodomains, and NUT recruits the p300 histone acetyltransferse (HAT) to activate transcription of oncogenic target genes. BET selective bromodomain inhibitors have demonstrated on-target activity in NMC patients, but with limited efficacy. P300, like BRD4, contains a bromodomain. We show that combining selective p300/CBP and BET bromodomain inhibitors, GNE-781 and OTX015, respectively, induces synergistic inhibition of NMC growth. Treatment of NMC cells with the novel dual p300/CBP and BET bromodomain selective inhibitor, NEO2734, potently inhibits growth and induces differentiation of NMC cells in vitro; findings that correspond with potentiated transcriptional effects from combined BET and p300 bromodomain inhibition. In three disseminated NMC xenograft models, NEO2734 provided greater growth inhibition, with tumor regression and significant survival benefit seen in two of three models, compared with a lead clinical BET inhibitor or 'standard' chemotherapy.
Project description:NUT, nuclear protein in testis is the universal fusion partner of BRD4 in the highly aggressive NUT Midline Carcinoma (NMC), but its physiological function was unknown. Here we show that Nut is exclusively expressed in post-meiotic spermatogenic cells, at the time of genome-wide histone hyperacetylation. Inactivation of Nut induces a spermatogenesis arrest at the histone-to-protamine replacement stage, leading to male infertility. Subsequent molecular investigations show that Nut sustains global histone H4 hyperacetylation in post-meiotic cells. Additionally, Nut mediates a p300/CBP-dependent gene expression program and, by enhancing acetylation of H4 at both K5 and K8 sites, provides binding sites for the first bromodomain of Brdt, which drives histone removal. Nut’s major function is therefore to use the ubiquitous HATs p300/CBP to direct a cell-type specific histone hyperacetylation. Its ectopic activity in NMC recreates a forced p300-induced histone hyperacetylation / bromodomain binding loop that normally operates in post-meiotic spermatogenic cells.
Project description:NUT carcinoma (NC), an aggressive carcinoma, is driven by the BRD4-NUT fusion oncoprotein. BRD4, a BET protein, binds to chromatin through its two bromodomains, and when fused to NUT forms very large super-enhancers, termed megadomains. Targeting BRD4-NUT with BET bromodomain inhibitors (BETi) are a promising treatment, but limited as monotherapy. To identify additional dependencies in NC, we performed a genetic rescue screen in NC cells depleted of BRD4-NUT and identified EZH2 as a top correlated hit. Indeed, inhibition of EZH2 using the clinical compound, tazemetostat (taz), potently blocked growth of NC cells, and when combined with BETi was highly synergistic. Epigenetic and transcriptomic analysis revealed that taz reversed the EZH2-specific H3K27me3 silencing mark, and restored expression of multiple tumor suppressor genes while having no effect on megadomain-associated genes. CDKN2A was identified as the only amongst all taz-derepressed genes to confer resistance to taz in a CRISPR-CAS9 screen. In pre-clinical models, combined taz and BETi synergistically blocked growth and prolonged survival of NC-xenografted mice, with all mice cured in one cohort.
Project description:NUT carcinoma (NC) is a highly aggressive subtype of squamous carcinoma driven by the BRD4-NUT fusion oncoprotein. Closely resembling human NC (hNC), GEMM tumors (mNC) are poorly differentiated squamous carcinomas that express high levels of MYC and metastasize to organs (liver, lung) and regional lymph nodes. Two GEMM-derived cell lines were developed whose transcriptomic and epigenetic landscapes, characterized by RNAseq and CUT&RUN, show striking overlap with those of primary GEMM tumors. As in hNC, BRD4-NUT functions to block differentiation and maintain growth of mNC, as evidenced by BRD4-NUT knockdown and treatment of mNC cell lines with BET bromodomain inhibitors (BETi). Mechanistically, GEMM primary tumor and cell lines form very large H3K27ac-enriched super-enhancers that are unique to hNC, termed megadomains, that are invariably associated with key hNC-defining transcriptional oncogenic targets, Myc and Trp63.