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.
Project description:DNA damage activates a complex signaling network in cells that blocks cell cycle progression, recruits factors involved in DNA repair, and/or triggers programs that control senescence or programmed cell death. Alterations in chromatin structure are known to be important for the initiation and propagation of the DNA damage response, although the molecular details are unclear. We investigated the role of chromatin structure in the DNA damage response by monitoring multiple timedependent checkpoint signaling and response events with a high-content multiplex image-based RNAi screen of chromatin modifying and interacting genes. We discovered that Brd4, a double bromodomain-containing protein, functions as an endogenous inhibitor of DNA damage signaling by binding to acetylated histones at sites of open chromatin and altering chromatin accessibility. Loss of Brd4 or disruption of acetyl-lysine binding results in an increase in both the number and size of radiation-induced !H2AX nuclear foci while overexpression of a Brd4 splice isoform completely suppresses !H2AX formation, despite equivalent double strand break formation. Brd4 knock-down cells displayed altered chromatin structure, prolonged cell cycle checkpoint arrest and enhanced survival after irradiation, while overexpression of Brd4 isoform B results in enhanced radiationinduced lethality. Brd4 is the target of the t(15;19) chromosomal translocation in a rare form of cancer, NUT Midline Carcinoma. Acetyl lysine-bromodomain interactions of the Brd4-NUT fusion protein suppresses !H2AX foci in discrete nuclear compartments, rendering cells more radiosensitive, mimicking overexpression of Brd4 isoform B. NUT Midline Carcinoma is sensitive to radiotherapy, however tumor material from this rare cancer is scarce. We therefore investigated Brd4 expression in another human cancer commonly treated with radiotherapy, glioblastoma multiforme, and found that expression of Brd4 isoform B correlated specifically with treatment response to radiotherapy. These data implicate Brd4 as an endogenous insulator of DNA damage signaling through recognition of epigenetic modifications in chromatin and suggest that expression of the Brd4 in human cancer can modulate the clinical response to DNA-damaging cancer therapy. Two replicates each of U2OS cells expressing either Brd4 shRNA or a control shRNA
Project description:DNA damage activates a complex signaling network in cells that blocks cell cycle progression, recruits factors involved in DNA repair, and/or triggers programs that control senescence or programmed cell death. Alterations in chromatin structure are known to be important for the initiation and propagation of the DNA damage response, although the molecular details are unclear. We investigated the role of chromatin structure in the DNA damage response by monitoring multiple timedependent checkpoint signaling and response events with a high-content multiplex image-based RNAi screen of chromatin modifying and interacting genes. We discovered that Brd4, a double bromodomain-containing protein, functions as an endogenous inhibitor of DNA damage signaling by binding to acetylated histones at sites of open chromatin and altering chromatin accessibility. Loss of Brd4 or disruption of acetyl-lysine binding results in an increase in both the number and size of radiation-induced !H2AX nuclear foci while overexpression of a Brd4 splice isoform completely suppresses !H2AX formation, despite equivalent double strand break formation. Brd4 knock-down cells displayed altered chromatin structure, prolonged cell cycle checkpoint arrest and enhanced survival after irradiation, while overexpression of Brd4 isoform B results in enhanced radiationinduced lethality. Brd4 is the target of the t(15;19) chromosomal translocation in a rare form of cancer, NUT Midline Carcinoma. Acetyl lysine-bromodomain interactions of the Brd4-NUT fusion protein suppresses !H2AX foci in discrete nuclear compartments, rendering cells more radiosensitive, mimicking overexpression of Brd4 isoform B. NUT Midline Carcinoma is sensitive to radiotherapy, however tumor material from this rare cancer is scarce. We therefore investigated Brd4 expression in another human cancer commonly treated with radiotherapy, glioblastoma multiforme, and found that expression of Brd4 isoform B correlated specifically with treatment response to radiotherapy. These data implicate Brd4 as an endogenous insulator of DNA damage signaling through recognition of epigenetic modifications in chromatin and suggest that expression of the Brd4 in human cancer can modulate the clinical response to DNA-damaging cancer therapy.
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: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: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:In this study, we sequenced two NUT midline carcinoma genomes. Analysis of rearrangement breakpoint provided information on the generating event of BRD-NUT rearrangements. Mutational signature analysis also revealed biological process during tumorigenesis of NUT midline carcinomas.
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.