Project description:Histone deacetylases (HDACs) and acetyltransferases control the epigenetic regulation of gene expression through modification of histone marks. Histone deacetylase inhibitors (HDACi) are small molecules that interfere with histone tail modification thus altering chromatin structure and epigenetically controlled pathways. They promote apoptosis in proliferating cells and are promising anti-cancer drugs. While some HDACis have already been approved for therapy and others are in different phases of clinical trials, the exact mechanism of action of this drug class remains elusive. Previous studies have shown that HDACis cause massive changes in chromatin structure but only moderate changes in gene expression. To which extent these changes manifest at the protein level has never been investigated on a proteome-wide scale. Here, we have studied HDACi-treated cells by large-scale mass spectrometry based proteomics. We show that HDACi treatment affects primarily the nuclear proteome and induces a selective decrease of bromodomain containing proteins (BCPs), the main readers of acetylated histone marks. By combining time-resolved proteome and transcriptome profiling, we show that BCPs are affected at the protein level as early as 12 hours after HDACi treatment and that their abundance is regulated by a combination of transcriptional and post-transcriptional mechanisms. Using gene silencing, we demonstrate that the decreased abundance of BCPs is sufficient to mediate important transcriptional changes induced by HDACi. Our data reveals a new aspect of the mechanism of action of HDACi that is mediated by an interplay between histone acetylation and the abundance of BCPs.
Project description:We report the application of RNA sequencing technology for high-throughput profiling of both host and human cytomegalovirus (HCMV) transcript levels in latenly infected CD14+ monocytes after treatment with histone deacetylase inhibitors (CHR-4487) and BET-bromodomain inhibitors (GSK726).
Project description:Epigenetic silencing can be mediated by various mechanisms and many regulators remain to be identified. We identified CSE1L as a factor essential for silencing of the reporter gene and a fraction of endogenous methylated genes. CSE1L depletion did not cause DNA demethylation or increase of global histone acetylation. Nevertheless, these methylated genes derepressed by CSE1L depletion largely overlapped with methylated genes that were also reactivated by treatment of histone deacetylase inhibitors (HDACi).
Project description:Diffuse Large B-Cell Lymphoma (DLBCL) is a biologically heterogeneous and clinically aggressive disease. Here, we explore the role of BET bromodomain proteins in DLBCL, using integrative chemical genetics and functional epigenomics. We observe highly asymmetric loading of BRD4 at enhancers, with approximately 33% of all BRD4 localizing to enhancers at 1.6% of occupied genes. These super-enhancers prove particularly sensitive to bromodomain inhibition, explaining the selective effect of BET inhibitors on oncogenic and lineage-specific transcriptional circuits. Functional study of genes marked by super-enhancers identifies DLBCLs dependent on OCA-B and suggests a strategy for discovering unrecognized cancer dependencies. Translational studies performed on a comprehensive panel of DLBCLs establish a therapeutic rationale for evaluating BET inhibitors in this disease. ChIP-Seq for various transcription factors and histone modifications in diffuse large B-cell lymphoma cells
Project description:Histone deacetylases (HDACs) and acetyltransferases control the epigenetic regulation of gene expression through modification of histone marks. Histone deacetylase inhibitors (HDACi) are small molecules that interfere with histone tail modification thus altering chromatin structure and epigenetically controlled pathways. They promote apoptosis in proliferating cells and are promising anti-cancer drugs. While some HDACis have already been approved for therapy and others are in different phases of clinical trials, the exact mechanism of action of this drug class remains elusive. Previous studies have shown that HDACis cause massive changes in chromatin structure but only moderate changes in gene expression. To which extent these changes manifest at the protein level has never been investigated on a proteome-wide scale. Here, we have studied HDACi-treated cells by large-scale mass spectrometry based proteomics. We show that HDACi treatment affects primarily the nuclear proteome and induces a selective decrease of bromodomain containing proteins (BCPs), the main readers of acetylated histone marks. By combining time-resolved proteome and transcriptome profiling, we show that BCPs are affected at the protein level as early as 12 hours after HDACi treatment and that their abundance is regulated by a combination of transcriptional and post-transcriptional mechanisms. Using gene silencing, we demonstrate that the decreased abundance of BCPs is sufficient to mediate important transcriptional changes induced by HDACi. Our data reveals a new aspect of the mechanism of action of HDACi that is mediated by an interplay between histone acetylation and the abundance of BCPs.
Project description:FDA-approved global (panobinostat, vorinostat) and selective (romidepsin) histone-deacetylase (HDAC) inhibitors elicit metabolic reprogramming in concert with disruption of several Warburg-effect related super-enhancers
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:Bromodomain-containing proteins are readers of acetylated lysine and play important roles in cancer.1,2 Bromodomain-containing protein 7 (BRD7) has been implicated in multiple malignancies; however, there are no selective chemical probes to study its function in disease.3–13 Using crystal structures of BRD7 and BRD9 bromodomains (BDs) bound to BRD9-selective ligands, we identified a hydrophobic region unique to BRD7. We synthesized a series of ligands designed to occupy this binding region and identified two BRD7-selective inhibitors, 1-78 and 2-77, which show high affinity for the BRD7 BD and selectivity over the BRD9 BD using thermal shift assays and competitive fluorescence polarization. Our binding mode analyses indicate that these ligands occupy the hydrophobic region in BRD7 and maintain key interactions with the Asn and Tyr residues critical for acetyllysine binding. Finally, we validated the utility and selectivity of the compounds in cell-based models of prostate cancer. We then performed gene expression profiling analysis using data obtained from RNA-seq of LNCaP cells with or without drug treatment.