Project description:We report BET bromodomain inhibitors (BETi) as regulators of keratinocyte stem cell fate. BETi displace BET proteins, including BRD4 from chromatin, inducing acute transcriptional changes at selected target genes. To gain insight into the compound mechanism of action, we assayed BRD4 chromatin occupancy genome-wide in keratinocytes subjected to BETi treatment. Specifically, BRD4 chromatin binding was analyzed following two treatments [125nM (low) versus 1250nM (high)] and three time points (30min, 6h and 6h treatment followed by compound removal for 3h (6m3h)).
Project description:To identify genes regulated by BRD4 and to provide insight into new mechanisms de-regulated by BRD4, such as the response to oxidative stress, we integrated BRD4-binding regions with BRD4 gene expression data. For this analysis we performed BRD4 chromatin immunoprecipitation experiments and BRD4 knock down experiments followed by RNA-Seq analyses. By integration of both gene lists we identified top candidate genes regulated by BRD4. HEK cells have been investigated for genomewide BRD4 binding sites and expression changes after knock down of BRD4. Illumina sequencing was used to gather data of the type ChIP Seq and mRNA Seq.
Project description:During the post-meiotic phase of spermatogenesis, transcription is progressively repressed as the nuclei of haploid spermatids are compacted through a dramatic chromatin reorganization involving hyper-acetylation and replacement of most histones with sperm-specific protamines. Although BRDT has been shown to function in transcription as well as histone removal in post-meiotic spermatids, it is unknown whether other BET family proteins play a role. Immunofluorescence of mouse testes revealed BRD4 in a complete ring around the nuclei of spermatids containing hyper-acetylated histones. The BRD4 ring lies directly adjacent to the acroplaxome, or the cytoskeletal base of the acrosome, and does not form in acrosomal mutant mice. ChIP sequencing in round spermatids revealed enrichment of BRD4 and acetylated histone H3 and H4 at the promoters of active genes. GO Term analysis showed that BRD4 and BRDT bind to distinct subsets of spermatogenesis-specific genes. Association of BRD4 with Cyclin T1 decreases as spermatogenesis progresses despite a persistence of association with acetylated H4. Moreover, acetylated histones are removed from the condensing spermatid nucleus in a wave following the progressing acrosome. These data provide evidence for an interesting mechanism in which BRD4 and perhaps acetylated histones are removed from the spermatid genome via the progressing acrosome as transcription is repressed. Single replicates each of Brd4, H3K9me3, H3K9ac, H4K5ac, H4K8ac, H4K12ac, H4K16ac, H4Kac (pan-acetyl antibody), and input in mouse round spermatid cells; input is used to control for local sonication efficiency bias.
Project description:The bromodomain and extraterminal (BET) protein BRD4 is a therapeutic target in acute myeloid leukemia (AML). Here, we demonstrate that the AML maintenance function of BRD4 requires its interaction with NSD3, which belongs to a subfamily of H3K36 methyltransferases. Unexpectedly, AML cells were found to only require a short isoform of NSD3 that lacks the methyltransferase domain. We show that NSD3-short is an adaptor protein that sustains leukemia by linking BRD4 to the CHD8 chromatin remodeler, by using a PWWP chromatin reader module, and by employing an acidic transactivation domain. Genetic targeting of NSD3 or CHD8 mimics the phenotypic and transcriptional effects of BRD4 inhibition. Furthermore, BRD4, NSD3, and CHD8 colocalize across the AML genome, and each is released from super-enhancer regions upon chemical inhibition of BET bromodomains. These findings suggest that BET inhibitors exert therapeutic effects in leukemia by evicting BRD4-NSD3-CHD8 complexes from chromatin to suppress transcription. ChIP-Seq for regulatory factors of BRD4, NSD3, CHD8 and histone modification H3K36me2 in MLL-AF9 transformed acute myeloid leukemia cells (RN2)
Project description:BRD4-NUT megadomains is an order of magnitude larger than super-enhancer regions and displays a more continuously enriched profile rather than appearing as a cluster of individual peaks. Chip-seq mapping of active chromatin marks in BRD4-NUT and different NMC cells
Project description:BRD4 is a key regulatory factor in multiple cancers and cellular stress responses with pleotropic functions. BRD4 regulates chromatin remodeling and transcription through its histone acetyltransferase (HAT) and kinase activities, respectively. The mechanism responsible for switching BRD4 from a chromatin to transcriptional regulator is currently unknown. Here, we report that in response to a broad range of stimuli, this switch is mediated by the JNK kinase which directly interacts with BRD4. JNK specifically phosphorylates human BRD4 at Ser1117, Thr1186 and Thr1212, triggering transient BRD4 release from chromatin. JNK phosphorylation of BRD4 halts its HAT-mediated chromatin regulation and activates its transcription-enhancing kinase function. BRD4 release from chromatin is necessary to toggle between its enzymatic activities: chromatin-bound BRD4 is kinase inactive and RNA Pol II-bound BRD4 does not acetylate chromatin. BRD4 release from chromatin augments its interaction with and phosphorylation of key transcriptional regulators RNA Pol II, PTEFb and c-MYC. The PP4 phosphatase dephosphorylates JNK phosphorylated BRD4 in the nucleoplasm, which promotes its interaction with RNA Pol II at transcriptionally active sites. Accordingly, JNK-mediated release of BRD4 from chromatin leads to significantly elevated transcription of BRD4-regulated immune and inflammatory response genes through enhanced BRD4-Pol II interaction at the promoters of these genes. JNK phosphorylation of BRD4 occurs during T-cell activation and is required for epithelial to mesenchymal transition (EMT) in prostate cancer cells. These findings thus characterize a novel mechanism that triggers the transition of BRD4 from a chromatin regulator to transcriptional activator during stress/immune/inflammatory responses and EMT.
Project description:Transcriptional elongation by RNA polymerase II (Pol II) is regulated by positive transcription elongation factor b (P-TEFb) in association with Bromodomain-containing protein 4 (BRD4). We used genome-wide chromatin immunoprecipitation sequencing in primary human CD4+ T cells to reveal that BRD4 co-localizes with Ser2-phosphorylated Pol II (Pol II Ser2) at both enhancers and promoters of active genes. Disruption of bromodomain:histone acetylation interactions by JQ1, a small-molecule bromodomain inhibitor, resulted in decreased BRD4 binding, reduced Pol II Ser2, and reduced expression of lineage-specific genes in primary human CD4+ T cells. A large number of JQ1-disrupted BRD4 binding regions exhibited di-acetylated H4 (lysine-5 and -8) and H3K27 acetylation (H3K27ac), which correlated with the presence of histone acetyltransferases and deacetylases. Genes associated with BRD4/H3K27ac co-occupancy exhibited significantly higher activity than those associated with H3K27ac or BRD4 binding alone. Comparison of BRD4 binding in T cells and in human embryonic stem cells revealed that enhancer BRD4 binding sites were predominantly lineage-specific. Our findings suggest that BRD4-driven Pol II phosphorylation at serine 2 plays an important role in regulating lineage-specific gene transcription in human CD4+ T cells. Examination of BRD4, total Pol II, serine 2 phosphorylated Pol II and serine 5 phosphorylated Pol II binding in CD4+ T cells (with and without JQ1 treatment) and BRD4 binding in human embryonic stems cell; PolyA RNA expression in CD4+ T cells( with and without JQ1 treatment) using RNA-seq
Project description:A series of Chromatin immunoprecipitation DNA-sequencing (ChIP-seq) experiments were conducted to investigate the effect and mechanism of KDM5C on the recruitment of BRD4 to chromatin, and the effect of this process on histone modification and gene expression. We then performed ChIP-seq for BRD4, KDM5C, H3K27ac, H3K4me3, and H3K4me1 in HeLa and its derivatives cell lines.