Project description:Clinical responses to kinase inhibitor therapy in acute myeloid leukemia (AML) are limited by the inevitable development of resistance. A major contributor to resistance is early epigenetic adaptation, leading to persistence of a small number of leukemia cells. Here we show that inhibition of the epigenetic regulator lysine-specific deme-thylase 1 (LSD1) augments the response to inhibitors of the FLT3 kinase in AML. We demonstrate that combined FLT3 and LSD1 inhibition results in synergistic cell death of FLT3-mutant AML cells via proliferative arrest and apoptosis. The drug combination synergistically activates a pro-differentiative epigenetic and transcriptional program while simultaneously suppressing the activity of MYC target genes. High resolution multi-modal epigenetic analyses revealed that combined FLT3 and LSD1 resulted in the suppression of MYC-bound promoters and the activation of PU.1-bound enhanc-ers. Forced expression of MYC partially abrogated the drug effect, and regulon en-richment analysis in primary AML samples nominated STAT5 as a putative regulator of MYC gene expression. STAT5 is highly bound to the MYC blood super-enhancer and inhibition of FLT3 results in a loss of STAT5 binding and a loss of super enhancer acti-vation. Furthermore, knockdown of STAT5 augments LSD1-inhibitor induced cell death. LSD1 inhibition also directly represses MYC target genes which show specific accumulation of the repressive LSD1 substrate H3K9me1. We validated these findings in 67 primary AML samples including 19 FLT3-ITD positive AML samples, with the vast majority demonstrating improved responses with the drug combination. High MYC regulon activity was a predictor of response to the drug combination and RNA-seq on drug treated AML samples revealed suppression of MYC target genes. Finally, single cell ATAC seq on primary AML blasts treated ex-vivo with combined FLT3 and LSD1 inhibition results in a shift from MYC super enhancer-high to a MYC super enhancer-low cell state. Collectively, these studies provide preclinical rationale for the investiga-tion of dual FLT3 and LSD1 inhibition in clinical trial.
Project description:The master transcription factors Oct4, Sox2 and Nanog bind enhancer elements and recruit the Mediator co-activator to activate much of the gene expression program of embryonic stem cells (ESCs). We report here that the ESC master transcription factors and Mediator form “super-enhancers” at most genes known to control the pluripotent state, including those encoding the master transcription factors themselves. These super-enhancers consist of extraordinarily large genomic domains occupied by exceptional amounts of Oct4, Sox2, Nanog, Klf4, Esrrb and Mediator. Super-enhancers stimulate considerably higher transcription than typical enhancers in vivo and in reporter vectors. Reduced levels of Oct4 or Mediator cause preferential loss of expression of super-enhancer-associated genes relative to other genes, suggesting how changes in gene expression programs might be accomplished during development. In other more differentiated cells, super-enhancers containing cell-type-specific master transcription factors are also found at genes that define cell identity. These results implicate super-enhancers in the control of mammalian cell identity and differentiation. ChIP-Seq and controls associated with Super-Enhancers in murine cell types
Project description:The transcription factor T-bet directs Th1 cell differentiation, but the molecular mechanisms that underlie this lineage-specific gene regulation are not completely understood. Here, we show that T-bet acts through super-enhancers in human and mouse Th1 cells to recruit Mediator and P-TEFb in the form of the super elongation complex (SEC). Th1-specific genes are poised in Th2 cells while T-bet-mediated recruitment of P-TEFb in Th1 cells activates transcriptional elongation. P-TEFb is recruited to both genes and super-enhancers, where it activates enhancer RNA transcription. P-TEFb inhibition and Mediator and SEC knockdown selectively block activation of T-bet target genes and P-TEFb inhibition abrogates Th1-associated experimental autoimmune uveitis. T-bet activity is independent of changes in NF-κB RelA and Brd4 binding, but T-bet- and NF-κB-mediated pathways converge to allow P-TEFb recruitment. These data support a model in which lineage-specifying factors allow recruitment of P-TEFb to poised genes to promote differentiation of alternative T cell fates.
Project description:The master transcription factors Oct4, Sox2 and Nanog bind enhancer elements and recruit the Mediator co-activator to activate much of the gene expression program of embryonic stem cells (ESCs). We report here that the ESC master transcription factors and Mediator form M-bM-^@M-^\super-enhancersM-bM-^@M-^] at most genes known to control the pluripotent state, including those encoding the master transcription factors themselves. These super-enhancers consist of extraordinarily large genomic domains occupied by exceptional amounts of Oct4, Sox2, Nanog, Klf4, Esrrb and Mediator. Super-enhancers stimulate considerably higher transcription than typical enhancers in vivo and in reporter vectors. Reduced levels of Oct4 or Mediator cause preferential loss of expression of super-enhancer-associated genes relative to other genes, suggesting how changes in gene expression programs might be accomplished during development. In other more differentiated cells, super-enhancers containing cell-type-specific master transcription factors are also found at genes that define cell identity. These results implicate super-enhancers in the control of mammalian cell identity and differentiation. Time-course of gene expression following shRNA knockdown of Oct4 and Med12.
Project description:NR4A nuclear receptors are tumor suppressors of acute myeloid leukemia (AML) that are silenced in AML at the level of transcription elongation. Using RNA-Seq, we show that NR4As inhibit leukemic cell growth largely through suppression of MYC pathway genes. MYC is highly expressed in AML and contributes to AML progression and therapeutic resistance. MYC expression in AML is driven by a super enhancer cluster 1.8Mbp downstream of the MYC locus, which is highly sensitive to therapeutic intervention, including treatment with BET inhibitors. We recently identified dihydroergotamine (DHE) as an FDA-approved drug that strongly induces NR4A transcription in AML cells and operates effectively as an antileukemic therapy. RNA-Seq in MOLM-14 identified MYC as the most statistically repressed target of DHE. Using ChIP-Seq for MED1 as a readout for Mediator occupancy, we identified super enhancers in MOLM-14 cells and show that treatment with DHE significantly suppresses MED1 signal across a subset of super enhancers, including the MYC super enhancer. Finally, we demonstrate that NR4As are broadly associated with global super enhancers, including sites where super enhancer activity is retained, reduced, or gained.
Project description:Cyclin Dependent Kinases CDK8 and CDK19 (Mediator kinase) are regulatory components of the Mediator complex, a highly conserved complex that fine tunes transcriptional output. While Mediator kinase has been implicated in the transcriptional control of key pathways necessary for development and growth, its function in vivo has not been well described. Herein, we report the consequences of complete ablation of both Cdk8/19 on tissue homeostasis. We show that intestinal epithelial specific deletion of Mediator kinase leads to a distinct defect in secretory progenitor differentiation with broad loss of the intestinal secretory cell types. Using a phospho-proteogenomic approach, we show that the Cdk8/19 kinase module interacts with and phosphorylates components of the chromatin remodeling complex Swi/Snf in intestinal epithelial cells. Genomic localisation of Swi/Snf and Mediator shows Cdk8/19-dependent genomic binding at distinct super-enhancer loci within key lineage specification genes, including the master regulator of secretory differentiation ATOH1. Using CRISPRi/CRISPRa, we identify a distinct Mediator- Swi/Snf bound enhancer element that is necessary and sufficient for ATOH1 expression in a Mediator-kinase dependent manner. As such, these studies uncover a newly described transcriptional mechanism of ATOH1-dependent intestinal cell specification that is dependent on the coordinated interaction of the chromatin remodeling complex Swi/Snf and Mediator complex.
Project description:Cyclin Dependent Kinases CDK8 and CDK19 (Mediator kinase) are regulatory components of the Mediator complex, a highly conserved complex that fine tunes transcriptional output. While Mediator kinase has been implicated in the transcriptional control of key pathways necessary for development and growth, its function in vivo has not been well described. Herein, we report the consequences of complete ablation of both Cdk8/19 on tissue homeostasis. We show that intestinal epithelial specific deletion of Mediator kinase leads to a distinct defect in secretory progenitor differentiation with broad loss of the intestinal secretory cell types. Using a phospho-proteogenomic approach, we show that the Cdk8/19 kinase module interacts with and phosphorylates components of the chromatin remodeling complex Swi/Snf in intestinal epithelial cells. Genomic localisation of Swi/Snf and Mediator shows Cdk8/19-dependent genomic binding at distinct super-enhancer loci within key lineage specification genes, including the master regulator of secretory differentiation ATOH1. Using CRISPRi/CRISPRa, we identify a distinct Mediator-Swi/Snf bound enhancer element that is necessary and sufficient for ATOH1 expression in a Mediator-kinase dependent manner. As such, these studies uncover a newly described transcriptional mechanism of ATOH1-dependent intestinal cell specification that is dependent on the coordinated interaction of the chromatin remodeling complex Swi/Snf and Mediator complex.
Project description:The master transcription factors Oct4, Sox2 and Nanog bind enhancer elements and recruit the Mediator co-activator to activate much of the gene expression program of embryonic stem cells (ESCs). We report here that these ESC master transcription factors and Mediator form M-bM-^@M-^\super-enhancersM-bM-^@M-^] at most genes that are known to control the pluripotent state, including those encoding the master transcription factors themselves. These super-enhancers consist of extraordinarily large genomic domains occupied by exceptional amounts of Oct4 and Mediator. Super-enhancers stimulate considerably higher transcription than typical enhancers in reporter vectors. ESC differentiation causes preferential loss of expression of super-enhancer -associated genes. Super-enhancers are also found at key cell identity genes in differentiated cells. These results implicate super-enhancers in the control of mammalian cell identity and differentiation and suggest that these elements might generally be used to identify genes that control cell-type specific gene expression programs in many mammalian cells. ChIP-Seq and RNA-seq of Med1 in ZHBTc4 ES during treatment with doxycycline. ChIP-Seq data of Med1 in 38B9 pro-B cells.