Project description:Enhancers are critical regulators of gene expression which are historically defined using plasmid-based approaches. Recent work has emphasized that enhancers operate by alleviating promoter-proximal pause release, implying that a single enhancer operates on a gene at any given moment. By contrast, our previous work postulated that two super-enhancers (SEs) may simultaneously operate on a single gene. To address this discrepancy we employed genomic editing, single cell analyses, and genome-wide approaches to assess how two SEs regulate Nanog expression in embryonic stem cells. We first demonstrate both distance and orientation independence in native chromatin, eliminating the issues raised with plasmid-based approaches. We also demonstrate that two SEs simultaneously operate on Nanog by regulating different phases of transcription, with one SE operating by recruiting and/or initiating RNA Polymerase II, and the second promoting transcriptional elongation after promoter-proximal pause release. These findings imply SEs can use different mechanisms to regulate expression.
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 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: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.
Project description:Super-enhancers are large clusters of transcriptional enhancers that drive expression of genes that control and define cell identity. Improved understanding of the roles super-enhancers play in biology would be afforded by knowing the constellation of factors that constitute these domains and by identifying super-enhancers across the spectrum of human cell types. We describe here the population of transcription factors, cofactors, chromatin regulators and core transcription apparatus that occupy super-enhancers in embryonic stem cells (ESCs) and evidence that super-enhancers are highly transcribed. We then use epigenomic data to produce a catalogue of super-enhancers in a broad range of human cell types. These super-enhancer domains are associated with genes encoding master transcription factors and other components that play important roles in the biology of these cells. Interestingly, sequence variation associated with a broad spectrum of diseases is especially enriched in the super-enhancers of disease-relevant cell types. Furthermore, we find that cancer cells generate super-enhancers at oncogenes and other genes that play important roles in tumor pathogenesis. We discuss these insights and their implications for future study of human health and disease. ChIP-Seq for transcription factors in mouse embryonic stem cells and H3K27ac in Jurkat T-ALL cell line RNA-Seq for mouse embryonic stem cells
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.
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.
Project description:Using GRO-Seq, we find extensive regulation of enhancer RNAs (eRNA) within super-enhancers in response to lipopolysaccharide treatment in macrophages. Both activation and repression of gene expression are associated with super-enhancers and eRNA transcription dynamics. Co-treatment of LPS and the anti-inflammatory drug dexamethasone targeted specific super-enhancers by attenuating their eRNA expression, leading to reduced expression of key inflammatory genes. We propose that super-enhancers function as molecular rheostats integrating the binding profiles of key regulators to produce dynamic profiles of gene expression. Nascent transcriptome (GRO-Seq) analysis over a time course (0, 20, 60, 180 min) of Lipopolisaccharide and Dexamethasone signaling in mouse bone marrow-derived macrophages.
Project description:Super-enhancers are tissue-specific cis-regulatory elements that drive expression of genes associated with cell identity and malignancy. A cardinal feature of super-enhancers is that they are transcribed to produce enhancer-derived RNAs (eRNAs). It remains unclear whether super-enhancers robustly activate genes in situ and whether their functions are attributable to eRNAs or the DNA element. CRISPR/Cas9 was used to systematically delete three discrete super-enhancers at the Nanog locus in embryonic stem cells, revealing functional differences in Nanog transcriptional regulation. One distal super-enhancer 45 kb upstream of Nanog (-45 enhancer) regulates both nearest neighbor genes, Nanog and Dppa3. Interestingly, eRNAs produced at the -45 enhancer specifically regulate Dppa3 expression by stabilizing looping of the -45 enhancer and Dppa3. Our work illustrates that genomic editing is required to determine enhancer function and points to a method to selectively target a subset of super-enhancer-regulated genes by depleting eRNAs.
Project description:Chromatin regulators have become highly attractive targets for cancer therapy, yet many of these regulators are expressed in a broad range of healthy cells and contribute generally to gene expression. An important conundrum has thus emerged: how can inhibition of a general regulator of gene expression produce selective effects at specific oncogenes? Here we investigate how inhibition of the transcriptional coactivator BRD4 (Bromodomain containing 4) leads to selective inhibition of disease-critical oncogenes in a highly malignant blood cancer, multiple myeloma (MM). We found that BRD4 generally occupies the promoter elements of active genes together with the Mediator coactivator, but remarkably high levels of these two coactivator proteins were associated with a small set of exceptionally large enhancers. These super-enhancers are associated with genes that feature prominently in MM biology, including the MYC oncogene. Treatment of MM tumor cells with the BET-bromodomain inhibitor JQ1 led to preferential loss of BRD4 at super-enhancers and consequent transcription elongation defects that preferentially impact genes with super-enhancers, including the c-MYC oncogene. Super-enhancers were found at key oncogenic drivers in many other tumor cells. Thus, super-enhancers can regulate oncogenic drivers in tumor cells, which in some cells can be preferentially disrupted by BRD4 inhibition, which in turn contributes to the selective transcriptional effects observed at these oncogenes. These observations have implications for the discovery of novel cancer therapeutics directed at components of super-enhancers in diverse tumor types. ChIP-Seq for chromatin regulators and RNA Polymerase II in multiple myeloma, glioblastoma multiforme, and small cell lung cancer