RNA Polymerase II Dynamics along the Intestinal Crypt-Villus Axis
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ABSTRACT: The mechanisms underlying intestinal epithelial differentiation are essential for maintaining intestinal health. Gene expression analysis reveals vast changes in the transcriptome as cells transition from crypts to villi, impacting nearly 4000 genes. The regulatory mechanisms driving transcriptome shifts during intestinal differentiation remain incompletely understood. Using ChIP-seq and multi-omic analyses, we have identified differential recruitment of Pol II to gene promoters as the primary driver of transcriptomic shifts during differentiation. Using genetic loss-of-function we show that HNF4, a crucial pro-differentiation transcription factor, is required for recruitment of Pol II to hundreds of genes that are activated during differentiation. Dynamic Pol II recruitment corresponds to dynamic enhancer-promoter looping and chromatin remodeling events, indicating a multi-step mechanism driving differentiation gene expression. Additional regulatory mechanisms, such as differential Pol II pause-release and post-transcriptional processes, may govern specific subsets of differentially expressed genes. In summary, our findings emphasize the central role of Pol II recruitment as the major regulator of intestinal differentiation and highlight the significance of HNF4 in this complex process.
Project description:The mechanisms driving gene expression changes during intestinal differentiation are unclear. Our studies have shown differential recruitment and occupancy of Pol II to be a major driver of these gene expression changes. Additionally, we have identified the transcription factor HNF4 as a key player in shaping this phenomenon. To gain insights into the protein-based mechanisms underlying HNF4-mediated Pol II recruitment, we performed RIME (Rapid Immunoprecipitation Mass Spectrometry of Endogenous proteins) using anti-HNF4A antibodies in primary mouse epithelium.
Project description:We find that HNF4G is an intestine-particular HNF4 paralog, and works redundantly with HNF4A for driving intestinal differentiation by controlling chromatin accessibility and regulating thousands of transcripts particular to differentiated cells. Without HNF4s, cells fail to achieve a differentiated state. A positive feedback loop between HNF4 transcriptional regulation and BMP/SMAD signaling stabilizes differentiation, and the two inputs cooperatively activate differentiation gene expression.
Project description:Poised RNA polymerase II is predominantly found at developmental control genes and is thought to allow their rapid and synchronous induction in response to extracellular signals. How the recruitment of poised RNA Pol II is regulated during development is not known. By isolating muscle tissue from Drosophila embryos at five stages of differentiation, we show that the recruitment of poised Pol II occurs at many genes de novo and this makes them permissive for future gene expression. When compared to other tissues, these changes are stage-specific and not tissue-specific. In contrast, Polycomb group repression is tissue-specific and in combination with Pol II (the balanced state) marks genes with highly dynamic expression. This suggests that poised Pol II is temporally regulated and is held in check in a tissue-specific fashion. We compare our data to mammalian embryonic stem cells and discuss a framework for predicting developmental programs based on chromatin state. MNase-seq data for examining nucleosome occupancy in specific Drosophila tissues during development
Project description:Poised RNA polymerase II is predominantly found at developmental control genes and is thought to allow their rapid and synchronous induction in response to extracellular signals. How the recruitment of poised RNA Pol II is regulated during development is not known. By isolating muscle tissue from Drosophila embryos at five stages of differentiation, we show that the recruitment of poised Pol II occurs at many genes de novo and this makes them permissive for future gene expression. When compared to other tissues, these changes are stage-specific and not tissue-specific. In contrast, Polycomb group repression is tissue-specific and in combination with Pol II (the balanced state) marks genes with highly dynamic expression. This suggests that poised Pol II is temporally regulated and is held in check in a tissue-specific fashion. We compare our data to mammalian embryonic stem cells and discuss a framework for predicting developmental programs based on chromatin state. mRNA-seq of Drosophila tissues during development
Project description:Poised RNA polymerase II is predominantly found at developmental control genes and is thought to allow their rapid and synchronous induction in response to extracellular signals. How the recruitment of poised RNA Pol II is regulated during development is not known. By isolating muscle tissue from Drosophila embryos at five stages of differentiation, we show that the recruitment of poised Pol II occurs at many genes de novo and this makes them permissive for future gene expression. When compared to other tissues, these changes are stage-specific and not tissue-specific. In contrast, Polycomb group repression is tissue-specific and in combination with Pol II (the balanced state) marks genes with highly dynamic expression. This suggests that poised Pol II is temporally regulated and is held in check in a tissue-specific fashion. We compare our data to mammalian embryonic stem cells and discuss a framework for predicting developmental programs based on chromatin state. ChIP-seq for Pol II, H3K4me3 and H3K27me3 in various Drosophila embryos and tissues
Project description:Cyclin-dependent kinase 7 (CDK7), part of the general transcription factor TFIIH, promotes gene transcription by phosphorylating the C-terminal domain of RNA polymerase II (RNA Pol II). Here, we combine rapid CDK7 kinase inhibition with multi-omics analysis to unravel the direct functions of CDK7 in human cells. CDK7 inhibition causes RNA Pol II retention at promoters, leading to decreased RNA Pol II initiation and immediate global downregulation of transcript synthesis. Elongation, termination, and recruitment of co-transcriptional factors are not directly affected. Although RNA Pol II, initiation factors, and Mediator accumulate at promoters, RNA Pol II complexes can also proceed into gene bodies without promoter-proximal pausing while retaining initiation factors and Mediator. Further downstream, RNA Pol II phosphorylation increases and initiation factors and Mediator are released, allowing recruitment of elongation factors and an increase in RNA Pol II elongation velocity. Collectively, CDK7 kinase activity promotes the release of initiation factors and Mediator from RNA Pol II, facilitating RNA Pol II escape from the promoter.
Project description:Cyclin-dependent kinase 7 (CDK7), part of general transcription factor TFIIH, promotes gene transcription by phosphorylating the C-terminal domain of RNA polymerase II (Pol II). Here, we combine rapid CDK7 kinase inhibition with multi-omics analysis to unravel the direct functions of CDK7 in human cells. CDK7 inhibition causes Pol II retention at promoters, leading to decreased Pol II initiation and immediate global downregulation of transcript synthesis. Elongation, termination, and recruitment of co-transcriptional factors are not directly affected. Although Pol II, initiation factors, and Mediator accumulate at promoters, Pol II complexes can also proceed into gene bodies without promoter-proximal pausing while retaining initiation factors and Mediator. Further downstream, Pol II phosphorylation increases, initiation factors and Mediator are released, allowing recruitment of elongation factors and increase in Pol II elongation velocity. Collectively, CDK7 kinase activity promotes the release of initiation factors and Mediator from Pol II, facilitating Pol II escape from the promoter.
Project description:Poised RNA polymerase II is predominantly found at developmental control genes and is thought to allow their rapid and synchronous induction in response to extracellular signals. How the recruitment of poised RNA Pol II is regulated during development is not known. By isolating muscle tissue from Drosophila embryos at five stages of differentiation, we show that the recruitment of poised Pol II occurs at many genes de novo and this makes them permissive for future gene expression. When compared to other tissues, these changes are stage-specific and not tissue-specific. In contrast, Polycomb group repression is tissue-specific and in combination with Pol II (the balanced state) marks genes with highly dynamic expression. This suggests that poised Pol II is temporally regulated and is held in check in a tissue-specific fashion. We compare our data to mammalian embryonic stem cells and discuss a framework for predicting developmental programs based on chromatin state.
Project description:Poised RNA polymerase II is predominantly found at developmental control genes and is thought to allow their rapid and synchronous induction in response to extracellular signals. How the recruitment of poised RNA Pol II is regulated during development is not known. By isolating muscle tissue from Drosophila embryos at five stages of differentiation, we show that the recruitment of poised Pol II occurs at many genes de novo and this makes them permissive for future gene expression. When compared to other tissues, these changes are stage-specific and not tissue-specific. In contrast, Polycomb group repression is tissue-specific and in combination with Pol II (the balanced state) marks genes with highly dynamic expression. This suggests that poised Pol II is temporally regulated and is held in check in a tissue-specific fashion. We compare our data to mammalian embryonic stem cells and discuss a framework for predicting developmental programs based on chromatin state.
Project description:Poised RNA polymerase II is predominantly found at developmental control genes and is thought to allow their rapid and synchronous induction in response to extracellular signals. How the recruitment of poised RNA Pol II is regulated during development is not known. By isolating muscle tissue from Drosophila embryos at five stages of differentiation, we show that the recruitment of poised Pol II occurs at many genes de novo and this makes them permissive for future gene expression. When compared to other tissues, these changes are stage-specific and not tissue-specific. In contrast, Polycomb group repression is tissue-specific and in combination with Pol II (the balanced state) marks genes with highly dynamic expression. This suggests that poised Pol II is temporally regulated and is held in check in a tissue-specific fashion. We compare our data to mammalian embryonic stem cells and discuss a framework for predicting developmental programs based on chromatin state.