Project description:Regulation by gene-distal enhancers is critical for cell-type and condition-specific patterns of gene expression. Thus, to understand the fundamental basis of gene activity in a given cell type or tissue, we must be able to identify the precise locations of enhancers, and to functionally characterize their behaviors. Herein, we demonstrate that transcription is nearly universal feature of enhancers in Drosophila and mammalian cells, and that nascent RNA-sequencing strategies are optimal for identification of both enhancers and super-enhancers. We dissect the mechanisms governing enhancer transcription and discover remarkable similarities with transcription at protein-coding genes. We show that RNA polymerase II (RNAPII) undergoes regulated pausing and release at enhancers. However, as compared to mRNA genes, RNAPII at enhancers is less stable and more prone to early termination. Further, we find that the level of histone H3 Lysine 4 (H3K4) methylation at enhancers corresponds to transcriptional activity, such that highly-active enhancers display H3K4 tri-methylation rather than H3K4 mono-methylation considered a hallmark of enhancers. Finally, our work provides insights into the unique characteristics of super-enhancers, which stimulate high-level gene expression through rapid pause release; interestingly, this property renders associated genes resistant to loss of factors that stabilize paused RNAPII.
Project description:The pause-release model of transcription proposes that pol II pauses 40-100 bases from the start site resulting in a pile-up that is relieved by subsequent release into productive elongation. Pause release is facilitated by PTEFb phosphorylation of the pol II elongation factor, Spt5. We mapped paused polymerases by eNETseq and found frequent pausing in zones that extend ~0.3-3kb into genes, even when PTEFb is inhibited. The fraction of paused polymerases or “pausiness” declines gradually over several kb, and not abruptly as predicted for a discrete pause release event. Spt5 depletion extends pausing zones suggesting that it promotes maturation of elongation complexes to a low-pausing state. Expression of mutants after Spt5 depletion showed that phosphomimetic substitutions in the Spt5 CTR1 domain diminished pausing throughout genes. In contrast mutants that prevent phosphorylation of the Spt5 RNA-binding domain strengthened pausing. Thus distinct Spt5 phospho-isoforms set the balance between pausing and elongation.
Project description:Gene transcription occurs via a cycle of linked events including initiation, promoter proximal pausing and elongation of RNA polymerase II (Pol 2). A key question is how do transcriptional enhancers influence these events to control gene expression? Here we have used a new approach to quantify transcriptional initiation and pausing in-vivo, while simultaneously identifying transcription start sites (TSSs) and pause-sites (TPSs). When analysed in parallel with nascent RNA-seq, these data show that differential gene expression is achieved predominantly via changes in transcription initiation rather than Pol 2 pausing or elongation. Using genetically engineered mouse models deleted for specific enhancers we show that these elements control gene expression via Pol 2 recruitment and/or initiation rather than via promoter proximal pause release. Using genome-wide analysis we show that enhancers, in general, control gene expression at the stage of Pol 2 recruitment and initiation rather than via pausing.
Project description:Gene transcription occurs via a cycle of linked events including initiation, promoter proximal pausing and elongation of RNA polymerase II (Pol 2). A key question is how do transcriptional enhancers influence these events to control gene expression? Here we have used a new approach to quantify transcriptional initiation and pausing in-vivo, while simultaneously identifying transcription start sites (TSSs) and pause-sites (TPSs). When analysed in parallel with nascent RNA-seq, these data show that differential gene expression is achieved predominantly via changes in transcription initiation rather than Pol 2 pausing or elongation. Using genetically engineered mouse models deleted for specific enhancers we show that these elements control gene expression via Pol 2 recruitment and/or initiation rather than via promoter proximal pause release. Using genome-wide analysis we show that enhancers, in general, control gene expression at the stage of Pol 2 recruitment and initiation rather than via pausing.
Project description:Gene transcription occurs via a cycle of linked events including initiation, promoter proximal pausing and elongation of RNA polymerase II (Pol 2). A key question is how do transcriptional enhancers influence these events to control gene expression? Here we have used a new approach to quantify transcriptional initiation and pausing in-vivo, while simultaneously identifying transcription start sites (TSSs) and pause-sites (TPSs). When analysed in parallel with nascent RNA-seq, these data show that differential gene expression is achieved predominantly via changes in transcription initiation rather than Pol 2 pausing or elongation. Using genetically engineered mouse models deleted for specific enhancers we show that these elements control gene expression via Pol 2 recruitment and/or initiation rather than via promoter proximal pause release. Using genome-wide analysis we show that enhancers, in general, control gene expression at the stage of Pol 2 recruitment and initiation rather than via pausing.
Project description:Gene transcription occurs via a cycle of linked events including initiation, promoter proximal pausing and elongation of RNA polymerase II (Pol 2). A key question is how do transcriptional enhancers influence these events to control gene expression? Here we have used a new approach to quantify transcriptional initiation and pausing in-vivo, while simultaneously identifying transcription start sites (TSSs) and pause-sites (TPSs). When analysed in parallel with nascent RNA-seq, these data show that differential gene expression is achieved predominantly via changes in transcription initiation rather than Pol 2 pausing or elongation. Using genetically engineered mouse models deleted for specific enhancers we show that these elements control gene expression via Pol 2 recruitment and/or initiation rather than via promoter proximal pause release. Using genome-wide analysis we show that enhancers, in general, control gene expression at the stage of Pol 2 recruitment and initiation rather than via pausing.
Project description:Gene transcription occurs via a cycle of linked events including initiation, promoter proximal pausing and elongation of RNA polymerase II (Pol 2). A key question is how do transcriptional enhancers influence these events to control gene expression? Here we have used a new approach to quantify transcriptional initiation and pausing in-vivo, while simultaneously identifying transcription start sites (TSSs) and pause-sites (TPSs). When analysed in parallel with nascent RNA-seq, these data show that differential gene expression is achieved predominantly via changes in transcription initiation rather than Pol 2 pausing or elongation. Using genetically engineered mouse models deleted for specific enhancers we show that these elements control gene expression via Pol 2 recruitment and/or initiation rather than via promoter proximal pause release. Using genome-wide analysis we show that enhancers, in general, control gene expression at the stage of Pol 2 recruitment and initiation rather than via pausing.
Project description:Gene transcription occurs via a cycle of linked events including initiation, promoter proximal pausing and elongation of RNA polymerase II (Pol 2). A key question is how do transcriptional enhancers influence these events to control gene expression? Here we have used a new approach to quantify transcriptional initiation and pausing in-vivo, while simultaneously identifying transcription start sites (TSSs) and pause-sites (TPSs). When analysed in parallel with nascent RNA-seq, these data show that differential gene expression is achieved predominantly via changes in transcription initiation rather than Pol 2 pausing or elongation. Using genetically engineered mouse models deleted for specific enhancers we show that these elements control gene expression via Pol 2 recruitment and/or initiation rather than via promoter proximal pause release. Using genome-wide analysis we show that enhancers, in general, control gene expression at the stage of Pol 2 recruitment and initiation rather than via pausing.