Project description:Transcription activation involves RNA polymerase II (Pol II) recruitment and release from the promoter into productive elongation, but how specific chromatin regulators control these steps is unclear. Here we identify a novel activity of the histone acetyltransferase p300/CBP in regulating promoter-proximal paused Pol II. We find that Drosophila CBP (nejire) inhibition impedes transcription through the +1 nucleosome leading to accumulation of Pol II at this position on all expressed genes. Promoters strongly occupied by CBP and GAGA-factor have high levels of paused Pol II, a unique chromatin signature and strong expression regardless of cell type. Interestingly, CBP activity is rate-limiting for Pol II recruitment to these highly-paused promoters through an interaction with TFIIB, but for transit into elongation by histone acetylation at other genes. Thus, CBP directly stimulates both Pol II recruitment and the ability to traverse the first nucleosome, thereby promoting transcription of most genes. This SuperSeries is composed of the SubSeries listed below.
Project description:Transcription activation involves RNA polymerase II (Pol II) recruitment and release from the promoter into productive elongation, but how specific chromatin regulators control these steps is not fully understood. Here we identify a novel activity of the co-regulator and histone acetyltransferase p300/CBP in positioning promoter-proximal paused Pol II. We find that CBP inhibition impedes transcription through the +1 nucleosome, causing âdribblingâ of Pol II from the canonical pause site genome-wide. We further discovered that promoters strongly occupied by Drosophila CBP and GAGA-factor have high levels of paused Pol II, a unique chromatin signature and strong expression regardless of cell type. Interestingly, CBP activity is rate-limiting for Pol II recruitment to these highly-paused promoters but for transit into elongation at other genes. Thus, we uncover a key role for CBP during transcription in directly controlling different rate-limiting steps depending on promoter features. Examination of transcriptional regulation with and without CBP inhibition for 10 minutes in Drosophila S2 cells. Two biological replicates for each condition.
Project description:Transcription activation involves RNA polymerase II (Pol II) recruitment and release from the promoter into productive elongation, but how specific chromatin regulators control these steps is not fully understood. Here we identify a novel activity of the co-regulator and histone acetyltransferase p300/CBP in positioning promoter-proximal paused Pol II. We find that CBP inhibition impedes transcription through the +1 nucleosome, causing “dribbling” of Pol II from the canonical pause site genome-wide. We further discovered that promoters strongly occupied by Drosophila CBP and GAGA-factor have high levels of paused Pol II, a unique chromatin signature and strong expression regardless of cell type. Interestingly, CBP activity is rate-limiting for Pol II recruitment to these highly-paused promoters but for transit into elongation at other genes. Thus, we uncover a key role for CBP during transcription in directly controlling different rate-limiting steps depending on promoter features.
Project description:The metazoan-specific acetyltransferase p300/CBP is involved in activating signalinduced, enhancer-mediated transcription of cell-type-specific genes. However, the global kinetics and mechanisms of p300/CBP activity-dependent transcription activation remain poorly understood. We performed genome-wide, time-resolved analyses to show that enhancers and super-enhancers are dynamically activated through p300/CBP-catalyzed acetylation, deactivated by the opposing deacetylase activity, and kinetic acetylation directly contributes to maintaining cell identity at very rapid timescales. The acetyltransferase activity is dispensable for the recruitment of p300/CBP and transcription factors, but essential for promoting the recruitment of TFIID and RNAPII at virtually all enhancers and enhancer-regulated genes. This identifies pre-initiation complex assembly as a dynamically controlled step in the transcription cycle and reveals p300/CBP-catalyzed acetylation as the signal that specifically promotes transcription initiation at enhancer-regulated genes. We propose that p300/CBP activity uses a ‘recruit-and-release’ mechanism to simultaneously promote RNAPII recruitment and pause release, and thereby, enables kinetic activation of enhancer-mediated transcription.
Project description:The metazoan-specific acetyltransferase p300/CBP is involved in activating signalinduced, enhancer-mediated transcription of cell-type-specific genes. However, the global kinetics and mechanisms of p300/CBP activity-dependent transcription activation remain poorly understood. We performed genome-wide, time-resolved analyses to show that enhancers and super-enhancers are dynamically activated through p300/CBP-catalyzed acetylation, deactivated by the opposing deacetylase activity, and kinetic acetylation directly contributes to maintaining cell identity at very rapid timescales. The acetyltransferase activity is dispensable for the recruitment of p300/CBP and transcription factors, but essential for promoting the recruitment of TFIID and RNAPII at virtually all enhancers and enhancer-regulated genes. This identifies pre-initiation complex assembly as a dynamically controlled step in the transcription cycle and reveals p300/CBP-catalyzed acetylation as the signal that specifically promotes transcription initiation at enhancer-regulated genes. We propose that p300/CBP activity uses a ‘recruit-and-release’ mechanism to simultaneously promote RNAPII recruitment and pause release, and thereby, enables kinetic activation of enhancer-mediated transcription.
Project description:The metazoan-specific acetyltransferase p300/CBP is involved in activating signalinduced, enhancer-mediated transcription of cell-type-specific genes. However, the global kinetics and mechanisms of p300/CBP activity-dependent transcription activation remain poorly understood. We performed genome-wide, time-resolved analyses to show that enhancers and super-enhancers are dynamically activated through p300/CBP-catalyzed acetylation, deactivated by the opposing deacetylase activity, and kinetic acetylation directly contributes to maintaining cell identity at very rapid timescales. The acetyltransferase activity is dispensable for the recruitment of p300/CBP and transcription factors, but essential for promoting the recruitment of TFIID and RNAPII at virtually all enhancers and enhancer-regulated genes. This identifies pre-initiation complex assembly as a dynamically controlled step in the transcription cycle and reveals p300/CBP-catalyzed acetylation as the signal that specifically promotes transcription initiation at enhancer-regulated genes. We propose that p300/CBP activity uses a ‘recruit-and-release’ mechanism to simultaneously promote RNAPII recruitment and pause release, and thereby, enables kinetic activation of enhancer-mediated transcription.
Project description:Despite the critical regulatory function of promoter-proximal pausing, the influence of pausing kinetics on transcriptional control remains an active area of investigation. Here, we present Start-TimeLapse-seq (STL-seq), a method that captures the genome-wide kinetics of short, capped RNA turnover and reveals principles of regulation at the pause site. By measuring the rates of release into elongation and premature termination through inhibition of pause release, we determine that pause-release rates are highly variable and most promoter-proximal paused RNA Polymerase II molecules prematurely terminate (~80%). The preferred regulatory mechanism upon a hormonal stimulus (20-hydroxyecdysone) is to influence pause-release rather than termination rates. Transcriptional shutdown occurs concurrently with induction of promoter-proximal termination under hyperosmotic stress but paused transcripts from TATA box-containing promoters remain stable, demonstrating an important role for cis-acting DNA elements in pausing. STL-seq dissects the kinetics of pause release and termination, providing an opportunity to identify mechanisms of transcriptional regulation.
Project description:Trimethylation of histone H3 lysine 4 (H3K4me3) is associated with transcriptional start sites and proposed to regulate transcription initiation. However, redundant functions of the H3K4 SET1/COMPASS methyltransferase complexes complicate elucidation of the specific role of H3K4me3 in transcriptional regulation. Here, by using mouse embryonic stem cells (mESCs) as a model system, we show that acute ablation of shared subunits of the SET1/COMPASS complexes leads to complete loss of all H3K4 methylation. H3K4me3 turnover occurs more rapidly than H3K4me1 and H3K4me2 and is dependent on KDM5 demethylases. Surprisingly, acute loss of H3K4me3 does not have detectable effects on transcriptional initiation but leads to a widespread decrease in transcriptional output, an increase in RNA polymerase II (RNAPII) pausing and slower elongation. Notably, we show that H3K4me3 is required for the recruitment of the Integrator Complex Subunit 11 (INTS11), which is essential for the eviction of paused RNAPII and transcriptional elongation. Thus, our study demonstrates a distinct role for H3K4me3 in transcriptional pause-release and elongation rather than transcriptional initiation.
Project description:The regulation of gene expression by RNA polymerase II (Pol II) is a multistep process requiring the concerted action of diverse transcription factors. Very little is known about in vivo function of transcription factor SPT5 as its deletion results in loss of viability. To circumvent this issue and define in vivo mechanism of action for SPT5, we employed acute degradation of SPT5 and studied its consequence on transcription. We find that SPT5 loss triggers degradation of the core Pol II subunit RPB1, a process which we show to be evolutionarily conserved from yeast to human. This RPB1 degradation requires the E3 ubiquitin ligase Cullin 3, the unfoldase VCP/p97 and a novel form of CDK9 kinase complex. SPT5 specifically stabilizes Pol II at promoter proximal regions, permitting Pol II release from promoters to gene bodies. Our findings provide mechanistic insight into the in vivo function of SPT5 in stabilization of promoter-proximal Pol II prior to release into gene bodies for safeguarding accurate gene expression.