Project description:Control of RNA transcription is critical for the development and homeostasis of all organisms, and can occur at multiple steps of the transcription cycle, including RNA polymerase II (Pol II) recruitment, initiation, promoter-proximal pausing, and elongation. That Pol II accumulates on many promoters in metazoans implies that steps other than Pol II recruitment are rate-limiting and regulated 1-6. By integrating genome-wide Pol II chromatin immunoprecipition (ChIP) and Global Run-On (GRO) genomic data sets from Drosophila cells, we examined critical features of Pol II near promoters. The accumulation of promoter-proximal polymerase is widespread, occurring on 70% of active genes; and unlike elongating Pol II within the body of genes, promoter Pol II are held paused by factors like NELF, unable to transcribe unless nuclei are treated with strong detergent. Notably, we find that the vast majority of promoter-proximal Pol II detected by ChIP are paused, thereby identifying the biochemical nature of this rate-limiting step in transcription. Finally, we demonstrate that Drosophila promoters do not have the upstream divergent Pol II that is seen so broadly and prominently on mammalian promoters. We postulate this is a consequence of Drosophila’s extensive use of directional core promoter sequence elements, which contrasts with mammals’ lack of directional elements and prevalence of CpG island core promoters. In support of this idea, we show that the fraction of mammalian promoters containing a TATA box core element is dramatically depleted of upstream divergent transcription.
Project description:Control of RNA transcription is critical for the development and homeostasis of all organisms, and can occur at multiple steps of the transcription cycle, including RNA polymerase II (Pol II) recruitment, initiation, promoter-proximal pausing, and elongation. That Pol II accumulates on many promoters in metazoans implies that steps other than Pol II recruitment are rate-limiting and regulated 1-6. By integrating genome-wide Pol II chromatin immunoprecipition (ChIP) and Global Run-On (GRO) genomic data sets from Drosophila cells, we examined critical features of Pol II near promoters. The accumulation of promoter-proximal polymerase is widespread, occurring on 70% of active genes; and unlike elongating Pol II within the body of genes, promoter Pol II are held paused by factors like NELF, unable to transcribe unless nuclei are treated with strong detergent. Notably, we find that the vast majority of promoter-proximal Pol II detected by ChIP are paused, thereby identifying the biochemical nature of this rate-limiting step in transcription. Finally, we demonstrate that Drosophila promoters do not have the upstream divergent Pol II that is seen so broadly and prominently on mammalian promoters. We postulate this is a consequence of Drosophila’s extensive use of directional core promoter sequence elements, which contrasts with mammals’ lack of directional elements and prevalence of CpG island core promoters. In support of this idea, we show that the fraction of mammalian promoters containing a TATA box core element is dramatically depleted of upstream divergent transcription. ChIP-seq data set for Pol II (rpb3) (2 replicates).
Project description:Control of RNA transcription is critical for the development and homeostasis of all organisms, and can occur at multiple steps of the transcription cycle, including RNA polymerase II (Pol II) recruitment, initiation, promoter-proximal pausing, and elongation. That Pol II accumulates on many promoters in metazoans implies that steps other than Pol II recruitment are rate-limiting and regulated 1-6. By integrating genome-wide Pol II chromatin immunoprecipition (ChIP) and Global Run-On (GRO) genomic data sets from Drosophila cells, we examined critical features of Pol II near promoters. The accumulation of promoter-proximal polymerase is widespread, occurring on 70% of active genes; and unlike elongating Pol II within the body of genes, promoter Pol II are held paused by factors like NELF, unable to transcribe unless nuclei are treated with strong detergent. Notably, we find that the vast majority of promoter-proximal Pol II detected by ChIP are paused, thereby identifying the biochemical nature of this rate-limiting step in transcription. Finally, we demonstrate that Drosophila promoters do not have the upstream divergent Pol II that is seen so broadly and prominently on mammalian promoters. We postulate this is a consequence of Drosophila’s extensive use of directional core promoter sequence elements, which contrasts with mammals’ lack of directional elements and prevalence of CpG island core promoters. In support of this idea, we show that the fraction of mammalian promoters containing a TATA box core element is dramatically depleted of upstream divergent transcription.
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.