HnRNP R negatively regulates transcription by modulating the association of P-TEFb with 7SK and BRD4
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ABSTRACT:
PROVIDER: PRJNA837107 | ENA |
REPOSITORIES: ENA
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Project description:The P-TEFb complex promotes transcription elongation by releasing paused RNA polymerase II. P-TEFb itself is known to be inactivated through binding to the non-coding RNA 7SK but there is only limited information about mechanisms regulating their association. Here, we show that cells deficient in the RNA-binding protein hnRNP R, a known 7SK interactor, exhibit increased transcription due to phosphorylation of RNA polymerase II. Intriguingly, loss of hnRNP R promotes the release of P-TEFb from 7SK, accompanied by enhanced hnRNP A1 binding to 7SK. Additionally, we found that hnRNP R interacts with BRD4, and that hnRNP R depletion increases BRD4 binding to the P-TEFb component CDK9. Finally, CDK9 is stabilized upon loss of hnRNP R and its association with Cyclin K is enhanced. Together, our results indicate that hnRNP R negatively regulates transcription by modulating the activity and stability of the P-TEFb complex, exemplifying the multimodal regulation of P-TEFb by an RNA-binding protein.
2022-07-21 | GSE202720 | GEO
Project description:Releasing promoter-proximally-paused RNA polymerase II (RNAPII) by the positive transcription elongation factor b (P-TEFb) is a central regulatory step of eukaryotic mRNA synthesis. The nuclear activity of P-TEFb is controlled mainly by the 7SK small nuclear RNP (snRNP) which sequesters active P-TEFb into inactive 7SK/P-TEFb snRNP. Here we demonstrate that under normal culture conditions, the lack of 7SK snRNP has only a minor impact on global RNAPII transcription and promoter-proximal pausing without detectable consequences on cell growth and proliferation. However, upon ultraviolet (UV) light-induced DNA damage, cells lacking 7SK have a defective transcriptional response and highly reduced viability. Both UV-induced release of ‘lesion-scanning’ polymerases and activation of key early responsive genes are compromised in the absence of 7SK. We show that proper induction of 7SK-dependent UV-responsive genes, namely efficient release of paused RNAPII and recruitment of key elongation factors, requires P-TEFb activity directly mobilized from the nucleoplasmic 7SK/P-TEFb snRNP.
2021-03-30 | GSE147055 | GEO
Project description:Disturbed RNA processing and subcellular transport contribute to the pathomechanisms of motoneuron diseases such as amyotrophic lateral sclerosis and spinal muscular atrophy. RNA-binding proteins are involved in these processes, but the mechanisms how they regulate the subcellular diversity of transcriptomes, in particular in axons, are not understood. hnRNP R interacts with several proteins involved in motoneuron diseases. It is located in axons of developing motoneurons and its depletion causes defects in axon growth. Here, we used iCLIP to determine the RNA interactome of hnRNP R in motoneurons. We identified ~3,500 RNA targets, predominantly with functions in synaptic transmission and axon guidance. Among the RNA targets identified by iCLIP, the non-coding RNA 7SK was the top interactor of hnRNP R. We detected 7SK in the nucleus but also in the cytosol of motoneurons. In axons, 7SK localized in close proximity to hnRNP R and depletion of hnRNP R reduced axonal 7SK. Furthermore, suppression of 7SK led to defective axon growth that was accompanied by axonal transcriptome alterations similar to those caused by hnRNP R depletion. Using a series of 7SK deletion mutants we show that the function of 7SK in axon elongation depends on its interaction with hnRNP R but not with the pTEF-B complex involved in transcriptional regulation. These results propose a role of 7SK as essential interactor of hnRNP R to regulate its function in axon maintenance.
2018-03-06 | GSE77101 | GEO
Project description:The P-TEFb complex promotes transcription elongation by releasing paused RNA polymerase II. P-TEFb itself is known to be inactivated through binding to the non-coding RNA 7SK but there is only limited information about mechanisms regulating their association. Here, we show that cells deficient in the RNA-binding protein hnRNP R, a known 7SK interactor, exhibit increased transcription due to phosphorylation of RNA polymerase II. Intriguingly, loss of hnRNP R promotes release of P-TEFb from 7SK, accompanied by enhanced hnRNP A1 binding to 7SK. Additionally, we found that hnRNP R interacts with BRD4, and that hnRNP R depletion increases BRD4 binding to the P-TEFb component CDK9. Finally, CDK9 is stabilized upon loss of hnRNP R and its association with Cyclin K is enhanced. Together, our results indicate that hnRNP R negatively regulates transcription by modulating the activity and stability of the P-TEFb complex, exemplifying the multimodal regulation of P-TEFb by an RNA-binding protein.
| S-SCDT-EMBOR-2022-55432-T | biostudies-other
Project description:The switch of RNAP II from the paused to the productive transcription elongation state is a pivotal regulatory step requiring specific phosphorylations catalyzed by the P-TEFb kinase. Nucleosolic P-TEFb activity is inhibited by its interaction with the ribonuclear protein complex built around the 7SK small nuclear RNA (7SK snRNP). MePCE is the RNA methyltransferase that methylates and stabilizes 7SK in the nucleosol. Here we report that MePCE also binds chromatin through the tail of histone H4 to serve as a P-TEFb activator at specific genes important for cellular identity. Notably, this histone binding abolishes MePCE’s RNA methyltransferase activity towards 7SK, explaining why MePCE-bound P-TEFb on chromatin may not be associated with the full 7SK snRNP and is competent for RNAP II activation. Overall, our results suggest that a crosstalk between the histone binding and RNA methylation activities of MePCE regulates P-TEFb activation on chromatin in a 7SK- and Brd4-independent manner.
2018-02-05 | GSE108830 | GEO
Project description:The dynamic phosphorylation process regulated by the positive transcription elongation factor b (P-TEFb), a CDK9-cyclin T heterodimer, is critical for transcription elongation of numerous mammalian genes. Most P-TEFb in cells are normally sequestered in the 7SK snRNP, and their release from this complex is well-controlled to maintain proper cell homeostasis and growth. The comprehensive profiling of CDK9 substrates is essential for understanding diverse functions of P-TEFb in controlling gene expression. Here, integrative proteomics methodologies are developed to globally identify the potential substrates of CDK9 in vivo. Our results show that the 7SK methylphosphate capping enzyme MePCE is directly phosphorylated by CDK9 within the 7SK snRNP, which is known to exhibit little kinase activity toward other known CDK9 substrates. Upon ultraviolet radiation, MePCE becomes phosphorylated, leading to the dissociation of 7SK snRNP and release of P-TEFb to activate transcription. Meanwhile, the phosphorylation of MePCE does not affect its methyltransferase activity toward 7SK RNA. Our data suggest that even though CDK9 in 7SK snRNP has little kinase activity toward external substrates, it can phosphorylate the snRNP integral component MePCE, which is required to release P-TEFb. This novel inside-to-outside mode of P-TEFb activation may serve as a critical checkpoint in regulating gene transcription under stressful conditions.
2024-07-03 | PXD053627 |
Project description:Eukaryotic genomes are extensively transcribed, but unfettered transcription alters gene expression and leads to genome damage by several means. Divergent transcription occurs at active enhancers and promoters, distinct classes of cis-regulatory elements critical for precise control of gene expression. A key step in RNA Polymerase II (Pol II) transcription is promoter-proximal pausing, which occurs bidirectionally ~25-60 nucleotides downstream of transcription start sites (TSS). Promoter-proximal pause release is gated by the positive transcription elongation factor b (P-TEFb)-7SK snRNA pathway; release from 7SK allows P-TEFb phosphorylation of Pol II and subsequent elongation. The 7SK small nuclear ribonucleoprotein (snRNP) is thought to reside in the nucleoplasm, but it has been suggested that 7SK could operate physically on chromatin. Notably, while enhancer transcription is one of the earliest steps of gene activation and some enhancer RNAs (eRNAs) participate in gene regulation, far less is known about the control of eRNA transcription. Here we show that 7SK inhibits enhancer transcription by modulating nucleosome position. 7SK occupies enhancers and super enhancers genome-wide, and 7SK is required to limit eRNA initiation and synthesis in a manner distinct from promoter pausing. Clustered elements at super enhancers uniquely require 7SK to prevent convergent transcription of colliding polymerases that lead to DNA damage. 7SK inhibits enhancer transcription by modulating chromatin structure, physically interacts with the BAF chromatin remodeling complex, and is required to recruit BAF to enhancers. In turn, 7SK occupancy at enhancers coincides with Brd4 and is exquisitely sensitive to the bromodomain inhibitor JQ1. Thus, 7SK employs distinct mechanisms to counteract diverse consequences of pervasive transcription that distinguish super enhancers, enhancers, and promoters.
2016-02-01 | GSE72599 | GEO
Project description:The hnRNP A1 and A2 proteins regulate processes such as alternative pre-mRNA splicing and mRNA stability. Here, we report that a reduction in the levels of hnRNP A1 and A2 by RNA interference or their cytoplasmic retention by osmotic stress drastically increases the transcription of a reporter gene. Based on previous work, we propose that this effect may be linked to a decrease in the activity of the transcription elongation factor P-TEFb. Consistent with this hypothesis, the transcription of the reporter gene was stimulated when the catalytic component of P-TEFb, CDK9, was inhibited with DRB. While low levels of A1/A2 stimulated the association of RNA polymerase II with the reporter gene, they also increased the association of CDK9 with the repressor 7SK RNA, and compromised the recovery of promoter-distal transcription on the Kitlg gene after the release of pausing. Transcriptome analysis revealed that more than 50% of the genes whose expression was affected by the siRNA-mediated depletion of A1/A2 were also affected by DRB. RNA polymerase II-chromatin immunoprecipitation assays on DRB-treated and A1/A2-depleted cells identified a common set of repressed genes displaying increased occupancy of polymerases at promoter-proximal locations, consistent with pausing. Overall, our results suggest that lowering the levels of hnRNP A1/A2 elicits defective transcription elongation on a fraction of P-TEFb-dependent genes, hence favoring the transcription of P-TEFb-independent genes. two treatements and one control
2015-04-07 | E-GEOD-67617 | biostudies-arrayexpress
Project description:RNAP II is frequently paused near gene promoters in mammals and its transition to productive elongation requires active recruitment of P-TEFb, a cyclin-dependent kinase for RNAP II and other key transcription elongation factors. A fraction of P-TEFb is sequestered in an inhibitory complex containing the 7SK noncoding RNA, but it has been unclear how P-TEFb is switched from the 7SK complex to RNAP II during transcription activation. We report that SRSF2 (also known as SC35, an SR splicing factor) is part of the 7SK complex assembled at gene promoters and plays a direct role in transcription pause release. We demonstrate RNA-dependent, coordinated release of SRSF2 and P-TEFb from the 7SK complex and transcription activation via SRSF2 binding to promoter-associated nascent RNA. These findings reveal an unanticipated SR protein function, a role for promoter-proximal nascent RNA in gene activation, and an analogous mechanism to HIV Tat/TAR for activating cellular genes. SR ChIP-seq, Pol II ChIP-seq, and Gro-seq
2013-05-09 | E-GEOD-45517 | biostudies-arrayexpress
Project description:DNA damage response (DDR) involves dramatic transcriptional alterations, the mechanisms of which remain obscure. Here we show that following DNA damage, the RNA-binding motif protein 7 (RBM7) stimulates RNA polymerase II (Pol II) elongation and increases cell viability by activating the positive transcription elongation factor b (P-TEFb). This is mediated by DNA damage-enhanced binding of RBM7 to 7SK, the scaffold of the 7SK small nuclear ribonucleoprotein (snRNP) that inhibits P-TEFb. As a result, P-TEFb relocates from 7SK snRNP to chromatin to activate transcription of key DDR genes and multiple classes of non-coding RNAs. By alleviating the inhibition of P-TEFb, RBM7 thus promotes Pol II elongation to activate a transcriptional response that is crucial for cell fate upon genotoxic insult. Our work highlights a novel paradigm in stress-dependent control of Pol II pause release, and offers the promise of combating cancer by RBM7 and P-TEFb antagonists in combination with established DNA damage-inducing chemotherapeutics.
2018-06-01 | E-MTAB-6475 | biostudies-arrayexpress