Project description:Activation of immune cells results in rapid functional changes, but how such fast changes are accomplished remains enigmatic. By combining time-courses of 4sU-Seq, RNA-Seq, ribosome profiling and RNA polymerase II (RNAPII) ChIP-Seq during T cell activation, we illustrate genome-wide temporal dynamics for ~10,000 genes. This approach reveals immediate-early as well as posttranscriptionally-regulated genes, but also coupled changes in transcription and translation for >90% of genes. Recruitment, rather than release of paused RNAPII, primarily mediates transcriptional changes. This coincides with a genome-wide temporary slowdown in cotranscriptional splicing, even for polyadenylated mRNAs that are localized at the chromatin. Subsequent splicing optimization correlates with increasing Ser-2 phosphorylation of the RNAPII carboxy-terminal domain (CTD) and activation of the positive transcription elongation factor complex (pTEFb). Thus, rapid de novo recruitment of RNAPII dictates the course of events during T cell activation, in particular transcription, splicing and consequently translation.
Project description:During eukaryotic transcription, RNA polymerase II undergoes dynamic post-translational modification on the C-terminal domain (CTD) of the largest subunit , generating a sophisticated PTM landscape for the spatiotemporal recruitment to transcriptional regulators. To delineate the protein interactomes recruited to Pol II at different stages of transcription, we in vitro reconstructed phosphorylation patterns of the CTD at Ser5 and Ser2 positions, the hallmark phosphorylation at the initation and productive elongation stages of transcription, respectively. Distinctive protein interactomes indicates different proteins are recruited to RNA polymerase II at different stages of transcription by the phosphorylation of Ser2 and Ser5 of the CTD heptads. Calcium Homeostasis Endoplasmic Reticulum Protein (CHERP) specifically binds to the Ser2 of the heptad. The loss of the interaction between CHERP and Pol II results in broad alternative splicing events. Our method points to a new method to distinguish the PTM codes that coordinate the transcription process.
Project description:TFIID is an essential basal transcription factor, crucial for RNA polymerase II (pol II) promoter recognition and transcription initiation. The TFIID complex consists of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs) that contain intrinsically disordered regions (IDRs) with currently unknown functions. Here, we show that a conserved IDR drives TAF2 condensation in nuclear speckles, independently of other TFIID subunits. Quantitative mass spectrometry analyses reveal that the TAF2 IDR specifically interacts with the nuclear speckle and spliceosome-associated protein SRRM2. Consequently, TAF2 recruits SRRM2 to TFIID to form non-canonical TFIID-SRRM2 complexes. Reduced SRRM2 recruitment elicits alternative splicing events in RNAs coding for proteins involved in transcription and transmembrane transport. Further, genome-wide binding analyses suggest TAF2 shuttling between nuclear speckles and pol II promoters. This study identifies an IDR of the basal transcription machinery as a molecular guide for protein partitioning into nuclear compartments, controlling protein complex composition and pre-mRNA splicing.
Project description:TFIID is an essential basal transcription factor, crucial for RNA polymerase II (pol II) promoter recognition and transcription initiation. The TFIID complex consists of the TATA-binding protein (TBP) and 13 TBP-associated factors (TAFs) that contain intrinsically disordered regions (IDRs) with currently unknown functions. Here, we show that a conserved IDR drives TAF2 condensation in nuclear speckles, independently of other TFIID subunits. Quantitative mass spectrometry analyses reveal that the TAF2 IDR specifically interacts with the nuclear speckle and spliceosome-associated protein SRRM2. Consequently, TAF2 recruits SRRM2 to TFIID to form non-canonical TFIID-SRRM2 complexes. Reduced SRRM2 recruitment elicits alternative splicing events in RNAs coding for proteins involved in transcription and transmembrane transport. Further, genome-wide binding analyses suggest TAF2 shuttling between nuclear speckles and pol II promoters. This study identifies an IDR of the basal transcription machinery as a molecular guide for protein partitioning into nuclear compartments, controlling protein complex composition and pre-mRNA splicing.
Project description:Activation of immune cells results in extremely rapid functional changes, yet it remains enigmatic how this is accomplished. By combining time-courses of RNA-polymerase-II (RNAPII) Chip-Seq, 4sU-Seq, RNA-Seq and ribosome profiling during Th1 activation we provide a genome-wide view on temporal dynamics for ~10.000 genes. Gene responses vary in time and magnitude and allow the identification of unknown immediate early (IEG) and posttranscriptionally regulated genes. However, >90% are regulated transcriptionally with coupled changes in translation. Surprisingly, not poised, but rather re-positioned RNAPII correlates with transcriptional changes and coincides with fluctuations in cotranscriptional splicing, which lags behind at first. Unspliced transcripts remain here at the chromatin, but are already poly-adenylated. Later splicing readjusts, correlating with progressive Ser-2 phosphorylation of the CTD domain of RNAPII and activation of the elongation-complex pTEFb. Thus, rapid re-positioning of RNAPII and regulating the phosphorylation state of its CTD dictates almost all events during immune responses, including post-transcriptional processes.
Project description:Under current models for signal-dependent transcription in eukaryotes, DNA-binding activator proteins regulate the recruitment of RNA polymerase II (Pol II) to a set of target promoters. Yet, recent studies, as well as our results herein, show that Pol II is widely distributed (i.e., "preloaded") at the promoters of many genes prior to specific signaling events. How Pol II recruitment and Pol II preloading fit within a unified model of gene regulation is unclear. In addition, the mechanisms through which cellular signals activate preloaded Pol II across mammalian genomes remain largely unknown. Here we show that the predominant genomic outcome of estrogen signaling is the post-recruitment regulation of Pol II activity through phosphorylation, rather than recruitment of Pol II. Furthermore, we show that negative elongation factor (NELF) binds to estrogen target promoters in conjunction with preloaded Pol II and represses gene expression until the appropriate signal is received. Finally, our studies reveal that the estrogen-dependent activation of preloaded Pol II facilitates rapid transcriptional and post-transcriptional responses which play important physiological roles in regulating estrogen signaling itself. Our results reveal a broad use of post-recruitment Pol II regulation by the estrogen signaling pathway, a mode of regulation that is likely to apply to a wide variety of signal-regulated pathways. ChIP-chip analysis for RNA Pol II, Ser5 phosphorylated RNA Pol II and NELF-A in MCF7 breast cancer cells.
Project description:TFIID is an essential eukaryotic transcription factor, which is required for RNA polymerase II promoter recognition and activation. As a multiprotein complex, TFIID contains several intrinsically disordered regions (IDRs), but the functions of these IDRs are unknown. Here, we show that a conserved IDR drives the TFIID subunit TAF2 to nuclear speckles, where it forms biomolecular condensates, separate from the TFIID complex. Quantitative mass spectrometry analyses reveal that the TAF2 IDR is required for the interaction with the nuclear speckle and spliceosome-associated protein SRRM2, which is thereby recruited to TFIID. The formation of SRRM2-free TFIID complexes elicits a set of unique alternative splicing events. These include events in RNAs coding for proteins involved in transcription and transmembrane transport. Together, these data identify an IDR of the basal transcription machinery as a molecular switch between nuclear compartments to control protein complex composition and pre-mRNA splicing.
Project description:Under current models for signal-dependent transcription in eukaryotes, DNA-binding activator proteins regulate the recruitment of RNA polymerase II (Pol II) to a set of target promoters. Yet, recent studies, as well as our results herein, show that Pol II is widely distributed (i.e., "preloaded") at the promoters of many genes prior to specific signaling events. How Pol II recruitment and Pol II preloading fit within a unified model of gene regulation is unclear. In addition, the mechanisms through which cellular signals activate preloaded Pol II across mammalian genomes remain largely unknown. Here we show that the predominant genomic outcome of estrogen signaling is the post-recruitment regulation of Pol II activity through phosphorylation, rather than recruitment of Pol II. Furthermore, we show that negative elongation factor (NELF) binds to estrogen target promoters in conjunction with preloaded Pol II and represses gene expression until the appropriate signal is received. Finally, our studies reveal that the estrogen-dependent activation of preloaded Pol II facilitates rapid transcriptional and post-transcriptional responses which play important physiological roles in regulating estrogen signaling itself. Our results reveal a broad use of post-recruitment Pol II regulation by the estrogen signaling pathway, a mode of regulation that is likely to apply to a wide variety of signal-regulated pathways.
Project description:The rate of RNA polymerase II (pol II) elongation can influence splice site selection in nascent transcripts, yet the extent and physiological relevance of this kinetic coupling between transcription and alternative splicing is not well understood. We performed experiments to perturb pol II elongation and then globally compared alternative splicing patterns with genome-wide pol II occupancy. RNA binding and RNA processing functions were significantly enriched among the genes with pol II elongation inhibition-dependent changes in alternative splicing. Under conditions that interfere with pol II elongation, including cell stress, increased pol II occupancy was detected in the intronic regions flanking the alternative exons in these genes, and these exons generally became more included. A disproportionately high fraction of these exons introduced premature termination codons that elicited nonsense-mediated mRNA decay (NMD), thereby further reducing transcript levels. Our results provide evidence that kinetic coupling between transcription, alternative splicing and NMD affords a rapid mechanism by which cells can respond to changes in growth conditions, including cell stress, to coordinate the levels of RNA processing factors with mRNA levels. In order to identify alternative splicing events influenced by changes in pol II elongation, we performed quantitative alternative splicing microarray profiling (Pan et al., 2004 (PMID 15610736); Shai et al., 2006 (PMID 16403798)) of RNA isolated from stimulated Jurkat T lymphoma cells, cultured separately in the presence or absence of two different drugs that can inhibit pol II elongation: 5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) and camptothecin.
Project description:The rate of RNA polymerase II (pol II) elongation can influence splice site selection in nascent transcripts, yet the extent and physiological relevance of this kinetic coupling between transcription and alternative splicing is not well understood. We performed experiments to perturb pol II elongation and then globally compared alternative splicing patterns with genome-wide pol II occupancy. RNA binding and RNA processing functions were significantly enriched among the genes with pol II elongation inhibition-dependent changes in alternative splicing. Under conditions that interfere with pol II elongation, including cell stress, increased pol II occupancy was detected in the intronic regions flanking the alternative exons in these genes, and these exons generally became more included. A disproportionately high fraction of these exons introduced premature termination codons that elicited nonsense-mediated mRNA decay (NMD), thereby further reducing transcript levels. Our results provide evidence that kinetic coupling between transcription, alternative splicing and NMD affords a rapid mechanism by which cells can respond to changes in growth conditions, including cell stress, to coordinate the levels of RNA processing factors with mRNA levels. To monitor pol II distributions, chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-Seq) was performed using an anti-pol II antibody (4H8) and cross-linked chromatin preparations from Jurkat cells, treated with or without pol II elongation inhibitor 5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) at 10 and 25 ug/ml respectively prior to phorbol 12-myristate 13-acetate (PMA) stimulation, for 5000+ alternative splicing events.