Project description:Pharmacological perturbation is a powerful tool for understanding gene expression, but identification of the specific steps of this multi-step process targeted by small molecules remains challenging. Here we apply total RNA-Seq to distinguish specific pharmacological effects on transcription and pre-mRNA processing, revealing unexpectedly that the splicing inhibitor isoginkgetin blocks transcription elongation.An RNA-Seq screen reveals that the compounds TBBz and CYT387 mimic the transcriptional effects of isoginkgetin and are inhibitors of CSNK2A2, suggesting that isoginkgetin blocks transcription elongation via inhibition of CSNK2A2. Our results reveal RNA-Seq screening as a tool for disentangling complex pharmacological effects on gene expression.
Project description:SARS-CoV-2 causes the COVID-19 pandemic. It is urgent to develop disease models to dissect mechanisms regulating SARS-CoV-2 infection. Here, we derive airway organoids from human pluripotent stem cells (hPSC-AOs). The hPSC-AOs, particularly ciliated-like cells, are permissive to SARS-CoV-2 infection. Using this platform, we perform a high content screen and identify GW6471, which blocks SARS-CoV-2 infection. GW6471 can also block infection of the B.1.351 SARS-CoV-2 variant. RNA-seq analysis suggests that GW6471 blocks SARS-CoV-2 infection at least in part by inhibiting HIF1α, which is further validated by chemical inhibitor and genetic perturbation targeting HIF1α. Metabolic profiling identifies decreased rates of glycolysis upon GW6471 treatment, consistent with transcriptome profiling. Finally, xanthohumol, 5-(Tetradecyloxy)-2-furoic acid, and ND-646, three compounds that suppress fatty acid biosynthesis, also block SARS-CoV-2 infection. Together, a high content screen coupled with transcriptome and metabolic profiling reveals a key role of the HIF1α-glycolysis axis in mediating SARS-CoV-2 infection of human airway epithelium.
Project description:Complex functional coupling exists between transcriptional elongation and pre-mRNA alternative splicing. Pausing sites and changes in the rate of transcription by RNAPII may therefore have a fundamental impact in the regulation of alternative splicing. Here, we show that the elongation and splicing-related factor TCERG1 regulates alternative splicing of the apoptosis gene Bcl-x in a promoter-dependent manner. TCERG1 promotes the splicing of the short isoform of Bcl-x (Bcl-xs) through the SB1 regulatory element located in the first half of exon 2. Consistent with these results, we show evidence for in vitro and in vivo interaction of TCERG1 with the Bcl-x pre-mRNA. Transcription profile analysis reveals that the RNA sequences required for the effect of TCERG1 on Bcl-x alternative splicing coincide with a putative polymerase pause site. Furthermore, TCERG1 modifies the impact of a slow polymerase on Bcl-x alternative splicing. In support of a role for an elongation mechanism in the transcriptional control of Bcl-x alternative splicing, we found that TCERG1 modifies the amount of pre-mRNAs generated at distal regions of the endogenous Bcl-x. Most importantly, TCERG1 affects the rate of RNAPII transcription of endogenous human Bcl-x. We propose that TCERG1 modulates the elongation rate of RNAPII to relieve pausing, thereby activating the pro-apoptotic Bcl-xS 5’ splice site. ChIP-Seq
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.
Project description:RNA polymerases deal with obstacles during transcription elongation that need to be removed. One important type of hindrance consists of DNA lesions, which are removed by transcription-coupled repair (TCR). To improve our knowledge of transcription elongation and its coupling to TCR, we performed DNA microarray experiments and used the yeast library of nonessential knock-out mutations to screen for genes conferring resistance to the transcription-elongation inhibitor micophenolic acid and the DNA-damaging agent 4- nitroquinoline-N-oxide. A single sample for each treatment was analyzed.
Project description:Transcription and pre-mRNA alternative splicing was analyzed by in isogenic human HEK293 cell lines that inducibly express a-amanitin resistant mutants of the RNA polymerase II large subunit with slow and fast elongation rates. Alternative splicing was analyzed by, RNA-seq and RASL-seq of polyA+ RNA from a-amanitin treated cells; transcription elongation rate was analyzed by BrUTP-labelled GRO-seq of a-amanitin treated cells at time points after release from a DRB (5,6-dichloro-1-bold beta-D-ribofuranosylbenzimidazole) block.
Project description:Transcription and pre-mRNA splicing are coupled to promote gene expression and regulation. However, mechanisms by which transcription and splicing influence each other are still under investigation. The ATPase Prp5p is required for pre-spliceosome assembly and splicing proofreading at the branch-point region. From an open UV mutagenesis screen for genetic suppressors of prp5 defects and subsequent targeted testing, we identify components of the TBP-binding module of the Spt–Ada–Gcn5 Acetyltransferase (SAGA) complex, Spt8p and Spt3p. Spt8Δ and spt3Δ rescue the cold-sensitivity of prp5-GAR allele, and prp5 mutants restore growth of spt8Δ and spt3Δ strains on 6-azauracil. By chromatin immunoprecipitation (ChIP), we find that prp5 alleles decrease recruitment of RNA polymerase II (Pol II) to an intron-containing gene, which is rescued by spt8Δ. Further ChIP-seq reveals that global effects on Pol II-binding is mutually rescued by prp5 mutant and spt8Δ. Inhibited splicing caused by prp5-GAR is also restored by spt8Δ. In vitro assay indicates that Prp5p directly interacts with Spt8p, but not Spt3p. We demonstrate that Prp5p’s splicing proofreading is modulated by Spt8p and Spt3p. Therefore, this study reveals that interactions between the TBP-binding module of SAGA and the spliceosomal ATPase Prp5p mediate a balance between transcription initiation/elongation and pre-spliceosome assembly.
Project description:CDK9 is a critical kinase required for the productive transcription of protein-coding genes by RNA polymerase II (pol II) in higher eukaryotes. Phosphorylation of targets including the elongation factor SPT5 and the carboxyl-terminal domain (CTD) of RNA pol II allow the polymerase to pass an early elongation checkpoint (EEC), which is encountered soon after initiation. In addition to halting RNA polymerase II at the EEC, CDK9 inhibition also causes premature termination of transcription across the last exon, loss of polyadenylation factors from chromatin, and loss of polyadenylation of nascent transcripts. Inhibition of the phosphatase PP2A abrogates the premature termination and loss of polyadenylation caused by CDK9 inhibition, suggesting that CDK9 and PP2A, working together, regulate the coupling of elongation and transcription termination to RNA maturation. Our phosphoproteomic analyses, using either DRB or an analog-sensitive CDK9 cell line confirm the splicing factor SF3B1 as an additional key target of this kinase. CDK9 inhibition causes loss of interaction of splicing and export factors with SF3B1, suggesting that CDK9 also helps to co-ordinates coupling of splicing and export to transcription.
Project description:MYCN amplification in neuroblastoma leads to aberrant expression of MYCN oncoprotein, which binds active genes promoting transcriptional amplification. Yet how MYCN coordinates transcription elongation to meet productive transcriptional amplification and which elongation machinery represents MYCN-driven vulnerability remain to be identified. We conducted a targeted screen of transcription elongation factors and identified the super elongation complex (SEC) as a unique vulnerability in MYCN-amplified neuroblastomas. MYCN directly binds EAF1 and recruits SEC to enhance processive transcription elongation. Depletion of EAF1 or AFF1/AFF4, another core subunit of SEC, leads to a global reduction in transcription elongation and elicits selective apoptosis of MYCN-amplified neuroblastoma cells. A combination screen reveals SEC inhibition synergistically potentiates the therapeutic efficacies of FDA-approved BCL2 antagonist ABT-199, in part due to suppression of MCL1 expression, both in MYCN-amplified neuroblastoma cells and in patient-derived xenografts. These findings identify disruption of the MYCN-SEC regulatory axis as a promising therapeutic strategy in neuroblastoma.
Project description:WIN Site inhibitors bind the WIN Site of WDR5 resulting in decreased transcription of WDR5 target genes, many of which encode components of the protein synthesis machinery. In this study, we determined proteome alterations in an MLL-rearranged leukemia cell line treated for either 24 or 72 hours with a WIN Site inhibitor. The data from these studies, along with Ribo-Seq, RNA-Seq, and CRISPR screen experiments, guided us in assembling a collection of compounds that, when combined with WIN Site inhibitor, synergistically inhibit growth of MLL-rearranged leukemia cells.