The exon junction complex is restricted to a specific subset of splice junctions
ABSTRACT: We employ multi-step affinity purification followed by high-throughput sequencing to determine the location of EJC complexes assembled on a cellular transcriptome in Drosophila S2 cells, finding 6% of the intron-containing genes were not associated with EJCs, and within genes with multiple introns, only specific exon-exon junctions assembled an EJC. RIP-Seq, 3 samples
Project description:Elavl1/HuR is a ubiquitous and conserved RNA-binding protein that binds to a U-rich RNA motif that shuttles between nucleus and cytoplasm. In epithelia, the elevated expression of HuR assumingly promotes degeneration and cancer suggesting that its generic suppression may provide clinical benefits. In this study we focused on biological and clinical functions of HuR in intestinal epithelial cells and we presented evidence that changes in HuR levels induce polarized distortions in these cells to support different pathologic outcomes. In this experiment we investigate Elavl1 targets via Elavl1 Immunopercipitation (RIP-chip) by arrays and compare relative to background. Control and TgATF-HuR mice were treated with Dimethylhydrazine (DMH)/Dextran Sodium Sulphate (DSS) for 60 days and tumors where dissected from large intestines; those with sizes between 10-15mm2 were pooled to generate samples with 4 tumors/sample and snap frozen. Three samples per genotype were used either for RIP analyses or total RNA extraction. Isolated RNA was used for microarray or qRT-PCR analyses.
Project description:Transcription by RNA Polymerase II (Pol II) in metazoan is regulated in several steps, including preinitiation complex (PIC) formation, initiation, Pol II escape, productive elongation, cotranscriptional RNA-processing and termination. Genome-wide studies have demonstrated that the phenomenon of promoter-bound Pol II pausing is widespread, especially for genes involved in developmental and stimulus-responsive pathways. However, a mechanistic understanding of the paused Pol II states at promoters is limited. For example, at a global level, it’s unclear to what extent the engaged paused Pol II is stably tethered to the promoter or undergoes rapid cycles of initiation and termination. Here we used the small molecule Triptolide (TPL), an XPB/TFIIH inhibitor, to block transcriptional initiation followed by measuring Pol II occupancy by ChIP-seq. This inhibition of initiation enables us to investigate different states of paused Pol II. Specifically, our global analysis reveals that most genes with paused Pol II, as defined by pausing index, show significant clearance of Pol II during the period of TPL treatment. Our study further identifies a group of genes with unexpectedly stably-paused Pol II, with unchanged Pol II occupancy even after one hour of inhibition of initiation. This group of genes constitutes a small portion of all paused genes defined by the conventional criterion of pausing index. These findings could pave the way for evaluating the contribution of different elongation/pausing factors on different states of Pol II pausing in developmental and other stimulus-responsive pathways. ChIP-Seq of total/Ser5P Pol II in HCT116 cells treated with DMSO or TPL in serum starvation/activation or normal conditions. Nascent RNA-seq in HCT116 cells treated with DMSO or TPL in starved condition.
Project description:Loss of function of the tumor suppressor BRCA1 (Breast Cancer 1) protein is responsible for numerous familial and sporadic breast cancers. We previously identified PABP1 as a novel BRCA1 partner and showed that BRCA1 modulates translation through its interaction with PABP1. We showed that the global translation was diminished in BRCA1-depleted cells and increased in BRCA1-overexpressing cells. Our findings raised the question whether BRCA1 affects translation of all cytoplasmic cellular mRNAs or whether it specifically targets a subset of mRNAs. In the present study, we investigated which mRNAs are regulated by BRCA1 using a microarray analysis of polysome-associated RNAs from BRCA1-depleted MCF7 cells, a human breast cancer cell line. We isolated mRNAs from the high-molecular-weight polysomes (fractions 12 to 18) and total cellular cytoplasmic mRNAs from the cytoplasmic fraction of MCF7 cells transiently expressing either siRNA directed against BRCA1 or control siRNA. Since we were interested in identifying the mRNAs that were translationally regulated by BRCA1, we determined the relative translatability of each mRNA. The relative translatability of an mRNA was determined by normalizing the change in abundance in polysomal mRNA to the change in abundance in total cytoplasmic mRNA for each mRNA.
Project description:During embryonic development, maintenance of cell identity and lineage commitment requires the Polycomb-group PRC2 complex, which catalyzes histone H3 K27 trimethylation (H3K27me3). However, the developmental origins of this regulation are unknown. Here, we report on H3K27me3 deposition dynamics in Xenopus embryos, on sequence elements that initiate deposition during pluripotency, and the sequence characteristics that segregate Polycomb-regulated domains from the rest of the genome. Strikingly, although PRC2 binds widely to active enhancers, H3K27me3 is only deposited at a small subset of these sites. Using a Support Vector Machine algorithm these sequences can be predicted accurately on basis of DNA sequence alone, with a sequence signature conserved between humans, frog and fish. The results suggest a genetic-default model in which genomic sequence constrains Polycomb regulation. ChIP-seq profiles of three histone modifications (H3K4me3, H3K27me3 and H3K4me1) and RNA Polymerase II, EZH2 and Jarid2 of Xenopus tropicalis embryos during development
Project description:InvF ChIP-chip on Salmonella enterica serovar Typhimurium SL1344 using anti-Myc antibody against strain with chromosomally 9Myc-tagged InvF (IP samples) and wildtype strain (mock IP samples) Salmonella enterica serovar Typhimurium causes a range of diseases from self-limiting gastroenteritis to life-threatening systemic infections. Its complex infection process is initiated by the invasion of the intestinal epithelial monolayer by means of a type three secretion system. InvF is one of the key regulators governing the invasion of epithelial cells. By mapping the InvF regulon, i.e. locating its direct target genes, the gene network underlying invasion can be further examined, including identifying possible new effector-encoding genes. In order to map the InvF regulon, we performed chromatin immunoprecipitation combined with tiling microarray analysis (ChIP-chip) and compared expression of the identified target genes in an invF mutant and a wildtype strain. In addition, the promoter regions of these target genes were searched for the presence of an InvF recognition site. Finally, a query-driven biclustering method, combined with a microarray compendium containing publically available S. Typhimurium gene expression data, was applied as an in silico validation technique for functional relatedness between newly identified target genes and known invasion genes. As expected, under invasion inducing conditions, InvF activates the expression of invasion chaperone encoding sicA and the effector-encoding genes sopB, sopE, sopE2 and sopA by binding their promoter region. Newly identified InvF targets are steB, encoding a secreted effector, and STM1239. The presence of an InvF recognition site in the promoter regions of these target genes further supports this observation. In addition, the query-driven biclustering method revealed similarities in expression profiles between STM1239 and known InvF regulated invasion genes over a range of experimental conditions. In conclusion, we here deliver the first evidence for direct binding of InvF to the promoter regions of sopA and sopE2, and associate genes encoding a secreted effector (steB) and a putative novel effector (STM1239) with the Salmonella invasion regulator InvF. Three IP samples (from three biological replicates using anti-Myc antibody against Salmonella Typhimurium SL1344 strain encoding chromosomally 9Myc-tagged InvF) and three control mock IP samples (from three biological replicates using anti-Myc antibody against Salmonella Typhimurium SL1344 wildtype strain) were labeled with Cy5 and hybridized against a common genomic DNA reference, labeled with Cy3, on 6 S. Typhimurium LT2 whole genome tiling arrays
Project description:The PhoPR two-component system is essential for virulence in Mycobacterium tuberculosis where it controls expression of approximately 2% of the genes, including those for the ESX-1 secretion apparatus, a major virulence determinant. Mutations in phoP lead to compromised production of pathogen-specific cell wall components and attenuation both ex vivo and in vivo. Using antibodies against the native protein in ChIP-seq experiments (chromatin immunoprecipitation followed by high-throughput sequencing) we demonstrated that PhoP binds to at least 35 loci on the M. tuberculosis genome. The PhoP regulon comprises several transcriptional regulators as well as genes for polyketide synthases and PE/PPE proteins. Integration of ChIP-seq results with high-resolution transcriptomic analysis (RNA-seq) revealed that PhoP controls 30 genes directly, whilst regulatory cascades are responsible for signal amplification and downstream effects. The most prominent site of PhoP regulation was located in the intergenic region between rv2395 and PE_PGRS41, where the mcr7 gene codes for a small non-coding RNA (ncRNA). Northern blot experiments confirmed the absence of Mcr7 in the M. tuberculosis phoP mutant as well as low-level expression of the ncRNA in M. tuberculosis complex members other than M. tuberculosis. By means of genetic and proteomic analyses we demonstrated that Mcr7 modulates translation of the tatC mRNA thereby impacting the activity of the Twin Arginine Translocation (Tat) protein secretion apparatus. As a result, secretion of the immunodominant Ag85 complex and the beta-lactamase BlaC is affected, among others. Mcr7, the first ncRNA of M. tuberculosis whose function has been established, therefore represents a missing link between the PhoPR two-component system and the downstream functions necessary for successful infection of the host. ChiP-Seq: M. tuberculosis H37Rv (GC1237) cultures grown in vitro to exponential phase. Two wild type samples plus one isogenic phoP mutant as control
Project description:Low oxygen stress dynamically regulates the translation of cellular mRNAs as a means of energy conservation in seedlings of Arabidopsis thaliana. Most of the highly hypoxia-induced mRNAs are recruited to polysomes and actively translated, whereas other cellular mRNAs become translationally inactive and are either targeted for stabilization or degradation. Here we identify the involvement of OLIGOURIDYLATE BINDING PROTEIN 1 (UBP1), a triple RNA Recognition Motif protein, in dynamic and reversible aggregation of translationally repressed mRNAs during hypoxia. Mutation or downregulation of UBP1C interferes with seedling establishment and reduces survival of low oxygen stress. By use of messenger ribonucleoprotein immunopurification, we show that UBP1C constitutively binds a subpopulation of mRNAs characterized by U-rich 3’-untranslated regions under normoxic conditions. During hypoxia, UBP1C association with non-U-rich mRNAs is enhanced concomitant with its aggregation into microscopically visible cytoplasmic foci, referred to as UBP1 stress granules (SGs). This UBP1C-mRNA association occurs as global levels of protein synthesis decline. Upon reoxygenation, rapid UBP1 SG disaggregation coincides with the return of the stabilized mRNAs to polysomes. The mRNAs that are highly induced and translated during hypoxia largely circumvent UBP1C sequestration. Thus, UBP1 is established as a component of dynamically assembled cytoplasmic mRNPs that sequester mRNAs that are poorly translated during a transient low energy stress. Immunoprecipated RNA associated with Arabidopsis UBP1C (IP) was compared with total cellular RNA from light (L), mock dark (D), 2 h hypoxia, and 2 h hypoxia + 20 min reoxygenation treated samples with duplicate hybridizations to the Affymetrix ATH1 Genechip array.
Project description:The control of promoter-proximal pausing and the release of RNA polymerase II (RNA Pol II) is a widely used mechanism for regulating gene expression in metazoans, especially for genes that respond to environmental and developmental cues. Here, we identify Pol II associated Factor 1 (PAF1) as a major regulator of promoter-proximal pausing. Knockdown of PAF1 leads to increased release of paused Pol II into gene bodies at thousands of genes. Genes with the highest levels of paused Pol II exhibit the largest redistribution of Pol II from the promoter-proximal region into the gene body in the absence of PAF1. PAF1 depletion results in increased nascent transcription and increased levels of phosphorylation of Pol II’s c-terminal domain on serine 2 (Ser2P). These changes can be explained by the recruitment of the Ser2P kinase Super Elongation Complex (SEC) effecting increased release of paused Pol II into productive elongation, thus establishing a novel function for PAF1 as a major regulator of pausing in metazoans. ChIP-seq of Pol II of different forms, SEC subunits, PAFc subunits and H2Bub in human cell lines targeted by PAF1 or scramble shRNA. ChIP-seq of total Pol II in HCT116 cells targeted by BRE1A or scramble shRNA. ChIP-seq of total Pol II in S2 cells targeted by Paf1 or LacZ RNAi. Total RNA-seq, nascent RNA-seq and GRO-seq in HCT116 cells targeted by PAF1 or scramble shRNA.
Project description:We used ChIP-chip analysis to identify where the nucleoid associated protein StpA binds on the Salmonella Typhimurium genome. We identified 285 chromosomal regions bound by StpA, ranging in size from 400 to 3500 base pairs and containing 572 genes. Comparison of the ChIP data revealed that StpA displayed an identical binding profile to H-NS; all genomic regions associated with StpA were also bound by H-NS. Of the 88 StpA-dependent genes that are de-repressed in the absence of StpA, only 25 were bound by StpA, suggesting that StpA generally regulates gene expression indirectly. To identify the direct StpA targets, we co-immunoprecipitated DNA from a strain expressing a 3xFLAG-tagged StpA-protein using an anti-3xFLAG antibody. As a negative control, we used the same antibody (anti-3xFLAG) to co-immunoprecipitate DNA from an isogenic strain expressing the non-tagged StpA-protein. Three independent biological replicates were generated. For comparative purposes we also performed the co-immunoprecipitation on wild type Salmonella using a monoclonal anti-H-NS antibody. In that case, the negative control was obtained by performing the co-immunoprecipitation protocol on wild type Salmonella without adding antibody.