Project description:Acinus (Apoptotic Chromatin Condensation Inducer in the Nucleus) is an RNA-binding protein (RBP) originally identified for its role in apoptosis. It was later found to be an auxiliary component of the Exon Junction Complex (EJC), which is deposited at exon junctions as a consequence of pre-mRNA splicing. To uncover the cellular functions of Acinus and investigate its role in splicing, we mapped its endogenous RNA targets using individual-nucleotide resolution UV-crosslinking and immunoprecipitation (iCLIP). We observed that Acinus binds to pre-mRNAs, associating specifically to a subset of suboptimal introns, but also to spliced mRNAs. We also confirmed the presence of Acinus as a peripheral factor of the EJC. RNA-seq was used to investigate changes in gene expression and alternative splicing following siRNA-mediated depletion of Acinus in HeLa cells. This analysis revealed that Acinus is preferentially required for the inclusion of specific alternative cassette exons and also controls the faithful splicing of a subset of introns. Moreover, a large number of splicing changes can be related to Acinus binding, suggesting a direct role of Acinus in exon and intron definition. In particular, Acinus regulates the splicing of DFFA/ICAD transcript, a major regulator of DNA fragmentation. Globally, the genome-wide identification of RNA targets of Acinus revealed its role in splicing regulation as well as its involvement in other cellular pathways, including cell cycle progression. Altogether, this study uncovers new cellular functions of an RBP transiently associated with the EJC
Project description:We report two knockouts of the CASC3 (Barentsz, MLN51) gene and further depletion of gene expression with small interfering RNAs (siRNAs). CASC3 is a component of the exon-junction complex (EJC) which is deposited upstream of splice junctions on the mRNA. The EJC core and peripheral interacting factors are involved in RNA splicing, export, translation and nonsense-mediated decay. Contrasting to the other factors that form the exon-junction complex, CASC3 individual role on these processes was relatively poorly understood in the literature. To further elucidate the role of CASC3 in these processes we have established 2 different CRISPR-Cas9 genetic knockouts (KO) of CASC3. We extracted the total RNA by using the NucleoSpin RNA Plus kit (Macherey-Nagel), and performed ribosomal depletion and strand-specific library preparation with the TruSeq Stranded Total RNA protocol with Ribo-Zero Gold. Sequencing of the KO clones as well as the KO clones treated with CASC3 siRNA was carried out with the Illumina NovaSeq6000 sequencer with 2×100bp, targeting approximately 50 million read-pairs per sample. By studying the RNA-Seq of the 4 conditions, one with minimal CASC3 expression (condition H) or and three with complete depletion of the protein expression (conditions H-KD, T, T-KD), we observed the up-regulation of known and novel nonsense mediated decay substrates, thus establishing CASC3 as a critical factor for efficient nonsense mediated decay of certain transcripts.
Project description:This experiment uses iCLIP to identify the binding pattern of the spliceosomal protein PRPF8 on RNA. The data shows that PRPF8 binds strongly and specifically in the region 12 to 14nt upstream of 5' splice sites (5ss). Due to PRPF8's role in the formation of the catalytically active spliceosome, this data can be used as a readout of 5ss selection. Here, we performed iCLIP on HeLa cells treated with control or EIF4A3 siRNA, with 4 replicate samples per condition and eIF4A3 protein levels reduced ~50% in knockdown. We investigated the role of the exon junction complex (EJC) in suppressing 5ss that are reconstituted at the junction of two canonical exons (RS-5ss) - selection of these splice sites would result in recursive splicing of canonical exons. We plotted the crosslink sites of reads that span an exon-exon junction, seperating reads that span RS-5ss from those that do not. We found that reads that span an RS-5ss are enriched at the 12-14nt window associated with 5ss selection, while reads that span other exon-exon junctions are not enriched. This effect is magnified greatly by knockdown of eIF4A3. The results indicate that RS-5ss can be used by the spliceosome, but that this process is usually repressed by the EJC. This data is evidence of recursive splicing of canonical exons and the role of the EJC in repressing recursive splicing.
Project description:RNPS1 is a splicing regulatory protein and a component of the ASAP/PSAP complex, which is associated with the exon junction complex and modulates alternative splicing. It was previously postulated that the isolated RRM domain of RNPS1 in complex with ASAP/PSAP is able to regulate certain alternative splicing events. We aimed to investigate in HeLa Tet-Off cells which alternative splicing events are rescued by the expression of the isolated RRM domain of RNPS1 in a RNPS1 knockdown background by using RNA-Seq analyses. The rescue construct was stably integrated into the genome using the PiggyBac transposon system. As controls, either Luciferase (Luc) siRNA was used or RNPS1 was knocked down without rescue.
Project description:In metazoans, mRNA quality is tightly monitored from transcription to translation. A key role lies with the exon junction complex (EJC) that is placed upstream of the exon-exon junction after splicing. The EJC inner core is composed of Magoh, Y14, eIF4AIII and BTZ and the outer core of proteins involved in mRNA splicing (CWC22), export (Yra1), translation (PYM) and non-sense mediated decay (NMD, UPF1/2/3). The protozoan parasite Trypanosoma brucei encodes only two genes with introns, but all mRNAs are processed by trans-splicing. The presence of the three core EJC proteins and a potential BTZ homologue (Rbp25) in trypanosomes has been suggested as an adaptation of the EJC function to mark trans-spliced mRNAs. Here we explore the interactome of Magoh, Y14, eIF4AIII in T. brucei by TurboID proximity labelling.
Project description:Alternative pre-mRNA splicing is a prevalent mechanism in mammals that promotes proteomic diversity, including expression of cell-type specific protein isoforms. We characterized a role for RBM38 (RNPC1) in regulation of alternative splicing during late erythroid differentiation. We used an affymetrix human exon junction (HJAY) splicing microarray to identify a panel of RBM38-regulated alternatively spliced transcripts. Using microarray databases, we noted high RBM38 expression levels in CD71+ erythroid cells and thus chose to examine RBM38 expression during erythroid differentiation of human hematopoietic stem cells, detecting enhanced RBM38 expression during late erythroid differentiation. In differentiated erythroid cells, we validated a subset of RBM38-regulated splicing events and determined that RBM38 regulates activation of Protein 4.1R (EPB41) exon 16 during late erythroid differentiation. Using Epb41 minigenes, Rbm38 was found to be a robust activator of exon 16 splicing. To further address the mechanism of RBM38-regulated alternative splicing, a novel mammalian protein expression system, followed by SELEX-Seq, was used to identify a GU-rich RBM38 binding motif. Lastly, using a tethering assay, we determined that RBM38 can directly activate splicing when recruited to a downstream intron. Together, our data support the role of RBM38 in regulating alternative splicing during erythroid differentiation. siRNA knockdown of RBM38 was perfomed in human MCF-7 breast cancer cells. The efficiency of RBM38 knockdown was monitored by western blot using an RBM38 antibody (Santa Cruz Biotechnology, SC-85873). We conducted HJAY exon and exon junction array profiling on RNAs from four siRBM38 treated MCF-7 samples vs. four sicontrol treated MCF-7 samples Control / knockdown comparison.
Project description:RNPS1 is a splicing regulatory protein and a component of the ASAP/PSAP complex, which is associated with the exon junction complex and modulates alternative splicing. It was previously postulated that the isolated RRM domain of RNPS1 in complex with ASAP/PSAP is able to regulate certain alternative splicing events. We aimed to investigate in Flp-In T-REx 293 cells which alternative splicing events are rescued by the expression of the wild type RNPS1 or the isolated RRM domain of RNPS1 in a RNPS1 knockdown background by using RNA-Seq analyses. The rescue construct was stably integrated into the genome using the PiggyBac transposon system. As controls, either Luciferase (Luc) siRNA was used or RNPS1 was knocked down without rescue.
Project description:SOX9 is known as a crucial transcription factor for various developmental processes and for tissue homeostasis. We examined here its potential role in alternative splicing by analyzing global splicing changes, using RNA-seq of colon tumor cells. We show that SOX9 knockdown alters the splicing of hundreds of genes without affecting their expression levels, revealing that SOX9 controls distinct splicing and transcriptional programs. SOX9 does not affect splicing patterns through the control of splicing factors expression. We identify mutants that uncouple SOX9 splicing function from its transcriptional activity. We demonstrate that SOX9 binds to RNA and associates with several RNA-binding proteins, including the core Exon Junction Complex component Y14. Half of SOX9 splicing targets are also modulated by Y14 and are no longer regulated by SOX9 upon Y14 depletion. Altogether, our work reveals that SOX9 is a moonlighting protein which modulates either transcription or splicing of distinct sets of targets.
Project description:RBM10 is an RNA binding protein that was identified as a component of spliceosome complex, suggesting its potential role in splicing regulation. However, the direct experimental evidence for this function has been lacking. Here we characterized in vivo RBM10-RNA interactions and investigated the role of RBM10 in splicing regulation at the global level. We observed significant RBM10-RNA interactions in the vicinity of splice sites and identified hundreds of splicing changes following perturbation of cellular RBM10 abundance. A RNA splicing map integrating the binding pattern and splicing profiles revealed a significant correlation between RBM10-enhanced exon skipping events and its binding close to the splicing sites of both upstream and downstream introns. Furthermore, we demonstrated the splicing defects in a patient carrying a RBM10 mutation. Overall, our data provided insights into the mechanistic model of RBM10-mediated splicing regulation and established genomic resources for future studies on its function in different pathophysiological contexts.