Systematic identification of RNA-binding proteins and tethered domains that activate exon splicing inclusion [eCLIP-seq]
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE232597 | GEO | 2023/09/25
REPOSITORIES: GEO
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Project description:RNA-binding proteins (RBPs) modulate alternative splicing outcomes to determine isoform expression and cellular survival. To identify RBPs that directly drive alternative exon inclusion, we evaluated 718 human RBPs with tethered function luciferase-based splicing reporter assays to identify 58 candidates, including known splicing factors such as RBFOX and serine-arginine proteins. We performed enhanced CLIP, RNA-seq, and affinity purification-mass spectrometry to investigate a subset of the 11 candidates with no prior association with splicing. Integrative analysis of these assays indicated the surprising roles of TRNAU1AP, SCAF8, and RTCA in modulating hundreds of endogenous splicing events. We also leveraged our tethering assays and top candidates to identify potent and compact exon inclusion activation domains for splicing modulation applications. Using identified domains, we engineered programmable fusion proteins which outperformed current artificial splicing factors at manipulating inclusion of reporter and endogenous exons. Altogether, our tethering approach characterized the ability of RBPs to induce exon inclusion and yielded new molecular parts for programmable splicing control.
2023-09-25 | GSE232598 | GEO
Project description:Splicing of precursor mRNA (pre-mRNA) is an important regulatory step in gene expression. Recent evidence points to a regulatory role of chromatin-related proteins in alternative splicing (AS) regulation. Using an unbiased approach, we have identified the acetyltransferase p300 as a key chromatin-related regulator of AS. P300 promotes genome-wide exon inclusion in both a transcription-dependent and ‑independent manner. Using CD44 as a paradigm, we found that p300 regulates AS by modulating the binding of splicing factors to pre-mRNA. Employing a tethering strategy, we found that binding of p300 to the CD44 promoter region promotes CD44v exon inclusion independently of RNAPII transcriptional elongation rate. Promoter-bound p300 regulates AS by acetylating splicing factors, leading to exclusion of hnRNP M from CD44 pre-mRNA and activation of Sam68. P300-mediated CD44 AS reduces cell motility and promotes epithelial features. Our findings reveal a mechanism through which chromatin-related proteins regulate AS and show the impact of this mechanism on cell function.
2019-10-31 | GSE109957 | GEO
Project description:Alternative RNA splicing analysis in Hep3B cell cultured under 21% (N1,3,5) or 1.2% (H2,4,6) oxygen Hypoxia is a common characteristic of many solid tumors. The hypoxic microenvironment stabilizes hypoxia-inducible transcription factor 1? (HIF1?) and 2? (HIF2?) to activate gene transcription, which promotes tumor cell survival. 95% of human genes are alternatively spliced, producing RNA isoforms that code functionally distinct proteins. Thus, effective hypoxia response requires increased HIF target gene transcription as well as proper RNA splicing of these HIF target genes. However, it is unclear if and how hypoxia regulates RNA splicing of HIF target genes. This study determined the effects of hypoxia on alternative splicing (AS) of HIF and non-HIF target genes in Hep3B cells and characterized the role of HIF in regulating AS of HIF induced genes. The results indicated that hypoxia generally promotes exon inclusion for hypoxia-induced, but reduces exon inclusion for hypoxia reduced genes. Mechanistically, HIF activity, but not hypoxia per se is found to be necessary and sufficient to increase exon inclusion of several HIF target genes including pyruvate dehydrogenase kinase 1 (PDK1). PDK1 splicing reporters confirmed that transcriptional activation by HIF is sufficient to increase exon inclusion of PDK1 splicing reporter. In contrast, transcriptional activation of the PDK1 minigene by other transcription factor in the absence of endogenous HIF target gene activation fails to alter PDK1 RNA splicing, demonstrating a novel role of HIF target gene(s) in regulating RNA splicing of HIF target genes. Implications:This study demonstrates a novel function of HIF in regulating RNA splicing of HIF target genes. We analyzed total RNA from Hep3B cells cultured under 21% (N1,3,5) or 1.2% (H2,4,6) oxygen using the Affymetrix Human Exon 1.0 ST platform. Array data was processed by Altanalyze software version 2.0.7. Techinical replicates were performed for Nx and Hx treated Hep3B cells
2014-05-14 | E-GEOD-57613 | biostudies-arrayexpress
Project description:Alternative RNA splicing analysis in Hep3B cell cultured under 21% (N1,3,5) or 1.2% (H2,4,6) oxygen Hypoxia is a common characteristic of many solid tumors. The hypoxic microenvironment stabilizes hypoxia-inducible transcription factor 1α (HIF1α) and 2α (HIF2α) to activate gene transcription, which promotes tumor cell survival. 95% of human genes are alternatively spliced, producing RNA isoforms that code functionally distinct proteins. Thus, effective hypoxia response requires increased HIF target gene transcription as well as proper RNA splicing of these HIF target genes. However, it is unclear if and how hypoxia regulates RNA splicing of HIF target genes. This study determined the effects of hypoxia on alternative splicing (AS) of HIF and non-HIF target genes in Hep3B cells and characterized the role of HIF in regulating AS of HIF induced genes. The results indicated that hypoxia generally promotes exon inclusion for hypoxia-induced, but reduces exon inclusion for hypoxia reduced genes. Mechanistically, HIF activity, but not hypoxia per se is found to be necessary and sufficient to increase exon inclusion of several HIF target genes including pyruvate dehydrogenase kinase 1 (PDK1). PDK1 splicing reporters confirmed that transcriptional activation by HIF is sufficient to increase exon inclusion of PDK1 splicing reporter. In contrast, transcriptional activation of the PDK1 minigene by other transcription factor in the absence of endogenous HIF target gene activation fails to alter PDK1 RNA splicing, demonstrating a novel role of HIF target gene(s) in regulating RNA splicing of HIF target genes. Implications:This study demonstrates a novel function of HIF in regulating RNA splicing of HIF target genes.
2014-05-14 | GSE57613 | GEO
Project description:MSI (Microsatellite Instability) colorectal cancer (CRC) show improved survival, are less prone to metastasis and show poor response to chemotherapy (compared to MSS tumors). The underlying reasons for these characteristics are still not understood and no specific therapeutic approach for MSI colon tumours (15% of CRC overall) has yet been developed.
The MSI process is oncogenic when it affects DNA repeat sequences that have a functional role, e.g. Small Coding Repeats (SCR). MSI also frequently affects Long Non-Coding Repeats (LNCR) in tumour DNA. In contrast to SCR, only a few LNCR are endowed with biological activity. Consequently, this area has received very little attention. Our group recently identified HSP110 mutant chaperone protein in MSI CRC that was generated by somatic deletion of a LNCR. Of interest, HSP110 mutant (due to exon skipping) have anti-oncogenic properties and the survival of MSI CRC patients receiving chemotherapy is positively associated with HSP110 mutations in tumour DNA.
The aim of the current project is to identify additional clinically relevant MSI-associated splicing aberrations due to mutations in LNCR located in splice acceptor sites. The four main steps are as follows:
1. To identify exon/intron sites affected by aberrant splicing events due to MSI in CRC . All RNASeq data will be exploited to identify recurrent splicing aberrations (mostly exon skipping) that occur specifically in MSI colon tumours;
2. To investigate for possible functional links between MSI and any detected aberrant splicing events . All specific aberrant splicing events detected by RNAseq in MSI CRC samples will be first confirmed (quantitative RT-PCR) in order to eliminate false positive cases. For validated exon candidates, the allelic profiles of adjacent intronic LNCR will be analysed (PCR and fluorescence genotyping) in CRC cell lines and primary tumours (MSI and MSS), as well as in matching normal mucosa samples in order to assess their polymorphic status;
3. To identify splicing events and LNCR mutations with clinical relevance in MSI CRC patients . All LNCR with a confirmed role in gene splicing in MSI CRC will be analysed. The clinical relevance of candidate genes will be assessed using multivariate survival regression models for Relapse- Free Survival, with interaction terms (response to chemotherapy);
4. To initiate functional studies on a limited number of clinically relevant, cancer-related genes whose splicing is perturbed in MSI cancer cells, and to develop biological tools to simplify screening in future clinical assays Similar to HSP110, we will focus on 4 or 5 mutant proteins that are promising drug therapeutic targets. Functional assays will be developed to further elucidate their role in the pathophysiology of MSI tumours. We also aim to develop biological tools for these candidate genes, such as the detection of wild-type or mutant proteins by immunohistochemistry.
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Project description:Alternative splicing (AS) is an important component of RNA processing controlled by cis- and trans-acting component. Here we investigate modes and mechanisms of AS co-regulation by MBNL1 and RBFOX1. We generated two cell models (human and mouse) whereby the expression of both RBPs can be independently modulated and utilize these cell lines to perform RNAseq and transcriptome wide alternative splicing analysis. Categorization of alternative splicing outcomes of the impacts of RBFOX1 expression on MBNL1 splicing revealed a common co-regulatory mode whereby RBFOX1 buffers MBNL1 dose-dependent splicing regulation by reducing the total range of exon inclusion induced. Overall, our studies define a conserved co-regulatory mechanism through which RBFOX1 and MBNL1 can fine-tune and provide redundancy for AS outcomes.
2021-03-25 | GSE169518 | GEO
Project description:Alternative splicing (AS) is a dynamic RNA processing step that produces multiple RNA isoforms from a single pre-mRNA transcript and contributes to the complexity of the cellular transcriptome and proteome. This process is regulated through a network of cis-regulatory sequence elements and trans-acting factors, most-notably RNA binding proteins (RBPs). The muscleblind-like (MBNL) and RNA binding fox-1 homolog (RBFOX) are two well characterized families of RBPs that regulate fetal to adult AS transitions critical for proper muscle, heart, and central nervous system development. To better understand how the concentration of these RBPs influences AS transcriptome wide, we engineered an MBNL1 and RBFOX1 inducible HEK-293 cell line. We found that induction of exogenous RBFOX1 modulated AS outcomes, despite significant levels of endogenous RBFOX1 and RBFOX2 expression. We characterized AS outcomes by RNAseq following dose-dependent MBNL1 induction to generate transcriptome wide dose-response curves of skipped exon events. Analysis of 43 validated splicing events by RT-PCR revealed a spectrum of dose-response splicing curves with a 2-fold range for EC50 values and slope values ranging from 4 to 10. Analysis of this data suggests that exclusion events, when compared to inclusion events, regulated by MBNL1, may require higher protein concentrations to regulate, and that multiple arrangements of YGCY motifs produce similar splicing outcomes. Together these data suggest that rather than a simple association between the configuration of RBP binding sites and a specific splicing outcome, that a complex network governs both AS inclusion and exclusion events that operates in an RBP dose-dependent manner.
2023-01-01 | GSE221838 | GEO
Project description:SRSF2 is an RNA binding protein that plays important roles in splicing of mRNA precursors. Mutations in SRSF2 are frequently found in patients with myelodysplastic syndromes and certain leukemias, but how they affect SRSF2 function has only begun to be examined. Here we used CRISPR/Cas9 to introduce the P95H mutation to SRSF2 in K562 leukemia cells, generating an isogenic model so that splicing alterations can be attributed solely to mutant SRSF2. We found that SRSF2 (P95H) misregulates 548 splicing events (<1% of total). Of these, 374 involve the inclusion of cassette exons, and the inclusion was either increased (206) or decreased (168). We detected a specific motif (UCCA/UG) enriched in the more included exons and a distinct motif (UGGA/UG) in the more excluded exons. RNA gel shift assays showed that a mutant SRSF2 derivative bound more tightly than its wild-type counterpart to RNA sites containing UCCAG, but less tightly to UGGAG sites. The pattern of exon inclusion or exclusion thus correlated in most cases with stronger or weaker RNA binding, respectively. We further show that the P95H mutation does not affect other functions of SRSF2, i.e., protein-protein interactions with key splicing factors. Our results thus demonstrate that the P95H mutation positively or negatively alters the binding affinity of SRSF2 for cognate RNA sites in target transcripts, leading to misregulation of exon inclusion. Our findings not only shed light on the mechanism of the disease-associated SRSF2 mutation in splicing regulation, but also reveal a group of mis-spliced mRNA isoforms for potential therapeutic targeting. Examination of differentially spliced events in K562 CRISPR cell clones (with wild-type or mutant SRSF2) by RNA sequencing
2015-08-10 | E-GEOD-71299 | biostudies-arrayexpress
Project description:Spinal muscular atrophy (SMA) is an autosomal recessive, pediatric-onset disorder caused by the loss of spinal motor neurons thereby leading to generalized muscle atrophy. SMA is caused by the loss of or mutations in the survival motor neuron 1 (SMN1) gene. SMN1 is duplicated only in human to give rise to the paralogous SMN2 gene. These paralogs are nearly identical except for a cytosine to thymine (C-to-T) transition within an exonic splicing enhancer (ESE) element within exon 7. As a result, the majority of SMN2 transcripts lack exon 7 (SMNΔ7) which produces a truncated and unstable SMN protein. Since SMN2 copy number is inversely related to disease severity, it is a well-established target for SMA therapeutics development. 5-(N-ethyl-N-isopropyl)amiloride (EIPA), an inhibitor of sodium/proton exchangers (NHEs), has previously been shown to increase exon 7 inclusion and SMN protein levels in SMA cells. In this study several different types of NHE inhibitors were evaluated for their ability to modulate SMN2 expression. EIPA as well as 5-(N,N-hexamethylene)amiloride (HMA) increase exon 7 inclusion in SMN2 splicing reporter lines as well as in SMA fibroblasts. The EIPA-induced exon 7 inclusion occurs via a mechanism unique from that used by RG7800, another SMN2 splicing modulator, and does not involve previously identified splicing factors. Transcriptome analysis identified novel targets, including TIA1 and FABP3, for further characterization. EIPA and HMA are more selective at inhibiting the NHE5 isoform, which is expressed in fibroblasts as well as in neuronal cells. These results show that NHE5 inhibition increases SMN2 expression and may be a novel target for therapeutics development.
2022-06-16 | GSE179861 | GEO
Project description:Most human transcripts are alternatively spliced, and many disease-causing mutations affect RNA splicing. Towards better modeling the sequence determinants of alternative splicing, we measured the splicing patterns of nearly 2 million (M) synthetic mini-genes, which include degenerate subsequences totaling to nearly 100M bases of variation. The massive size of these training data allowed us to improve upon current models of splicing as well as to gain new mechanistic insights. Our results show that a vast majority of hexamer sequence motifs measurably influence splice site selection when positioned within alternative exons, with multiple motifs acting additively rather than cooperatively. Intriguingly, motifs that enhance (suppress) exon inclusion in alternative 5’ splicing also enhance (suppress) exon inclusion in alternative 3’ or cassette exon splicing, suggesting a universal mechanism for alternative exon recognition. Finally, our empirically trained models are highly predictive of the effects of naturally occurring variants on alternative splicing in vivo.
2015-10-21 | GSE74070 | GEO