Conserved intronic secondary structures with concealed branch sites regulate alternative splicing of poison exons
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA925017 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR23106941_1.fastq.gz | Fastqsanger.gz | |||
| SRR23106941_2.fastq.gz | Fastqsanger.gz | |||
| SRR23106942_1.fastq.gz | Fastqsanger.gz | |||
| SRR23106942_2.fastq.gz | Fastqsanger.gz | |||
| SRR23106943_1.fastq.gz | Fastqsanger.gz |
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Project description:Alternative splicing (AS) generates large amounts of RNA isoforms and dramatically increases the complexities of transcriptomes and proteomes. However, it remains unclear how RNA structures contribute to AS regulation. Here, we systematically search transcriptomes for secondary structures with concealed branch-sites (BSs) in the alternatively spliced introns and predict thousands from six organisms, of which many are evolutionarily conserved. Intriguingly, a highly conserved stem-loop structure with concealed BSs is found in animal SF3B3 genes and colocalizes with a downstream poison exon (PE). Destabilization of this structure allows increased usage of the branch sites and results in enhanced PE inclusion in both human and Drosophila cells, leading to decreased expression of SF3B3. Through an RNAi screen of 28 RNA-binding proteins, we find that this stem-loop structure is sensitive to U2 and U2-associated proteins. Furthermore, we find that SF3B3 also facilitates DNA repair and protects genome stability by enhancing interaction between ERCC6/CSB and arrested RNA polymerase II. Importantly, both Drosophila and human cells with the secondary structure mutated by genome editing exhibit altered DNA repair in vivo. This study provides a novel and common mechanism for AS regulation of PEs and reveals a physiological function of SF3B3 in DNA repair.
2024-06-12 | GSE223117 | GEO
Project description:Eukaryotic cells express a large number of transcripts from a single gene due to alternative splicing. Despite hundreds of thousands of splice isoforms being annotated in databases, it has been reported that the current exon catalogs remain incomplete. At the same time, introns of human protein-coding genes contain a large number of evolutionarily conserved elements with unknown function. Here, we explore the possibility that some of them represent cryptic exons that are expressed in rare conditions. We identified a group of cryptic exons that are similar to the annotated exons in terms of evolutionary conservation and RNA-seq read coverage in the GTEx dataset. Most of them were poison, i.e. generated an NMD isoform upon inclusion, and many showed signs of tissue-specific and cancer-specific expression and regulation. We performed RNA-seq in A549 cell line treated with cycloheximide to inactivate NMD, and confirmed using qPCR that seven of eight exons tested are, indeed, expressed. This study shows that introns of human protein-coding genes contain cryptic poison exons, which reside in conserved intronic regions and remain not fully annotated due to insufficient representation in RNA-seq libraries.
2024-11-20 | GSE270310 | GEO
Project description:Human introns contain conserved tissue-specific cryptic poison exons
| PRJNA1126174 | ENA
Project description:Both canonical and alternative splicing of RNAs is governed by intronic sequence elements and produces transient lariat structures fastened by branch-points within introns. To map precisely the location of branch-points on a genomic scale, we developed LaSSO (Lariat Sequence Site Origin), a data-driven algorithm which utilizes RNA-seq data. Using fission yeast cells lacking the debranching enzyme Dbr1, LaSSO not only accurately identified canonical splicing events, but also pinpointed novel, but rare, exon-skipping events, which may reflect aberrantly spliced transcripts. Compromised intron turnover perturbed gene regulation at multiple levels, including splicing and protein translation. Notably, Dbr1 function was also critical for the expression of mitochondrial genes, and for the processing of self-spliced mitochondrial introns. LaSSO showed better sensitivity and accuracy than algorithms used for computational branch-point prediction or for empirical branch-point determination. Even when applied to a human data set acquired in the presence of debranching activity, LaSSO identified both canonical and exon skipping branch-points. LaSSO thus provides an effective, accurate and unbiased approach for defining high-resolution maps of branch-site sequences and intronic elements on a genomic scale. LaSSO should be useful to validate introns and uncover branch-point sequences in any eukaryote, and it could be integrated to RNA-seq pipelines. Interrogation of the S. pombe transcriptome using rRNA depleted strand specific RNA sequencing (Illumina HiSeq 2000) in wild type and dbr1.M-NM-^T cultures. A total of 4 samples were analyzed: two biological repeates of wild-type strain and two biological repeats of dbr1.M-NM-^T
2014-03-18 | E-GEOD-50246 | biostudies-arrayexpress
Project description:Both canonical and alternative splicing of RNAs is governed by intronic sequence elements and produces transient lariat structures fastened by branch-points within introns. To map precisely the location of branch-points on a genomic scale, we developed LaSSO (Lariat Sequence Site Origin), a data-driven algorithm which utilizes RNA-seq data. Using fission yeast cells lacking the debranching enzyme Dbr1, LaSSO not only accurately identified canonical splicing events, but also pinpointed novel, but rare, exon-skipping events, which may reflect aberrantly spliced transcripts. Compromised intron turnover perturbed gene regulation at multiple levels, including splicing and protein translation. Notably, Dbr1 function was also critical for the expression of mitochondrial genes, and for the processing of self-spliced mitochondrial introns. LaSSO showed better sensitivity and accuracy than algorithms used for computational branch-point prediction or for empirical branch-point determination. Even when applied to a human data set acquired in the presence of debranching activity, LaSSO identified both canonical and exon skipping branch-points. LaSSO thus provides an effective, accurate and unbiased approach for defining high-resolution maps of branch-site sequences and intronic elements on a genomic scale. LaSSO should be useful to validate introns and uncover branch-point sequences in any eukaryote, and it could be integrated to RNA-seq pipelines.
2014-03-18 | GSE50246 | GEO
Project description:Alternative splicing-induced inclusion of poison exons containing in-frame stop codons is a mechanism that can be used to attenuate gene expression. Poison exon have been implicated in cancer, but how they operate within the context of normal development and physiology is poorly understood. Several splicing regulator genes, including Tra2b, contain ultra-conserved poison exons that function within regulatory loops to fine-tune their activity. To investigate the physiological role of poison exons in vivo, we created mice lacking either Tra2b or its poison exon, specifically during spermatogenesis to reveal both are essential for male fertility. The mouse Tra2b gene is essential for mitotic proliferation of germ cells, whereas, in contrast, the Tra2b poison exon is critically required during meiosis and not needed by mitotically proliferating cell populations within the germline. Poison exon deletion causes infertility, with a block in male meiotic prophase where Tra2β protein expression levels normally increase. Deletion of the Tra2b poison exon changes expression patterns of genes important for meiosis and splicing patterns of Tra2β target exons, suggesting Tra2b poison exon splicing prevents meiotic cells accumulating toxic levels of Tra2b expression. Our data provide a new physiological explanation for Tra2b poison exon ultra-conservation and indicate the importance of evaluating poison exon function within a physiological context.
2024-12-19 | GSE235084 | GEO
Project description:Alternative splicing-induced inclusion of poison exons containing in-frame stop codons is a mechanism that can be used to attenuate gene expression. Poison exon have been implicated in cancer, but how they operate within the context of normal development and physiology is poorly understood. Several splicing regulator genes, including Tra2b, contain ultra-conserved poison exons that function within regulatory loops to fine-tune their activity. To investigate the physiological role of poison exons in vivo, we created mice lacking either Tra2b or its poison exon, specifically during spermatogenesis to reveal both are essential for male fertility. The mouse Tra2b gene is essential for mitotic proliferation of germ cells, whereas, in contrast, the Tra2b poison exon is critically required during meiosis and not needed by mitotically proliferating cell populations within the germline. Poison exon deletion causes infertility, with a block in male meiotic prophase where Tra2β protein expression levels normally increase. Deletion of the Tra2b poison exon changes expression patterns of genes important for meiosis and splicing patterns of Tra2β target exons, suggesting Tra2b poison exon splicing prevents meiotic cells accumulating toxic levels of Tra2b expression. Our data provide a new physiological explanation for Tra2b poison exon ultra-conservation and indicate the importance of evaluating poison exon function within a physiological context.
2024-12-19 | GSE235083 | GEO
Project description:RNA isoform screens reveal the essentiality and tumor suppressor activity of ultraconserved poison exons
| PRJNA494172 | ENA
Project description:Systematic mutagenesis has revealed that synonymous, non-synonymous and intronic mutations frequently alter the inclusion levels of alternatively spliced exons, suggesting that altered splicing might be a common mechanism by which mutations cause disease. However, most exons expressed in any cell are highly-included in mature mRNAs. Here, by performing deep mutagenesis of highly-included exons and by analysing the association between sequence variation and exon inclusion across the genome, we report that mutations only very rarely alter the inclusion of highly-included exons. This is true for both exonic and intronic mutations as well as for perturbations in trans. Therefore, mutations that affect splicing are not evenly distributed across the genome but are focussed in and around alternatively spliced exons with intermediate inclusion levels. These results provide a resource for prioritising synonymous and other variants as disease-causing mutations.
2020-06-29 | GSE151942 | GEO
Project description:Somatic SF3b1 mutations occur in many cancers, and the highly conserved H662 residue is one of the most frequently mutated sites. To address their mechanism on splicing alteration and effects on development, we constructed mutant strains at the corresponding residue H698 in Drosophila using CRISPR-Cas9 system. Two mutations, H698D and H698R, were selected due to their presence in patients and the significantly opposite charges. Both the sf3b1-H698D and –H698R mutant flies exhibit developmental defects including less egg-laying, decreased hatching rates, delayed morphogenesis and shorter lifespan. Interestingly, the H698D mutant has decreased resistance to fungi infection, while the H698R mutant has impaired climbing ability. Further RNA-seq data finds altered expression of immunity response genes and changed alternative splicing of muscle and neural-related genes in the two mutants respectively. Lariat sequencing reveal that the sf3b1-H662 mutations cause aberrant selection of multiple intronic branch sites and the H698R mutant prefers to use upstream branch sites in the alternative splicing changed events. This study provides in vivo evidence from Drosophila to elucidate how the highly conserved SF3b1 cancer mutations alter splicing and their consequences in the development and immune systems.
2021-10-08 | GSE171002 | GEO