Profiling lariat intermediates reveals genetic determinants of early and late co-transcriptional splicing
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE204834 | GEO | 2022/11/26
REPOSITORIES: GEO
Similar Datasets
Project description:How the splicing machinery defines exons or introns as the spliced unit has remained a puzzle for 30 years. Here we demonstrate that peripheral and central regions of the nucleus harbor genes with two distinct exon-intron GC content architectures that differ in the splicing outcome. Genes with low GC content exons, flanked by long introns with lower GC content, are localized in the periphery, and the exons are defined as the spliced unit. Alternative splicing of these genes results in exon skipping. In contrast, the nuclear center contains genes with a high GC content in the exons and short flanking introns. Most splicing of these genes occurs via intron definition, and aberrant splicing leads to intron retention. We demonstrate that the nuclear periphery and center generate different environments for the regulation of alternative splicing, and that two sets of splicing factors form discrete regulatory subnetworks for the two gene architectures. Our study connects 3D genome organization and splicing, thus demonstrating that exon and intron definition modes of splicing occur in different nuclear regions.
2021-05-14 | GSE174396 | GEO
Project description:The majority of genic transcription is intronic. Introns are removed by splicing as branched lariat RNAs which require rapid recycling. The branch site is recognized during splicing catalysis and later debranched by Dbr1 in the rate-limiting step of lariat turnover. Through generation of the first viable DBR1 knockout cell line, we find the predominantly nuclear Dbr1 enzyme to encode the sole debranching activity in human cells. Dbr1 preferentially debranches substrates that contain canonical U2 binding motifs, suggesting that branchsites discovered through sequencing do not necessarily represent those favored by the spliceosome. We find that Dbr1 also exhibits specificity for particular 5' splice site sequences. We identify Dbr1 interactors through co-immunoprecipitation mass spectroscopy. We present a mechanistic model for Dbr1 recruitment to the branchpoint through the intron-binding protein AQR. In addition to a 20-fold increase in lariats, Dbr1 depletion increases exon skipping. Using ADAR fusions to timestamp lariats, we demonstrate a defect in spliceosome recycling. In the absence of Dbr1, spliceosomal components remain associated with the lariat for a longer period of time. As splicing is co-transcriptional, slower recycling increases the likelihood that downstream exons will be available for exon skipping.
2023-06-26 | MSV000092263 | MassIVE
Project description:Background: Substantial progress has been made in the identification of sequence elements that control mRNA splicing and the genetic variants in these elements that alter mRNA splicing (referred to as splicing quantitative trait loci -- sQTLs). Genetic variants that affect mRNA splicing in trans are harder to identify because their effects can be more subtle and diffuse, and the variants are not co-located with their targets. We carried out a transcriptome-wide analysis of the effects of a mutation in a ubiquitous splicing factor that causes retinitis pigmentosa (RP) on mRNA splicing, using exon microarrays. Results: Exon microarray data was generated from whole blood samples obtained from four individuals with a mutation in the splicing factor PRPF8 and four sibling controls. Although the mutation has no known phenotype in blood, there was evidence of widespread differences in splicing between cases and controls (affecting between 10\% and 25\% of exons). Most probesets with significantly different inclusion (defined as the expression intensity of the exon divided by the expression of the corresponding transcript) between cases and controls had higher inclusion in cases and corresponded to exons that were shorter than average, AT-rich, located towards the 5' end of the gene and flanked by long introns. Introns flanking affected probesets were particularly depleted for the shortest category of introns, associated with splicing via intron definition. Conclusions: Our results show that a mutation in a splicing factor, with a phenotype that is restricted to retinal tissue, acts as a trans-sQTL cluster in whole blood samples. Characteristics of the affected exons suggest that they are spliced co-transcriptionally and via exon definition. Eight samples consisting of four sibling pairs were analysed. One individual in each pair harboured an RP-causing mutation on the PRPF8 gene (cases). Unaffected siblings were used as controls.
2012-12-25 | E-GEOD-43134 | biostudies-arrayexpress
Project description:Analysis of splicing defects in Schizosaccharomyces pombe upon chemical genetic inhibition of splicing kinases dsk1, lkh1, and prp4, as well as alanine-mutation of phosphorylated residues in the splicing factors bpb1, prp2, rsd1, srp1, srp2, usp101, usp103, sum3, prp22, cdc5, and cwf22. This study shows the splicing kinase dsk1 modulates splicing efficiency of introns with non-consensus splice sites, likely through phosphorylation of bpb1. Modulation of splicing efficiency of transcripts through kinase signaling pathways may afford the necessary flexibility to tune the gene expression profile in response to environmental and developmental cues. Experiments were conducted as direct two-color designs with 2-3 biological replicates per genotype pairing. Raw microarray data was normalized with loess normalization using the R package limma. Log2-fold changes (perturbation over reference) are reported. Each splicing event on the custom-designed splicing microarray was monitored with an exon probe reading out mRNA changes, an intron probe for unspliced pre-mRNA, and a splice junction probe spanning the junction between two spliced exons. For the analysis of the splicing efficiency for a given intron, a score was calculated as exon*intron/junction.
2015-07-13 | E-GEOD-62752 | biostudies-arrayexpress
Project description:Widespread co-transcriptional splicing has been demonstrated from yeast to human. However, measuring the kinetics of splicing relative to transcription has been hampered by technical challenges. Here, we took advantage of native elongating transcript sequencing (NET-seq) to identify the position of RNA polymerase II (Pol II) when exons become ligated in the newly synthesized RNA. We analyzed Drosophila melanogaster embryos because the genes transcribed initially during development have few and short introns (like yeast genes), whereas genes transcribed later contain multiple long introns (more similar to human genes). Moreover, compared to human, the Drosophila genome is more compact and thus the coverage of NET-seq reads on intragenic regions is higher. We detected spliced NET-seq reads connected to Pol II molecules that were positioned just a few nucleotides downstream of the 3’ splice site. Although the majority of splice junctions were covered by spliced reads, many introns remained unspliced, resulting in a complex range of heterogeneity in splicing dynamics. Introns that show splicing completion before Pol II has reached the end of the downstream exon are necessarily intron-defined. As expected, we found a relationship between the proportion of spliced reads and intron size. However, intron definition was observed at all intron sizes. Both canonical and recursive splicing were associated with a higher Pol II density, suggesting a splicing-coupled mechanism that slows down transcription elongation. We further observed that transcription termination was very efficient for isolated genes but that the presence of an overlapping antisense gene was often associated with transcriptional read-through. Taken together, our data unravels novel dynamic features of Pol II transcription and splicing in the developing Drosophila embryo.
2020-06-17 | GSE152585 | GEO
Project description:Background: Substantial progress has been made in the identification of sequence elements that control mRNA splicing and the genetic variants in these elements that alter mRNA splicing (referred to as splicing quantitative trait loci -- sQTLs). Genetic variants that affect mRNA splicing in trans are harder to identify because their effects can be more subtle and diffuse, and the variants are not co-located with their targets. We carried out a transcriptome-wide analysis of the effects of a mutation in a ubiquitous splicing factor that causes retinitis pigmentosa (RP) on mRNA splicing, using exon microarrays. Results: Exon microarray data was generated from whole blood samples obtained from four individuals with a mutation in the splicing factor PRPF8 and four sibling controls. Although the mutation has no known phenotype in blood, there was evidence of widespread differences in splicing between cases and controls (affecting between 10\% and 25\% of exons). Most probesets with significantly different inclusion (defined as the expression intensity of the exon divided by the expression of the corresponding transcript) between cases and controls had higher inclusion in cases and corresponded to exons that were shorter than average, AT-rich, located towards the 5' end of the gene and flanked by long introns. Introns flanking affected probesets were particularly depleted for the shortest category of introns, associated with splicing via intron definition. Conclusions: Our results show that a mutation in a splicing factor, with a phenotype that is restricted to retinal tissue, acts as a trans-sQTL cluster in whole blood samples. Characteristics of the affected exons suggest that they are spliced co-transcriptionally and via exon definition.
2012-12-25 | GSE43134 | GEO
Project description:We identified a landscape of FUS-binding RNA targets in HeLa cells. The majority of the FUS binding sites are in introns of pre-mRNAs and less are in exons and untranslated regions. Significant FUS binding in introns flanking cassette exons, long intron (>100kb) containing transcripts and noncoding RNAs were detected in our study. We specifically determined the function of FUS in regulating the alternative splicing of cassette exons. The top FUS-associated cassette exon is exon 7 of the pre-mRNA of FUS itself. We demonstrated that FUS is a repressor of its own exon 7 splicing. FUS autoregulates its own protein levels by exon 7 alternative splicing and nonsense mediated decay. Moreover, Amyotrophic Lateral Sclerosis (ALS) linked FUS mutants are deficient in FUS autoregulation. CLIP-seq of FUS in HeLa cells
2013-12-16 | E-GEOD-50178 | biostudies-arrayexpress
Project description:Lariat is formed by excised intron, in which the 5' splice site joints with the branchpoint (BP) during splicing. Although lariat RNAs are usually degraded by DBR1 (RNA debranching enzyme 1), recent findings in animals showed that many lariat RNAs were widely detected under physiological conditions. In contrast, the features of BPs and to what extent lariat RNAs accumulate naturally are largely unexplored in plants. Here, we analyzed 948 RNA sequencing datasets to document plant BPs and lariat RNAs on a genome-wide scale. In total, we identified 13872, 5199, 29582, and 13478 BPs in Arabidopsis, tomato, rice, and maize, respectively. Features of plant BPs are highly similar to those in yeast and human, in that BPs are adenine-preferred and flanked by uracil-enriched sequences. Intriguingly, ~20% of introns harbor multiple BPs, and BP usage is tissue-specific. Furthermore, 10580 lariat RNAs accumulate in wild type Arabidopsis plants, and most of these lariat RNAs originate from longer or retroelement-depleted introns, and the expression of these lariat RNAs significantly correlated with the incidence of back-splicing of parent exons. Collectively, our results provide the first comprehensive map of intron BPs and lariat RNAs in plants, and uncover a novel link between lariat turnover and splicing.
2019-04-17 | GSE117416 | GEO
Project description:Pre-mRNA splicing is carried out by the spliceosome and involves splice site recognition, removal of introns, and ligation of exons. Components of the spliceosome have been shown to interact with the elongating RNA polymerase II (RNAPII), which is thought to allow splicing to occur concurrently with transcription. However, little is known about the regulation and efficiency of cotranscriptional splicing in human cells. In this study, we used Bru-seq and BruChase-seq to determine the cotranscriptional splicing efficiencies of 17,000 introns expressed across six human cell lines. We found that less than half of all introns across these six cell lines were cotranscriptionally spliced. Splicing efficiencies for individual introns showed variations across cell lines, suggesting that splicing may be regulated in a cell type–specific manner. Moreover, the splicing efficiency of introns varied within genes. The efficiency of cotranscriptional splicing did not correlate with gene length, intron position, splice site strengths, or the intron/neighboring exons GC content. However, we identified binding signals from multiple RNA binding proteins (RBPs) that correlated with splicing efficiency, including core spliceosomal machinery components—such as SF3B4, U2AF1, and U2AF2 showing higher binding signals in poorly spliced introns. In addition, multiple RBPs, such as BUD13, PUM1, and SND1, showed preferential binding in exons that flank introns with high splicing efficiencies. The nascent RNA splicing patterns presented here across multiple cell types add to our understanding of the complexity in RNA splicing, wherein RNA-binding proteins may play important roles in determining splicing outcomes in a cell type– and intron-specific manner.
2021-05-25 | GSE160759 | GEO
Project description:We identified a landscape of FUS-binding RNA targets in HeLa cells. The majority of the FUS binding sites are in introns of pre-mRNAs and less are in exons and untranslated regions. Significant FUS binding in introns flanking cassette exons, long intron (>100kb) containing transcripts and noncoding RNAs were detected in our study. We specifically determined the function of FUS in regulating the alternative splicing of cassette exons. The top FUS-associated cassette exon is exon 7 of the pre-mRNA of FUS itself. We demonstrated that FUS is a repressor of its own exon 7 splicing. FUS autoregulates its own protein levels by exon 7 alternative splicing and nonsense mediated decay. Moreover, Amyotrophic Lateral Sclerosis (ALS) linked FUS mutants are deficient in FUS autoregulation.
2013-12-16 | GSE50178 | GEO