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Nascent-Seq Indicates Widespread Cotranscriptional pre-mRNA Splicing in Drosophila

ABSTRACT: To determine the prevalence of cotranscriptional splicing in Drosophila, we sequenced nascent RNA transcripts from Drosophila S2 cells as well as from Drosophila heads. 87% of introns assayed manifest more than 50% cotranscriptional splicing. The remaining 13% are cotranscriptionally spliced poorly, or slowly, with ~3% being almost completely retained in nascent pre-mRNA. Although individual introns showed slight but statistically significant differences in splicing efficiency, similar global levels of splicing were seen from both sources. Importantly, introns with low cotranscriptional splicing efficiencies are present in the same primary transcript with efficiently spliced introns, indicating that splicing is intron-specific. The analysis also indicates that cotranscriptional splicing is less efficient for first introns, longer introns and introns annotated as alternative. FinallyFinally, S2 cells expressing the slow RpII215C4 mutant manifest substantially less intron retention than wild-type S2 cells.

ORGANISM(S): Drosophila melanogaster

PROVIDER: GSE32950 | GEO | 2011/12/01

SECONDARY ACCESSION(S): PRJNA146467

REPOSITORIES: GEO

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Nascent-Seq Indicates Widespread Cotranscriptional pre-mRNA Splicing in Drosophila

Project description:To determine the prevalence of cotranscriptional splicing in Drosophila, we sequenced nascent RNA transcripts from Drosophila S2 cells as well as from Drosophila heads. 87% of introns assayed manifest more than 50% cotranscriptional splicing. The remaining 13% are cotranscriptionally spliced poorly, or slowly, with ~3% being almost completely retained in nascent pre-mRNA. Although individual introns showed slight but statistically significant differences in splicing efficiency, similar global levels of splicing were seen from both sources. Importantly, introns with low cotranscriptional splicing efficiencies are present in the same primary transcript with efficiently spliced introns, indicating that splicing is intron-specific. The analysis also indicates that cotranscriptional splicing is less efficient for first introns, longer introns and introns annotated as alternative. FinallyFinally, S2 cells expressing the slow RpII215C4 mutant manifest substantially less intron retention than wild-type S2 cells. Examination of Total pA and Nascent RNA from 2 different cell populations and isolated fly heads.

2011-12-01 | E-GEOD-32950 | biostudies-arrayexpress

Co-transcriptional splicing efficiencies differ within genes and between cell types

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

Nascent-seq indicates widespread cotranscriptional RNA editing in Drosophila

2012-05-31 | GSE37232 | GEO

Nascent-seq indicates widespread cotranscriptional RNA editing in Drosophila

Project description:The RNA editing enzyme ADAR chemically modifies adenosine (A) to inosine (I), which is interpreted by the ribosome as a guanosine. Here we assess cotranscriptional A-to-I editing in Drosophila, by isolating nascent RNA from adult fly heads and subjecting samples to high-throughput sequencing. There are a large number of edited sites within nascent exons. Nascent RNA from an ADAR null mutant strain was also sequenced, indicating that almost all A-to-I events require ADAR. Moreover, mRNA editing levels correlate with editing levels within the cognate nascent RNA sequence, indicating that the extent of editing is set cotranscriptionally. Surprisingly, the nascent data also identify an excess of intronic over exonic editing sites. These intronic sites occur preferentially within introns that are poorly spliced cotranscriptionally, suggesting a link between editing and splicing. We conclude that ADAR-mediated editing is more widespread than previously indicated and largely occurs cotranscriptionally. GSM914095: Fly genomic DNA sequencing. Sequenced on the Illumina GA II. GSM914102-GSM914113: Fly head nascent RNA profiles over 6 time points of a 12hr light:dark cycle in duplicate; sequenced on the Illumina GA II. GSM914114-GSM914119: Fly head nascent RNA profiles of yw, FM7, ADAR0 males in duplicate; sequenced on the HiSeq2000. GSM915213-GSM915214: Fly head mRNA profiles over 2 time points of a 12hr light:dark cycle; sequenced on the Illumina GA II. GSM915215-GSM915220: Fly head mRNA profiles over 6 time points of a 12hr light:dark cycle; paired-end sequenced on the Illumina GA II. GSM915221-GSM91526: Fly head mRNA profiles over 6 time points of a 12hr light:dark cycle; sequenced on the Illumina GA II.

2012-05-31 | E-GEOD-37232 | biostudies-arrayexpress

Global co-transcriptional splicing in Arabidopsis and the correlation with splicing regulation in mature RNAs

Project description:RNA splicing and spliceosome assembly in eukaryotes occur mainly during transcription. However, co-transcriptional splicing has not yet been explored in plants. Here, we showed that in Arabidopsis thaliana, nearly all introns undergo co-transcriptional splicing and this occurs with higher efficiency for introns in protein-coding genes than for noncoding RNAs. Co-transcriptional splicing efficiency correlates with density of 19 epigenetic modifications. Total intron number and intron position are two predominant sequence features that correlate with co-transcriptional splicing efficiency, and introns with alternative 5′ or 3′ splice sites are less efficiently spliced. Furthermore, we found that trans-acting protein mutations lead to more introns with increased splicing defects in nascent RNAs than in mature RNAs, and that introns with increased splicing defects in mature RNAs are inefficiently spliced at the co-transcriptional level. Our results not only uncovered widespread co-transcriptional splicing in Arabidopsis, but also uncovered features that may affect or be affected by co-transcriptional splicing efficiency.

2019-11-25 | GSE126064 | GEO

pre-mRNA splicing order is defined and maintains splicing fidelity across multi-intronic transcripts [I]

Project description:Combinatorially, intron excision within a given nascent transcript could proceed down any of thousands of paths, each of which would expose different dynamic landscapes of cis-elements and contribute to alternative splicing. In this study, we found that post-transcriptional multi-intron splicing order in human cells is largely predetermined, with most genes spliced in one or a few predominant orders. Strikingly, these orders were conserved across cell types and stages of motor neuron differentiation. Introns flanking alternatively spliced exons were frequently excised last, after their neighboring introns. Perturbations to the spliceosomal U2 snRNA altered the preferred splicing order of many genes, and these alterations were associated with the retention of other introns in the same transcript. In one gene, early removal of specific introns was sufficient to induce delayed excision of three proximal introns, and this delay was caused by two distinct cis-regulatory mechanisms. Together, our results demonstrate that multi-intron splicing order in human cells is predetermined, is influenced by a component of the spliceosome and ensures splicing fidelity across long pre-mRNAs.

2023-05-14 | GSE208197 | GEO

pre-mRNA splicing order is defined and maintains splicing fidelity across multi-intronic transcripts [II]

2023-05-14 | GSE208259 | GEO

Dynamic properties of transcription and co-transcriptional splicing during early stages of Drosophila development

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

A genome-wide analysis indicates that yeast pre-mRNA splicing is predominantly post-transcriptional

Project description:Recent ChIP experiments indicate that spliceosome assembly and splicing can occur cotranscriptionally in S. cerevisiae. However, only a few genes have been examined, and all have long second exons. To extend these studies, we analyzed intron-containing genes with different second exon lengths, by ChIP as well as by whole-genome tiling arrays (ChIP-CHIP). The data indicate that U1 snRNP recruitment is independent of exon length. Recursive splicing constructs, which uncouple U1 recruitment from transcription, suggest that cotranscriptional U1 recruitment contributes to optimal splicing efficiency. In contrast, U2 snRNP recruitment as well as cotranscriptional splicing is deficient on short second exon-genes. We estimate that approximately 90% of endogenous yeast splicing is post-transcriptional, consistent with an analysis of post-transcriptional snRNP-associated pre-mRNA. Keywords: ChIP-CHIP

2007-01-22 | GSE6417 | GEO

Spliceosome specifically associates with CTD phospho-serine 5 isoform of RNA polymerase II to promote co-transcriptional splicing

Project description:Co-transcriptional splicing of introns is a defining feature of eukaryotic gene expression. We show that the mammalian spliceosome specifically associates with the S5P CTD isoform of RNA polymerase II (Pol II) as it elongates across spliced exons of protein coding genes, both in human Hela and murine lymphoid cell lines. Immuno-precipitation of MNase digested chromatin with phospho CTD specific antibodies reveals that components of the active spliceosome (both snRNA and proteins) form a specific complex with S5P CTD Pol II. Furthermore a dominant splicing intermediate formed by cleavage at intron 5’ss results in the tethering of upstream exons to this complex at all spliced exons. These are invariably connected to upstream spliced constitutive and less frequently to alternative exons. Finally S5P CTD Pol II accumulates over spliced exons but not adjacent introns. We propose that mammalian splicing employs a rapid, co-transcriptional splicing mechanism based on CTD phosphorylation transitions.

2018-10-05 | PXD008197 | Pride

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