Project description:Alternative polyadenylation has been implicated as an important regulator of gene expression. In some cases, alternative polyadenylation is known to couple with alternative splicing to influence last intron removal. However, it is unknown whether alternative polyadenylation events influence alternative splicing decisions at upstream exons. Knockdown of the polyadenylation factors CFIm25 or CstF64 was used as an approach in identifying alternative polyadenylation and alternative splicing events on a genome-wide scale. Although hundreds of alternative splicing events were found to be differentially spliced in the knockdown of CstF64, genes associated with alternative polyadenylation did not exhibit an increased incidence of alternative splicing. These results demonstrate that the coupling between alternative polyadenylation and alternative splicing is usually limited to defining the last exon. The striking influence of CstF64 knockdown on alternative splicing can be explained through its effects on UTR selection of known splicing regulators such as hnRNP A2/B1, thereby indirectly influencing splice site selection. We conclude that changes in the expression of the polyadenylation factor CstF64 influences alternative splicing through indirect effects. HeLa cell line was stably transfected with shRNA plasmids targeting CstF64. Total RNA was isolated from CstF64 KD cells and wild-type control cells using Trizol according to manufacturerâs protocols. Samples were deep sequenced in duplicate using the Illumina GAIIx system.
Project description:B cells treated with LPS undergo stress and Ire1 phosphorylation by 18 hours. We measured the effect of inhibiting the Ire1 phosphorylation with the drug 4u8c on gene expression and RNA splicing.
Project description:Removal of introns during pre-mRNA splicing, which is central to gene expression, initiates by base pairing of U1 snRNA with a 5' splice site (5'SS). In mammals, many introns contain weak 5'SSs that are not efficiently recognized by the canonical U1 snRNP, suggesting alternative mechanisms exist. Here, we develop a cross-linking immunoprecipitation coupled to a high-throughput sequencing method, BCLIP-seq, to identify NRDE2 (Nuclear RNAi defective-2) and CCDC174 (Coiled-Coil Domain-Containing 174) as novel RNA-binding proteins in mouse ES cells that associate with U1 snRNA and unspliced 5'SSs. Both proteins bind directly to U1 snRNA independently of canonical U1 snRNP specific proteins, and they are required for the selection and effective processing of weak 5'SSs. Our results reveal that mammalian cells use non-canonical splicing factors bound directly to U1 snRNA to effectively select suboptimal 5'SS sequences in hundreds of genes, promoting proper splice site choice and accurate pre-mRNA splicing.
Project description:Alternative polyadenylation has been implicated as an important regulator of gene expression. In some cases, alternative polyadenylation is known to couple with alternative splicing to influence last intron removal. However, it is unknown whether alternative polyadenylation events influence alternative splicing decisions at upstream exons. Knockdown of the polyadenylation factors CFIm25 or CstF64 was used as an approach in identifying alternative polyadenylation and alternative splicing events on a genome-wide scale. Although hundreds of alternative splicing events were found to be differentially spliced in the knockdown of CstF64, genes associated with alternative polyadenylation did not exhibit an increased incidence of alternative splicing. These results demonstrate that the coupling between alternative polyadenylation and alternative splicing is usually limited to defining the last exon. The striking influence of CstF64 knockdown on alternative splicing can be explained through its effects on UTR selection of known splicing regulators such as hnRNP A2/B1, thereby indirectly influencing splice site selection. We conclude that changes in the expression of the polyadenylation factor CstF64 influences alternative splicing through indirect effects.
Project description:Our study represents the first detailed analysis of the transcriptional and alternative splicing landscape of intestinal organoids undergoing stress, with biologic replicates, generated by RNA-seq technology. We report significant changes in the expression of genes involved in inflammation, proliferation and transcription, among others. Splicing events commonly regulated by both stresses affected genes regulating splicing and were associated with nonsense-mediated decay (NMD), suggesting that splicing is modulated by an auto-regulatory feedback loop during stress. Murine intestinal organoids were stimulated in triplicate with conditions for either ER stress or nutrient starvation and RNA-seq was conducted to analyze global changes in both gene expression at the transcriptional level and alternative splicing
Project description:In this study we investigated snRNA-mediated modulation of pre-mRNA splicing across the human transcriptome. We first quantified the relative abundance of snRNAs across a comprehensive range of healthy adult and fetal tissues, revealing a surprising variation in the relative snRNA levels both inter- and intra-tissue. To study the role of snRNAs in cancer-relevant splicing, we used breast cancer as a model, since it exhibits a high rate of aberrant splicing48, but a low frequency of mutations in the splicing machinery52. We observed fluctuations in snRNA adundance across the majority of patients, across all breast cancer subtypes. To investigate the impact of snRNA levels using a controlled system, we knocked down snRNAs in vitro, to analyze splicing both transcriptome-wide and at the level of individual exons and introns. Depletion of each specific snRNA resulted in differential splicing across more than a thousand exon junctions within mRNA transcripts. Knock-down of U1 and U2 levels was primarily associated with changes in exon inclusion rates, whereas U4 and U6 depletion predominantly caused incomplete intron removal and a resulting retention of introns in the mature mRNA. Rather than being driven by a single factor, the observed splicing changes were associated with multiple other splicing-relevant features and mechanisms, including mRNA transcription, intron size, and nucleotide composition. The snRNA-mediated changes to the splicing program were enriched within genes encoding components of core cellular pathways and processes, including multiple aspects of RNA and protein metabolism, and thereby have the potential to impact cell growth and identity. The exons and introns that were sensitive to snRNA levels displayed a high variability in splicing in vivo across primary breast cancer samples, indicating that snRNA dysregulation may contribute to aberrant splicing in cancer. We suggest that the cellular composition of snRNAs constitutes a previously unrecognized layer of splicing regulation within the cell, and that variations or disruptions in the relative abundance of the snRNAs can affect the transcriptome of both healthy and malignant cells.
Project description:Small nuclear RNAs (snRNAs) are core spliceosome components and mediate pre-mRNA splicing. Here we show that snRNAs contain a regulated and reversible nucleotide modification causing them to exist as two different methyl isoforms, m 1 and m 2 , reflecting the methylation state of the adenosine adjacent to the snRNA cap. We find that snRNA biogenesis involves the formation of an initial m 1 isoform with a single-methylated adenosine (2′-O-methyladenosine, Am), which is then converted to a dimethylated m 2 isoform (N 6 ,2′-O-dimethyladenosine, m 6 Am). The relative m 1 and m 2 isoform levels are determined by the RNA demethylase FTO, which selectively demethylates the m 2 isoform. We show FTO is inhibited by the oncometabolite d-2-hydroxyglutarate, resulting in increased m 2 -snRNA levels. Furthermore, cells that exhibit high m 2 -snRNA levels show altered patterns of alternative splicing. Together, these data reveal that FTO controls a previously unknown central step of snRNA processing involving reversible methylation, and suggest that epitranscriptomic information in snRNA may influence mRNA splicing.
Project description:This SuperSeries is composed of the following subset Series: GSE23513: Position-dependent alternative splicing activity revealed by global profiling of alternative splicing events regulated by PTB (HJAY) GSE23514: Position-dependent alternative splicing activity revealed by global profiling of alternative splicing events regulated by PTB (Exon array) Refer to individual Series
Project description:Removal of introns during pre-mRNA splicing, which is central to gene expression, initiates by base pairing of U1 snRNA with a 5' splice site (5'SS). In mammals, many introns contain weak 5'SSs that are not efficiently recognized by the canonical U1 snRNP, suggesting alternative mechanisms exist. Here, we develop a cross-linking immunoprecipitation coupled to a high-throughput sequencing method, BCLIP-seq, to identify NRDE2 (Nuclear RNAi defective-2) and CCDC174 (Coiled-Coil Domain-Containing 174) as novel RNA-binding proteins in mouse ES cells that associate with U1 snRNA and unspliced 5'SSs. Both proteins bind directly to U1 snRNA independently of canonical U1 snRNP specific proteins, and they are required for the selection and effective processing of weak 5'SSs. Our results reveal that mammalian cells use non-canonical splicing factors bound directly to U1 snRNA to effectively select suboptimal 5'SS sequences in hundreds of genes, promoting proper splice site choice and accurate pre-mRNA splicing.