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
Project description:Using RNA-Seq analysis of nonsense-mediated mRNA decay (NMD) mutant strains, we show that many Saccharomyces cerevisiae intron-containing genes exhibit usage of alternative splice sites, but most transcripts generated by splicing from these sites are non-functional because they introduce premature termination codons leading to transcript degradation by NMD. Analysis of splicing mutants combined with NMD inactivation revealed the role of specific splicing factors in governing the use of these alternative splice sites and identified novel functions for Prp17p in enhancing the use of branchpoint-proximal upstream 3M-bM-^@M-^Y splice sites and for Prp18p in suppressing the usage of a non-canonical AUG 3M-bM-^@M-^Y-splice site. The use of non-productive alternative splice sites can limit the expression of some transcripts and can be increased in stress conditions in a promoter-dependent manner, contributing to the down-regulation of genes during stress. These results reveal that alternative splicing is frequent in S.cerevisiae but masked by RNA degradation and that the use of alternative splice sites is mostly aimed at controlling transcript levels rather than increasing proteome diversity. mRNA-Seq profiling of 3 mutants in the nonsense-mediated mRNA decay pathway and wildtype yeast
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.
Project description:Nonsense-mediated mRNA decay (NMD) is a eukaryotic surveillance pathway that recognizes aberrant transcripts arising from mutations and transcriptional mistakes. Moreover, differential transcript processing such as alternative precursor mRNA splicing (AS) can generate NMD substrates, however, the extent of coupled AS and NMD remained unclear. To investigate NMD targeting of AS variants, we performed transcriptome-wide splicing studies using Arabidopsis thaliana single and double mutants in the NMD factor homologues UPF1 and UPF3, as well as samples treated with the translation inhibitor cycloheximide (CHX). Our analyses revealed that at least 17.5% of all multi-exon, protein-coding genes produce splicing variants of all major types that are targeted by NMD, with a significant fraction originating from the splicing of cryptic introns. Furthermore, accumulation of many intron-retained mRNAs in the mutants, but not in response to CHX suggests the action of distinct routes of NMD with variable impact of translation. Importantly, 92.3% of the NMD-responsive mRNAs exhibit classical NMD-eliciting features, supporting their authenticity as direct targets. NMD-dependent AS variants are linked to diverse biological functions, including the poison exon-mediated regulation of signaling and posttranslational protein modification components. In addition to mRNAs, numerous non-coding RNAs as well as newly identified transcripts derived from intergenic regions were shown to be NMD responsive. In summary, our comprehensive analysis of AS-coupled NMD provides strong evidence for a major function of this pathway in shaping the transcriptome, having fundamental implications in gene regulation and quality control of transcript processing steps in higher eukaryotes. Comparison of gene expression and alternative splicing patterns in control and nonsense-mediated decay (NMD)-impaired Arabidopsis seedlings
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:Mammalian SR proteins are a family of reversibly phosphorylated RNA binding proteins primarily studied for their roles in alternative splicing. While budding yeast lack alternative splicing, they do have three SR-like proteins: Npl3, Gbp2, and Hrb1. However, these have been primarily studied for their roles in mRNA export, leaving their potential roles in splicing largely unexplored. Here we combined high-density genetic interaction profiling and genome-wide splicing-sensitive microarray analysis to demonstrate that a single SR-like protein, Npl3, is required for efficient splicing of a large set of pre-mRNAs in Saccharomyces cerevisiae. We tested the hypothesis that Npl3 promotes splicing by facilitating co-transcriptional recruitment of splicing factors. Using chromatin immunoprecipitation, we showed that mutation of NPL3 reduces the occupancy of U1 and U2 snRNPs at Npl3-stimulated genes. This provides the first evidence that an SR protein can promote recruitment of splicing factors to chromatin. Splicing-specific microarrays were used to assay changes to splicing in single and double deletion mutants of non-essential SR proteins, in a deletion mutant of a non-essential component of the nonsense-mediated decay pathway, and in a double deletion mutant of in an SR protein plus a non-sense mediated decay factor in Saccharomyces cerevisiae. The data includes both samples obtained at the permissive temperature and also shifts to the non-permissive temperature for some mutants, as well as dye-flipped technical replicates.
Project description:Goal of the study is the identification of transcriptome deregulation of smg7 pad4 mutants, which are deficient in nonsense-mediated mRNA decay and are blocked in immune signaling, which should avoid secondary responses from immune signaling
Project description:The rate of RNA polymerase II (pol II) elongation can influence splice site selection in nascent transcripts, yet the extent and physiological relevance of this kinetic coupling between transcription and alternative splicing is not well understood. We performed experiments to perturb pol II elongation and then globally compared alternative splicing patterns with genome-wide pol II occupancy. RNA binding and RNA processing functions were significantly enriched among the genes with pol II elongation inhibition-dependent changes in alternative splicing. Under conditions that interfere with pol II elongation, including cell stress, increased pol II occupancy was detected in the intronic regions flanking the alternative exons in these genes, and these exons generally became more included. A disproportionately high fraction of these exons introduced premature termination codons that elicited nonsense-mediated mRNA decay (NMD), thereby further reducing transcript levels. Our results provide evidence that kinetic coupling between transcription, alternative splicing and NMD affords a rapid mechanism by which cells can respond to changes in growth conditions, including cell stress, to coordinate the levels of RNA processing factors with mRNA levels. In order to identify alternative splicing events influenced by changes in pol II elongation, we performed quantitative alternative splicing microarray profiling (Pan et al., 2004 (PMID 15610736); Shai et al., 2006 (PMID 16403798)) of RNA isolated from stimulated Jurkat T lymphoma cells, cultured separately in the presence or absence of two different drugs that can inhibit pol II elongation: 5,6-dichloro-1-β-D-ribofuranosyl-benzimidazole (DRB) and camptothecin.