Project description:Multiple lines of evidence implicate chromatin in the regulation of pre-mRNA splicing. However, the influence of chromatin factors on co-transcriptional splice-site usage remains unclear. Here we investigated the function of the highly conserved histone variant H2A.Z in pre-mRNA splicing using the intron-rich model yeast, Schizosaccharomyces pombe. Using Epistatic Mini-Array Profiles (EMAPs) to survey the genetic interaction landscape of the Swr1 nucleosome remodeling complex, which deposits H2A.Z, we uncovered evidence for functional interactions with components of the spliceosome. In support of these genetic connections, splicing-specific microarrays show that H2A.Z and the Swr1 ATPase are required during temperature stress for the efficient splicing of a sub-set of introns. Notably, affected introns are enriched for H2A.Z occupancy, and more likely to contain non-consensus splice sites. To test the significance of the latter correlation, we mutated the splice sites in an affected intron to consensus and found this suppressed the requirement for H2A.Z in splicing of that intron. These data suggest that H2A.Z occupancy promotes co-transcriptional splicing of sub-optimal introns that may otherwise be discarded via proofreading ATPases. Consistent with this model, we show that over-expression of splicing ATPase Prp16 suppresses both the growth and splicing defects seen in the absence of H2A.Z.
Project description:Multiple lines of evidence implicate chromatin in the regulation of pre-mRNA splicing. However, the influence of chromatin factors on co-transcriptional splice-site usage remains unclear. Here we investigated the function of the highly conserved histone variant H2A.Z in pre-mRNA splicing using the intron-rich model yeast, Schizosaccharomyces pombe. Using Epistatic Mini-Array Profiles (EMAPs) to survey the genetic interaction landscape of the Swr1 nucleosome remodeling complex, which deposits H2A.Z, we uncovered evidence for functional interactions with components of the spliceosome. In support of these genetic connections, splicing-specific microarrays show that H2A.Z and the Swr1 ATPase are required during temperature stress for the efficient splicing of a sub-set of introns. Notably, affected introns are enriched for H2A.Z occupancy, and more likely to contain non-consensus splice sites. To test the significance of the latter correlation, we mutated the splice sites in an affected intron to consensus and found this suppressed the requirement for H2A.Z in splicing of that intron. These data suggest that H2A.Z occupancy promotes co-transcriptional splicing of sub-optimal introns that may otherwise be discarded via proofreading ATPases. Consistent with this model, we show that over-expression of splicing ATPase Prp16 suppresses both the growth and splicing defects seen in the absence of H2A.Z.
Project description:In eukaryotes, a dynamic ribonucleic protein machine known as the spliceosome catalyzes the removal of introns from pre-messenger RNA (pre-mRNA). Recent studies show the process of RNA-synthesis and RNA-processing to be spatio-temporally coordinated, indicating that RNA splicing takes place in the context of chromatin. H2A.Z is a highly conserved histone variant of the canonical histone H2A. In S. cerevisiae, H2A.Z is deposited into chromatin by the SWR1-complex, is found near the 5’ ends of protein-coding genes, and has been implicated in transcription regulation. Here we show that splicing of intron-containing genes in cells lacking H2A.Z is impaired, particularly under suboptimal splicing conditions. Cells lacking H2A.Z are especially dependent on a functional U2 snRNP, as H2A.Z shows extensive genetic interactions with U2 snRNP associated proteins, and RNA-seq reveals introns with non-consensus branch points are particularly sensitive to H2A.Z loss. Consistently, H2A.Z promotes efficient spliceosomal rearrangements involving the U2 snRNP, as H2A.Z loss results in persistent U2 snRNP association and decreased recruitment of downstream snRNPs to nascent RNA. H2A.Z impairs transcription elongation, suggesting that spliceosome rearrangements are tied to H2A.Z’s role in elongation. Depletion of disassembly factor Prp43 suppresses H2A.Z-mediated splice defects, indicating that, in the absence of H2A.Z, stalled spliceosomes are disassembled and unspliced RNAs are released. Together these data demonstrate that H2A.Z is required for efficient pre-mRNA splicing and indicate a role for H2A.Z in coordinating the kinetics of transcription elongation and splicing.
Project description:Multiple lines of evidence implicate chromatin in the regulation of premessenger RNA (pre-mRNA) splicing. However, the influence of chromatin factors on cotranscriptional splice site usage remains unclear. Here we investigated the function of the highly conserved histone variant H2A.Z in pre-mRNA splicing using the intron-rich model yeast Schizosaccharomyces pombe Using epistatic miniarray profiles (EMAPs) to survey the genetic interaction landscape of the Swr1 nucleosome remodeling complex, which deposits H2A.Z, we uncovered evidence for functional interactions with components of the spliceosome. In support of these genetic connections, splicing-specific microarrays show that H2A.Z and the Swr1 ATPase are required during temperature stress for the efficient splicing of a subset of introns. Notably, affected introns are enriched for H2A.Z occupancy and more likely to contain nonconsensus splice sites. To test the significance of the latter correlation, we mutated the splice sites in an affected intron to consensus and found that this suppressed the requirement for H2A.Z in splicing of that intron. These data suggest that H2A.Z occupancy promotes cotranscriptional splicing of suboptimal introns that may otherwise be discarded via proofreading ATPases. Consistent with this model, we show that overexpression of splicing ATPase Prp16 suppresses both the growth and splicing defects seen in the absence of H2A.Z.
Project description:Cancer cells often exhibit extreme sensitivity to splicing inhibitors. We identified food-derived flavonoids, apigenin and luteolin, as compounds that modulate mRNA splicing at the genome-wide level, followed by proliferation inhibition. They bind to mRNA splicing-related proteins to induce a widespread change of splicing patterns in treated cells. Their inhibitory activity on splicing is relatively moderate, and introns with weak splice sites tend to be sensitive to them. Such introns remain unspliced, and the resulting intron-containing mRNAs are retained in the nucleus, resulting in the nuclear accumulation of poly(A)+ RNAs in these flavonoid-treated cells. Tumorigenic cells are more susceptible to these flavonoids than non-tumorigenic cells, both for the nuclear poly(A)+ RNA-accumulating phenotype and cell viability. This study illustrates the possible mechanism of these flavonoids to suppress tumor progression in vivo that were demonstrated by previous studies, and provides the potential of daily intake of moderate splicing inhibitors to prevent cancer development.
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.