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U2AF65Prp2 promotes intron definition by stabilizing U1 snRNP at the 5’ splice site

ABSTRACT: Prp2 (U2AF65) is an essential splicing factor, that recognizes the poly-Py track near the 3' SS. We have previously observed that when Prp2 is inactivated using a prp2 temperature-sensitive allele, while most of the pre-mRNA is not processed, some are normally spliced. This observation even more noticeable during meiosis, since pre-mRNA regulation is executed at different levels (splicing, polyadenylation and stability). Using RNAseq, we have determined genome-wide the splicing efficiency of fission yeast cells as they progress into synchronous meiosis, in the presence or absence of functional Prp2. To our surprise, the main characteristic that defines if any given intron requires Prp2 to be spliced depends on the last nucleotides of the preceding exon, next to the 5’ SS in the nucleotide that anneal with U1 RNA. Thus, by simple genetic manipulation, we can modulate the dependency of any given intron on Prp2. We propose that the role of Prp2 consist in the stabilization of a loop between the 5’SS and the 3’ SS, which also depends on the annealing strength between U1 and the 5’ SS.

ORGANISM(S): Schizosaccharomyces pombe

PROVIDER: GSE97203 | GEO | 2021/10/01

REPOSITORIES: GEO

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mRNA splicing is modulated by intronic microRNAs

Project description:Splicing of transcripts is catalyzed by the spliceosome, a mega-complex consisting of hundreds of proteins and five snRNAs, which employs direct interactions. When U1 snRNA forms high affinity binding, namely more than eight base-pairs, with the 5’SS, the result is usually a suppressing effect on the splicing activity. This likely occurs due to the inefficient unwinding of U1/5’SS base-pairing, or other regulatory obstructions. Here we show in vitro and in patient-derived cell lines that pre-microRNAs can modulate the splicing reaction by interacting with U1 snRNA. This leads to reduced binding affinity to the 5’SS, and hence promotes the inclusion of exons containing 5’SS, despite sequence-based high affinity to U1. Application of the mechanism resulted in correction of the splicing defect in the disease-causing VCAN gene from an individual with Wagner syndrome. This pre-miRNA/U1 interaction can regulate the expression of alternatively spliced exons, thus extending the scope of mechanisms regulating splicing.

2023-09-21 | GSE236090 | GEO

Identification of New Branch Points and Unconventional Introns in Saccharomyces cerevisiae

Project description:Spliced messages constitute one-fourth of expressed mRNAs in the yeast Saccharomyces cerevisiae, and most mRNAs in metazoans. Splicing requires 5' splice site (5'SS), branch point (BP), and 3' splice site (3'SS) elements, but the role of the BP in splicing control is poorly understood because BP identification remains difficult. We developed a high-throughput method, Branch-seq, to map BP and 5'SS of isolated RNA lariats. Applied to S. cerevisiae, Branch-seq detected 76% of expressed, annotated BPs and identified a comparable number of novel BPs. We used RNA-seq to confirm associated 3'SS locations, identifying some 200 novel splice junctions, including an AT-AC intron. We show that several yeast introns use two or even three different BPs, with effects on 3'SS choice, protein coding potential, or RNA stability and identify novel introns whose splicing changes during meiosis or in response to stress. Together, these findings reveal BP-based regulation and demonstrate unanticipated complexity of splicing in yeast.

2016-08-01 | GSE68022 | GEO

Identification of New Branch Points and Unconventional Introns in Saccharomyces cerevisiae

2016-08-01 | E-GEOD-68022 | biostudies-arrayexpress

Splicing factors and chromatin organization enhance exon recognition by alleviating constraints generated by gene nucleotide composition bias

Project description:To characterize the rules governing exon recognition during splicing, we analyzed RNA-seq datasets and identified ~4,000 GC-rich and ~5,000 AT-rich exons, labelled GC-exons and AT-exons, respectively whose inclusion depends on different sets of splicing factors. We show that a high GC-load is associated with predicted RNA secondary structures at 5'ss and that GC-exons are dependent on U1 snRNP-associated proteins. Meanwhile, a high AT-load is associated with a large number of decoy splicing-related signals upstream exons such as the number of branchpoints and SF1- or U2AF65-binding sites and AT-exons are dependent on U2 snRNP-associated proteins. Nucleotide composition bias also influences local chromatin organization. Since the GC content of exons correlates with that of their hosting-genes, -isochores and – topologically-associated domains, we propose that regional nucleotide composition bias leaves a footprint locally, at the exon level, inducing, during splicing, constraints that are alleviated by the local chromatin organization and specific splicing factors.

2019-10-25 | GSE138397 | 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

Cooperative engagement and subsequent selective displacement of SR proteins define the pre-mRNA 3D structural scaffold for early spliceosome assembly

Project description:We recently reported that serine-arginine-rich (SR) protein-mediated pre-mRNA structural remodeling generates a pre-mRNA 3D structural scaffold that is stably recognized by the early spliceosomal components. However, the intermediate steps between the free pre-mRNA and the assembled early spliceosome are not yet characterized. By probing the early spliceosomal complexes in vitro and RNA-protein interactions in vivo, we show that the SR proteins bind the pre-mRNAs cooperatively generating a substrate that recruits U1 snRNP and U2AF65 in a splice signal-independent manner. Excess U1 snRNP selectively displaces some of the SR protein molecules from the pre-mRNA generating the substrate for splice signal-specific, sequential recognition by U1 snRNP, U2AF65, and U2AF35. Our work thus identifies a novel function of U1 snRNP in mammalian splicing substrate definition, explains the need for excess U1 snRNP compared to other U snRNPs in vivo, demonstrates how excess SR proteins could inhibit splicing, and provides a conceptual basis to examine if this mechanism of splicing substrate definition is employed by other splicing regulatory proteins.

2022-07-05 | GSE188652 | GEO

Novel RNA-binding Proteins Bind U1 snRNA to Promote Splicing of Weak 5' Splice Sites

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.

2023-09-07 | PXD029392 | Pride

Competition between pre-mRNAs for a limiting splicing machinery drives global changes in splicing

Project description:During meiosis in yeast, global splicing efficiency increases. The mechanism for this is relief of competition for the splicing machinery by repression of intron-containing ribosomal protein genes (RPGs). Repression of RPGs with rapamycin also increases splicing efficiency in vegetative cells. Reducing levels of an RPG-dedicated transcription factor globally improves splicing and suppresses the temperature-sensitive growth defect of a spliceosome mutation. These results indicate that the spliceosome is limiting and pre-mRNAs compete with each other. Under these conditions, splicing efficiency of a given pre-mRNA therefore depends on both its concentration and affinity for the limiting splicing factor(s) as well as those of the competing pre-mRNAs. We propose that trans-competition control of splicing helps repress meiotic gene expression in vegetative cells, and promotes efficient meiosis. Competition between RNAs for a limiting factor may be a general condition important for function of a variety of post-transcriptional control mechanisms. Splicing and gene expression profiles of 1) wild type yeast cells treated with rapamycin (2 biological replicates) relative to untreated cells and 2) prp4-1 pGAL-IFH1 (down-regulated expression of IFH1 transcription factor(specific for ribosomal protein genes)) relative to prp4-1 yeast.

2013-10-22 | E-GEOD-44219 | biostudies-arrayexpress

Selected humanization of yeast U1 snRNP leads to global suppression of pre-mRNA splicing and mitochondrial dysfunction in the budding yeast

Project description:The recognition of 5’ splice site (5’ ss) is one of the earliest steps of pre-mRNA splicing. To better understand the mechanism and regulation of 5’ ss recognition, we selectively humanized components of the yeast U1 snRNP to reveal the function of these components in 5’ ss recognition and splicing. We targeted U1C and Luc7, two proteins that interact with and stabilize the yeast U1 (yU1) snRNA and the 5’ ss RNA duplex. We replaced the Zinc-Finger (ZnF) domain of yU1C with its human counterpart, which resulted in cold-sensitive growth phenotype and moderate splicing defects. Next, we added an auxin-inducible degron to yLuc7 protein and found that Luc7-depleted yU1 snRNP resulted in the concomitant loss of PRP40 and Snu71 (two other essential yeast U1 snRNP proteins), and further biochemical analyses suggest a model of how these three proteins interact with each other in the U1 snRNP. The loss of these proteins resulted in a significant growth retardation accompanied by a global suppression of pre-mRNA splicing. The splicing suppression led to mitochondrial dysfunction as revealed by a release of Fe2+ into the growth medium and an induction of mitochondrial reactive oxygen species. Together, these observations indicate that the human U1C ZnF can substitute that of yeast, Luc7 is essential for the incorporation of the Luc7-Prp40-Snu71 trimer into yeast U1 snRNP, and splicing plays a major role in the regulation of mitochondria function in yeast.

2024-01-03 | GSE252348 | GEO

Novel RNA-binding Proteins Bind U1 snRNA to Promote Splicing of Weak 5' Splice Sites

2023-05-04 | GSE179744 | GEO

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