Functional characterization of splicing regulatory elements
Ontology highlight
ABSTRACT: RNA binding protein-RNA interactions mediate a variety of processes including pre-mRNA splicing, translation, decay, polyadenylation and many others. Previous high -throughput studies have characterized general sequence features associated with increased and decreased splicing of certain exons, but these studies are limited by not knowing the mechanisms underlying these associations. Here we utilize ENCODE data from diverse data modalities to identify functional splicing regulatory elements and their associated RNA binding proteins (RBPs). We identify features which make splicing events more sensitive to depletion of RBPs, as well as which RBPs act as splicing regulators sensitive tupon RBP depletion. To analyze the sequence determinants underlying RBP-RNA interactions impacting splicing, we assay tens of thousands of sequence variants in a high-throughput splicing reporter called Vex-seq and confirm a small subset in their endogenous loci using CRISPR base editors. Finally, we leverage other large transcriptomic datasets to confirm the importance of RBPs which we designed experiments around and identify additional RBPs which may act as additional splicing regulators of the exons studied.
Project description:RNAs are continuously associated with RNA-binding proteins (RBPs), and these interactions are necessary for many key cellular processes ranging from splicing to chromatin regulation. Although numerous approaches have been developed to map RNA-binding sites of individual RBPs, few methods exist that allow assessment of global RBP-RNA interactions. Here, we describe a universal, high-throughput, ribonuclease-mediated protein footprint sequencing approach that reveals RNA-protein interaction sites throughout a transcriptome of interest. We apply this method to the HeLa transcriptome and compare RBP binding sites found using different cross-linkers and ribonucleases. From this analysis, we identify numerous putative RBP binding motifs, reveal novel insights into co-binding by RBPs, and uncover a significant enrichment for disease-associated polymorphisms within RBP interaction sites. Protein interaction profile sequencing (PIP-seq) in HeLa cells. Two crosslinkers (formaldehyde and UV) with two RNases (dsRNase and ssRNase) each, as well as a no-crosslink sample. Performed with and without proteins. Three replicates for formaldehyde, two replicates for UV, single replicate for no crosslinker.
Project description:RNA-binding proteins (RBPs) are crucial factors of post-transcriptional gene regulation and their modes of action are intensely investigated. At the center of attention are RNA motifs that guide where RBPs bind. However, sequence motifs recognized by RBPs are typically a poor predictor of RBP-RNA interactions in vivo. It is hence believed that many RBPs recognize RNAs as complexes, to increase specificity and regulatory potential. To probe the potential for RBP–RBP complex formation, we assembled a library of 978 mammalian RBPs and used rec-Y2H screening to detect direct interactions between RBPs, sampling >1M possible interactions. We discovered 1994 new interactions and demonstrate that our interaction screening discovers RBP pairs that bind RNAs adjacently. We further find that the mRNA binding region preferences of an RBP can deviate, depending on its adjacently binding interaction partner. Finally, we reveal novel RBP–RBP interaction networks among major RNA processing steps and show that RBP mutations observed in cancer rewire spliceosomal interaction networks.
Project description:Post-transcriptional regulation in eukaryotes requires cis- and trans-acting features and factors including RNA secondary structure, and RNA-binding proteins (RBPs). However, a comprehensive view of the structural and RBP interaction landscape of RNAs in the nucleus has yet to be compiled for any organism. Here, we use our ribonuclease-mediated structure and RBP binding site mapping approach on Arabidopsis seedling nuclei in vivo to globally profile these features within the nuclear compartment. We reveal opposing patterns of secondary structure and RBP binding levels throughout native messenger RNAs that demarcate alternative splicing and polyadenylation. We also uncover a collection of protein bound sequence motifs, and identify their structural contexts, co-occurrences in transcripts encoding functionally related proteins, and interactions with putative RBPs. Finally, we identify a nuclear role for the chloroplast RBP, CP29A. In total, we provide the first simultaneous view of the RNA secondary structure and RBP interaction landscapes in a eukaryotic nucleus. Protein interaction profile sequencing (PIP-seq) in Arabidopsis seedling nuclei. These are crosslinked with formaldehyde and treated with two RNases (ssRNase and dsRNase) with two replicates
Project description:Increasing evidence suggests that transcriptional control and chromatin activities at large involve regulatory RNAs, which likely enlist specific RNA binding proteins (RBPs). Although multiple RBPs have been implicated in transcriptional control, it has remained unclear how extensively RBPs directly act on chromatin. We embarked on a large-scale RBP ChIP-seq analysis, revealing widespread RBP presence in active chromatin regions in the human genome. Like transcription factors (TFs), RBPs also showed strong preference for hotspots in the genome, particularly gene promoters, where their association is frequently linked to transcriptional output. Unsupervised clustering reveals extensive co-association between TFs and RBPs, as exemplified by YY1, a known RNA-dependent TF, and RBM25, an RBP involved in splicing regulation. Remarkably, RBM25 depletion attenuates all YY1-dependent activities, including chromatin binding, DNA looping and transcription. We propose that various RBPs may enhance network interaction through harnessing regulatory RNAs to control transcription.
Project description:Increasing evidence suggests that transcriptional control and chromatin activities at large involve regulatory RNAs, which likely enlist specific RNA binding proteins (RBPs). Although multiple RBPs have been implicated in transcriptional control, it has remained unclear how extensively RBPs directly act on chromatin. We embarked on a large-scale RBP ChIP-seq analysis, revealing widespread RBP presence in active chromatin regions in the human genome. Like transcription factors (TFs), RBPs also showed strong preference for hotspots in the genome, particularly gene promoters, where their association is frequently linked to transcriptional output. Unsupervised clustering reveals extensive co-association between TFs and RBPs, as exemplified by YY1, a known RNA-dependent TF, and RBM25, an RBP involved in splicing regulation. Remarkably, RBM25 depletion attenuates all YY1-dependent activities, including chromatin binding, DNA looping and transcription. We propose that various RBPs may enhance network interaction through harnessing regulatory RNAs to control transcription.
Project description:The paralog RNA binding proteins (RBPs) Sam68 and SLM2 are co-expressed in the cerebral cortex and display very similar splicing activity. However, their relative function(s) in this context is unknown. By performing a time-course analysis, we found that these RBPs exhibit an opposite expression pattern during development. Sam68 expression declines postnatally while SLM2 increases after birth, and this developmental pattern is reinforced by hierarchical control of Sam68 expression by SLM2. Analysis of Sam68:Slm2 double knockout (Sam68:Slm2dko) mice revealed hundreds of exons that are sensitive to concomitant ablation of these proteins. Moreover, parallel analysis of single and double knockout cortices indicated that exons regulated mainly by SLM2 are characterized by a dynamic splicing pattern during development, whereas Sam68-dependent exons are spliced at relatively constant rates. Dynamic splicing of SLM2-sensitive exons is completely suppressed in the Sam68:Slm2dko developing cortex. Sam68:Slm2dko mice die perinatally with defects in neurogenesis and in neuronal differentiation, and the development of a hydrocephalus, consistent with splicing alterations in genes related to these biological processes. Thus, our study reveals that maintenance of the Sam68 and Slm2 paralog genes encoding homologous RBPs enables the orchestration of a dynamic splicing program while ensuring a robust redundant mechanism that supports proper cortical development.
Project description:Increasing evidence suggests that transcriptional control and chromatin activities at large involve regulatory RNAs, which likely enlist specific RNA binding proteins (RBPs). Although multiple RBPs have been implicated in transcriptional control, it has remained unclear how extensively RBPs directly act on chromatin. We embarked on a large-scale RBP ChIP-seq analysis, revealing widespread RBP presence in active chromatin regions in the human genome. Like transcription factors (TFs), RBPs also showed strong preference for hotspots in the genome, particularly gene promoters, where their association is frequently linked to transcriptional output. Unsupervised clustering reveals extensive co-association between TFs and RBPs, as exemplified by YY1, a known RNA-dependent TF, and RBM25, an RBP involved in splicing regulation. Remarkably, RBM25 depletion attenuates all YY1-dependent activities, including chromatin binding, DNA looping and transcription. We propose that various RBPs may enhance network interaction through harnessing regulatory RNAs to control transcription. As part of the ENCODE consortium, we embarked on a large-scale RBP ChIP-seq analysis, revealing broad presence of RBPs in active chromatin regions in the human genome. Like transcription factors (TFs), RBPs also show great preference for hotspots in the genome, particularly gene promoters, where their binding is frequently linked to transcriptional output. Self-organizing map reveals extensive co-binding events between TFs and RBPs, as exemplified by those between YY1, a known RNA-dependent TF, and RBM25, an RBP involved in alternative splicing. Remarkably, RBM25 depletion attenuates all YY1-dependent activities, including chromatin binding, DNA looping and transcription. We propose that various RBPs may bridge specific TF-RNA interactions to control transcription.
Project description:RNAs are continuously associated with RNA-binding proteins (RBPs), and these interactions are necessary for many key cellular processes ranging from splicing to chromatin regulation. Although numerous approaches have been developed to map RNA-binding sites of individual RBPs, few methods exist that allow assessment of global RBP-RNA interactions. Here, we describe a universal, high-throughput, ribonuclease-mediated protein footprint sequencing approach that reveals RNA-protein interaction sites throughout a transcriptome of interest. We apply this method to the HeLa transcriptome and compare RBP binding sites found using different cross-linkers and ribonucleases. From this analysis, we identify numerous putative RBP binding motifs, reveal novel insights into co-binding by RBPs, and uncover a significant enrichment for disease-associated polymorphisms within RBP interaction sites.
Project description:Interactions between RNAs and RNA binding proteins (RBPs) regulate gene expression in eukaryotic cells. RNA-RBP affinities measured in vitro reveal diverse binding specificities, yet approaches to directly compare specificities across RBPs are lacking. Here, we introduce two quantitative metrics: inherent specificity, which measures how selectively an RBP distinguishes its strongest binding motif from all possible motifs, and mutational sensitivity, which assesses tolerance to single nucleotide variations within preferred motifs. Analyzing high-throughput sequencing datasets, we compared these metrics across 100 RBPs in vitro and 27 RBPs in cells, finding strong correlation between in vitro and cellular measurements for RBPs that bind RNA independently of a local structural context. Through CLIP experiments with swapped RNA recognition motifs between a low-specificity RBP (RBM25) and a high-specificity RBP (HNRNPC), we demonstrated that sequence specificity can be transferred between protein contexts. Using these insights, we developed mathematical models showing how RBPs with different specificity profiles compete for binding sites, revealing how variations in inherent specificity and mutational sensitivity influence target selection. Together, our results provide a quantitative framework for modeling RNA-RBP interactions and designing RBPs with targeted specificity.
Project description:We generated a global analysis of Rbfox2 splicing regulation combined with a highly specific, single nucleotide-resolution Rbfox2 RNA binding map. We found that Rbfox2 regulates the splicing and expression of many previously unknown targets, and particularly a number of RNA binding proteins (RBPs), by modulating alternative splicing coupled-NMD. Based on our observations of RBP-Rbfox2 co-regulation with a polarity predicted by Rbfox2 binding, we propose a model whereby Rbfox2 tunes autoregulatory splicing events to control RBP expression levels and in turn alter their respective splicing networks. iCLIP for epitope-tagged Rbfox2 and control untagged Rbfox2; RNAseq of control and Rbfox2 knockdown in mouse embryonic stem cells