1
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Zhang Z, Kumar V, Dybkov O, Will CL, Zhong J, Ludwig SEJ, Urlaub H, Kastner B, Stark H, Lührmann R. Structural insights into the cross-exon to cross-intron spliceosome switch. Nature 2024:10.1038/s41586-024-07458-1. [PMID: 38778104 DOI: 10.1038/s41586-024-07458-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Accepted: 04/23/2024] [Indexed: 05/25/2024]
Abstract
Early spliceosome assembly can occur through an intron-defined pathway, whereby U1 and U2 small nuclear ribonucleoprotein particles (snRNPs) assemble across the intron1. Alternatively, it can occur through an exon-defined pathway2-5, whereby U2 binds the branch site located upstream of the defined exon and U1 snRNP interacts with the 5' splice site located directly downstream of it. The U4/U6.U5 tri-snRNP subsequently binds to produce a cross-intron (CI) or cross-exon (CE) pre-B complex, which is then converted to the spliceosomal B complex6,7. Exon definition promotes the splicing of upstream introns2,8,9 and plays a key part in alternative splicing regulation10-16. However, the three-dimensional structure of exon-defined spliceosomal complexes and the molecular mechanism of the conversion from a CE-organized to a CI-organized spliceosome, a pre-requisite for splicing catalysis, remain poorly understood. Here cryo-electron microscopy analyses of human CE pre-B complex and B-like complexes reveal extensive structural similarities with their CI counterparts. The results indicate that the CE and CI spliceosome assembly pathways converge already at the pre-B stage. Add-back experiments using purified CE pre-B complexes, coupled with cryo-electron microscopy, elucidate the order of the extensive remodelling events that accompany the formation of B complexes and B-like complexes. The molecular triggers and roles of B-specific proteins in these rearrangements are also identified. We show that CE pre-B complexes can productively bind in trans to a U1 snRNP-bound 5' splice site. Together, our studies provide new mechanistic insights into the CE to CI switch during spliceosome assembly and its effect on pre-mRNA splice site pairing at this stage.
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Affiliation(s)
- Zhenwei Zhang
- Department of Structural Dynamics, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
- State Key Laboratory of Biotherapy and Department of Rheumatology and Immunology, West China Hospital, Sichuan University, Chengdu, China
| | - Vinay Kumar
- Cellular Biochemistry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Olexandr Dybkov
- Cellular Biochemistry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
- Bioanalytical Mass Spectrometry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Cindy L Will
- Cellular Biochemistry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Jiayun Zhong
- State Key Laboratory of Biotherapy and Department of Rheumatology and Immunology, West China Hospital, Sichuan University, Chengdu, China
| | - Sebastian E J Ludwig
- Cellular Biochemistry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
- Vincerx Pharma, Monheim am Rhein, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
- Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Berthold Kastner
- Cellular Biochemistry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany
| | - Holger Stark
- Department of Structural Dynamics, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany.
| | - Reinhard Lührmann
- Cellular Biochemistry, Max-Planck-Institute for Multidisciplinary Sciences, Göttingen, Germany.
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2
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Yang Y, Lee GC, Nakagaki-Silva E, Huang Y, Peacey M, Partridge R, Gooding C, Smith CJ. Cell-type specific regulator RBPMS switches alternative splicing via higher-order oligomerization and heterotypic interactions with other splicing regulators. Nucleic Acids Res 2023; 51:9961-9982. [PMID: 37548402 PMCID: PMC10570038 DOI: 10.1093/nar/gkad652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 06/28/2023] [Accepted: 07/26/2023] [Indexed: 08/08/2023] Open
Abstract
Alternative pre-mRNA splicing decisions are regulated by RNA binding proteins (RBPs) that can activate or repress regulated splice sites. Repressive RBPs typically harness multivalent interactions to bind stably to target RNAs. Multivalency can be achieved by homomeric oligomerization and heteromeric interactions with other RBPs, often mediated by intrinsically disordered regions (IDRs), and by possessing multiple RNA binding domains. Cell-specific splicing decisions often involve the action of widely expressed RBPs, which are able to bind multivalently around target exons, but without effect in the absence of a cell-specific regulator. To address how cell-specific regulators can collaborate with constitutive RBPs in alternative splicing regulation, we used the smooth-muscle specific regulator RBPMS. Recombinant RBPMS is sufficient to confer smooth muscle cell specific alternative splicing of Tpm1 exon 3 in cell-free assays by preventing assembly of ATP-dependent splicing complexes. This activity depends upon a C-terminal IDR that facilitates dynamic higher-order self-assembly, cooperative binding to multivalent RNA and interactions with widely expressed splicing co-regulators, including MBNL1 and RBFOX2, allowing cooperative assembly of stable cell-specific regulatory complexes.
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Affiliation(s)
- Yi Yang
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
| | - Giselle C Lee
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
| | | | - Yuling Huang
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
| | - Matthew Peacey
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
| | - Ruth Partridge
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
| | - Clare Gooding
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
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3
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Dai S, Wang C, Zhang C, Feng L, Zhang W, Zhou X, He Y, Xia X, Chen B, Song W. PTB: Not just a polypyrimidine tract-binding protein. J Cell Physiol 2022; 237:2357-2373. [PMID: 35288937 DOI: 10.1002/jcp.30716] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 02/19/2022] [Accepted: 02/22/2022] [Indexed: 01/21/2023]
Abstract
Polypyrimidine tract-binding protein (PTB), as a member of the heterogeneous nuclear ribonucleoprotein family, functions by rapidly shuttling between the nucleus and the cytoplasm. PTB is involved in the alternative splicing of pre-messenger RNA (mRNA) and almost all steps of mRNA metabolism. PTB regulation is organ-specific; brain- or muscle-specific microRNAs and long noncoding RNAs partially contribute to regulating PTB, thereby modulating many physiological and pathological processes, such as embryonic development, cell development, spermatogenesis, and neuron growth and differentiation. Previous studies have shown that PTB knockout can inhibit tumorigenesis and development. The knockout of PTB in glial cells can be reprogrammed into functional neurons, which shows great promise in the field of nerve regeneration but is controversial.
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Affiliation(s)
- Shirui Dai
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China.,Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, P. R. China
| | - Chao Wang
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Cheng Zhang
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Lemeng Feng
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Wulong Zhang
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Xuezhi Zhou
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Ye He
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Xiaobo Xia
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
| | - Baihua Chen
- Department of Ophthalmology, The Second Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Clinical Research Center of Ophthalmic Disease, Changsha, Hunan, P. R. China
| | - Weitao Song
- National Clinical Research Center for Geriatric Diseases, Xiangya Hospital of Central South University, Changsha, Hunan, P. R. China.,Eye Center of Xiangya Hospital, Central South University, Changsha, Hunan, P. R. China.,Hunan Key Laboratory of Ophthalmology, Changsha, Hunan, P. R. China
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4
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Gañez-Zapater A, Mackowiak SD, Guo Y, Tarbier M, Jordán-Pla A, Friedländer MR, Visa N, Östlund Farrants AK. The SWI/SNF subunit BRG1 affects alternative splicing by changing RNA binding factor interactions with nascent RNA. Mol Genet Genomics 2022; 297:463-484. [PMID: 35187582 PMCID: PMC8960663 DOI: 10.1007/s00438-022-01863-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 01/23/2022] [Indexed: 11/29/2022]
Abstract
BRG1 and BRM are ATPase core subunits of the human SWI/SNF chromatin remodelling complexes mainly associated with transcriptional initiation. They also have a role in alternative splicing, which has been shown for BRM-containing SWI/SNF complexes at a few genes. Here, we have identified a subset of genes which harbour alternative exons that are affected by SWI/SNF ATPases by expressing the ATPases BRG1 and BRM in C33A cells, a BRG1- and BRM-deficient cell line, and analysed the effect on splicing by RNA sequencing. BRG1- and BRM-affected sub-sets of genes favouring both exon inclusion and exon skipping, with only a minor overlap between the ATPase. Some of the changes in alternative splicing induced by BRG1 and BRM expression did not require the ATPase activity. The BRG1-ATPase independent included exons displayed an exon signature of a high GC content. By investigating three genes with exons affected by the BRG-ATPase-deficient variant, we show that these exons accumulated phosphorylated RNA pol II CTD, both serine 2 and serine 5 phosphorylation, without an enrichment of the RNA polymerase II. The ATPases were recruited to the alternative exons, together with both core and signature subunits of SWI/SNF complexes, and promoted the binding of RNA binding factors to chromatin and RNA at the alternative exons. The interaction with the nascent RNP, however, did not reflect the association to chromatin. The hnRNPL, hnRNPU and SAM68 proteins associated with chromatin in cells expressing BRG1 and BRM wild type, but the binding of hnRNPU to the nascent RNP was excluded. This suggests that SWI/SNF can regulate alternative splicing by interacting with splicing-RNA binding factor and influence their binding to the nascent pre-mRNA particle.
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Affiliation(s)
- Antoni Gañez-Zapater
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, The Arrhenius Laboratories F4, 106 91, Stockholm, Sweden
- Center for Genomic Regulation, 08003, Barcelona, Spain
| | - Sebastian D Mackowiak
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91, Stockholm, Sweden
- Max Planck Institute for Molecular Genetics, Ihnestraße 63-73, 14195, Berlin, Germany
| | - Yuan Guo
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, The Arrhenius Laboratories F4, 106 91, Stockholm, Sweden
| | - Marcel Tarbier
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91, Stockholm, Sweden
| | - Antonio Jordán-Pla
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, The Arrhenius Laboratories F4, 106 91, Stockholm, Sweden
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencies Biológicas, Valencia University, C/Dr. Moliner, 50, 46100, Burjassot, Spain
| | - Marc R Friedländer
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, 106 91, Stockholm, Sweden
| | - Neus Visa
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, The Arrhenius Laboratories F4, 106 91, Stockholm, Sweden
| | - Ann-Kristin Östlund Farrants
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, The Arrhenius Laboratories F4, 106 91, Stockholm, Sweden.
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5
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Cretu C, Gee P, Liu X, Agrawal A, Nguyen TV, Ghosh AK, Cook A, Jurica M, Larsen NA, Pena V. Structural basis of intron selection by U2 snRNP in the presence of covalent inhibitors. Nat Commun 2021; 12:4491. [PMID: 34301950 PMCID: PMC8302644 DOI: 10.1038/s41467-021-24741-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Accepted: 07/01/2021] [Indexed: 12/27/2022] Open
Abstract
Intron selection during the formation of prespliceosomes is a critical event in pre-mRNA splicing. Chemical modulation of intron selection has emerged as a route for cancer therapy. Splicing modulators alter the splicing patterns in cells by binding to the U2 snRNP (small nuclear ribonucleoprotein)—a complex chaperoning the selection of branch and 3′ splice sites. Here we report crystal structures of the SF3B module of the U2 snRNP in complex with spliceostatin and sudemycin FR901464 analogs, and the cryo-electron microscopy structure of a cross-exon prespliceosome-like complex arrested with spliceostatin A. The structures reveal how modulators inactivate the branch site in a sequence-dependent manner and stall an E-to-A prespliceosome intermediate by covalent coupling to a nucleophilic zinc finger belonging to the SF3B subunit PHF5A. These findings support a mechanism of intron recognition by the U2 snRNP as a toehold-mediated strand invasion and advance an unanticipated drug targeting concept. Chemical modulation of intron selection has emerged as a route for cancer therapy. Here, structures of the U2 snRNP’s SF3B module and of prespliceosome- both in complexes with splicing modulators- provide insight into the mechanisms of intron recognition and branch site inactivation.
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Affiliation(s)
- Constantin Cretu
- Research Group Mechanisms and Regulation of Splicing, The Institute of Cancer Research, London, UK.,Cluster of Excellence Multiscale Bioimaging (MBExC), Universitätsmedizin Göttingen, Göttingen, Germany
| | | | - Xiang Liu
- H3 Biomedicine, Inc, Cambridge, MA, USA
| | | | | | - Arun K Ghosh
- Departments of Chemistry and Medicinal Chemistry, Purdue University, West Lafayette, IN, USA
| | | | - Melissa Jurica
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, CA, USA
| | | | - Vladimir Pena
- Research Group Mechanisms and Regulation of Splicing, The Institute of Cancer Research, London, UK.
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6
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A first exon termination checkpoint preferentially suppresses extragenic transcription. Nat Struct Mol Biol 2021; 28:337-346. [PMID: 33767452 PMCID: PMC7610630 DOI: 10.1038/s41594-021-00572-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 02/12/2021] [Indexed: 01/31/2023]
Abstract
Interactions between the splicing machinery and RNA polymerase II increase protein-coding gene transcription. Similarly, exons and splicing signals of enhancer-generated long noncoding RNAs (elncRNAs) augment enhancer activity. However, elncRNAs are inefficiently spliced, suggesting that, compared with protein-coding genes, they contain qualitatively different exons with a limited ability to drive splicing. We show here that the inefficiently spliced first exons of elncRNAs as well as promoter-antisense long noncoding RNAs (pa-lncRNAs) in human and mouse cells trigger a transcription termination checkpoint that requires WDR82, an RNA polymerase II-binding protein, and its RNA-binding partner of previously unknown function, ZC3H4. We propose that the first exons of elncRNAs and pa-lncRNAs are an intrinsic component of a regulatory mechanism that, on the one hand, maximizes the activity of these cis-regulatory elements by recruiting the splicing machinery and, on the other, contains elements that suppress pervasive extragenic transcription.
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7
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Microexons: at the nexus of nervous system development, behaviour and autism spectrum disorder. Curr Opin Genet Dev 2020; 65:22-33. [PMID: 32535349 DOI: 10.1016/j.gde.2020.03.007] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 03/30/2020] [Indexed: 12/19/2022]
Abstract
The discovery and characterization of a network of highly conserved neuronal microexons has provided fundamental new insight into mechanisms underlying nervous system development and function, as well as an important basis for pathway convergence in autism spectrum disorder. In the past few years, considerable progress has been made in comprehensively determining the repertoires of factors that control neuronal microexons. These results have illuminated molecular mechanisms that activate the splicing of microexons, including those that control gene expression programs critical for neurogenesis, as well as synaptic protein translation and neuronal activity. Remarkably, individual disruption of specific microexons in these pathways results in autism-like phenotypes and cognitive impairment in mice. This review discusses these findings and their implications for delivering new therapeutic strategies for neurological disorders.
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8
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Yamazaki T, Liu L, Manley JL. TCF3 mutually exclusive alternative splicing is controlled by long-range cooperative actions between hnRNPH1 and PTBP1. RNA (NEW YORK, N.Y.) 2019; 25:1497-1508. [PMID: 31391218 PMCID: PMC6795145 DOI: 10.1261/rna.072298.119] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 07/31/2019] [Indexed: 05/22/2023]
Abstract
TCF3, also known as E2A, is a well-studied transcription factor that plays an important role in stem cell maintenance and hematopoietic development. The TCF3 gene encodes two related proteins, E12 and E47, which arise from mutually exclusive alternative splicing (MEAS). Since these two proteins have different DNA binding and dimerization domains, this AS event must be strictly regulated to ensure proper isoform ratios. Previously, we found that heterogeneous nuclear ribonucleoprotein (hnRNP) H1/F regulates TCF3 AS by binding to exonic splicing silencers (ESSs) in exon 18b. Here, we identify conserved intronic splicing silencers (ISSs) located between, and far from, the two mutually exclusive exons, and show that they are essential for MEAS. Further, we demonstrate that the hnRNP PTBP1 binds the ISS and is a regulator of TCF3 AS. We also demonstrate that hnRNP H1 and PTBP1 regulate TCF3 AS reciprocally, and that position-dependent interactions between these factors are essential for proper TCF3 MEAS. Our study provides a new model in which MEAS is regulated by cooperative actions of distinct hnRNPs bound to ISSs and ESSs.
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Affiliation(s)
- Takashi Yamazaki
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Lizhi Liu
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - James L Manley
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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9
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Jobbins AM, Reichenbach LF, Lucas CM, Hudson AJ, Burley GA, Eperon IC. The mechanisms of a mammalian splicing enhancer. Nucleic Acids Res 2019; 46:2145-2158. [PMID: 29394380 PMCID: PMC5861446 DOI: 10.1093/nar/gky056] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 01/19/2018] [Indexed: 12/21/2022] Open
Abstract
Exonic splicing enhancer (ESE) sequences are bound by serine & arginine-rich (SR) proteins, which in turn enhance the recruitment of splicing factors. It was inferred from measurements of splicing around twenty years ago that Drosophila doublesex ESEs are bound stably by SR proteins, and that the bound proteins interact directly but with low probability with their targets. However, it has not been possible with conventional methods to demonstrate whether mammalian ESEs behave likewise. Using single molecule multi-colour colocalization methods to study SRSF1-dependent ESEs, we have found that that the proportion of RNA molecules bound by SRSF1 increases with the number of ESE repeats, but only a single molecule of SRSF1 is bound. We conclude that initial interactions between SRSF1 and an ESE are weak and transient, and that these limit the activity of a mammalian ESE. We tested whether the activation step involves the propagation of proteins along the RNA or direct interactions with 3' splice site components by inserting hexaethylene glycol or abasic RNA between the ESE and the target 3' splice site. These insertions did not block activation, and we conclude that the activation step involves direct interactions. These results support a model in which regulatory proteins bind transiently and in dynamic competition, with the result that each ESE in an exon contributes independently to the probability that an activator protein is bound and in close proximity to a splice site.
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Affiliation(s)
- Andrew M Jobbins
- Leicester Institute of Structural & Chemical Biology and Department of Molecular & Cell Biology, University of Leicester, UK
| | | | - Christian M Lucas
- Leicester Institute of Structural & Chemical Biology and Department of Molecular & Cell Biology, University of Leicester, UK
| | - Andrew J Hudson
- Leicester Institute of Structural & Chemical Biology and Department of Chemistry, University of Leicester, UK
| | - Glenn A Burley
- Department of Pure and Applied Chemistry, University of Strathclyde, UK
| | - Ian C Eperon
- Leicester Institute of Structural & Chemical Biology and Department of Molecular & Cell Biology, University of Leicester, UK
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10
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Hamid FM, Makeyev EV. A mechanism underlying position-specific regulation of alternative splicing. Nucleic Acids Res 2019; 45:12455-12468. [PMID: 30053257 PMCID: PMC5716086 DOI: 10.1093/nar/gkx901] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Accepted: 09/26/2017] [Indexed: 01/01/2023] Open
Abstract
Many RNA-binding proteins including a master regulator of splicing in developing brain and muscle, polypyrimidine tract-binding protein 1 (PTBP1), can either activate or repress alternative exons depending on the pre-mRNA recruitment position. When bound upstream or within regulated exons PTBP1 tends to promote their skipping, whereas binding to downstream sites often stimulates inclusion. How this switch is orchestrated at the molecular level is poorly understood. Using bioinformatics and biochemical approaches we show that interaction of PTBP1 with downstream intronic sequences can activate natural cassette exons by promoting productive docking of the spliceosomal U1 snRNP to a suboptimal 5' splice site. Strikingly, introducing upstream PTBP1 sites to this circuitry leads to a potent splicing repression accompanied by the assembly of an exonic ribonucleoprotein complex with a tightly bound U1 but not U2 snRNP. Our data suggest a molecular mechanism underlying the transition between a better-known repressive function of PTBP1 and its role as a bona fide splicing activator. More generally, we argue that the functional outcome of individual RNA contacts made by an RNA-binding protein is subject to extensive context-specific modulation.
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Affiliation(s)
- Fursham M Hamid
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK.,School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore
| | - Eugene V Makeyev
- Centre for Developmental Neurobiology, King's College London, London SE1 1UL, UK
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11
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A novel protein domain in an ancestral splicing factor drove the evolution of neural microexons. Nat Ecol Evol 2019; 3:691-701. [DOI: 10.1038/s41559-019-0813-6] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 01/16/2019] [Indexed: 02/02/2023]
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12
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View from an mRNP: The Roles of SR Proteins in Assembly, Maturation and Turnover. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1203:83-112. [PMID: 31811631 DOI: 10.1007/978-3-030-31434-7_3] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Serine- and arginine-rich proteins (SR proteins) are a family of multitasking RNA-binding proteins (RBPs) that are key determinants of messenger ribonucleoprotein (mRNP) formation, identity and fate. Apart from their essential functions in pre-mRNA splicing, SR proteins display additional pre- and post-splicing activities and connect nuclear and cytoplasmic gene expression machineries. Through changes in their post-translational modifications (PTMs) and their subcellular localization, they provide functional specificity and adjustability to mRNPs. Transcriptome-wide UV crosslinking and immunoprecipitation (CLIP-Seq) studies revealed that individual SR proteins are present in distinct mRNPs and act in specific pairs to regulate different gene expression programmes. Adopting an mRNP-centric viewpoint, we discuss the roles of SR proteins in the assembly, maturation, quality control and turnover of mRNPs and describe the mechanisms by which they integrate external signals, coordinate their multiple tasks and couple subsequent mRNA processing steps.
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13
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Structural-functional interactions of NS1-BP protein with the splicing and mRNA export machineries for viral and host gene expression. Proc Natl Acad Sci U S A 2018; 115:E12218-E12227. [PMID: 30538201 DOI: 10.1073/pnas.1818012115] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The influenza virulence factor NS1 protein interacts with the cellular NS1-BP protein to promote splicing and nuclear export of the viral M mRNAs. The viral M1 mRNA encodes the M1 matrix protein and is alternatively spliced into the M2 mRNA, which is translated into the M2 ion channel. These proteins have key functions in viral trafficking and budding. To uncover the NS1-BP structural and functional activities in splicing and nuclear export, we performed proteomics analysis of nuclear NS1-BP binding partners and showed its interaction with constituents of the splicing and mRNA export machineries. NS1-BP BTB domains form dimers in the crystal. Full-length NS1-BP is a dimer in solution and forms at least a dimer in cells. Mutations suggest that dimerization is important for splicing. The central BACK domain of NS1-BP interacts directly with splicing factors such as hnRNP K and PTBP1 and with the viral NS1 protein. The BACK domain is also the site for interactions with mRNA export factor Aly/REF and is required for viral M mRNA nuclear export. The crystal structure of the C-terminal Kelch domain shows that it forms a β-propeller fold, which is required for the splicing function of NS1-BP. This domain interacts with the polymerase II C-terminal domain and SART1, which are involved in recruitment of splicing factors and spliceosome assembly, respectively. NS1-BP functions are not only critical for processing a subset of viral mRNAs but also impact levels and nuclear export of a subset of cellular mRNAs encoding factors involved in metastasis and immunity.
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14
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Genome-wide CRISPR-Cas9 Interrogation of Splicing Networks Reveals a Mechanism for Recognition of Autism-Misregulated Neuronal Microexons. Mol Cell 2018; 72:510-524.e12. [DOI: 10.1016/j.molcel.2018.10.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 08/27/2018] [Accepted: 10/04/2018] [Indexed: 12/22/2022]
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15
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Sutandy FXR, Ebersberger S, Huang L, Busch A, Bach M, Kang HS, Fallmann J, Maticzka D, Backofen R, Stadler PF, Zarnack K, Sattler M, Legewie S, König J. In vitro iCLIP-based modeling uncovers how the splicing factor U2AF2 relies on regulation by cofactors. Genome Res 2018; 28:699-713. [PMID: 29643205 PMCID: PMC5932610 DOI: 10.1101/gr.229757.117] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 02/09/2018] [Indexed: 01/26/2023]
Abstract
Alternative splicing generates distinct mRNA isoforms and is crucial for proteome diversity in eukaryotes. The RNA-binding protein (RBP) U2AF2 is central to splicing decisions, as it recognizes 3′ splice sites and recruits the spliceosome. We establish “in vitro iCLIP” experiments, in which recombinant RBPs are incubated with long transcripts, to study how U2AF2 recognizes RNA sequences and how this is modulated by trans-acting RBPs. We measure U2AF2 affinities at hundreds of binding sites and compare in vitro and in vivo binding landscapes by mathematical modeling. We find that trans-acting RBPs extensively regulate U2AF2 binding in vivo, including enhanced recruitment to 3′ splice sites and clearance of introns. Using machine learning, we identify and experimentally validate novel trans-acting RBPs (including FUBP1, CELF6, and PCBP1) that modulate U2AF2 binding and affect splicing outcomes. Our study offers a blueprint for the high-throughput characterization of in vitro mRNP assembly and in vivo splicing regulation.
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Affiliation(s)
| | | | - Lu Huang
- Institute of Molecular Biology (IMB) gGmbH, 55128 Mainz, Germany
| | - Anke Busch
- Institute of Molecular Biology (IMB) gGmbH, 55128 Mainz, Germany
| | - Maximilian Bach
- Institute of Molecular Biology (IMB) gGmbH, 55128 Mainz, Germany
| | - Hyun-Seo Kang
- Institute of Structural Biology, Helmholtz Center Munich, 85764 Neuherberg, Germany.,Biomolecular NMR and Center for Integrated Protein Science Munich at Department of Chemistry, Technical University of Munich, 85747 Garching, Germany
| | - Jörg Fallmann
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, University of Leipzig, 04107 Leipzig, Germany
| | - Daniel Maticzka
- Bioinformatics Group, Department of Computer Science, University of Freiburg, 79110 Freiburg, Germany
| | - Rolf Backofen
- Bioinformatics Group, Department of Computer Science, University of Freiburg, 79110 Freiburg, Germany.,Centre for Biological Signalling Studies (BIOSS), University of Freiburg, 79104 Freiburg, Germany
| | - Peter F Stadler
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, University of Leipzig, 04107 Leipzig, Germany
| | - Kathi Zarnack
- Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University Frankfurt, 60438 Frankfurt a.M., Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Center Munich, 85764 Neuherberg, Germany.,Biomolecular NMR and Center for Integrated Protein Science Munich at Department of Chemistry, Technical University of Munich, 85747 Garching, Germany
| | - Stefan Legewie
- Institute of Molecular Biology (IMB) gGmbH, 55128 Mainz, Germany
| | - Julian König
- Institute of Molecular Biology (IMB) gGmbH, 55128 Mainz, Germany
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16
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Callow MG, Watanabe C, Wickliffe KE, Bainer R, Kummerfield S, Weng J, Cuellar T, Janakiraman V, Chen H, Chih B, Liang Y, Haley B, Newton K, Costa MR. CRISPR whole-genome screening identifies new necroptosis regulators and RIPK1 alternative splicing. Cell Death Dis 2018; 9:261. [PMID: 29449584 PMCID: PMC5833675 DOI: 10.1038/s41419-018-0301-y] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 01/04/2018] [Indexed: 12/04/2022]
Abstract
The necroptotic cell death pathway is a key component of human pathogen defense that can become aberrantly derepressed during tissue homeostasis to contribute to multiple types of tissue damage and disease. While formation of the necrosome kinase signaling complex containing RIPK1, RIPK3, and MLKL has been extensively characterized, additional mechanisms of its regulation and effector functions likely remain to be discovered. We screened 19,883 mouse protein-coding genes by CRISPR/Cas9-mediated gene knockout for resistance to cytokine-induced necroptosis and identified 112 regulators and mediators of necroptosis, including 59 new candidate pathway components with minimal or no effect on cell growth in the absence of necroptosis induction. Among these, we further characterized the function of PTBP1, an RNA binding protein whose activity is required to maintain RIPK1 protein abundance by regulating alternative splice-site selection.
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Affiliation(s)
- Marinella G Callow
- Department of Discovery Oncology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Colin Watanabe
- Department of Bioinformatics and Computational Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Katherine E Wickliffe
- Department of Physiological Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Russell Bainer
- Department of Bioinformatics and Computational Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Sarah Kummerfield
- Department of Bioinformatics and Computational Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Julie Weng
- Department of Discovery Oncology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Trinna Cuellar
- Department of Molecular Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA.,Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Washington Road, Princeton, NJ, 08544, USA
| | | | - Honglin Chen
- Department of Molecular Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Ben Chih
- Department of Biochemical and Cellular Pharmacology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Yuxin Liang
- Department of Molecular Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Benjamin Haley
- Department of Molecular Biology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Kim Newton
- Department of Physiological Chemistry, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA
| | - Michael R Costa
- Department of Discovery Oncology, Genentech, Inc., 1 DNA Way, South San Francisco, CA, 94080, USA.
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17
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Transcriptional regulation of macrophage cholesterol efflux and atherogenesis by a long noncoding RNA. Nat Med 2018; 24:304-312. [PMID: 29431742 PMCID: PMC5839972 DOI: 10.1038/nm.4479] [Citation(s) in RCA: 161] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 12/20/2017] [Indexed: 02/06/2023]
Abstract
Nuclear receptors regulate gene expression in response to environmental cues, but the molecular events governing the cell-type specificity of nuclear receptors remain poorly understood. Here we outline a role for a non-coding RNA in modulating the cell type-specific actions of LXRs, sterol-activated nuclear receptors that regulate the expression of genes involved in cholesterol homeostasis and that have been causally linked to the pathogenesis of atherosclerosis. We identify the lncRNA MeXis as an amplifier of LXR-dependent transcription of the critical cholesterol efflux gene Abca1. Mice lacking the MeXis gene show reduced Abca1 expression in a tissue-selective manner. Furthermore, loss of MeXis in mouse bone marrow cells alters chromosome architecture at the Abca1 locus, impairs cellular responses to cholesterol overload, and accelerates the development of atherosclerosis. Mechanistic studies reveal that MeXis interacts with and guides promoter binding of the transcriptional coactivator DDX17. The identification of MeXis as a lncRNA modulator of LXR-dependent gene expression expands our understanding of the mechanisms underlying cell-type selective actions of nuclear receptors in physiology and disease.
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