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; 630:1012-1019. [PMID: 38778104 PMCID: PMC11208138 DOI: 10.1038/s41586-024-07458-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [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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Caizzi L, Monteiro-Martins S, Schwalb B, Lysakovskaia K, Schmitzova J, Sawicka A, Chen Y, Lidschreiber M, Cramer P. Efficient RNA polymerase II pause release requires U2 snRNP function. Mol Cell 2021; 81:1920-1934.e9. [PMID: 33689748 DOI: 10.1016/j.molcel.2021.02.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 01/07/2021] [Accepted: 02/10/2021] [Indexed: 12/21/2022]
Abstract
Transcription by RNA polymerase II (Pol II) is coupled to pre-mRNA splicing, but the underlying mechanisms remain poorly understood. Co-transcriptional splicing requires assembly of a functional spliceosome on nascent pre-mRNA, but whether and how this influences Pol II transcription remains unclear. Here we show that inhibition of pre-mRNA branch site recognition by the spliceosome component U2 snRNP leads to a widespread and strong decrease in new RNA synthesis from human genes. Multiomics analysis reveals that inhibition of U2 snRNP function increases the duration of Pol II pausing in the promoter-proximal region, impairs recruitment of the pause release factor P-TEFb, and reduces Pol II elongation velocity at the beginning of genes. Our results indicate that efficient release of paused Pol II into active transcription elongation requires the formation of functional spliceosomes and that eukaryotic mRNA biogenesis relies on positive feedback from the splicing machinery to the transcription machinery.
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Affiliation(s)
- Livia Caizzi
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Sara Monteiro-Martins
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Björn Schwalb
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Kseniia Lysakovskaia
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Jana Schmitzova
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Anna Sawicka
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Ying Chen
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Michael Lidschreiber
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
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3
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Mol AA, Vogel M, Suess B. Inducible nuclear import by TetR aptamer-controlled 3' splice site selection. RNA (NEW YORK, N.Y.) 2021; 27:234-241. [PMID: 33148600 PMCID: PMC7812871 DOI: 10.1261/rna.077453.120] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 10/20/2020] [Indexed: 06/11/2023]
Abstract
Correct cellular localization is essential for the function of many eukaryotic proteins and hence cell physiology. Here, we present a synthetic genetic device that allows the control of nuclear and cytosolic localization based on controlled alternative splicing in human cells. The device is based on the fact that an alternative 3' splice site is located within a TetR aptamer that in turn is positioned between the branch point and the canonical splice site. The novel splice site is only recognized when the TetR repressor is bound. Addition of doxycycline prevents TetR aptamer binding and leads to recognition of the canonical 3' splice site. It is thus possible to produce two independent splice isoforms. Since the terminal loop of the aptamer may be replaced with any sequence of choice, one of the two isoforms may be extended by the respective sequence of choice depending on the presence of doxycycline. In a proof-of-concept study, we fused a nuclear localization sequence to a cytosolic target protein, thus directing the protein into the nucleus. However, the system is not limited to the control of nuclear localization. In principle, any target sequence can be integrated into the aptamer, allowing not only the production of a variety of different isoforms on demand, but also to study the function of mislocalized proteins. Moreover, it also provides a valuable tool for investigating the mechanism of alternative splicing in human cells.
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Affiliation(s)
- Adam A Mol
- Department of Biology, Technical University of Darmstadt, D-64287 Darmstadt, Germany
| | - Marc Vogel
- Department of Biology, Technical University of Darmstadt, D-64287 Darmstadt, Germany
| | - Beatrix Suess
- Department of Biology, Technical University of Darmstadt, D-64287 Darmstadt, Germany
- Centre for Synthetic Biology, Technical University of Darmstadt, D-64287 Darmstadt, Germany
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4
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Zhang S, Aibara S, Vos SM, Agafonov DE, Lührmann R, Cramer P. Structure of a transcribing RNA polymerase II–U1 snRNP complex. Science 2021; 371:305-309. [DOI: 10.1126/science.abf1870] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 12/07/2020] [Indexed: 12/15/2022]
Affiliation(s)
- Suyang Zhang
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Shintaro Aibara
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Seychelle M. Vos
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Dmitry E. Agafonov
- Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Reinhard Lührmann
- Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Patrick Cramer
- Department of Molecular Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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5
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Niwa M, Berget SM. Polyadenylation precedes splicing in vitro. Gene Expr 2018; 1:5-14. [PMID: 1726467 PMCID: PMC5952195] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Vertebrate premessenger RNAs are usually spliced and polyadenylated. In vivo analysis of the relative kinetics of the two reactions is difficult. We have used in vitro processing systems to investigate the order of splicing and polyadenylation of chimeric precursor RNAs containing a single intron and a poly(A) site. Polyadenylated, but not spliced, intermediate RNA appeared first and reached a low steady-state level early during incubation, properties consistent with its being a reaction intermediate in the production of doubly-processed spliced and polyadenylated product RNA. The kinetics of polyadenylation suggested that polyadenylated RNA was the only intermediate in the production of doubly-processed RNA. Spliced, but not polyadenylated, RNA also appeared. This species, however, continued to accumulate during reaction, and could not be chased into product spliced and polyadenylated RNA. These data support a preferred order of reaction for 3' terminal introns and exons in which polyadenylation precedes splicing.
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Affiliation(s)
- M Niwa
- Marrs McClean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030
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6
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Wilkinson ME, Lin PC, Plaschka C, Nagai K. Cryo-EM Studies of Pre-mRNA Splicing: From Sample Preparation to Model Visualization. Annu Rev Biophys 2018; 47:175-199. [PMID: 29494253 DOI: 10.1146/annurev-biophys-070317-033410] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The removal of noncoding introns from pre-messenger RNA (pre-mRNA) is an essential step in eukaryotic gene expression and is catalyzed by a dynamic multi-megadalton ribonucleoprotein complex called the spliceosome. The spliceosome assembles on pre-mRNA substrates by the stepwise addition of small nuclear ribonucleoprotein particles and numerous protein factors. Extensive remodeling is required to form the RNA-based active site and to mediate the pre-mRNA branching and ligation reactions. In the past two years, cryo-electron microscopy (cryo-EM) structures of spliceosomes captured in different assembly and catalytic states have greatly advanced our understanding of its mechanism. This was made possible by long-standing efforts in the purification of spliceosome intermediates as well as recent developments in cryo-EM imaging and computational methodology. The resulting high-resolution densities allow for de novo model building in core regions of the complexes. In peripheral and less ordered regions, the combination of cross-linking, bioinformatics, biochemical, and genetic data is essential for accurate modeling. Here, we summarize these achievements and highlight the critical steps in obtaining near-atomic resolution structures of the spliceosome.
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Affiliation(s)
- Max E Wilkinson
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom; , , ,
| | - Pei-Chun Lin
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom; , , ,
| | - Clemens Plaschka
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom; , , ,
| | - Kiyoshi Nagai
- MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom; , , ,
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7
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Pozzi B, Bragado L, Will CL, Mammi P, Risso G, Urlaub H, Lührmann R, Srebrow A. SUMO conjugation to spliceosomal proteins is required for efficient pre-mRNA splicing. Nucleic Acids Res 2017; 45:6729-6745. [PMID: 28379520 PMCID: PMC5499870 DOI: 10.1093/nar/gkx213] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Accepted: 03/24/2017] [Indexed: 12/26/2022] Open
Abstract
Pre-mRNA splicing is catalyzed by the spliceosome, a multi-megadalton ribonucleoprotein machine. Previous work from our laboratory revealed the splicing factor SRSF1 as a regulator of the SUMO pathway, leading us to explore a connection between this pathway and the splicing machinery. We show here that addition of a recombinant SUMO-protease decreases the efficiency of pre-mRNA splicing in vitro. By mass spectrometry analysis of anti-SUMO immunoprecipitated proteins obtained from purified splicing complexes formed along the splicing reaction, we identified spliceosome-associated SUMO substrates. After corroborating SUMOylation of Prp3 in cultured cells, we defined Lys 289 and Lys 559 as bona fide SUMO attachment sites within this spliceosomal protein. We further demonstrated that a Prp3 SUMOylation-deficient mutant while still capable of interacting with U4/U6 snRNP components, is unable to co-precipitate U2 and U5 snRNA and the spliceosomal proteins U2-SF3a120 and U5-Snu114. This SUMOylation-deficient mutant fails to restore the splicing of different pre-mRNAs to the levels achieved by the wild type protein, when transfected into Prp3-depleted cultured cells. This mutant also shows a diminished recruitment to active spliceosomes, compared to the wild type protein. These findings indicate that SUMO conjugation plays a role during the splicing process and suggest the involvement of Prp3 SUMOylation in U4/U6•U5 tri-snRNP formation and/or recruitment.
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Affiliation(s)
- Berta Pozzi
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Fisiología, Biología Molecular y Celular, Buenos Aires, Argentina.,CONICET-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Buenos Aires, Argentina
| | - Laureano Bragado
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Fisiología, Biología Molecular y Celular, Buenos Aires, Argentina.,CONICET-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Buenos Aires, Argentina
| | - Cindy L Will
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany
| | - Pablo Mammi
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Fisiología, Biología Molecular y Celular, Buenos Aires, Argentina.,CONICET-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Buenos Aires, Argentina
| | - Guillermo Risso
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Fisiología, Biología Molecular y Celular, Buenos Aires, Argentina.,CONICET-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Buenos Aires, Argentina
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, MPI for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany.,Bioanalytics Group, Institute for Clinical Chemistry, University Medical Center Göttingen, Robert-Koch-Straße 40, D-37075 Göttingen, Germany
| | - Reinhard Lührmann
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, D-37077 Göttingen, Germany
| | - Anabella Srebrow
- Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Fisiología, Biología Molecular y Celular, Buenos Aires, Argentina.,CONICET-Universidad de Buenos Aires, Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Buenos Aires, Argentina
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8
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Zhang P, Hastert FD, Ludwig AK, Breitwieser K, Hofstätter M, Cardoso MC. DNA base flipping analytical pipeline. Biol Methods Protoc 2017; 2:bpx010. [PMID: 32161792 PMCID: PMC6994035 DOI: 10.1093/biomethods/bpx010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 06/01/2017] [Accepted: 06/07/2017] [Indexed: 11/20/2022] Open
Abstract
DNA base modifications and mutations are observed in all genomes throughout the kingdoms of life. Proteins involved in their establishment and removal were shown to use a base flipping mechanism to access their substrates. To better understand how proteins flip DNA bases to modify or remove them, we optimized and developed a pipeline of methods to step-by-step detect the process starting with protein–DNA interaction, base flipping itself and the ensuing DNA base modification or excision. As methylcytosine is the best-studied DNA modification, here we focus on the process of writing, modifying and reading this DNA base. Using multicolor electrophoretic mobility shift assays, we show that the methylcytosine modifier Tet1 exhibits little DNA sequence specificity with only a slight preference for methylated CpG containing DNA. A combination of chloroacetaldehyde treatment and high-resolution melting temperature analysis allowed us to detect base flipping induced by the methylcytosine modifier Tet1 as well as the methylcytosine writer M.HpaII. Finally, we show that high-resolution melting temperature analysis can be used to detect the activity of glycosylases, methyltransferases and dioxigenases on DNA substrates. Taken together, this DNA base flipping analytical pipeline (BaFAP) provide a complete toolbox for the fast and sensitive analysis of proteins that bind, flip and modify or excise DNA bases.
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Affiliation(s)
- Peng Zhang
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Germany
| | - Florian D Hastert
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Germany
| | - Anne K Ludwig
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Germany
| | - Kai Breitwieser
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Germany
| | | | - M Cristina Cardoso
- Cell Biology and Epigenetics, Department of Biology, Technische Universität Darmstadt, Germany
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9
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Sidarovich A, Will CL, Anokhina MM, Ceballos J, Sievers S, Agafonov DE, Samatov T, Bao P, Kastner B, Urlaub H, Waldmann H, Lührmann R. Identification of a small molecule inhibitor that stalls splicing at an early step of spliceosome activation. eLife 2017; 6. [PMID: 28300534 PMCID: PMC5354520 DOI: 10.7554/elife.23533] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Accepted: 02/26/2017] [Indexed: 11/13/2022] Open
Abstract
Small molecule inhibitors of pre-mRNA splicing are important tools for identifying new spliceosome assembly intermediates, allowing a finer dissection of spliceosome dynamics and function. Here, we identified a small molecule that inhibits human pre-mRNA splicing at an intermediate stage during conversion of pre-catalytic spliceosomal B complexes into activated Bact complexes. Characterization of the stalled complexes (designated B028) revealed that U4/U6 snRNP proteins are released during activation before the U6 Lsm and B-specific proteins, and before recruitment and/or stable incorporation of Prp19/CDC5L complex and other Bact complex proteins. The U2/U6 RNA network in B028 complexes differs from that of the Bact complex, consistent with the idea that the catalytic RNA core forms stepwise during the B to Bact transition and is likely stabilized by the Prp19/CDC5L complex and related proteins. Taken together, our data provide new insights into the RNP rearrangements and extensive exchange of proteins that occurs during spliceosome activation. DOI:http://dx.doi.org/10.7554/eLife.23533.001
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Affiliation(s)
- Anzhalika Sidarovich
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Cindy L Will
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Maria M Anokhina
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Javier Ceballos
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Sonja Sievers
- Compound Management and Screening Center, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Dmitry E Agafonov
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Timur Samatov
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Penghui Bao
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Berthold Kastner
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytics Group, Institute for Clinical Chemistry Göttingen, University Medical Center, Göttingen, Germany
| | - Herbert Waldmann
- Department of Chemical Biology, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Reinhard Lührmann
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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10
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Bertram K, Agafonov DE, Liu WT, Dybkov O, Will CL, Hartmuth K, Urlaub H, Kastner B, Stark H, Lührmann R. Cryo-EM structure of a human spliceosome activated for step 2 of splicing. Nature 2017; 542:318-323. [DOI: 10.1038/nature21079] [Citation(s) in RCA: 179] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 01/04/2017] [Indexed: 12/18/2022]
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11
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Abstract
Northwestern assays detect a direct binding of a given RNA molecule to a protein immobilized on a nitrocellulose membrane. Here, we describe protocols to prepare (32)P-labeled RNA probes and to use them to assay for RNA-protein interactions after partially purified protein preparations are resolved on denaturing SDS-polyacrylamide gels. The method can unambiguously determine whether the protein of interest can directly and independently bind RNA even in the presence of contaminating bacterial proteins or degradation products that at times may hinder interpretation of results obtained from gel mobility shift or RNP immunoprecipitation assays.
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12
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Jagtap PKA, Garg D, Kapp TG, Will CL, Demmer O, Lührmann R, Kessler H, Sattler M. Rational Design of Cyclic Peptide Inhibitors of U2AF Homology Motif (UHM) Domains To Modulate Pre-mRNA Splicing. J Med Chem 2016; 59:10190-10197. [PMID: 27753493 DOI: 10.1021/acs.jmedchem.6b01118] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
U2AF homology motifs (UHMs) are atypical RNA recognition motif domains that mediate critical protein-protein interactions during the regulation of alternative pre-mRNA splicing and other processes. The recognition of UHM domains by UHM ligand motif (ULM) peptide sequences plays important roles during early steps of spliceosome assembly. Splicing factor 45 kDa (SPF45) is an alternative splicing factor implicated in breast and lung cancers, and splicing regulation of apoptosis-linked pre-mRNAs by SPF45 was shown to depend on interactions between its UHM domain and ULM motifs in constitutive splicing factors. We have developed cyclic peptide inhibitors that target UHM domains. By screening a focused library of linear and cyclic peptides and performing structure-activity relationship analysis, we designed cyclic peptides with 4-fold improved binding affinity for the SPF45 UHM domain compared to native ULM ligands and 270-fold selectivity to discriminate UHM domains from alternative and constitutive splicing factors. These inhibitors are useful tools to modulate and dissect mechanisms of alternative splicing regulation.
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Affiliation(s)
- Pravin Kumar Ankush Jagtap
- Institute of Structural Biology, Helmholtz Zentrum München , Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.,Center for Integrated Protein Science Munich (CIPSM), Department Chemie, Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Divita Garg
- Institute of Structural Biology, Helmholtz Zentrum München , Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.,Center for Integrated Protein Science Munich (CIPSM), Department Chemie, Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Tobias G Kapp
- Center for Integrated Protein Science Munich (CIPSM), Department Chemie, Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany.,Institute for Advanced Study (IAS), Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Cindy L Will
- Max Planck Institute for Biophysical Chemistry , Department of Cellular Biochemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Oliver Demmer
- Center for Integrated Protein Science Munich (CIPSM), Department Chemie, Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany.,Institute for Advanced Study (IAS), Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Reinhard Lührmann
- Max Planck Institute for Biophysical Chemistry , Department of Cellular Biochemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Horst Kessler
- Center for Integrated Protein Science Munich (CIPSM), Department Chemie, Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany.,Institute for Advanced Study (IAS), Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Michael Sattler
- Institute of Structural Biology, Helmholtz Zentrum München , Ingolstaedter Landstrasse 1, 85764 Neuherberg, Germany.,Center for Integrated Protein Science Munich (CIPSM), Department Chemie, Technische Universität München , Lichtenbergstrasse 4, 85747 Garching, Germany
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13
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Pichon X, Bastide A, Safieddine A, Chouaib R, Samacoits A, Basyuk E, Peter M, Mueller F, Bertrand E. Visualization of single endogenous polysomes reveals the dynamics of translation in live human cells. J Cell Biol 2016; 214:769-81. [PMID: 27597760 PMCID: PMC5021097 DOI: 10.1083/jcb.201605024] [Citation(s) in RCA: 130] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Accepted: 08/16/2016] [Indexed: 12/13/2022] Open
Abstract
Pichon et al. describe a method to visualize translation of single endogenous mRNPs in live cells and provide evidence for specialized translation factories, as well as measurements of translation elongation rate, ribosome loading, and movements of single polysomes. Translation is an essential step in gene expression. In this study, we used an improved SunTag system to label nascent proteins and image translation of single messenger ribonucleoproteins (mRNPs) in human cells. Using a dedicated reporter RNA, we observe that translation of single mRNPs stochastically turns on and off while they diffuse through the cytoplasm. We further measure a ribosome density of 1.3 per kilobase and an elongation rate of 13–18 amino acids per second. Tagging the endogenous POLR2A gene revealed similar elongation rates and ribosomal densities and that nearly all messenger RNAs (mRNAs) are engaged in translation. Remarkably, tagging of the heavy chain of dynein 1 (DYNC1H1) shows this mRNA accumulates in foci containing three to seven RNA molecules. These foci are translation sites and thus represent specialized translation factories. We also observe that DYNC1H1 polysomes are actively transported by motors, which may deliver the mature protein at appropriate cellular locations. The SunTag should be broadly applicable to study translational regulation in live single cells.
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Affiliation(s)
- Xavier Pichon
- Institut de Génétique Moléculaire de Montpellier, UMR5535 CNRS, 34293 Montpellier Cedex 5, France; Université de Montpellier, 34090 Montpellier, France
| | - Amandine Bastide
- Institut de Génétique Moléculaire de Montpellier, UMR5535 CNRS, 34293 Montpellier Cedex 5, France; Université de Montpellier, 34090 Montpellier, France
| | - Adham Safieddine
- Institut de Génétique Moléculaire de Montpellier, UMR5535 CNRS, 34293 Montpellier Cedex 5, France; Université de Montpellier, 34090 Montpellier, France
| | - Racha Chouaib
- Institut de Génétique Moléculaire de Montpellier, UMR5535 CNRS, 34293 Montpellier Cedex 5, France; Université de Montpellier, 34090 Montpellier, France
| | - Aubin Samacoits
- Unité Imagerie et Modélisation, Institut Pasteur, UMR3691, Centre National de la Recherche Scientifique, 75015 Paris, France
| | - Eugenia Basyuk
- Institut de Génétique Moléculaire de Montpellier, UMR5535 CNRS, 34293 Montpellier Cedex 5, France; Université de Montpellier, 34090 Montpellier, France
| | - Marion Peter
- Institut de Génétique Moléculaire de Montpellier, UMR5535 CNRS, 34293 Montpellier Cedex 5, France; Université de Montpellier, 34090 Montpellier, France
| | - Florian Mueller
- Unité Imagerie et Modélisation, Institut Pasteur, UMR3691, Centre National de la Recherche Scientifique, 75015 Paris, France
| | - Edouard Bertrand
- Institut de Génétique Moléculaire de Montpellier, UMR5535 CNRS, 34293 Montpellier Cedex 5, France; Université de Montpellier, 34090 Montpellier, France
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14
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De Maio FA, Risso G, Iglesias NG, Shah P, Pozzi B, Gebhard LG, Mammi P, Mancini E, Yanovsky MJ, Andino R, Krogan N, Srebrow A, Gamarnik AV. The Dengue Virus NS5 Protein Intrudes in the Cellular Spliceosome and Modulates Splicing. PLoS Pathog 2016; 12:e1005841. [PMID: 27575636 PMCID: PMC5004807 DOI: 10.1371/journal.ppat.1005841] [Citation(s) in RCA: 156] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 08/03/2016] [Indexed: 11/22/2022] Open
Abstract
Dengue virus NS5 protein plays multiple functions in the cytoplasm of infected cells, enabling viral RNA replication and counteracting host antiviral responses. Here, we demonstrate a novel function of NS5 in the nucleus where it interferes with cellular splicing. Using global proteomic analysis of infected cells together with functional studies, we found that NS5 binds spliceosome complexes and modulates endogenous splicing as well as minigene-derived alternative splicing patterns. In particular, we show that NS5 alone, or in the context of viral infection, interacts with core components of the U5 snRNP particle, CD2BP2 and DDX23, alters the inclusion/exclusion ratio of alternative splicing events, and changes mRNA isoform abundance of known antiviral factors. Interestingly, a genome wide transcriptome analysis, using recently developed bioinformatics tools, revealed an increase of intron retention upon dengue virus infection, and viral replication was improved by silencing specific U5 components. Different mechanistic studies indicate that binding of NS5 to the spliceosome reduces the efficiency of pre-mRNA processing, independently of NS5 enzymatic activities. We propose that NS5 binding to U5 snRNP proteins hijacks the splicing machinery resulting in a less restrictive environment for viral replication.
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Affiliation(s)
| | - Guillermo Risso
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | - Priya Shah
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Berta Pozzi
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | - Pablo Mammi
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
| | | | | | - Raul Andino
- Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, California, United States of America
| | - Nevan Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California, United States of America
| | - Anabella Srebrow
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, UBA-CONICET), Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires
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15
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Zhang Z, Shen M, Gresch PJ, Ghamari-Langroudi M, Rabchevsky AG, Emeson RB, Stamm S. Oligonucleotide-induced alternative splicing of serotonin 2C receptor reduces food intake. EMBO Mol Med 2016; 8:878-94. [PMID: 27406820 PMCID: PMC4967942 DOI: 10.15252/emmm.201506030] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The serotonin 2C receptor regulates food uptake, and its activity is regulated by alternative pre-mRNA splicing. Alternative exon skipping is predicted to generate a truncated receptor protein isoform, whose existence was confirmed with a new antiserum. The truncated receptor sequesters the full-length receptor in intracellular membranes. We developed an oligonucleotide that promotes exon inclusion, which increases the ratio of the full-length to truncated receptor protein. Decreasing the amount of truncated receptor results in the accumulation of full-length, constitutively active receptor at the cell surface. After injection into the third ventricle of mice, the oligonucleotide accumulates in the arcuate nucleus, where it changes alternative splicing of the serotonin 2C receptor and increases pro-opiomelanocortin expression. Oligonucleotide injection reduced food intake in both wild-type and ob/ob mice. Unexpectedly, the oligonucleotide crossed the blood-brain barrier and its systemic delivery reduced food intake in wild-type mice. The physiological effect of the oligonucleotide suggests that a truncated splice variant regulates the activity of the serotonin 2C receptor, indicating that therapies aimed to change pre-mRNA processing could be useful to treat hyperphagia, characteristic for disorders like Prader-Willi syndrome.
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Affiliation(s)
- Zhaiyi Zhang
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Manli Shen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Paul J Gresch
- Department of Pharmacology, Vanderbilt University, Nashville, TN, USA
| | | | | | - Ronald B Emeson
- Department of Molecular Physiology & Biophysics, Vanderbilt University, Nashville, TN, USA
| | - Stefan Stamm
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
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16
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Haudek KC, Voss PG, Wang JL, Patterson RJ. A 10S galectin-3-U1 snRNP complex assembles into active spliceosomes. Nucleic Acids Res 2016; 44:6391-7. [PMID: 27105840 PMCID: PMC5291251 DOI: 10.1093/nar/gkw303] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 04/12/2016] [Indexed: 12/13/2022] Open
Abstract
In previous studies, we reported that fractionation of HeLa cell nuclear extracts on glycerol gradients revealed an endogenous ∼10S particle that contained galectin-3 and U1 snRNP and this particle was sufficient to load the galectin polypeptide onto a pre-mRNA substrate. We now document that this interaction between the galectin-3–U1 snRNP particle and the pre-mRNA results in a productive spliceosomal complex, leading to intermediates and products of the splicing reaction. Nuclear extracts were depleted of U1 snRNP with a concomitant loss of splicing activity. Splicing activity in the U1-depleted extract can be reconstituted by the galectin-3–U1 snRNP particle, isolated by immunoprecipitation of the 10S region (fractions 3–5) of the glycerol gradient with anti-galectin-3 antibodies. In contrast, parallel anti-galectin-3 immunoprecipitation of free galectin-3 molecules not in a complex with U1 snRNP (fraction 1 of the same gradient), failed to restore splicing activity. These results indicate that the galectin-3–U1 snRNP-pre-mRNA ternary complex is a functional E complex and that U1 snRNP is required to assemble galectin-3 onto an active spliceosome.
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Affiliation(s)
- Kevin C Haudek
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Patricia G Voss
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - John L Wang
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Ronald J Patterson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
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17
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Patterson RJ, Haudek KC, Voss PG, Wang JL. Examination of the role of galectins in pre-mRNA splicing. Methods Mol Biol 2015; 1207:431-49. [PMID: 25253157 DOI: 10.1007/978-1-4939-1396-1_28] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Several lines of evidence have been accumulated to indicate that galectin-1 and galectin-3 are two of the many proteins involved in nuclear splicing of pre-mRNA. First, nuclear extracts, capable of carrying out splicing of pre-mRNA in a cell-free assay, contain both of the galectins. Second, depletion of the galectins from nuclear extracts, using either lactose affinity chromatography or immunoadsorption with antibodies, results in concomitant loss of splicing activity. Third, addition of either galectin-1 or galectin-3 to the galectin-depleted extract reconstitutes the splicing activity. Fourth, the addition of saccharides that bind to galectin-1 and galectin-3 with high affinity (e.g., lactose or thiodigalactoside) to nuclear extract results in inhibition of splicing whereas parallel addition of saccharides that do not bind to the galectins (e.g., cellobiose) fail to yield the same effect. Finally, when a splicing reaction is subjected to immunoprecipitation by antibodies directed against galectin-1, radiolabeled RNA species corresponding to the starting pre-mRNA substrate, the mature mRNA product, and intermediates of the splicing reaction are coprecipitated with the galectin. Similar results were also obtained with antibodies against galectin-3. This chapter describes two key assays used in our studies: one reports on the splicing activity by looking at product formation on a denaturing gel; the other reports on the intermediates of spliceosome assembly using non-denaturing or native gels.
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Affiliation(s)
- Ronald J Patterson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
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18
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Steckelberg AL, Gehring NH. Studying the composition of mRNPs in vitro using splicing-competent cell extracts. Methods 2014; 65:342-9. [DOI: 10.1016/j.ymeth.2013.08.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 08/27/2013] [Accepted: 08/30/2013] [Indexed: 10/26/2022] Open
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19
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Nawroth I, Mueller F, Basyuk E, Beerens N, Rahbek UL, Darzacq X, Bertrand E, Kjems J, Schmidt U. Stable assembly of HIV-1 export complexes occurs cotranscriptionally. RNA (NEW YORK, N.Y.) 2014; 20:1-8. [PMID: 24255166 PMCID: PMC3866638 DOI: 10.1261/rna.038182.113] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 09/13/2013] [Indexed: 06/02/2023]
Abstract
The HIV-1 Rev protein mediates export of unspliced and singly spliced viral transcripts by binding to the Rev response element (RRE) and recruiting the cellular export factor CRM1. Here, we investigated the recruitment of Rev to the transcription sites of HIV-1 reporters that splice either post- or cotranscriptionally. In both cases, we observed that Rev localized to the transcription sites of the reporters and recruited CRM1. Rev and CRM1 remained at the reporter transcription sites when cells were treated with the splicing inhibitor Spliceostatin A (SSA), showing that the proteins associate with RNA prior to or during early spliceosome assembly. Fluorescence recovery after photobleaching (FRAP) revealed that Rev and CRM1 have similar kinetics as the HIV-1 RNA, indicating that Rev, CRM1, and RRE-containing RNAs are released from the site of transcription in one single export complex. These results suggest that cotranscriptional formation of a stable export complex serves as a means to ensure efficient export of unspliced viral RNAs.
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Affiliation(s)
- Isabel Nawroth
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
| | - Florian Mueller
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), CNRS UMR 8197, 75230 Paris cedex 05, France
- Institut Pasteur, Imaging and Modeling Unit, CNRS URA 2582, 75015 Paris, France
| | - Eugenia Basyuk
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
| | - Nancy Beerens
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Ulrik L. Rahbek
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Xavier Darzacq
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), CNRS UMR 8197, 75230 Paris cedex 05, France
| | - Edouard Bertrand
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
| | - Jørgen Kjems
- Department of Molecular Biology and Genetics, Aarhus University, 8000 Aarhus, Denmark
- Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 Aarhus, Denmark
| | - Ute Schmidt
- Institut de Génétique Moléculaire de Montpellier?CNRS UMR 5535, 34293 Montpellier cedex 5, France
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20
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Voss PG, Haudek KC, Patterson RJ, Wang JL. Inhibition of Cell-Free Splicing by Saccharides That Bind Galectins and SR Proteins. J Carbohydr Chem 2012. [DOI: 10.1080/07328303.2012.666688] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Patricia G. Voss
- a Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , MI , 48824 , USA
| | - Kevin C. Haudek
- a Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , MI , 48824 , USA
| | - Ronald J. Patterson
- b Department of Microbiology and Molecular Genetics , Michigan State University , East Lansing , MI , 48824 , USA
| | - John L. Wang
- a Department of Biochemistry and Molecular Biology , Michigan State University , East Lansing , MI , 48824 , USA
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21
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Daguenet E, Baguet A, Degot S, Schmidt U, Alpy F, Wendling C, Spiegelhalter C, Kessler P, Rio MC, Le Hir H, Bertrand E, Tomasetto C. Perispeckles are major assembly sites for the exon junction core complex. Mol Biol Cell 2012; 23:1765-82. [PMID: 22419818 PMCID: PMC3338441 DOI: 10.1091/mbc.e12-01-0040] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The exon junction complex (EJC) allows the spliceosome to communicate with other cellular machinery. This study shows that assembled EJC cores are enriched in nuclear regions around speckles, called perispeckles. Speckles and perispeckles may represent specialized nuclear regions for messenger ribonucleoprotein maturation. The exon junction complex (EJC) is loaded onto mRNAs as a consequence of splicing and regulates multiple posttranscriptional events. MLN51, Magoh, Y14, and eIF4A3 form a highly stable EJC core, but where this tetrameric complex is assembled in the cell remains unclear. Here we show that EJC factors are enriched in domains that we term perispeckles and are visible as doughnuts around nuclear speckles. Fluorescence resonance energy transfer analyses and EJC assembly mutants show that perispeckles do not store free subunits, but instead are enriched for assembled cores. At the ultrastructural level, perispeckles are distinct from interchromatin granule clusters that may function as storage sites for splicing factors and intermingle with perichromatin fibrils, where nascent RNAs and active RNA Pol II are present. These results support a model in which perispeckles are major assembly sites for the tetrameric EJC core. This subnuclear territory thus represents an intermediate region important for mRNA maturation, between transcription sites and splicing factor reservoirs and assembly sites.
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Affiliation(s)
- Elisabeth Daguenet
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Unité Mixte de Recherche 7104, Centre National de la Recherche Scientifique/U964 Institut National de Santé et de Recherche Médicale/Université de Strasbourg, 67404 Illkirch, France
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22
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Makarov EM, Owen N, Bottrill A, Makarova OV. Functional mammalian spliceosomal complex E contains SMN complex proteins in addition to U1 and U2 snRNPs. Nucleic Acids Res 2011; 40:2639-52. [PMID: 22110043 PMCID: PMC3315330 DOI: 10.1093/nar/gkr1056] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spliceosomes remove introns from primary gene transcripts. They assemble de novo on each intron through a series of steps that involve the incorporation of five snRNP particles and multiple non-snRNP proteins. In mammals, all the intermediate complexes have been characterized on one transcript (MINX), with the exception of the very first, complex E. We have purified this complex by two independent procedures using antibodies to either U1-A or PRPF40A proteins, which are known to associate at an early stage of assembly. We demonstrate that the purified complexes are functional in splicing using commitment assays. These complexes contain components expected to be in the E complex and a number of previously unrecognized factors, including survival of motor neurons (SMN) and proteins of the SMN-associated complex. Depletion of the SMN complex proteins from nuclear extracts inhibits formation of the E complex and causes non-productive complexes to accumulate. This suggests that the SMN complex stabilizes the association of U1 and U2 snRNPs with pre-mRNA. In addition, the antibody to PRPF40A precipitated U2 snRNPs from nuclear extracts, indicating that PRPF40A associates with U2 snRNPs.
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Affiliation(s)
- Evgeny M Makarov
- Department of Biochemistry, University of Leicester, Leicester LE1 9HN, UK
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23
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Álvarez E, Castelló A, Carrasco L, Izquierdo JM. Alternative splicing, a new target to block cellular gene expression by poliovirus 2A protease. Biochem Biophys Res Commun 2011; 414:142-7. [PMID: 21945619 DOI: 10.1016/j.bbrc.2011.09.040] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Accepted: 09/08/2011] [Indexed: 11/29/2022]
Abstract
Viruses have developed multiple strategies to interfere with the gene expression of host cells at different stages to ensure their own survival. Here we report a new role for poliovirus 2A(pro) modulating the alternative splicing of pre-mRNAs. Expression of 2A(pro) potently inhibits splicing of reporter genes in HeLa cells. Low amounts of 2A(pro) abrogate Fas exon 6 skipping, whereas higher levels of protease fully abolish Fas and FGFR2 splicing. In vitro splicing of MINX mRNA using nuclear extracts is also strongly inhibited by 2A(pro), leading to accumulation of the first exon and the lariat product containing the unspliced second exon. These findings reveal that the mechanism of action of 2A(pro) on splicing is to selectively block the second catalytic step.
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Affiliation(s)
- Enrique Álvarez
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Nicolás Cabrera, 1 Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain.
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24
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Pradet-Balade B, Girard C, Boulon S, Paul C, Azzag K, Bordonné R, Bertrand E, Verheggen C. CRM1 controls the composition of nucleoplasmic pre-snoRNA complexes to licence them for nucleolar transport. EMBO J 2011; 30:2205-18. [PMID: 21522132 PMCID: PMC3117649 DOI: 10.1038/emboj.2011.128] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Accepted: 03/28/2011] [Indexed: 01/04/2023] Open
Abstract
Transport of C/D snoRNPs to nucleoli involves nuclear export factors. In particular, CRM1 binds nascent snoRNPs, but its precise role remains unknown. We show here that both CRM1 and nucleocytoplasmic trafficking are required to transport snoRNPs to nucleoli, but the snoRNPs do not transit through the cytoplasm. Instead, CRM1 controls the composition of nucleoplasmic pre-snoRNP complexes. We observed that Tgs1 long form (Tgs1 LF), the long isoform of the cap hypermethylase, contains a leucine-rich nuclear export signal, shuttles in a CRM1-dependent manner, and binds to the nucleolar localization signal (NoLS) of the core snoRNP protein Nop58. In vitro data indicate that CRM1 binds Tgs1 LF and promotes its dissociation from Nop58 NoLS, and immunoprecipitation experiments from cells indicate that the association of Tgs1 LF with snoRNPs increases upon CRM1 inhibition. Thus, CRM1 appears to promote nucleolar transport of snoRNPs by removing Tgs1 LF from the Nop58 NoLS. Microarray/IP data show that this occurs on most snoRNPs, from both C/D and H/ACA families, and on the telomerase RNA. Hence, CRM1 provides a general molecular link between nuclear events and nucleocytoplasmic trafficking.
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Affiliation(s)
- Bérengère Pradet-Balade
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
| | - Cyrille Girard
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
| | - Séverine Boulon
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
| | - Conception Paul
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
| | - Karim Azzag
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
| | - Rémy Bordonné
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
| | - Edouard Bertrand
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
| | - Céline Verheggen
- Institut de Génétique Moléculaire de Montpellier, UMR 5535 CNRS, Université Montpellier I and II, Montpellier Cedex 5, France
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25
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Schmidt U, Basyuk E, Robert MC, Yoshida M, Villemin JP, Auboeuf D, Aitken S, Bertrand E. Real-time imaging of cotranscriptional splicing reveals a kinetic model that reduces noise: implications for alternative splicing regulation. J Cell Biol 2011; 193:819-29. [PMID: 21624952 PMCID: PMC3105549 DOI: 10.1083/jcb.201009012] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2010] [Accepted: 04/25/2011] [Indexed: 01/19/2023] Open
Abstract
Splicing is a key process that expands the coding capacity of genomes. Its kinetics remain poorly characterized, and the distribution of splicing time caused by the stochasticity of single splicing events is expected to affect regulation efficiency. We conducted a small-scale survey on 40 introns in human cells and observed that most were spliced cotranscriptionally. Consequently, we constructed a reporter system that splices cotranscriptionally and can be monitored in live cells and in real time through the use of MS2-GFP. All small nuclear ribonucleoproteins (snRNPs) are loaded on nascent pre-mRNAs, and spliceostatin A inhibits splicing but not snRNP recruitment. Intron removal occurs in minutes and is best described by a model where several successive steps are rate limiting. Each pre-mRNA molecule is predicted to require a similar time to splice, reducing kinetic noise and improving the regulation of alternative splicing. This model is relevant to other kinetically controlled processes acting on few molecules.
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Affiliation(s)
- Ute Schmidt
- Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique UMR 5535, 34293 Montpellier Cedex 5, France
| | - Eugenia Basyuk
- Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique UMR 5535, 34293 Montpellier Cedex 5, France
| | - Marie-Cécile Robert
- Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique UMR 5535, 34293 Montpellier Cedex 5, France
| | - Minoru Yoshida
- Chemical Genomics Research Group and Chemical Genetics Laboratory, Institute of Physical and Chemical Research Institute, Saitama 351-0198, Japan
| | - Jean-Philippe Villemin
- Centre de Recherche en Cancérologie de Lyon, UMR Institut National de la Santé et de la Recherche Médicale U1052, Centre National de la Recherche Scientifique U5286, Centre Léon Bérard, 69008 Lyon, France
| | - Didier Auboeuf
- Centre de Recherche en Cancérologie de Lyon, UMR Institut National de la Santé et de la Recherche Médicale U1052, Centre National de la Recherche Scientifique U5286, Centre Léon Bérard, 69008 Lyon, France
| | - Stuart Aitken
- School of Informatics and Centre for Systems Biology at Edinburgh, University of Edinburgh, Edinburgh, Scotland EH9 3JD, UK
| | - Edouard Bertrand
- Institut de Génétique Moléculaire de Montpellier, Centre National de la Recherche Scientifique UMR 5535, 34293 Montpellier Cedex 5, France
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26
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Spiluttini B, Gu B, Belagal P, Smirnova AS, Nguyen VT, Hébert C, Schmidt U, Bertrand E, Darzacq X, Bensaude O. Splicing-independent recruitment of U1 snRNP to a transcription unit in living cells. J Cell Sci 2010; 123:2085-93. [PMID: 20519584 DOI: 10.1242/jcs.061358] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Numerous non-coding RNAs are known to be involved in the regulation of gene expression. In this work, we analyzed RNAs that co-immunoprecipitated with human RNA polymerase II from mitotic cell extracts and identified U1 small nuclear RNA (snRNA) as a major species. To investigate a possible splicing-independent recruitment of U1 snRNA to transcription units, we established cell lines having integrated a reporter gene containing a functional intron or a splicing-deficient construction. Recruitment of U snRNAs and some splicing factors to transcription sites was evaluated using fluorescence in situ hybridization (FISH) and immunofluorescence. To analyze imaging data, we developed a quantitative procedure, 'radial analysis', based on averaging data from multiple fluorescence images. The major splicing snRNAs (U2, U4 and U6 snRNAs) as well as the U2AF65 and SC35 splicing factors were found to be recruited only to transcription units containing a functional intron. By contrast, U1 snRNA, the U1-70K (also known as snRNP70) U1-associated protein as well as the ASF/SF2 (also known as SFRS1) serine/arginine-rich (SR) protein were efficiently recruited both to normally spliced and splicing-deficient transcription units. The constitutive association of U1 small nuclear ribonucleoprotein (snRNP) with the transcription machinery might play a role in coupling transcription with pre-mRNA maturation.
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Affiliation(s)
- Béatrice Spiluttini
- Ecole Normale Supérieure, Institut de Biologie de l'ENS, IBENS, Paris, France
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27
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Schneider M, Will CL, Anokhina M, Tazi J, Urlaub H, Lührmann R. Exon definition complexes contain the tri-snRNP and can be directly converted into B-like precatalytic splicing complexes. Mol Cell 2010; 38:223-35. [PMID: 20417601 DOI: 10.1016/j.molcel.2010.02.027] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2009] [Revised: 11/18/2009] [Accepted: 02/09/2010] [Indexed: 10/19/2022]
Abstract
The first step in splicing of pre-mRNAs with long introns is exon definition, where U1 and U2 snRNPs bind at opposite ends of an exon. After exon definition, these snRNPs must form a complex across the upstream intron to allow splicing catalysis. Exon definition and conversion of cross-exon to cross-intron spliceosomal complexes are poorly understood. Here we demonstrate that, in addition to U1 and U2 snRNPs, cross-exon complexes contain U4, U5, and U6 (which form the tri-snRNP). Tri-snRNP docking involves the formation of U2/U6 helix II. This interaction is stabilized by a 5' splice site (SS)-containing oligonucleotide, which can bind the tri-snRNP and convert the cross-exon complex into a cross-intron, B-like complex. Our data suggest that the switch from cross-exon to cross-intron complexes can occur directly when an exon-bound tri-snRNP interacts with an upstream 5'SS, without prior formation of a cross-intron A complex, revealing an alternative spliceosome assembly pathway.
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Affiliation(s)
- Marc Schneider
- Department of Cellular Biochemistry, MPI of Biophysical Chemistry, Göttingen, Germany
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28
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Schneider M, Hsiao HH, Will CL, Giet R, Urlaub H, Lührmann R. Human PRP4 kinase is required for stable tri-snRNP association during spliceosomal B complex formation. Nat Struct Mol Biol 2010; 17:216-21. [PMID: 20118938 DOI: 10.1038/nsmb.1718] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 10/09/2009] [Indexed: 11/09/2022]
Abstract
Reversible protein phosphorylation has an essential role during pre-mRNA splicing. Here we identify two previously unidentified phosphoproteins in the human spliceosomal B complex, namely the pre-mRNA processing factors PRP6 and PRP31, both components of the U4/U6-U5 tri-small nuclear ribonucleoprotein (snRNP). We provide evidence that PRP6 and PRP31 are directly phosphorylated by human PRP4 kinase (PRP4K) concomitant with their incorporation into B complexes. Immunodepletion and complementation studies with HeLa splicing extracts revealed that active human PRP4K is required for the phosphorylation of PRP6 and PRP31 and for the assembly of stable, functional B complexes. Thus, the phosphorylation of PRP6 and PRP31 is likely to have a key role during spliceosome assembly. Our data provide new insights into the molecular mechanism by which PRP4K contributes to splicing. They further indicate that numerous phosphorylation events contribute to spliceosome assembly and, thus, that splicing can potentially be modulated at multiple regulatory checkpoints.
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Affiliation(s)
- Marc Schneider
- Department of Cellular Biochemistry, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany
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29
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Wolf E, Kastner B, Deckert J, Merz C, Stark H, Lührmann R. Exon, intron and splice site locations in the spliceosomal B complex. EMBO J 2009; 28:2283-92. [PMID: 19536130 DOI: 10.1038/emboj.2009.171] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2008] [Accepted: 05/26/2009] [Indexed: 02/03/2023] Open
Abstract
In recent years, electron microscopy (EM) has allowed the generation of three-dimensional structure maps of several spliceosomal complexes. However, owing to their limited resolution, little is known at present about the location of the pre-mRNA, the spliceosomal small nuclear ribonucleoprotein or the spliceosome's active site within these structures. In this work, we used EM to localise the intron and the 5' and 3' exons of a model pre-mRNA, as well as the U2-associated protein SF3b155, in pre-catalytic spliceosomes (i.e. B complexes) by labelling them with an antibody that bears colloidal gold. Our data reveal that the intron and both exons, together with SF3b155, are located in specific regions of the head domain of the B complex. These results represent an important first step towards identifying functional sites in the spliceosome. The gold-labelling method adopted here can be applied to other spliceosomal complexes and may thus contribute significantly to our overall understanding of the pre-mRNA splicing process.
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Affiliation(s)
- Elmar Wolf
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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30
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Kuhn AN, van Santen MA, Schwienhorst A, Urlaub H, Lührmann R. Stalling of spliceosome assembly at distinct stages by small-molecule inhibitors of protein acetylation and deacetylation. RNA (NEW YORK, N.Y.) 2009; 15:153-75. [PMID: 19029308 PMCID: PMC2612777 DOI: 10.1261/rna.1332609] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The removal of intervening sequences from a primary RNA transcript is catalyzed by the spliceosome, a large complex consisting of five small nuclear (sn) RNAs and more than 150 proteins. At the start of the splicing cycle, the spliceosome assembles anew onto each pre-mRNA intron in an ordered process. Here, we show that several small-molecule inhibitors of protein acetylation/deacetylation block the splicing cycle: by testing a small number of bioactive compounds, we found that three small-molecule inhibitors of histone acetyltransferases (HATs), as well as three small-molecule inhibitors of histone deacetylases (HDACs), block pre-mRNA splicing in vitro. By purifying and characterizing the stalled spliceosomes, we found that the splicing cycle is blocked at distinct stages by different inhibitors: two inhibitors allow only the formation of A-like spliceosomes (as determined by the size of the stalled complexes and their snRNA composition), while the other compounds inhibit activation for catalysis after incorporation of all U snRNPs into the spliceosome. Mass-spectrometric analysis of affinity-purified stalled spliceosomes indicated that the intermediates differ in protein composition both from each other and from previously characterized native A and B splicing complexes. This suggests that the stalled complexes represent hitherto unobserved intermediates of spliceosome assembly.
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Affiliation(s)
- Andreas N Kuhn
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
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31
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Voss PG, Gray RM, Dickey SW, Wang W, Park JW, Kasai KI, Hirabayashi J, Patterson RJ, Wang JL. Dissociation of the carbohydrate-binding and splicing activities of galectin-1. Arch Biochem Biophys 2008; 478:18-25. [PMID: 18662664 PMCID: PMC2590671 DOI: 10.1016/j.abb.2008.07.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2008] [Revised: 06/28/2008] [Accepted: 07/08/2008] [Indexed: 01/12/2023]
Abstract
Galectin-1 (Gal1) and galectin-3 (Gal3) are two members of a family of carbohydrate-binding proteins that are found in the nucleus and that participate in pre-mRNA splicing assayed in a cell-free system. When nuclear extracts (NE) of HeLa cells were subjected to adsorption on a fusion protein containing glutathione S-transferase (GST) and Gal3, the general transcription factor II-I (TFII-I) was identified by mass spectrometry as one of the polypeptides specifically bound. Lactose and other saccharide ligands of the galectins inhibited GST-Gal3 pull-down of TFII-I while non-binding carbohydrates failed to yield the same effect. Similar results were also obtained using GST-Gal1. Site-directed mutants of Gal1, expressed and purified as GST fusion proteins, were compared with the wild-type (WT) in three assays: (a) binding to asialofetuin-Sepharose as a measure of the carbohydrate-binding activity; (b) pull-down of TFII-I from NE; and (c) reconstitution of splicing in NE depleted of galectins as a test of the in vitro splicing activity. The binding of GST-Gal1(N46D) to asialofetuin-Sepharose was less than 10% of that observed for GST-Gal1(WT), indicating that the mutant was deficient in carbohydrate-binding activity. In contrast, both GST-Gal1(WT) and GST-Gal1(N46D) were equally efficient in pull-down of TFII-I and in reconstitution of splicing activity in the galectin-depleted NE. Moreover, while the splicing activity of the wild-type protein can be inhibited by saccharide ligands, the carbohydrate-binding deficient mutant was insensitive to such inhibition. Together, all of the results suggest that the carbohydrate-binding and the splicing activities of Gal1 can be dissociated and therefore, saccharide-binding, per se, is not required for the splicing activity.
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Affiliation(s)
- Patricia G. Voss
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Richard M. Gray
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Seth W. Dickey
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Weizhong Wang
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Jung W. Park
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Ken-ichi Kasai
- Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 199-0195, Japan
| | - Jun Hirabayashi
- Research Center for Medical Glycoscience, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8568, Japan
| | - Ronald J. Patterson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - John L. Wang
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
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32
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Gray RM, Davis MJ, Ruby KM, Voss PG, Patterson RJ, Wang JL. Distinct effects on splicing of two monoclonal antibodies directed against the amino-terminal domain of galectin-3. Arch Biochem Biophys 2008; 475:100-8. [PMID: 18455493 PMCID: PMC2515097 DOI: 10.1016/j.abb.2008.04.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2008] [Revised: 04/11/2008] [Accepted: 04/13/2008] [Indexed: 11/25/2022]
Abstract
Previous experiments had established that galectin-3 (Gal3) is a factor involved in cell-free splicing of pre-mRNA. Addition of monoclonal antibody NCL-GAL3, whose epitope maps to the NH2-terminal 14 amino acids of Gal3, to a splicing-competent nuclear extract inhibited the splicing reaction. In contrast, monoclonal antibody anti-Mac-2, whose epitope maps to residues 48-100 containing multiple repeats of a 9-residue motif PGAYPGXXX, had no effect on splicing. Consistent with the notion that this region bearing the PGAYPGXXX repeats is sequestered through interaction with the splicing machinery and is inaccessible to the anti-Mac-2 antibody, a synthetic peptide containing three perfect repeats of the sequence PGAYPGQAP (27-mer) inhibited the splicing reaction, mimicking a dominant-negative mutant. Addition of a peptide corresponding to a scrambled sequence of the same composition (27-mer-S) failed to yield the same effect. Finally, GST-hGal3(1-100), a fusion protein containing glutathione-S-transferase and a portion of the Gal3 polypeptide including the PGAYPGXXX repeats, also exhibited a dominant-negative effect on splicing.
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Affiliation(s)
- Richard M. Gray
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Michael J. Davis
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Katherine M. Ruby
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Patricia G. Voss
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Ronald J. Patterson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - John L. Wang
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
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33
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Shen H, Green MR. RS domain-splicing signal interactions in splicing of U12-type and U2-type introns. Nat Struct Mol Biol 2007; 14:597-603. [PMID: 17603499 DOI: 10.1038/nsmb1263] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Accepted: 05/24/2007] [Indexed: 11/08/2022]
Abstract
Serine-arginine (SR) proteins are general metazoan splicing factors that contain an essential arginine/serine-rich (RS) domain. On typical U2-type introns, RS domains contact the branchpoint and 5' splice site to promote base-pairing with U small nuclear RNAs (snRNAs). Here we analyze the role of SR proteins in splicing of U12-type introns and in the second step of U2-type intron splicing. We show that RS domains contact the branchpoint and 5' splice site of a U12-type intron. On a U2-type intron, we find that the RS domain contacts the site of the U6 snRNA-5' splice site interaction during the first step of splicing and shifts to contact the site of the U5 snRNA-exon 1 interaction during the second step. Our results reveal alternative interactions between the RS domain and 5' splice site region that coincide with remodeling of the spliceosome between the two catalytic steps.
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Affiliation(s)
- Haihong Shen
- Howard Hughes Medical Institute and Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
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34
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Dönmez G, Hartmuth K, Kastner B, Will CL, Lührmann R. The 5′ End of U2 snRNA Is in Close Proximity to U1 and Functional Sites of the Pre-mRNA in Early Spliceosomal Complexes. Mol Cell 2007; 25:399-411. [PMID: 17289587 DOI: 10.1016/j.molcel.2006.12.019] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2006] [Revised: 12/06/2006] [Accepted: 12/20/2006] [Indexed: 10/23/2022]
Abstract
Recognition and pairing of the correct 5' and 3' splice sites (ss) of a pre-mRNA are critical events that occur early during spliceosome assembly. Little is known about the spatial organization in early spliceosomal complexes of the U1 and U2 snRNPs, which together with several non-snRNP proteins, are involved in juxtapositioning the functional sites of the pre-mRNA. To better understand the molecular mechanisms of splice-site recognition/pairing, we have examined the organization of U2 relative to U1 and pre-mRNA in spliceosomal complexes via hydroxyl-radical probing with Fe-BABE-tethered U2 snRNA. These studies reveal that functional sites of the pre-mRNA are located close to the 5' end of U2 both in E and A complexes. U2 is also positioned close to U1 in a defined orientation already in the E complex, and their relative spatial organization remains largely unchanged during the E to A transition.
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Affiliation(s)
- Gizem Dönmez
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
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35
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Smith HC. Measuring editing activity and identifying cytidine-to-uridine mRNA editing factors in cells and biochemical isolates. Methods Enzymol 2007; 424:389-416. [PMID: 17662851 DOI: 10.1016/s0076-6879(07)24018-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Cytidine deaminases with the capacity to act on nucleic acids play a critical role in regulating the proteome through diversification of expressed sequence beyond that encoded in the genome. A family of these enzymes, known as the APOBEC family of cytidine deaminases, has been identified in mammalian cells. APOBEC-1 edits messenger RNA, whereas other family members affect mRNA coding capacity by editing single-stranded DNA in expressed regions of the genomes. Biochemical isolation and analysis of APOBEC proteins and their interacting factors have led to an understanding of the diverse cellular processes including lipoprotein metabolism, antibody production, viral infectivity, and cancer. Practical approaches will be described for the measurement of editing activity and the analysis of proteins involved in C-to-U and dC-to-dU editing.
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Affiliation(s)
- Harold C Smith
- Department of Biochemistry, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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36
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Wang W, Park JW, Wang JL, Patterson RJ. Immunoprecipitation of spliceosomal RNAs by antisera to galectin-1 and galectin-3. Nucleic Acids Res 2006; 34:5166-74. [PMID: 16998182 PMCID: PMC1636441 DOI: 10.1093/nar/gkl673] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
We have shown that galectin-1 and galectin-3 are functionally redundant splicing factors. Now we provide evidence that both galectins are directly associated with spliceosomes by analyzing RNAs and proteins of complexes immunoprecipitated by galectin-specific antisera. Both galectin antisera co-precipitated splicing substrate, splicing intermediates and products in active spliceosomes. Protein factors co-precipitated by the galectin antisera included the Sm core polypeptides of snRNPs, hnRNP C1/C2 and Slu7. Early spliceosomal complexes were also immunoprecipitated by these antisera. When splicing reactions were sequentially immunoprecipitated with galectin antisera, we found that galectin-1 containing spliceosomes did not contain galectin-3 and vice versa, providing an explanation for the functional redundancy of nuclear galectins in splicing. The association of galectins with spliceosomes was (i) not due to a direct interaction of galectins with the splicing substrate and (ii) easily disrupted by ionic conditions that had only a minimal effect on snRNP association. Finally, addition of excess amino terminal domain of galectin-3 inhibited incorporation of galectin-1 into splicing complexes, explaining the dominant-negative effect of the amino domain on splicing activity. We conclude that galectins are directly associated with splicing complexes throughout the splicing pathway in a mutually exclusive manner and they bind a common splicing partner through weak protein–protein interactions.
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Affiliation(s)
| | | | - John L. Wang
- Department of Biochemistry and Molecular Biology, Michigan State UniversityEast Lansing, MI 48824, USA
| | - Ronald J. Patterson
- To whom correspondence should be addressed. Tel: +1 517 355 6463/1541; Fax: +1 517 353 8957;
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37
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Behzadnia N, Hartmuth K, Will CL, Lührmann R. Functional spliceosomal A complexes can be assembled in vitro in the absence of a penta-snRNP. RNA (NEW YORK, N.Y.) 2006; 12:1738-46. [PMID: 16880538 PMCID: PMC1557700 DOI: 10.1261/rna.120606] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2006] [Accepted: 06/12/2006] [Indexed: 05/11/2023]
Abstract
Two different models currently exist for the assembly pathway of the spliceosome, namely, the traditional model, in which spliceosomal snRNPs associate in a stepwise, ordered manner with the pre-mRNA, and the holospliceosome model, in which all spliceosomal snRNPs preassemble into a penta-snRNP complex. Here we have tested whether the spliceosomal A complex, which contains solely U1 and U2 snRNPs bound to pre-mRNA, is a functional, bona fide assembly intermediate. Significantly, A complexes affinity-purified from nuclear extract depleted of U4/U6 snRNPs (and thus unable to form a penta-snRNP) supported pre-mRNA splicing in nuclear extract depleted of U2 snRNPs, whereas naked pre-mRNA did not. Mixing experiments with purified A complexes and naked pre-mRNA additionally confirmed that under these conditions, A complexes do not form de novo. Thus, our studies demonstrate that holospliceosome formation is not a prerequisite for generating catalytically active spliceosomes and that, at least in vitro, the U1 and U2 snRNPs can functionally associate with the pre-mRNA, prior to and independent of the tri-snRNP. The ability to isolate functional spliceosomal A complexes paves the way to study in detail subsequent spliceosome assembly steps using purified components.
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Affiliation(s)
- Nastaran Behzadnia
- Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, D-37077 Göttingen, Germany
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38
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Kim DS, Gusti V, Pillai SG, Gaur RK. An artificial riboswitch for controlling pre-mRNA splicing. RNA (NEW YORK, N.Y.) 2005; 11:1667-77. [PMID: 16244133 PMCID: PMC1370853 DOI: 10.1261/rna.2162205] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Riboswitches, as previously reported, are natural RNA aptamers that regulate the expression of numerous bacterial metabolic genes in response to small molecule ligands. It has recently been shown that these RNA genetic elements are also present near the splice site junctions of plant and fungal introns, thus raising the possibility of their involvement in regulating mRNA splicing. Here it is shown for the first time that a riboswitch can be engineered to regulate pre-mRNA splicing in vitro. We show that insertion of a high-affinity theophylline binding aptamer into the 3' splice site (3' ss) region of a model pre-mRNA (AdML-Theo29AG) enables its splicing to be repressed by the addition theophylline. Our results indicate that the location of 3' ss AG within the aptamer plays a crucial role in conferring theophylline-dependent control of pre-mRNA splicing. We also show that theophylline-mediated control of pre-mRNA splicing is highly specific by first demonstrating that a small molecule ligand similar in shape and size to theophylline had no effect on the splicing of AdML-Theo29AG pre-mRNA. Second, theophylline failed to exert any influence on the splicing of a pre-mRNA that does not contain its binding site. Third, theophylline specifically blocks the step II of the splicing reaction. Finally, we provide evidence that theophylline-dependent control of pre-mRNA splicing is functionally relevant.
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Affiliation(s)
- Dong-Suk Kim
- Division of Molecular Biology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
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39
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Shen H, Green MR. A Pathway of Sequential Arginine-Serine-Rich Domain-Splicing Signal Interactions during Mammalian Spliceosome Assembly. Mol Cell 2004; 16:363-73. [PMID: 15525510 DOI: 10.1016/j.molcel.2004.10.021] [Citation(s) in RCA: 150] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2004] [Revised: 08/17/2004] [Accepted: 10/12/2004] [Indexed: 11/23/2022]
Abstract
Serine-arginine (SR) proteins are general splicing factors and can function through binding to exonic splicing enhancers (ESEs). SR proteins and several other mammalian splicing factors contain an arginine-serine-rich (RS) domain required to promote splicing. We have recently found that the ESE bound RS domain functions by contacting the branchpoint. Here, we perform RNA-protein crosslinking experiments to show that the branchpoint is sequentially contacted first in complex E by the RS domain of the essential splicing factor U2AF(65) and then in the prespliceosome by the ESE bound RS domain. Although the ESE bound RS domain can promote formation of the prespliceosome, at least one additional SR protein is required for complete spliceosome assembly. We show that the RS domain of this additional SR protein contacts the 5' splice site specifically in the mature spliceosome. We propose that direct contact with splicing signals is a general mechanism by which RS domains promote splicing.
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Affiliation(s)
- Haihong Shen
- Howard Hughes Medical Institute, Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA 01605, USA
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40
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Shen H, Kan JLC, Ghigna C, Biamonti G, Green MR. A single polypyrimidine tract binding protein (PTB) binding site mediates splicing inhibition at mouse IgM exons M1 and M2. RNA (NEW YORK, N.Y.) 2004; 10:787-94. [PMID: 15100434 PMCID: PMC1370569 DOI: 10.1261/rna.5229704] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2003] [Accepted: 01/12/2004] [Indexed: 05/03/2023]
Abstract
Splicing of mouse immunoglobulin (IgM) exons M1 and M2 is directed by two juxtaposed regulatory elements, an enhancer and an inhibitor, located within the M2 exon. A primary function of the enhancer is to counteract the inhibitor, allowing splicing to occur. Here we show that the inhibitor contains two binding sites for polypyrimidine tract binding protein (PTB). Mutational analysis indicates that only one of these sites is necessary and sufficient to direct splicing inhibition both in vitro and in vivo. We demonstrate that the difference in activity of the two sites is explained by proximity to the intron. We further show that the presence of the enhancer results in the disruption of the PTB-inhibitor interaction, enabling splicing to occur. In the absence of the enhancer, splicing can be artificially activated by immuno-inhibition of PTB. Collectively, our results indicate that a single PTB binding site can function as an inhibitor that regulates alternative splicing both in vitro and in vivo.
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Affiliation(s)
- Haihong Shen
- Howard Hughes Medical Institute, Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
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41
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Pacheco TR, Gomes AQ, Barbosa-Morais NL, Benes V, Ansorge W, Wollerton M, Smith CW, Valcárcel J, Carmo-Fonseca M. Diversity of vertebrate splicing factor U2AF35: identification of alternatively spliced U2AF1 mRNAS. J Biol Chem 2004; 279:27039-49. [PMID: 15096518 DOI: 10.1074/jbc.m402136200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
U2 small nuclear ribonucleoprotein auxiliary factor small subunit (U2AF(35)) is encoded by a conserved gene designated U2AF1. Here we provide evidence for the existence of alternative vertebrate transcripts encoding different U2AF(35) isoforms. Three mRNA isoforms (termed U2AF(35)a-c) were produced by alternative splicing of the human U2AF1 gene. U2AF(35)c contains a premature stop codon that targets the resulting mRNA to nonsense-mediated mRNA decay. U2AF(35)b differs from the previously described U2AF(35)a isoform in 7 amino acids located at the atypical RNA Recognition Motif involved in dimerization with U2AF(65). Biochemical experiments indicate that isoform U2AF(35)b, which has been highly conserved from fish to man, maintains the ability to interact with U2AF(65), stimulates U2AF(65) binding to a pre-mRNA, and promotes U2AF splicing activity in vitro. Real time, quantitative PCR analysis indicates that U2AF(35)a is the most abundant isoform expressed in murine tissues, although the ratio between U2AF(35)a and U2AF(35)b varies from 10-fold in the brain to 20-fold in skeletal muscle. We propose that post-transcriptional regulation of U2AF1 gene expression may provide a mechanism by which the relative cellular concentration and availability of U2AF(35) protein isoforms are modulated, thus contributing to the finely tuned control of splicing events in different tissues.
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Affiliation(s)
- Teresa R Pacheco
- Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, 1649-028 Lisbon, Portugal
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42
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Rhode BM, Hartmuth K, Urlaub H, Luhrmann R. Analysis of site-specific protein-RNA cross-links in isolated RNP complexes, combining affinity selection and mass spectrometry. RNA (NEW YORK, N.Y.) 2003; 9:1542-51. [PMID: 14624009 PMCID: PMC1370507 DOI: 10.1261/rna.5175703] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2003] [Accepted: 09/03/2003] [Indexed: 05/22/2023]
Abstract
An important aspect of the assembly of RNPs, and in particular of spliceosomes, is the succession of proteins bound to any given site on the RNA. Protein-RNA cross-linking is a well-established technique for investigating this, but the identification of a cross-linked protein has so far relied upon the availability of antibodies for immunoprecipitation or Western blot studies. To facilitate identification of proteins independent of these techniques, site-specific protein-RNA cross-links were purified in a large scale, which were then used for mass spectrometry (MS). This approach was carried out by the use of a minimal pre-mRNA construct containing a single photoactivatable azidophenacyl group and an adjacent biotin-dT tag for affinity purification of the cross-linked product. To test the feasibility of the method, we purified cross-links to nucleotide 9 downstream of the 5' splice site of pre-mRNA in the spliceosomal complexes A ("pre-spliceosome") and H. By this method, we were able to identify several proteins by MS; the hnRNP proteins A2/B1 were cross-linked to the pre-mRNA in complex A, and FUSE 2/FBP (a homolog of the intronic splicing enhancer KSRP) was cross-linked in complex H.
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Affiliation(s)
- Britta M Rhode
- Max Planck Institute of Biophysical Chemistry, Department of Cellular Biochemistry, Am Fassberg 11, D-37077 Göttingen, Germany
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43
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Lallena MJ, Chalmers KJ, Llamazares S, Lamond AI, Valcárcel J. Splicing regulation at the second catalytic step by Sex-lethal involves 3' splice site recognition by SPF45. Cell 2002; 109:285-96. [PMID: 12015979 DOI: 10.1016/s0092-8674(02)00730-4] [Citation(s) in RCA: 128] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Drosophila protein Sex-lethal (SXL) promotes skipping of exon 3 from its own pre-mRNA. An unusual sequence arrangement of two AG dinucleotides and an intervening polypyrimidine (Py)-tract at the 3' end of intron 2 is important for Sxl autoregulation. Here we show that U2AF interacts with the Py-tract and downstream AG, whereas the spliceosomal protein SPF45 interacts with the upstream AG and activates it for the second catalytic step of the splicing reaction. SPF45 represents a new class of second step factors, and its interaction with SXL blocks splicing at the second step. These results are in contrast with other known mechanisms of splicing regulation, which target early events of spliceosome assembly. A similar role for SPF45 is demonstrated in the activation of a cryptic 3' ss generated by a mutation that causes human beta-thalassemia.
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Affiliation(s)
- María José Lallena
- Gene Expression Programme, European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117, Heidelberg, Germany
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44
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Gangwani L, Mikrut M, Theroux S, Sharma M, Davis RJ. Spinal muscular atrophy disrupts the interaction of ZPR1 with the SMN protein. Nat Cell Biol 2001; 3:376-83. [PMID: 11283611 DOI: 10.1038/35070059] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The survival motor neurons (smn) gene in mice is essential for embryonic viability. In humans, mutation of the telomeric copy of the SMN1 gene causes spinal muscular atrophy, an autosomal recessive disease. Here we report that the SMN protein interacts with the zinc-finger protein ZPR1 and that these proteins colocalize in small subnuclear structures, including gems and Cajal bodies. SMN and ZPR1 redistribute from the cytoplasm to the nucleus in response to serum. This process is disrupted in cells from patients with Werdnig-Hoffman syndrome (spinal muscular atrophy type I) that have SMN1 mutations. Similarly, decreased ZPR1 expression prevents SMN localization to nuclear bodies. Our data show that ZPR1 is required for the localization of SMN in nuclear bodies.
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Affiliation(s)
- L Gangwani
- Program in Molecular Medicine, University of Massachussetts Medical School, 373 Plantation St, Worcester, Massachussetts 01605, USA
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45
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Melcák I, Melcáková S, Kopský V, Vecerová J, Raska I. Prespliceosomal assembly on microinjected precursor mRNA takes place in nuclear speckles. Mol Biol Cell 2001; 12:393-406. [PMID: 11179423 PMCID: PMC30951 DOI: 10.1091/mbc.12.2.393] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2000] [Revised: 11/03/2000] [Accepted: 12/19/2000] [Indexed: 11/11/2022] Open
Abstract
Nuclear speckles (speckles) represent a distinct nuclear compartment within the interchromatin space and are enriched in splicing factors. They have been shown to serve neighboring active genes as a reservoir of these factors. In this study, we show that, in HeLa cells, the (pre)spliceosomal assembly on precursor mRNA (pre-mRNA) is associated with the speckles. For this purpose, we used microinjection of splicing competent and mutant adenovirus pre-mRNAs with differential splicing factor binding, which form different (pre)spliceosomal complexes and followed their sites of accumulation. Splicing competent pre-mRNAs are rapidly targeted into the speckles, but the targeting is temperature-dependent. The polypyrimidine tract sequence is required for targeting, but, in itself, is not sufficient. The downstream flanking sequences are particularly important for the targeting of the mutant pre-mRNAs into the speckles. In supportive experiments, the behavior of the speckles was followed after the microinjection of antisense deoxyoligoribonucleotides complementary to the specific domains of snRNAs. Under these latter conditions prespliceosomal complexes are formed on endogenous pre-mRNAs. We conclude that the (pre)spliceosomal complexes on microinjected pre-mRNA are formed inside the speckles. Their targeting into and accumulation in the speckles is a result of the cumulative loading of splicing factors to the pre-mRNA and the complexes formed give rise to the speckled pattern observed.
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Affiliation(s)
- I Melcák
- Department of Cell Biology, Institute of Experimental Medicine, Academy of Sciences of Czech Republic, Prague
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46
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Abstract
In the current model for spliceosome assembly, U1 snRNP binds to the 5' splice site in the E complex followed by ATP-dependent binding of U2 snRNP to the branchpoint sequence (BPS) in the A complex. Here we report the characterization of highly purified, functional E complex. We provide evidence that this complex contains functional U2 snRNP and that this snRNP is required for E complex assembly. The BPS is not required for U2 snRNP binding in the E complex. These data suggest a model for spliceosome assembly in which U1 and U2 snRNPs first associate with the spliceosome in the E complex and then an ATP-dependent step results in highly stable U2 snRNP binding to the BPS in the A complex.
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Affiliation(s)
- R Das
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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47
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Clement JQ, Qian L, Kaplinsky N, Wilkinson MF. The stability and fate of a spliced intron from vertebrate cells. RNA (NEW YORK, N.Y.) 1999; 5:206-220. [PMID: 10024173 PMCID: PMC1369753 DOI: 10.1017/s1355838299981190] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Introns constitute most of the length of typical pre-mRNAs in vertebrate cells. Thus, the turnover rate of introns may significantly influence the availability of ribonucleotides and splicing factors for further rounds of transcription and RNA splicing, respectively. Given the importance of intron turnover, it is surprising that there have been no reports on the half-life of introns from higher eukaryotic cells. Here, we determined the stability of IVS1Cbeta1, the first intron from the constant region of the mouse T-cell receptor-beta, (TCR-beta) gene. Using a tetracycline (tet)-regulated promoter, we demonstrate that spliced IVS1Cbeta1 and its pre-mRNA had half-lives of 6.0+/-1.4 min and 3.7+/-1.0 min, respectively. We also examined the half-lives of these transcripts by using actinomycin D (Act.D). Act.D significantly stabilized IVS1Cbeta1 and its pre-mRNA, suggesting that Act.D not only blocks transcription but exerts rapid and direct posttranscriptional effects in the nucleus. We observed that in vivo spliced IVS1Cbeta1 accumulated predominantly as lariat molecules that use a consensus branchpoint nucleotide. The accumulation of IVS1Cbeta1 as a lariat did not result from an intrinsic inability to be debranched, as it could be debranched in vitro, albeit somewhat less efficiently than an adenovirus intron. Subcellular-fractionation and sucrose-gradient analyses showed that most spliced IVS1Cbeta1 lariats cofractionated with pre-mRNA, but not always with mRNA in the nucleus. Some IVS1Cbeta1 also appeared to be selectively exported to the cytoplasm, whereas TCR-beta pre-mRNA remained in the nucleus. This study constitutes the first detailed analysis of the stability and fate of a spliced nuclear intron in vivo.
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Affiliation(s)
- J Q Clement
- Department of Immunology, The University of Texas M.D. Anderson Cancer Center, Houston 77030, USA
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48
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Rimmele ME, Belasco JG. Target discrimination by RNA-binding proteins: role of the ancillary protein U2A' and a critical leucine residue in differentiating the RNA-binding specificity of spliceosomal proteins U1A and U2B". RNA (NEW YORK, N.Y.) 1998; 4:1386-96. [PMID: 9814759 PMCID: PMC1369711 DOI: 10.1017/s1355838298981171] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The spliceosomal proteins U1A and U2B" each use a homologous RRM domain to bind specifically to their respective snRNA targets, U1hpll and U2hpIV, two stem-loops that are similar yet distinct in sequence. Previous studies have shown that binding of U2B" to U2hpIV is facilitated by the ancillary protein U2A', whereas specific binding of U1A to U1hpll requires no cofactor. Here we report that U2A' enables U2B" to distinguish the loop sequence of U2hpIV from that of U1hpll but plays no role in stem sequence discrimination. Although U2A' can also promote heterospecific binding of U1A to U2hpIV, a much higher concentration of the ancillary protein is required due to the approximately 500-fold greater affinity of U2A' for U2B". Additional experiments have identified a single leucine residue in U1A(Leu-44) that is critical for the intrinsic specificity of this protein for the loop sequence of U1 hpll in preference to that of U2hpIV. Our data suggest that most of the difference in RNA-binding specificity between U1A and U2B" can be accounted for by this leucine residue and by the contribution of the ancillary protein U2A' to the specificity of U2B".
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MESH Headings
- Amino Acid Sequence
- Autoantigens
- Base Sequence
- Binding Sites
- Electrophoresis, Polyacrylamide Gel
- Humans
- Leucine/metabolism
- Molecular Sequence Data
- Mutation
- Nucleic Acid Conformation
- Phenotype
- RNA, Small Nuclear/biosynthesis
- RNA, Small Nuclear/metabolism
- RNA-Binding Proteins/biosynthesis
- RNA-Binding Proteins/metabolism
- Recombinant Fusion Proteins/biosynthesis
- Recombinant Fusion Proteins/metabolism
- Ribonucleoprotein, U1 Small Nuclear/biosynthesis
- Ribonucleoprotein, U1 Small Nuclear/chemistry
- Ribonucleoprotein, U1 Small Nuclear/metabolism
- Ribonucleoprotein, U2 Small Nuclear/biosynthesis
- Ribonucleoprotein, U2 Small Nuclear/chemistry
- Ribonucleoprotein, U2 Small Nuclear/metabolism
- Ribonucleoprotein, U2 Small Nuclear/pharmacology
- Ribonucleoprotein, U2 Small Nuclear/physiology
- Ribonucleoproteins, Small Nuclear
- Spliceosomes/metabolism
- Thermodynamics
- snRNP Core Proteins
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Affiliation(s)
- M E Rimmele
- Skirball Institute of Biomolecular Medicine and Department of Microbiology, New York University School of Medicine, New York 10016, USA
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49
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Ortlepp D, Laggerbauer B, Müllner S, Achsel T, Kirschbaum B, Lührmann R. The mammalian homologue of Prp16p is overexpressed in a cell line tolerant to Leflunomide, a new immunoregulatory drug effective against rheumatoid arthritis. RNA (NEW YORK, N.Y.) 1998; 4:1007-18. [PMID: 9701291 PMCID: PMC1369677 DOI: 10.1017/s1355838298980554] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Prp2p, Prp16p, Prp22p, and Prp43p are members of the DEAH-box family of ATP-dependent putative RNA helicases required for pre-mRNA splicing in Saccharomyces cerevisiae. Recently, mammalian homologues of Prp43p and Prp22p have been described, supporting the idea that splicing in yeast and man is phylogenetically conserved. In this study, we show that a murine cell line resistant to the novel immunoregulatory drug Leflunomide (Arava) overexpresses a 135-kDa protein that is a putative DEAH-box RNA helicase. We have cloned the human counterpart of this protein and show that it shares pronounced sequence homology with Prp16p. Apart from its N-terminal domain, which is rich in RS, RD, and RE dipeptides, this human homologue of Prp16p (designated hPrp16p) is 41% identical to Prp16p. Significantly, homology is not only observed within the phylogenetically conserved helicase domain, but also in Prp16p-specific sequences. Immunofluorescence microscopy studies demonstrated that hPrp16p co-localizes with snRNPs in subnuclear structures referred to as speckles. Antibodies specific for hPrp16p inhibited pre-mRNA splicing in vitro prior to the second step. Thus, like its yeast counterpart, hPrp16p also appears to be required for the second catalytic step of splicing. Taken together, our data indicate that the human 135-kDa protein identified here is the structural and functional homologue of the yeast putative RNA helicase, Prp16p.
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Affiliation(s)
- D Ortlepp
- HMR Deutschland GmbH Biotechnologie, Zentrum für angewandte Genomforschung, Martinsried, Germany
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50
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Smith HC. Analysis of protein complexes assembled on apolipoprotein B mRNA for mooring sequence-dependent RNA editing. Methods 1998; 15:27-39. [PMID: 9614650 DOI: 10.1006/meth.1998.0603] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Apolipoprotein B (apoB) mRNA editing involves a cytidine-to-uridine transition at a select site catalyzed by a cytidine deaminase known as APOBEC-1. This enzyme cannot edit RNA alone but acquires site-specific editing capacity in the context of additional protein factors (auxiliary proteins). These proteins are currently hypothesized to assemble with APBEC-1 as a holoenzyme complex or editosome. Auxiliary proteins are the focus of ongoing research as they presumably serve important structural and regulatory roles in the editosome. The abilities of auxiliary proteins to interact with APOBEC-1 and apoB RNA and to promote RNA editing activity are important endpoints used as proof that proteins are functionally involved in apoB RNA editing. This article reviews the discovery of the editosome and provides detailed protocols for its isolation and subfractionation.
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Affiliation(s)
- H C Smith
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, New York 14642, USA
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