1
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Asthana S, Mott J, Tong M, Pei Z, Mao Y. The Exon Junction Complex Factor RBM8A in Glial Fibrillary Acid Protein-Expressing Astrocytes Modulates Locomotion Behaviors. Cells 2024; 13:498. [PMID: 38534343 DOI: 10.3390/cells13060498] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/01/2024] [Accepted: 03/11/2024] [Indexed: 03/28/2024] Open
Abstract
The role of RNA Binding Motif Protein 8a (RBM8A), an exon junction complex (EJC) component, in neurodevelopmental disorders has been increasingly studied for its crucial role in regulating multiple levels of gene expression. It regulates mRNA splicing, translation, and mRNA degradation and influences embryonic development. RBM8A protein is expressed in both neurons and astrocytes, but little is known about RBM8A's specific role in glial fibrillary acid protein (GFAP)-positive astrocytes. To address the role of RBM8A in astrocytes, we generated a conditional heterozygous knockout (KO) mouse line of Rbm8a in astrocytes using a GFAP-cre line. We confirmed a decreased expression of RBM8A in astrocytes of heterozygous conditional KO mice via RT-PCR and Sanger sequencing, as well as qRT-PCR, immunohistochemistry, and Western blot. Interestingly, these mice exhibit significantly increased movement and mobility, alongside sex-specific altered anxiety in the open field test (OFT) and elevated plus maze (OPM) tests. These tests, along with the rotarod test, suggest that these mice have normal motor coordination but hyperactive phenotypes. In addition, the haploinsufficiency of Rbm8a in astrocytes leads to a sex-specific change in astrocyte density in the dentate gyrus. This study further reveals the contribution of Rbm8a deletion to CNS pathology, generating more insights via the glial lens of an Rbm8a model of neurodevelopmental disorder.
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Affiliation(s)
- Shravan Asthana
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
- Feinberg School of Medicine, Northwestern University, 303 East Superior Street, Chicago, IL 60611, USA
| | - Jennifer Mott
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Mabel Tong
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Zifei Pei
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Yingwei Mao
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
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2
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Kolakada D, Campbell AE, Baquero Galvis L, Li Z, Lore M, Jagannathan S. A system of reporters for comparative investigation of EJC-independent and EJC-enhanced nonsense-mediated mRNA decay. bioRxiv 2023:2023.11.14.567061. [PMID: 38014198 PMCID: PMC10680754 DOI: 10.1101/2023.11.14.567061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) is a network of pathways that degrades transcripts that undergo premature translation termination. In mammals, NMD can be divided into the exon junction complex (EJC)-enhanced and EJC-independent branches. Fluorescence- and luminescence-based reporters have long been effective tools to investigate NMD, yet existing reporters largely focus on the EJC-enhanced pathway. Here, we present a system of reporters for comparative studies of EJC-independent and EJC-enhanced NMD. This system also enables the study of NMD-associated outcomes such as premature termination codon (PTC) readthrough and truncated protein degradation. These reporters are compatible with fluorescence or luminescence-based readouts via transient transfection or stable integration. Using this reporter system, we show that EJC-enhanced NMD RNA levels are reduced by 2- or 9-fold and protein levels are reduced by 7- or 12-fold compared to EJC-independent NMD, depending on the reporter gene used. Additionally, the extent of readthrough induced by G418 and SMG1i, alone and in combination, varies across NMD substrates. When combined, G418 and SMG1i increase readthrough product levels in an additive manner for EJC-independent reporters, while EJC-enhanced reporters show a synergistic effect. We present these reporters as a valuable toolkit to deepen our understanding of NMD and its associated mechanisms.
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Affiliation(s)
- Divya Kolakada
- Molecular Biology Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Amy E. Campbell
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Laura Baquero Galvis
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Zhongyou Li
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Mlana Lore
- Molecular Biology Graduate Program, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
| | - Sujatha Jagannathan
- Department of Biochemistry and Molecular Genetics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
- RNA Bioscience Initiative, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA
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3
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McSweeney C, Chen M, Dong F, Sebastian A, Reynolds DJ, Mott J, Pei Z, Zou J, Shi Y, Mao Y. Transcriptomic Analyses of Brains of RBM8A Conditional Knockout Mice at Different Developmental Stages Reveal Conserved Signaling Pathways Contributing to Neurodevelopmental Diseases. Int J Mol Sci 2023; 24:4600. [PMID: 36902031 PMCID: PMC10003467 DOI: 10.3390/ijms24054600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 03/03/2023] Open
Abstract
RNA-binding motif 8A (RBM8A) is a core component of the exon junction complex (EJC) that binds pre-mRNAs and regulates their splicing, transport, translation, and nonsense-mediated decay (NMD). Dysfunction in the core proteins has been linked to several detriments in brain development and neuropsychiatric diseases. To understand the functional role of Rbm8a in brain development, we have generated brain-specific Rbm8a knockout mice and used next-generation RNA-sequencing to identify differentially expressed genes (DEGs) in mice with heterozygous, conditional knockout (cKO) of Rbm8a in the brain at postnatal day 17 (P17) and at embryonic day 12. Additionally, we analyzed enriched gene clusters and signaling pathways within the DEGs. At the P17 time point, between the control and cKO mice, about 251 significant DEGs were identified. At E12, only 25 DEGs were identified in the hindbrain samples. Bioinformatics analyses have revealed many signaling pathways related to the central nervous system (CNS). When E12 and P17 results were compared, three DEGs, Spp1, Gpnmb, and Top2a, appeared to peak at different developmental time points in the Rbm8a cKO mice. Enrichment analyses suggested altered activity in pathways affecting cellular proliferation, differentiation, and survival. The results support the hypothesis that loss of Rbm8a causes decreased cellular proliferation, increased apoptosis, and early differentiation of neuronal subtypes, which may lead ultimately to an altered neuronal subtype composition in the brain.
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Affiliation(s)
- Colleen McSweeney
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Miranda Chen
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Fengping Dong
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
- Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Aswathy Sebastian
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Derrick James Reynolds
- Department of Microbiology & Molecular Genetics, School of Medicine, University of California, Irvine, CA 92697, USA
| | - Jennifer Mott
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Zifei Pei
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Jizhong Zou
- Systems Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, Rockville, MD 20892, USA
| | - Yongsheng Shi
- Department of Microbiology & Molecular Genetics, School of Medicine, University of California, Irvine, CA 92697, USA
| | - Yingwei Mao
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
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4
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Uzonyi A, Dierks D, Nir R, Kwon OS, Toth U, Barbosa I, Burel C, Brandis A, Rossmanith W, Le Hir H, Slobodin B, Schwartz S. Exclusion of m6A from splice-site proximal regions by the exon junction complex dictates m6A topologies and mRNA stability. Mol Cell 2023; 83:237-251.e7. [PMID: 36599352 DOI: 10.1016/j.molcel.2022.12.026] [Citation(s) in RCA: 42] [Impact Index Per Article: 42.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 11/04/2022] [Accepted: 12/21/2022] [Indexed: 01/05/2023]
Abstract
N6-methyladenosine (m6A), a widespread destabilizing mark on mRNA, is non-uniformly distributed across the transcriptome, yet the basis for its selective deposition is unknown. Here, we propose that m6A deposition is not selective. Instead, it is exclusion based: m6A consensus motifs are methylated by default, unless they are within a window of ∼100 nt from a splice junction. A simple model which we extensively validate, relying exclusively on presence of m6A motifs and exon-intron architecture, allows in silico recapitulation of experimentally measured m6A profiles. We provide evidence that exclusion from splice junctions is mediated by the exon junction complex (EJC), potentially via physical occlusion, and that previously observed associations between exon-intron architecture and mRNA decay are mechanistically mediated via m6A. Our findings establish a mechanism coupling nuclear mRNA splicing and packaging with the covalent installation of m6A, in turn controlling cytoplasmic decay.
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Affiliation(s)
- Anna Uzonyi
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7630031, Israel
| | - David Dierks
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7630031, Israel
| | - Ronit Nir
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7630031, Israel
| | - Oh Sung Kwon
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Ursula Toth
- Center for Anatomy & Cell Biology, Medical University of Vienna, 1090 Vienna, Austria
| | - Isabelle Barbosa
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Cindy Burel
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Alexander Brandis
- Life Sciences Core Facilities, Weizmann Institute of Science, Rehovot 7630031, Israel
| | - Walter Rossmanith
- Center for Anatomy & Cell Biology, Medical University of Vienna, 1090 Vienna, Austria
| | - Hervé Le Hir
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Boris Slobodin
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7630031, Israel; Department of Biochemistry, Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa 31096, Israel.
| | - Schraga Schwartz
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 7630031, Israel.
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5
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Soederberg A, Meißgeier T, Bosserhoff AK, Linck-Paulus L. MAGOH and MAGOHB Knockdown in Melanoma Cells Decreases Nonsense-Mediated Decay Activity and Promotes Apoptosis via Upregulation of GADD45A. Cells 2022; 11:cells11233859. [PMID: 36497117 PMCID: PMC9738831 DOI: 10.3390/cells11233859] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 11/22/2022] [Accepted: 11/29/2022] [Indexed: 12/05/2022] Open
Abstract
Cutaneous malignant melanoma is a highly proliferative and aggressive skin cancer with a steadily increasing incidence and a low long-term survival rate after metastatic progression. The protein MAGOH and its highly identical homologue MAGOHB are core components of the exon junction complex (EJC), which regulates splicing, stability and translation of mRNAs. The EJC, and especially MAGOH, has been shown to be involved in the development and progression of several cancers. In melanoma, the expression and function of both homologues remain essentially unexplored. This study identifies high MAGOH and MAGOHB protein expression in cutaneous melanoma cell lines and patient derived tissue samples. An siRNA-mediated knockdown of MAGOH significantly inhibits melanoma cell proliferation. The loss of MAGOH does not affect cell cycle progression, but induces apoptosis, an effect that is enhanced by a simultaneous knockdown of MAGOH and MAGOHB. MAGOH and MAGOHB do not influence the expression of the pro-apoptotic protein Bcl-XS or exon skipping. However, the knockdown of MAGOH and MAGOHB strongly decreases nonsense-mediated decay (NMD) activity, leading to an upregulation of the pro-apoptotic protein GADD45A. In conclusion, simultaneous inhibition of MAGOH and MAGOHB expression substantially affects cell survival, indicating both MAGOH homologues as promising new targets for the treatment of melanoma.
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Affiliation(s)
- Agnes Soederberg
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Fahrstraße 17, 91054 Erlangen, Germany
| | - Tina Meißgeier
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Fahrstraße 17, 91054 Erlangen, Germany
| | - Anja Katrin Bosserhoff
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Fahrstraße 17, 91054 Erlangen, Germany
- Comprehensive Cancer Center (CCC) Erlangen-EMN, 91054 Erlangen, Germany
| | - Lisa Linck-Paulus
- Institute of Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Fahrstraße 17, 91054 Erlangen, Germany
- Correspondence:
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6
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Yi Z, Arvola RM, Myers S, Dilsavor CN, Abu Alhasan R, Carter BN, Patton RD, Bundschuh R, Singh G. Mammalian UPF3A and UPF3B can activate nonsense-mediated mRNA decay independently of their exon junction complex binding. EMBO J 2022; 41:e109202. [PMID: 35451102 PMCID: PMC9108626 DOI: 10.15252/embj.2021109202] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 03/21/2022] [Accepted: 03/31/2022] [Indexed: 12/30/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is governed by the three conserved factors-UPF1, UPF2, and UPF3. While all three are required for NMD in yeast, UPF3B is dispensable for NMD in mammals, and its paralog UPF3A is suggested to only weakly activate or even repress NMD due to its weaker binding to the exon junction complex (EJC). Here, we characterize the UPF3A/B-dependence of NMD in human cell lines deleted of one or both UPF3 paralogs. We show that in human colorectal cancer HCT116 cells, NMD can operate in a UPF3B-dependent and -independent manner. While UPF3A is almost dispensable for NMD in wild-type cells, it strongly activates NMD in cells lacking UPF3B. Notably, NMD remains partially active in cells lacking both UPF3 paralogs. Complementation studies in these cells show that EJC-binding domain of UPF3 paralogs is dispensable for NMD. Instead, the conserved "mid" domain of UPF3 paralogs is consequential for their NMD activity. Altogether, our results demonstrate that the mammalian UPF3 proteins play a more active role in NMD than simply bridging the EJC and the UPF complex.
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Affiliation(s)
- Zhongxia Yi
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.,Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA
| | - René M Arvola
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.,Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA
| | - Sean Myers
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - Corinne N Dilsavor
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA
| | - Rabab Abu Alhasan
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.,Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA
| | - Bayley N Carter
- Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA
| | - Robert D Patton
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.,Department of Physics, The Ohio State University, Columbus, OH, USA
| | - Ralf Bundschuh
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.,Department of Physics, The Ohio State University, Columbus, OH, USA.,Department of Chemistry and Biochemistry, The Ohio State University , Columbus, OH, USA.,Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH, USA
| | - Guramrit Singh
- Center for RNA Biology, The Ohio State University, Columbus, OH, USA.,Department of Molecular Genetics, The Ohio State University, Columbus, OH, USA
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7
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Ho CH, Paolantoni C, Bawankar P, Tang Z, Brown S, Roignant J, Treisman JE. An exon junction complex-independent function of Barentsz in neuromuscular synapse growth. EMBO Rep 2022; 23:e53231. [PMID: 34726300 PMCID: PMC8728599 DOI: 10.15252/embr.202153231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 10/14/2021] [Accepted: 10/15/2021] [Indexed: 01/07/2023] Open
Abstract
The exon junction complex controls the translation, degradation, and localization of spliced mRNAs, and three of its core subunits also play a role in splicing. Here, we show that a fourth subunit, Barentsz, has distinct functions within and separate from the exon junction complex in Drosophila neuromuscular development. The distribution of mitochondria in larval muscles requires Barentsz as well as other exon junction complex subunits and is not rescued by a Barentsz transgene in which residues required for binding to the core subunit eIF4AIII are mutated. In contrast, interactions with the exon junction complex are not required for Barentsz to promote the growth of neuromuscular synapses. We find that the Activin ligand Dawdle shows reduced expression in barentsz mutants and acts downstream of Barentsz to control synapse growth. Both barentsz and dawdle are required in motor neurons, muscles, and glia for normal synapse growth, and exogenous Dawdle can rescue synapse growth in the absence of barentsz. These results identify a biological function for Barentsz that is independent of the exon junction complex.
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Affiliation(s)
- Cheuk Hei Ho
- Skirball Institute for Biomolecular Medicine and Department of Cell BiologyNYU School of MedicineNew YorkNYUSA
| | - Chiara Paolantoni
- Center for Integrative Genomics, Génopode Building, Faculty of Biology and MedicineUniversity of LausanneLausanneSwitzerland
| | - Praveen Bawankar
- Institute of Pharmaceutical and Biomedical SciencesJohannes Gutenberg‐University MainzMainzGermany
| | - Zuojian Tang
- Center for Health Informatics and BioinformaticsNYU Langone Medical CenterNew YorkNYUSA
- Present address:
Computational Biology at Ridgefield US, Global Computational Biology and Digital ScienceBoehringer IngelheimRidgefieldCTUSA
| | - Stuart Brown
- Center for Health Informatics and BioinformaticsNYU Langone Medical CenterNew YorkNYUSA
- Present address:
ExxonMobil Corporate Strategic ResearchAnnandaleNJUSA
| | - Jean‐Yves Roignant
- Center for Integrative Genomics, Génopode Building, Faculty of Biology and MedicineUniversity of LausanneLausanneSwitzerland
- Institute of Pharmaceutical and Biomedical SciencesJohannes Gutenberg‐University MainzMainzGermany
| | - Jessica E Treisman
- Skirball Institute for Biomolecular Medicine and Department of Cell BiologyNYU School of MedicineNew YorkNYUSA
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8
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Patton RD, Sanjeev M, Woodward LA, Mabin JW, Bundschuh R, Singh G. Chemical crosslinking enhances RNA immunoprecipitation for efficient identification of binding sites of proteins that photo-crosslink poorly with RNA. RNA 2020; 26:1216-1233. [PMID: 32467309 PMCID: PMC7430673 DOI: 10.1261/rna.074856.120] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 05/17/2020] [Indexed: 05/14/2023]
Abstract
In eukaryotic cells, proteins that associate with RNA regulate its activity to control cellular function. To fully illuminate the basis of RNA function, it is essential to identify such RNA-associated proteins, their mode of action on RNA, and their preferred RNA targets and binding sites. By analyzing catalogs of human RNA-associated proteins defined by ultraviolet light (UV)-dependent and -independent approaches, we classify these proteins into two major groups: (i) the widely recognized RNA binding proteins (RBPs), which bind RNA directly and UV-crosslink efficiently to RNA, and (ii) a new group of RBP-associated factors (RAFs), which bind RNA indirectly via RBPs and UV-crosslink poorly to RNA. As the UV crosslinking and immunoprecipitation followed by sequencing (CLIP-seq) approach will be unsuitable to identify binding sites of RAFs, we show that formaldehyde crosslinking stabilizes RAFs within ribonucleoproteins to allow for their immunoprecipitation under stringent conditions. Using an RBP (CASC3) and an RAF (RNPS1) within the exon junction complex (EJC) as examples, we show that formaldehyde crosslinking combined with RNA immunoprecipitation in tandem followed by sequencing (xRIPiT-seq) far exceeds CLIP-seq to identify binding sites of RNPS1. xRIPiT-seq reveals that RNPS1 occupancy is increased on exons immediately upstream of strong recursively spliced exons, which depend on the EJC for their inclusion.
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Affiliation(s)
- Robert D Patton
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Manu Sanjeev
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Lauren A Woodward
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Justin W Mabin
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Ralf Bundschuh
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
- Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, Ohio 43210, USA
| | - Guramrit Singh
- Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA
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9
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Obrdlik A, Lin G, Haberman N, Ule J, Ephrussi A. The Transcriptome-wide Landscape and Modalities of EJC Binding in Adult Drosophila. Cell Rep 2020; 28:1219-1236.e11. [PMID: 31365866 DOI: 10.1016/j.celrep.2019.06.088] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Revised: 04/30/2019] [Accepted: 06/24/2019] [Indexed: 12/27/2022] Open
Abstract
Exon junction complex (EJC) assembles after splicing at specific positions upstream of exon-exon junctions in mRNAs of all higher eukaryotes, affecting major regulatory events. In mammalian cell cytoplasm, EJC is essential for efficient RNA surveillance, while in Drosophila, EJC is essential for localization of oskar mRNA. Here we developed a method for isolation of protein complexes and associated RNA targets (ipaRt) to explore the EJC RNA-binding landscape in a transcriptome-wide manner in adult Drosophila. We find the EJC at canonical positions, preferably on mRNAs from genes comprising multiple splice sites and long introns. Moreover, EJC occupancy is highest at junctions adjacent to strong splice sites, CG-rich hexamers, and RNA structures. Highly occupied mRNAs tend to be maternally localized and derive from genes involved in differentiation or development. These modalities, which have not been reported in mammals, specify EJC assembly on a biologically coherent set of transcripts in Drosophila.
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Affiliation(s)
- Ales Obrdlik
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| | - Gen Lin
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Nejc Haberman
- Department for Neuromuscular Diseases, UCL Institute of Neurology, London WC1N 3BG, UK
| | - Jernej Ule
- Department for Neuromuscular Diseases, UCL Institute of Neurology, London WC1N 3BG, UK; The Francis Crick Institute, London NW1 1AT, UK
| | - Anne Ephrussi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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10
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Kumar-Singh A, Shrinet J, Parniewska MM, Fuxe J, Dobra K, Hjerpe A. Mapping the Interactome of the Nuclear Heparan Sulfate Proteoglycan Syndecan-1 in Mesothelioma Cells. Biomolecules 2020; 10:biom10071034. [PMID: 32664515 PMCID: PMC7408266 DOI: 10.3390/biom10071034] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 07/04/2020] [Accepted: 07/08/2020] [Indexed: 01/27/2023] Open
Abstract
Syndecan-1 (SDC1) is a cell surface heparan sulfate proteoglycan (HSPG), which regulates various signaling pathways controlling the proliferation and migration of malignant mesothelioma and other types of cancer. We have previously shown that SDC1 can translocate to the nucleus in mesothelioma cells through a tubulin-dependent transport mechanism. However, the role of nuclear SDC1 is largely unknown. Here, we performed co-immunoprecipitation (Co-IP) of SDC1 in a mesothelioma cell line to identify SDC1 interacting proteins. The precipitates contained a large number of proteins, indicating the recovery of protein networks. Proteomic analysis with a focus on nuclear proteins revealed an association with pathways related to cell proliferation and RNA synthesis, splicing and transport. In support of this, the top RNA splicing candidates were verified to interact with SDC1 by Co-IP and subsequent Western blot analysis. Further loss- and gain-of-function experiments showed that SDC1 influences RNA levels in mesothelioma cells. The results identify a proteomic map of SDC1 nuclear interactors in a mesothelioma cell line and suggest a previously unknown role for SDC1 in RNA biogenesis. The results should serve as a fundament for further studies to discover the role of nuclear SDC1 in normal and cancer cells of different origin.
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Affiliation(s)
- Ashish Kumar-Singh
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, SE-14186 Stockholm, Sweden; (A.K.-S.); (J.F.); (M.M.P.); (A.H.)
| | - Jatin Shrinet
- Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA;
| | - Malgorzata Maria Parniewska
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, SE-14186 Stockholm, Sweden; (A.K.-S.); (J.F.); (M.M.P.); (A.H.)
| | - Jonas Fuxe
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, SE-14186 Stockholm, Sweden; (A.K.-S.); (J.F.); (M.M.P.); (A.H.)
| | - Katalin Dobra
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, SE-14186 Stockholm, Sweden; (A.K.-S.); (J.F.); (M.M.P.); (A.H.)
- Division of Clinical Pathology/Cytology, Karolinska University Laboratory, Karolinska University Hospital, SE-14186 Stockholm, Sweden
- Correspondence: ; Tel.:+46-8-484-1093
| | - Anders Hjerpe
- Division of Pathology, Department of Laboratory Medicine, Karolinska Institutet, SE-14186 Stockholm, Sweden; (A.K.-S.); (J.F.); (M.M.P.); (A.H.)
- Division of Clinical Pathology/Cytology, Karolinska University Laboratory, Karolinska University Hospital, SE-14186 Stockholm, Sweden
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11
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Ryu I, Won YS, Ha H, Kim E, Park Y, Kim MK, Kwon DH, Choe J, Song HK, Jung H, Kim YK. eIF4A3 Phosphorylation by CDKs Affects NMD during the Cell Cycle. Cell Rep 2019; 26:2126-2139.e9. [PMID: 30784594 DOI: 10.1016/j.celrep.2019.01.101] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 10/16/2018] [Accepted: 01/25/2019] [Indexed: 12/24/2022] Open
Abstract
Exon junction complexes (EJCs) loaded onto spliced mRNAs during splicing serve as molecular markers for various post-transcriptional gene-regulatory processes, including nonsense-mediated mRNA decay (NMD). Although the composition and structure of EJCs are well characterized, the mechanism regulating EJC deposition remains unknown. Here we find that threonine 163 (T163) within the RNA-binding motif of eIF4A3 (a core EJC component) is phosphorylated by cyclin-dependent protein kinases 1 and 2 in a cell cycle-dependent manner. T163 phosphorylation hinders binding of eIF4A3 to spliced mRNAs and other EJC components. Instead, it promotes association of eIF4A3 with CWC22, which guides eIF4A3 to an active spliceosome. These molecular events ensure the fidelity of specific deposition of the EJC ∼20-24 nt upstream of an exon-exon junction. Accordingly, NMD is affected by T163 phosphorylation. Collectively, our data provide evidence that T163 phosphorylation affects EJC formation and, consequently, NMD efficiency in a cell cycle-dependent manner.
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12
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Boussion S, Escande F, Jourdain AS, Smol T, Brunelle P, Duhamel C, Alembik Y, Attié-Bitach T, Baujat G, Bazin A, Bonnière M, Carassou P, Carles D, Devisme L, Goizet C, Goldenberg A, Grotto S, Guichet A, Jouk PS, Loeuillet L, Mechler C, Michot C, Pelluard F, Putoux A, Whalen S, Ghoumid J, Manouvrier-Hanu S, Petit F. TAR syndrome: Clinical and molecular characterization of a cohort of 26 patients and description of novel noncoding variants of RBM8A. Hum Mutat 2020; 41:1220-1225. [PMID: 32227665 DOI: 10.1002/humu.24021] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 02/18/2020] [Accepted: 03/22/2020] [Indexed: 11/07/2022]
Abstract
Thrombocytopenia-absent radius (TAR) syndrome is characterized by radial defect and neonatal thrombocytopenia. It is caused by biallelic variants of RBM8A gene (1q21.1) with the association of a null allele and a hypomorphic noncoding variant. RBM8A encodes Y14, a core protein of the exon junction complex involved in messenger RNA maturation. To date, only two hypomorphic variants have been identified. We report on a cohort of 26 patients affected with TAR syndrome and carrying biallelic variants in RBM8A. Half patients carried a 1q21.1 deletion and one of the two known hypomorphic variants. Four novel noncoding variants of RBM8A were identified in the remaining patients. We developed experimental models enabling their functional characterization in vitro. Two variants, located respectively in the 5'-untranslated region (5'-UTR) and 3'-UTR regions, are responsible for a diminished expression whereas two intronic variants alter splicing. Our results bring new insights into the molecular knowledge of TAR syndrome and enabled us to propose genetic counseling for patients' families.
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Affiliation(s)
- Simon Boussion
- Clinical Genetics Department, Reference Center for Developmental Anomalies, CHU Lille, Lille, France
- EA7364-RADEME, Lille University, Lille, France
| | - Fabienne Escande
- EA7364-RADEME, Lille University, Lille, France
- Biochemistry and Molecular Oncology Laboratory, CHU Lille, Lille, France
| | - Anne-Sophie Jourdain
- EA7364-RADEME, Lille University, Lille, France
- Biochemistry and Molecular Oncology Laboratory, CHU Lille, Lille, France
| | - Thomas Smol
- EA7364-RADEME, Lille University, Lille, France
- Medical Genetics Department, CHU Lille, Lille, France
| | - Perrine Brunelle
- EA7364-RADEME, Lille University, Lille, France
- Biochemistry and Molecular Oncology Laboratory, CHU Lille, Lille, France
| | | | - Yves Alembik
- Medical Genetics Department, CHU Strasbourg, Strasbourg, France
| | - Tania Attié-Bitach
- Histology, Embryology and Cytogenetics Department, Necker-Enfants Malades Hospital, AP-HP, Paris, France
| | - Geneviève Baujat
- Clinical Genetics Department, Necker-Enfants Malades Hospital, AP-HP, INSERM UMR, IMAGINE Institute, Paris, France
| | - Anne Bazin
- Antenatal Diagnosis Department, René Dubois Hospital, Pontoise, France
| | - Maryse Bonnière
- Histology, Embryology and Cytogenetics Department, Necker-Enfants Malades Hospital, AP-HP, Paris, France
| | | | | | - Louise Devisme
- EA7364-RADEME, Lille University, Lille, France
- Anatomo-Pathology Institute, CHU Lille, Lille, France
| | - Cyril Goizet
- Medical Genetics Department, CHU Bordeaux, MRGM Laboratory, INSERM, Bordeaux University, Bordeaux, France
| | - Alice Goldenberg
- Genetics Department, Reference Center for Developmental Anomalies, CHU Rouen, Rouen, France
| | - Sarah Grotto
- Genetics Department, Robert Debré Hospital, AP-HP, Paris, France
| | | | | | | | - Charlotte Mechler
- Foetopathology Department, Robert Debré Hospital, AP-HP, Paris, France
| | - Caroline Michot
- Clinical Genetics Department, Necker-Enfants Malades Hospital, AP-HP, INSERM UMR, IMAGINE Institute, Paris, France
| | - Fanny Pelluard
- INSERM U1053-UMR BaRITOn, Foetopathology Department, Pellegrin Hospital, CHU Bordeaux, Bordeaux, France
| | - Audrey Putoux
- Genetics Department, Hospices Civils de Lyon, Lyon, France
- GENDEV Team, CRNL, INSERM U1028, CNRS UMR 5292, UCBL1, Lyon, France
| | - Sandra Whalen
- Clinical Genetics, Reference Center for Developmental Anomalies, Armand Trousseau Hospital, AP-HP, Paris, France
| | - Jamal Ghoumid
- Clinical Genetics Department, Reference Center for Developmental Anomalies, CHU Lille, Lille, France
- EA7364-RADEME, Lille University, Lille, France
| | - Sylvie Manouvrier-Hanu
- Clinical Genetics Department, Reference Center for Developmental Anomalies, CHU Lille, Lille, France
- EA7364-RADEME, Lille University, Lille, France
| | - Florence Petit
- Clinical Genetics Department, Reference Center for Developmental Anomalies, CHU Lille, Lille, France
- EA7364-RADEME, Lille University, Lille, France
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13
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Zou D, Li R, Huang X, Chen G, Liu Y, Meng Y, Wang Y, Wu Y, Mao Y. Identification of molecular correlations of RBM8A with autophagy in Alzheimer's disease. Aging (Albany NY) 2019; 11:11673-11685. [PMID: 31816601 PMCID: PMC6932873 DOI: 10.18632/aging.102571] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 11/23/2019] [Indexed: 01/09/2023]
Abstract
Our previous studies revealed RBM8A may play a role in various progressive neurological diseases. The present study aimed to explore the role of RBM8A in Alzheimer's disease (AD). RBM8A is significantly down-regulated in AD. Interestingly, 9186 differentially expressed genes are overlapped from comparisons of AD versus control and RBM8A-low versus RBM8A-high. Weight gene correlation analysis was performed and 9 functional modules were identified. Modules positively correlated with AD and RBM8A-low are significantly involved in the RAP1 signaling pathway, PI3K−AKT signaling pathway, hematopoietic cell lineage, autophagy and APELIN signaling pathway. Fifteen genes (RBM8A, RHBDF2, TNFRSF10B, ACP1, ANKRD39, CA10, CAMK4, CBLN4, LOC284214, NOVA1, PAK1, PPEF1, RGS4, TCEB1 and TMEM118) are identified as hub genes, and the hub gene-based LASSO model can accurately predict the occurrence of AD (AUC = 0.948). Moreover, the RBM8A-module-pathway network was constructed, and low expression of RBM8A down-regulates multiple module genes, including FIP200, Beclin 1, NRBF2, VPS15 and ATG12, which composes key complexes of autophagy. Thus, our study supports that low expression of RBM8A correlates with the decrease of the components of key complexes in autophagy, which could potentially contribute to pathophysiological changes of AD.
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Affiliation(s)
- Donghua Zou
- Department of Neurology, The Fifth Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530022, China
| | - Rongjie Li
- Department of Neurology, The Fifth Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530022, China
| | - Xiaohua Huang
- Department of Neurology, Affiliated Hospital of Youjiang Medical University for Nationalities, Baise 533000, China
| | - Guoying Chen
- Department of Neurology, The Fifth Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530022, China
| | - Ying Liu
- Department of Neurology, The Fifth Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530022, China
| | - Youshi Meng
- Department of Neurology, The Fifth Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530022, China
| | - Yimei Wang
- Department of Neurology, The Fifth Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530022, China
| | - Yuan Wu
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi 530021, China
| | - Yingwei Mao
- Department of Biology, Pennsylvania State University, University Park, PA 16802, USA
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14
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Kishor A, Fritz SE, Hogg JR. Nonsense-mediated mRNA decay: The challenge of telling right from wrong in a complex transcriptome. Wiley Interdiscip Rev RNA 2019; 10:e1548. [PMID: 31131562 DOI: 10.1002/wrna.1548] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 05/01/2019] [Accepted: 05/07/2019] [Indexed: 12/18/2022]
Abstract
The nonsense-mediated mRNA decay pathway selects and degrades its targets using a dense network of RNA-protein and protein-protein interactions. Together, these interactions allow the pathway to collect copious information about the translating mRNA, including translation termination status, splice junction positions, mRNP composition, and 3'UTR length and structure. The core NMD machinery, centered on the RNA helicase UPF1, integrates this information to determine the efficiency of decay. A picture of NMD is emerging in which many factors contribute to the dynamics of decay complex assembly and disassembly, thereby influencing the probability of decay. The ability of the NMD pathway to recognize mRNP features of diverse potential substrates allows it to simultaneously perform quality control and regulatory functions. In vertebrates, increased transcriptome complexity requires balance between these two functions since high NMD efficiency is desirable for maintenance of quality control fidelity but may impair expression of normal mRNAs. NMD has adapted to this challenge by employing mechanisms to enhance identification of certain potential substrates, while using sequence-specific RNA-binding proteins to shield others from detection. These elaborations on the conserved NMD mechanism permit more sensitive post-transcriptional gene regulation but can have severe deleterious consequences, including the failure to degrade pathogenic aberrant mRNAs in many B cell lymphomas. This article is categorized under: RNA Evolution and Genomics > RNA and Ribonucleoprotein Evolution RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Turnover and Surveillance > Turnover/Surveillance Mechanisms.
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Affiliation(s)
- Aparna Kishor
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Sarah E Fritz
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - J Robert Hogg
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
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15
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Gauvin TJ, Han B, Sun MJ, Griffin EE. PIE-1 Translation in the Germline Lineage Contributes to PIE-1 Asymmetry in the Early Caenorhabditis elegans Embryo. G3 (Bethesda) 2018; 8:3791-801. [PMID: 30279189 DOI: 10.1534/g3.118.200744] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the C. elegans embryo, the germline lineage is established through successive asymmetric cell divisions that each generate a somatic and a germline daughter cell. PIE-1 is an essential maternal factor that is enriched in embryonic germline cells and is required for germline specification. We estimated the absolute concentration of PIE-1::GFP in germline cells and find that PIE-1::GFP concentration increases by roughly 4.5 fold, from 92 nM to 424 nM, between the 1 and 4-cell stages. Previous studies have shown that the preferential inheritance of PIE-1 by germline daughter cells and the degradation of PIE-1 in somatic cells are important for PIE-1 enrichment in germline cells. In this study, we provide evidence that the preferential translation of maternal PIE-1::GFP transcripts in the germline also contributes to PIE-1::GFP enrichment. Through an RNAi screen, we identified Y14 and MAG-1 (Drosophila tsunagi and mago nashi) as regulators of embryonic PIE-1::GFP levels. We show that Y14 and MAG-1 do not regulate PIE-1 degradation, segregation or synthesis in the early embryo, but do regulate the concentration of maternally-deposited PIE-1::GFP. Taken together, or findings point to an important role for translational control in the regulation of PIE-1 levels in the germline lineage.
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16
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Mabin JW, Woodward LA, Patton RD, Yi Z, Jia M, Wysocki VH, Bundschuh R, Singh G. The Exon Junction Complex Undergoes a Compositional Switch that Alters mRNP Structure and Nonsense-Mediated mRNA Decay Activity. Cell Rep 2018; 25:2431-2446.e7. [PMID: 30466796 DOI: 10.1016/j.celrep.2018.11.046] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Revised: 09/22/2018] [Accepted: 11/12/2018] [Indexed: 01/08/2023] Open
Abstract
The exon junction complex (EJC) deposited upstream of mRNA exon junctions shapes structure, composition, and fate of spliced mRNA ribonucleoprotein particles (mRNPs). To achieve this, the EJC core nucleates assembly of a dynamic shell of peripheral proteins that function in diverse post-transcriptional processes. To illuminate consequences of EJC composition change, we purified EJCs from human cells via peripheral proteins RNPS1 and CASC3. We show that the EJC originates as an SR-rich mega-dalton-sized RNP that contains RNPS1 but lacks CASC3. Sometime before or during translation, the EJC undergoes compositional and structural remodeling into an SR-devoid monomeric complex that contains CASC3. Surprisingly, RNPS1 is important for nonsense-mediated mRNA decay (NMD) in general, whereas CASC3 is needed for NMD of only select mRNAs. The switch to CASC3-EJC slows down NMD. Overall, the EJC compositional switch dramatically alters mRNP structure and specifies two distinct phases of EJC-dependent NMD.
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Affiliation(s)
- Justin W Mabin
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA; Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Lauren A Woodward
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA; Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Robert D Patton
- Department of Physics, The Ohio State University, Columbus, OH 43210, USA; Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Zhongxia Yi
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA; Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Mengxuan Jia
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Vicki H Wysocki
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Ralf Bundschuh
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Department of Physics, The Ohio State University, Columbus, OH 43210, USA; Division of Hematology, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA; Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Guramrit Singh
- Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA; Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
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17
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Blazquez L, Emmett W, Faraway R, Pineda JMB, Bajew S, Gohr A, Haberman N, Sibley CR, Bradley RK, Irimia M, Ule J. Exon Junction Complex Shapes the Transcriptome by Repressing Recursive Splicing. Mol Cell 2018; 72:496-509.e9. [PMID: 30388411 PMCID: PMC6224609 DOI: 10.1016/j.molcel.2018.09.033] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Revised: 08/24/2018] [Accepted: 09/27/2018] [Indexed: 01/13/2023]
Abstract
Recursive splicing (RS) starts by defining an "RS-exon," which is then spliced to the preceding exon, thus creating a recursive 5' splice site (RS-5ss). Previous studies focused on cryptic RS-exons, and now we find that the exon junction complex (EJC) represses RS of hundreds of annotated, mainly constitutive RS-exons. The core EJC factors, and the peripheral factors PNN and RNPS1, maintain RS-exon inclusion by repressing spliceosomal assembly on RS-5ss. The EJC also blocks 5ss located near exon-exon junctions, thus repressing inclusion of cryptic microexons. The prevalence of annotated RS-exons is high in deuterostomes, while the cryptic RS-exons are more prevalent in Drosophila, where EJC appears less capable of repressing RS. Notably, incomplete repression of RS also contributes to physiological alternative splicing of several human RS-exons. Finally, haploinsufficiency of the EJC factor Magoh in mice is associated with skipping of RS-exons in the brain, with relevance to the microcephaly phenotype and human diseases.
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Affiliation(s)
- Lorea Blazquez
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK; The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
| | - Warren Emmett
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK; The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK; University College London Genetics Institute, Gower Street, London WC1E 6BT, UK
| | - Rupert Faraway
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK; The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Jose Mario Bello Pineda
- Computational Biology Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA; Medical Scientist Training Program, University of Washington, Seattle, WA 98195, USA
| | - Simon Bajew
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Andre Gohr
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Nejc Haberman
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK; The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Christopher R Sibley
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Robert K Bradley
- Computational Biology Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA 98109, USA; Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Manuel Irimia
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Jernej Ule
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK; The Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK.
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18
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Abstract
The nonsense-mediated mRNA decay (NMD) pathway detects aberrant transcripts containing premature termination codons (PTCs) and regulates expression of 5–10% of non-aberrant human mRNAs. To date, most proteins involved in NMD have been identified by genetic screens in model organisms; however, the increased complexity of gene expression regulation in human cells suggests that additional proteins may participate in the human NMD pathway. To identify proteins required for NMD, we performed a genome-wide RNAi screen against >21,000 genes. Canonical members of the NMD pathway were highly enriched as top hits in the siRNA screen, along with numerous candidate NMD factors, including the conserved ICE1/KIAA0947 protein. RNAseq studies reveal that depletion of ICE1 globally enhances accumulation and stability of NMD-target mRNAs. Further, our data suggest that ICE1 uses a putative MIF4G domain to interact with exon junction complex (EJC) proteins and promotes the association of the NMD protein UPF3B with the EJC. The DNA in our cells contains the hereditary information that makes each of us unique. Molecules called mRNAs are copies of this information and are used as templates for making proteins. When a strand of incorrectly copied mRNA, or one including errors from the original DNA template, is recognized, our cells destroy the mRNA to prevent it from producing a damaged protein. Organisms from yeast to humans have evolved a mechanism for finding and destroying faulty mRNAs, called mRNA surveillance. Animals are particularly reliant on mRNA surveillance, as their proteins are often made from cutting and pasting together mRNA from different portions of DNA, in a process known as splicing. Despite being a vital process, we still lack a good understanding of how mRNA surveillance works. Now, Baird et al. used human kidney cells that produced an error-containing mRNA that could be tracked. To investigate how efficient RNA surveillance is under different conditions, the levels of individual proteins were reduced one at a time. By tracking the amount of faulty mRNA, it was possible to find out if a single protein plays a role in human mRNA surveillance. If the number of faulty mRNAs is high when a protein is reduced, it suggests that this protein may be involved in mRNA surveillance. Baird et al. screened more than 21,000 proteins, the majority of proteins made in human cells. Many of the proteins that stood out as important in mRNA surveillance were the ones already known to be relevant in yeast and worm cells. But the experiments also identified new proteins that appear to play a role specifically in human RNA surveillance. One of the proteins, ICE1, is essential for the relationship between mRNA splicing and mRNA surveillance. Without ICE1, the mRNA surveillance machinery can no longer find and destroy faulty mRNAs. Nearly one-third of genetic diseases are caused by mutations that result in faulty mRNAs, which can be detected by mRNA surveillance pathways. Depending on the disease, destroying these error-containing mRNAs can either improve or worsen disease symptoms. A better understanding of the factors that control human RNA surveillance could one day help to develop treatments that affect mRNA surveillance to improve disease outcomes.
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Affiliation(s)
- Thomas D Baird
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Ken Chih-Chien Cheng
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, United States
| | - Yu-Chi Chen
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, United States
| | - Eugen Buehler
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, United States
| | - Scott E Martin
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, United States
| | - James Inglese
- National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, United States
| | - J Robert Hogg
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
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19
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Wang DO, Ninomiya K, Mori C, Koyama A, Haan M, Kitabatake M, Hagiwara M, Chida K, Takahashi SI, Ohno M, Kataoka N. Transport Granules Bound with Nuclear Cap Binding Protein and Exon Junction Complex Are Associated with Microtubules and Spatially Separated from eIF4E Granules and P Bodies in Human Neuronal Processes. Front Mol Biosci 2017; 4:93. [PMID: 29312956 PMCID: PMC5744441 DOI: 10.3389/fmolb.2017.00093] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 12/15/2017] [Indexed: 02/05/2023] Open
Abstract
RNA transport and regulated local translation play critically important roles in spatially restricting gene expression in neurons. Heterogeneous population of RNA granules serve as motile units to translocate, store, translate, and degrade mRNAs in the dendrites contain cis-elements and trans-acting factors such as RNA-binding proteins and microRNAs to convey stimulus-, transcript-specific local translation. Here we report a class of mRNA granules in human neuronal processes that are enriched in the nuclear cap-binding protein complex (CBC) and exon junction complex (EJC) core components, Y14 and eIF4AIII. These granules are physically associated with stabilized microtubules and are spatially segregated from eIF4E-enriched granules and P-bodies. The existence of mRNAs retaining both nuclear cap binding protein and EJC in the distal sites of neuronal processes suggests that some localized mRNAs have not yet undergone the “very first translation,” which contribute to the spatio-temporal regulation of gene expression.
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Affiliation(s)
- Dan O Wang
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan.,K-CONNEX (Keihanshin Consortium for Fostering Next Generation of Global Leaders in Research), Kyoto, Japan
| | - Kensuke Ninomiya
- Institute for Virus research, Kyoto University, Kyoto, Japan.,Laboratory of Anatomy and Developmental Biology, Kyoto University School of Medicine, Kyoto, Japan
| | - Chihiro Mori
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan
| | - Ayako Koyama
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan
| | - Martine Haan
- Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, Japan
| | | | - Masatoshi Hagiwara
- Laboratory of Anatomy and Developmental Biology, Kyoto University School of Medicine, Kyoto, Japan
| | - Kazuhiro Chida
- Laboratory of Cell Regulation, Departments of Applied Animal Sciences and Applied Biological Chemistry Graduate School of Agriculture and Life Sciences, The University of Tokyo, Kyoto, Japan
| | - Shin-Ichiro Takahashi
- Laboratory of Cell Regulation, Departments of Applied Animal Sciences and Applied Biological Chemistry Graduate School of Agriculture and Life Sciences, The University of Tokyo, Kyoto, Japan
| | - Mutsuhito Ohno
- Institute for Virus research, Kyoto University, Kyoto, Japan
| | - Naoyuki Kataoka
- Institute for Virus research, Kyoto University, Kyoto, Japan.,Laboratory of Anatomy and Developmental Biology, Kyoto University School of Medicine, Kyoto, Japan.,Laboratory of Cell Regulation, Departments of Applied Animal Sciences and Applied Biological Chemistry Graduate School of Agriculture and Life Sciences, The University of Tokyo, Kyoto, Japan.,Medical Innovation Center, Laboratory for Malignancy Control Research, Kyoto University Graduate School of Medicine, Kyoto, Japan.,Medical Top Track Program, Medical Research Institute, Tokyo Dental and Medical University, Tokyo, Japan
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20
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Garcia-Garcia E, Little JC, Kalderon D. The Exon Junction Complex and Srp54 Contribute to Hedgehog Signaling via ci RNA Splicing in Drosophila melanogaster. Genetics 2017; 206:2053-68. [PMID: 28637711 DOI: 10.1534/genetics.117.202457] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Hedgehog (Hh) regulates the Cubitus interruptus (Ci) transcription factor in Drosophila melanogaster by activating full-length Ci-155 and blocking processing to the Ci-75 repressor. However, the interplay between the regulation of Ci-155 levels and activity, as well as processing-independent mechanisms that affect Ci-155 levels, have not been explored extensively. Here, we identified Mago Nashi (Mago) and Y14 core Exon Junction Complex (EJC) proteins, as well as the Srp54 splicing factor, as modifiers of Hh pathway activity under sensitized conditions. Mago inhibition reduced Hh pathway activity by altering the splicing pattern of ci to reduce Ci-155 levels. Srp54 inhibition also affected pathway activity by reducing ci RNA levels but additionally altered Ci-155 levels and activity independently of ci splicing. Further tests using ci transgenes and ci mutations confirmed evidence from studying the effects of Mago and Srp54 that relatively small changes in the level of Ci-155 primary translation product alter Hh pathway activity under a variety of sensitized conditions. We additionally used ci transgenes lacking intron sequences or the presumed translation initiation codon for an alternatively spliced ci RNA to provide further evidence that Mago acts principally by modulating the levels of the major ci RNA encoding Ci-155, and to show that ci introns are necessary to support the production of sufficient Ci-155 for robust Hh signaling and may also be important mediators of regulatory inputs.
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21
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Cenik C, Chua HN, Singh G, Akef A, Snyder MP, Palazzo AF, Moore MJ, Roth FP. A common class of transcripts with 5'-intron depletion, distinct early coding sequence features, and N1-methyladenosine modification. RNA 2017; 23:270-283. [PMID: 27994090 PMCID: PMC5311483 DOI: 10.1261/rna.059105.116] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2016] [Accepted: 12/14/2016] [Indexed: 06/01/2023]
Abstract
Introns are found in 5' untranslated regions (5'UTRs) for 35% of all human transcripts. These 5'UTR introns are not randomly distributed: Genes that encode secreted, membrane-bound and mitochondrial proteins are less likely to have them. Curiously, transcripts lacking 5'UTR introns tend to harbor specific RNA sequence elements in their early coding regions. To model and understand the connection between coding-region sequence and 5'UTR intron status, we developed a classifier that can predict 5'UTR intron status with >80% accuracy using only sequence features in the early coding region. Thus, the classifier identifies transcripts with 5' proximal-intron-minus-like-coding regions ("5IM" transcripts). Unexpectedly, we found that the early coding sequence features defining 5IM transcripts are widespread, appearing in 21% of all human RefSeq transcripts. The 5IM class of transcripts is enriched for non-AUG start codons, more extensive secondary structure both preceding the start codon and near the 5' cap, greater dependence on eIF4E for translation, and association with ER-proximal ribosomes. 5IM transcripts are bound by the exon junction complex (EJC) at noncanonical 5' proximal positions. Finally, N1-methyladenosines are specifically enriched in the early coding regions of 5IM transcripts. Taken together, our analyses point to the existence of a distinct 5IM class comprising ∼20% of human transcripts. This class is defined by depletion of 5' proximal introns, presence of specific RNA sequence features associated with low translation efficiency, N1-methyladenosines in the early coding region, and enrichment for noncanonical binding by the EJC.
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Affiliation(s)
- Can Cenik
- Department of Genetics, Stanford University School of Medicine, Stanford, California 94305, USA
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Hon Nian Chua
- Donnelly Centre, Department of Molecular Genetics, and Department of Computer Science, University of Toronto, Toronto M5S 3E1, Ontario, Canada
- Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, Toronto M5G 1X5, Ontario, Canada
- DataRobot, Inc., Boston, Massachusetts 02109, USA
| | - Guramrit Singh
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
- Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Abdalla Akef
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Michael P Snyder
- Department of Genetics, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Alexander F Palazzo
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Melissa J Moore
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
- Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Frederick P Roth
- Donnelly Centre, Department of Molecular Genetics, and Department of Computer Science, University of Toronto, Toronto M5S 3E1, Ontario, Canada
- Lunenfeld-Tanenbaum Research Institute, Mt. Sinai Hospital, Toronto M5G 1X5, Ontario, Canada
- Center for Cancer Systems Biology (CCSB), Dana-Farber Cancer Institute, Boston 02215, Massachusetts, USA
- The Canadian Institute for Advanced Research, Toronto M5G 1Z8, Ontario, Canada
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22
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Rodor J, Pan Q, Blencowe BJ, Eyras E, Cáceres JF. The RNA-binding profile of Acinus, a peripheral component of the exon junction complex, reveals its role in splicing regulation. RNA 2016; 22:1411-26. [PMID: 27365209 PMCID: PMC4986896 DOI: 10.1261/rna.057158.116] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 05/24/2016] [Indexed: 05/21/2023]
Abstract
Acinus (apoptotic chromatin condensation inducer in the nucleus) is an RNA-binding protein (RBP) originally identified for its role in apoptosis. It was later found to be an auxiliary component of the exon junction complex (EJC), which is deposited at exon junctions as a consequence of pre-mRNA splicing. To uncover the cellular functions of Acinus and investigate its role in splicing, we mapped its endogenous RNA targets using the cross-linking immunoprecipitation protocol (iCLIP). We observed that Acinus binds to pre-mRNAs, associating specifically to a subset of suboptimal introns, but also to spliced mRNAs. We also confirmed the presence of Acinus as a peripheral factor of the EJC. RNA-seq was used to investigate changes in gene expression and alternative splicing following siRNA-mediated depletion of Acinus in HeLa cells. This analysis revealed that Acinus is preferentially required for the inclusion of specific alternative cassette exons and also controls the faithful splicing of a subset of introns. Moreover, a large number of splicing changes can be related to Acinus binding, suggesting a direct role of Acinus in exon and intron definition. In particular, Acinus regulates the splicing of DFFA/ICAD transcript, a major regulator of DNA fragmentation. Globally, the genome-wide identification of RNA targets of Acinus revealed its role in splicing regulation as well as its involvement in other cellular pathways, including cell cycle progression. Altogether, this study uncovers new cellular functions of an RBP transiently associated with the EJC.
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Affiliation(s)
- Julie Rodor
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
| | - Qun Pan
- Donnelly Centre, University of Toronto, Toronto, Ontario M5S 3E1, Canada
| | - Benjamin J Blencowe
- Donnelly Centre, University of Toronto, Toronto, Ontario M5S 3E1, Canada Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Eduardo Eyras
- Universitat Pompeu Fabra, E08003, Barcelona, Spain Catalan Institution for Research and Advanced Studies (ICREA), E08010 Barcelona, Spain
| | - Javier F Cáceres
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, United Kingdom
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23
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Marayati BF, Hoskins V, Boger RW, Tucker JF, Fishman ES, Bray AS, Zhang K. The fission yeast MTREC and EJC orthologs ensure the maturation of meiotic transcripts during meiosis. RNA 2016; 22:1349-59. [PMID: 27365210 PMCID: PMC4986891 DOI: 10.1261/rna.055608.115] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 05/21/2016] [Indexed: 06/06/2023]
Abstract
Meiosis is a highly regulated process by which genetic information is transmitted through sexual reproduction. It encompasses unique mechanisms that do not occur in vegetative cells, producing a distinct, well-regulated meiotic transcriptome. During vegetative growth, many meiotic genes are constitutively transcribed, but most of the resulting mRNAs are rapidly eliminated by the Mmi1-MTREC (Mtl1-Red1 core) complex. While Mmi1-MTREC targets premature meiotic RNAs for degradation by the nuclear 3'-5' exoribonuclease exosome during mitotic growth, its role in meiotic gene expression during meiosis is not known. Here, we report that Red5, an essential MTREC component, interacts with pFal1, an ortholog of eukaryotic translation initiation factor eIF4aIII in the fission yeast Schizosaccharomyces pombe In mammals, together with MAGO (Mnh1), Rnps1, and Y14, elF4AIII (pFal1) forms the core of the exon junction complex (EJC), which is essential for transcriptional surveillance and localization of mature mRNAs. In fission yeast, two EJC orthologs, pFal1 and Mnh1, are functionally connected with MTREC, specifically in the process of meiotic gene expression during meiosis. Although pFal1 interacts with Mnh1, Y14, and Rnps1, its association with Mnh1 is not disrupted upon loss of Y14 or Rnps1. Mutations of Red1, Red5, pFal1, or Mnh1 produce severe meiotic defects; the abundance of meiotic transcripts during meiosis decreases; and mRNA maturation processes such as splicing are impaired. Since studying meiosis in mammalian germline cells is difficult, our findings in fission yeast may help to define the general mechanisms involved in accurate meiotic gene expression in higher eukaryotes.
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Affiliation(s)
- Bahjat Fadi Marayati
- Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106, USA
| | - Victoria Hoskins
- Program of Human Genetics, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA
| | - Robert W Boger
- Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106, USA
| | - James F Tucker
- Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106, USA
| | - Emily S Fishman
- Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106, USA
| | - Andrew S Bray
- Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106, USA
| | - Ke Zhang
- Department of Biology and Center for Molecular Communication and Signaling, Wake Forest University, Winston-Salem, North Carolina 27106, USA
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24
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Liu M, Li Y, Liu A, Li R, Su Y, Du J, Li C, Zhu AJ. The exon junction complex regulates the splicing of cell polarity gene dlg1 to control Wingless signaling in development. eLife 2016; 5. [PMID: 27536874 PMCID: PMC5008907 DOI: 10.7554/elife.17200] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2016] [Accepted: 08/14/2016] [Indexed: 12/22/2022] Open
Abstract
Wingless (Wg)/Wnt signaling is conserved in all metazoan animals and plays critical roles in development. The Wg/Wnt morphogen reception is essential for signal activation, whose activity is mediated through the receptor complex and a scaffold protein Dishevelled (Dsh). We report here that the exon junction complex (EJC) activity is indispensable for Wg signaling by maintaining an appropriate level of Dsh protein for Wg ligand reception in Drosophila. Transcriptome analyses in Drosophila wing imaginal discs indicate that the EJC controls the splicing of the cell polarity gene discs large 1 (dlg1), whose coding protein directly interacts with Dsh. Genetic and biochemical experiments demonstrate that Dlg1 protein acts independently from its role in cell polarity to protect Dsh protein from lysosomal degradation. More importantly, human orthologous Dlg protein is sufficient to promote Dvl protein stabilization and Wnt signaling activity, thus revealing a conserved regulatory mechanism of Wg/Wnt signaling by Dlg and EJC. DOI:http://dx.doi.org/10.7554/eLife.17200.001 Animal development involves different signaling pathways that coordinate complex behaviors of the cells, such as changes in cell number or cell shape. One such pathway involves a protein called Wingless/Wnt, which controls cell fate and growth and is also involved in tumor formation in humans. In recent decades, scientists have made a lot of progress in understanding how this signaling pathway operates. However, it is not well understood how the Wingless/Wnt signaling pathway interacts with other regulatory networks during development. Now, Liu, Li et al. unveil a new regulatory network that controls the Wingless/Wnt pathway in fruit flies and in mammalian cells grown in the laboratory. The experiments show that an RNA binding protein family named the Exon Junction Complex positively regulates a protein called Dishevelled, which serves as a hub in the Wingless/Wnt pathway. The Exon Junction Complex keeps the amount of Dishevelled protein in check via an interaction with another protein referred to as Discs large. Further experiments indicated that Discs large binds to and protects Dishevelled from being degraded inside the cell. Liu et al.'s findings highlight a new control mechanism for the Wingless/Wnt signaling pathway. In the future, the findings may also aid the development of new approaches to prevent or treat birth defects and cancer. DOI:http://dx.doi.org/10.7554/eLife.17200.002
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Affiliation(s)
- Min Liu
- State Key Laboratory of Membrane Biology and Minstry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing, China.,School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisplinary Studies, Peking University, Beijing, China
| | - Yajuan Li
- State Key Laboratory of Membrane Biology and Minstry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing, China.,School of Life Sciences, Peking University, Beijing, China
| | - Aiguo Liu
- State Key Laboratory of Membrane Biology and Minstry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing, China.,School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisplinary Studies, Peking University, Beijing, China
| | - Ruifeng Li
- School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisplinary Studies, Peking University, Beijing, China.,Center for Bioinformatics, Peking University, Beijing, China.,Center for Statistical Science, Peking University, Beijing, China
| | - Ying Su
- School of Life Sciences, Peking University, Beijing, China
| | - Juan Du
- State Key Laboratory of Membrane Biology and Minstry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing, China.,School of Life Sciences, Peking University, Beijing, China
| | - Cheng Li
- School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisplinary Studies, Peking University, Beijing, China.,Center for Bioinformatics, Peking University, Beijing, China.,Center for Statistical Science, Peking University, Beijing, China
| | - Alan Jian Zhu
- State Key Laboratory of Membrane Biology and Minstry of Education Key Laboratory of Cell Proliferation and Differentiation, Peking University, Beijing, China.,School of Life Sciences, Peking University, Beijing, China.,Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisplinary Studies, Peking University, Beijing, China
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25
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Gong P, Quan H, He C. Targeting MAGO proteins with a peptide aptamer reinforces their essential roles in multiple rice developmental pathways. Plant J 2014; 80:905-14. [PMID: 25230811 DOI: 10.1111/tpj.12672] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 09/08/2014] [Accepted: 09/14/2014] [Indexed: 05/16/2023]
Abstract
Peptide aptamers are artificial short peptides that potentially interfere with the biological roles of their target proteins; however, this technology has not yet been applied to plant functional genomics. MAGO and Y14, the two core subunits of the exon junction complex (EJC), form obligate heterodimers in eukaryotes. In Oryza sativa L. (rice), each of the two genes has two homologs, designated OsMAGO1 and OsMAGO2, and OsY14a and OsY14b, respectively. Here, we characterized a 16-amino acida peptide aptamer (PAP) for the rice MAGO proteins. PAP and rice Y14 bound competitively to rice MAGO proteins. Specifically targeting the MAGO proteins by expressing the aptamer in transgenic rice plants did not affect the endogenous synthesis and accumulation of MAGO proteins; however, the phenotypic variations observed in multiple organs phenocopied those of transgenic rice plants harboring RNA interference (RNAi) constructs in which the accumulation of MAGO and/or OsY14a transcripts and MAGO proteins was downregulated severely. Morphologically, the aptamer transgenic plants were short with abnormally developed flowers, and the stamens exhibited reduced degradation and absorption of both the endothecium and tapetum, thus confirming that EJC core heterodimers play essential roles in rice development, growth and reproduction. This study reveals that as a complementary approach of RNAi, peptide aptamers are powerful tools for interfering with the function of proteins in higher plants.
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Affiliation(s)
- Pichang Gong
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Nanxincun 20, Xiangshan, 100093, Beijing, China
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26
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Hayashi R, Handler D, Ish-Horowicz D, Brennecke J. The exon junction complex is required for definition and excision of neighboring introns in Drosophila. Genes Dev 2014; 28:1772-85. [PMID: 25081352 DOI: 10.1101/gad.245738.114] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The exon junction complex (EJC) plays a central role in controlling RNA fate and aids faithful splicing of pre-mRNAs containing large introns via an unknown mechanism. Brennecke and colleagues show that the core EJC plus the accessory factors RnpS1 and Acinus aid in the definition and efficient splicing of neighboring introns. Interestingly, the most highly affected intron belongs to the piwi locus, which explains the reported transposon desilencing in EJC-depleted Drosophila ovaries. Based on transcriptome-wide analysis, the authors propose that the dependency of splicing on the EJC is exploited to control the temporal order of splicing events. Splicing of pre-mRNAs results in the deposition of the exon junction complex (EJC) upstream of exon–exon boundaries. The EJC plays crucial post-splicing roles in export, translation, localization, and nonsense-mediated decay of mRNAs. It also aids faithful splicing of pre-mRNAs containing large introns, albeit via an unknown mechanism. Here, we show that the core EJC plus the accessory factors RnpS1 and Acinus aid in definition and efficient splicing of neighboring introns. This requires prior deposition of the EJC in close proximity to either an upstream or downstream splicing event. If present in isolation, EJC-dependent introns are splicing-defective also in wild-type cells. Interestingly, the most affected intron belongs to the piwi locus, which explains the reported transposon desilencing in EJC-depleted Drosophila ovaries. Based on a transcriptome-wide analysis, we propose that the dependency of splicing on the EJC is exploited as a means to control the temporal order of splicing events.
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27
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McMahon JJ, Shi L, Silver DL. Generation of a Magoh conditional allele in mice. Genesis 2014; 52:752-8. [PMID: 24771530 DOI: 10.1002/dvg.22788] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 04/22/2014] [Accepted: 04/24/2014] [Indexed: 02/02/2023]
Abstract
Magoh encodes a core component of the exon junction complex (EJC), which binds mRNA and regulates mRNA metabolism. Magoh is highly expressed in proliferative tissues during development. EJC components have been implicated in several developmental disorders including TAR syndrome, Richieri-Costa-Pereira syndrome, and intellectual disability. Existing germline null Magoh mice are embryonic lethal as homozygotes and perinatal lethal as heterozygotes, precluding detailed analysis of embryonic and postnatal functions. Here, we report the generation of a new genetic tool to dissect temporal and tissue-specific roles for Magoh in development and adult homeostasis. This Magoh conditional allele has two loxP sites flanking the second exon. Ubiquitous Cre-mediated deletion of the floxed allele in a heterozygous mouse (Magoh(del/+) ) causes 50% reduction of both Magoh mRNA and protein. Magoh(del/+) mice exhibit both microcephaly and hypopigmentation, thus phenocopying germline haploinsufficient Magoh mice. Using Emx1-Cre, we further show that conditional Magoh deletion in neural progenitors during embryonic development also causes microcephaly. We anticipate this novel conditional allele will be a valuable tool for assessing tissue-specific roles for Magoh in mammalian development and postnatal processes.
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Affiliation(s)
- John J McMahon
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina
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28
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Ozoe A, Sone M, Fukushima T, Kataoka N, Arai T, Chida K, Asano T, Hakuno F, Takahashi SI. Insulin receptor substrate-1 (IRS-1) forms a ribonucleoprotein complex associated with polysomes. FEBS Lett 2013; 587:2319-24. [PMID: 23770097 DOI: 10.1016/j.febslet.2013.05.066] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2013] [Revised: 05/27/2013] [Accepted: 05/27/2013] [Indexed: 11/18/2022]
Abstract
Insulin receptor substrates (IRSs) are known to play important roles in mediating intracellular insulin-like growth factors (IGFs)/insulin signaling. In this study, we identified components of messenger ribonucleoprotein (mRNP) as IRS-1-associated proteins. IRS-1 complex formation analysis revealed that IRS-1 is incorporated into the complexes of molecular mass more than 1000 kDa, which were disrupted by treatment with RNase. Furthermore, oligo(dT) beads precipitated IRS-1 from cell lysates, showing that the IRS-1 complexes contained messenger RNA. Taken together with the data that IRS-1 was fractionated into the polysome-containing high-density fractions, we concluded that IRS-1 forms the novel complexes with mRNPs.
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Affiliation(s)
- Atsufumi Ozoe
- Graduate School of Agriculture and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan
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29
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Abstract
Transcription of protein-coding genes in mammalian cells is coordinated with pre-mRNA processing as well as the assembly and nuclear export of mRNPs. Btf (BCLAF1) and TRAP150 (THRAP3) were previously reported to associate with in vitro spliced mRNPs and also as a part of the spliceosome, suggesting they are involved in pre-mRNA processing. Btf and TRAP150 are serine-arginine-rich (SR) proteins with significant sequence similarity, but the extent of their functional overlap is not yet clear. We show that both Btf and TRAP150 localize at a constitutively active β-tropomyosin (BTM) reporter minigene locus in mammalian cells. Both proteins also localize at a U2OS 2-6-3 reporter gene locus in a RNA polymerase II (RNAPII) transcription-dependent manner. While Btf and TRAP150 showed some overlap with reporter RNA and other pre-mRNA processing factors at transcription loci, they showed the most precise overlap with the exon junction complex (EJC) protein Magoh. Since EJC components have roles in nuclear export, we examined nuclear/cytoplasmic mRNA distribution after Btf or TRAP150 knockdown. Btf depletion caused an increase of β-tropomyosin minigene reporter transcripts in the cytoplasm as well as global increase of endogenous polyadenylated RNA in the cytoplasm, while TRAP150 depletion did not. We provide evidence that Btf has functions distinct from TRAP150 in regulating the subcellular distribution of mRNAs in human cells.
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30
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Leal G, Comprido D, Duarte CB. BDNF-induced local protein synthesis and synaptic plasticity. Neuropharmacology 2013; 76 Pt C:639-56. [PMID: 23602987 DOI: 10.1016/j.neuropharm.2013.04.005] [Citation(s) in RCA: 416] [Impact Index Per Article: 37.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Revised: 03/25/2013] [Accepted: 04/03/2013] [Indexed: 12/16/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) is an important regulator of synaptic transmission and long-term potentiation (LTP) in the hippocampus and in other brain regions, playing a role in the formation of certain forms of memory. The effects of BDNF in LTP are mediated by TrkB (tropomyosin-related kinase B) receptors, which are known to be coupled to the activation of the Ras/ERK, phosphatidylinositol 3-kinase/Akt and phospholipase C-γ (PLC-γ) pathways. The role of BDNF in LTP is best studied in the hippocampus, where the neurotrophin acts at pre- and post-synaptic levels. Recent studies have shown that BDNF regulates the transport of mRNAs along dendrites and their translation at the synapse, by modulating the initiation and elongation phases of protein synthesis, and by acting on specific miRNAs. Furthermore, the effect of BDNF on transcription regulation may further contribute to long-term changes in the synaptic proteome. In this review we discuss the recent progress in understanding the mechanisms contributing to the short- and long-term regulation of the synaptic proteome by BDNF, and the role in synaptic plasticity, which is likely to influence learning and memory formation. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.
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Affiliation(s)
- Graciano Leal
- CNC-Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal; Department of Life Sciences, University of Coimbra, 3004-517 Coimbra, Portugal
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31
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Abstract
The majority of mammalian pre-mRNAs contains multiple introns that are excised prior to export and translation. After intron excision, ligated exon intermediates participate in subsequent intron excisions. However, exon ligation generates an exon of increased size, a feature of pre-mRNA splicing that can interfere with downstream splicing events. These considerations raise the question of whether unique mechanisms exist that permit efficient removal of introns neighboring ligated exons. Kinetic analyses of multiple intron-containing pre-mRNAs revealed that splicing is more efficient following an initial intron removal event, suggesting that either the recruitment of the exon junction complex (EJC) to ligated exons increases the efficiency of multiple intron excisions or that the initial definition of splice sites is sufficient to permit efficient splicing of introns neighboring ligated exons. Knockdown experiments show that the deposition of the EJC does not affect subsequent splicing kinetics. Instead, spliceosomal components that are not involved in the initial splicing event remain associated with the pre-mRNA to ensure efficient removal of neighboring introns. Thus, ligated exons do not require redefinition, providing an additional kinetic advantage for exon defined splice sites.
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Affiliation(s)
- Tara L Crabb
- Department of Microbiology and Molecular Genetics, University of California at Irvine, Irvine, California 92697-4025, USA
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32
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Koroleva OA, Brown JWS, Shaw PJ. Localization of eIF4A-III in the nucleolus and splicing speckles is an indicator of plant stress. Plant Signal Behav 2009; 4:1148-51. [PMID: 20514231 PMCID: PMC2819441 DOI: 10.4161/psb.4.12.9906] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Accepted: 08/25/2009] [Indexed: 05/05/2023]
Abstract
The mechanisms of long-term adaptation to low oxygen environment are quite well studied, but little is known about the sensing of oxygen shortage, the signal transduction and the shortterm effects of hypoxia in plant cells. We have found that an RNA helicase eIF4A-III, a putative component of the Exon Junction Complex, rapidly changes its pattern of localisation in the plant nucleus under hypoxic conditions. In normal cell growth conditions GFPeIF4A-III was mainly nucleoplasmic, but in hypoxia stress conditions it moved to the nucleolus and splicing speckles. This transition occurred within 15-20 min in Arabidopsis culture cells and seedling root cells, but took more than 2 h in tobacco BY-2 culture cells. Inhibition of respiration, transcription or phosphorylation in cells and ethanol treatment had similar effects to hypoxia. The most likely consequence is that a certain mRNA population will remain bound to the eIF4A-III and other mRNA processing proteins, rather than being transported from the nucleus to the cytoplasm, and thus its translation will be suspended.
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Affiliation(s)
- Olga A Koroleva
- Department of Cell Biology, John Innes Centre, Colney, Norwich, UK
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Abstract
The multiprotein exon junction complex (EJC) is deposited on mRNAs upstream of exon-exon junctions as a consequence of pre-mRNA splicing. In mammalian cells, this complex serves as a key modulator of spliced mRNA metabolism. To date, neither the complete composition nor the exact assembly pathway of the EJC has been entirely elucidated. Using in vitro splicing and a two-step chromatography procedure, we have purified the EJC and analyzed its components by mass spectrometry. In addition to finding most of the known EJC factors, we identified two novel EJC components, Acinus and SAP18. Heterokaryon analysis revealed that SAP18 is a shuttling protein whereas Acinus is restricted to the nucleus. In MS2 tethering assays Acinus stimulated gene expression at the RNA level, while MLN51, another EJC factor, stimulated mRNA translational efficiency. Using tandem affinity purification (TAP) of proteins overexpressed in HeLa cells, we demonstrated that Acinus binds directly to another EJC component, RNPS1, while stable association of SAP18 to form the trimeric apoptosis and splicing associated protein (ASAP) complex requires both Acinus and RNPS1. Using the same methodology, we further identified what appears to be the minimal stable EJC core, a heterotetrameric complex consisting of eIF4AIII, Magoh, Y14, and MLN51.
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Affiliation(s)
- Thomas Ø Tange
- Howard Hughes Medical Institute, Department of Biochemistry, Brandeis University, Waltham, MA 02454, USA
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Williams B, Boyne J, Goodwin D, Roaden L, Hautbergue G, Wilson S, Whitehouse A. The prototype gamma-2 herpesvirus nucleocytoplasmic shuttling protein, ORF 57, transports viral RNA through the cellular mRNA export pathway. Biochem J 2005; 387:295-308. [PMID: 15537388 PMCID: PMC1134957 DOI: 10.1042/bj20041223] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2004] [Revised: 10/27/2004] [Accepted: 11/10/2004] [Indexed: 12/27/2022]
Abstract
HVS (herpesvirus saimiri) is the prototype gamma-2 herpesvirus. This is a subfamily of herpesviruses gaining importance since the identification of the first human gamma-2 herpesvirus, Kaposi's sarcoma-associated herpesvirus. The HVS ORF 57 (open reading frame 57) protein is a multifunctional transregulatory protein homologous with genes identified in all classes of herpesviruses. Recent work has demonstrated that ORF 57 has the ability to bind viral RNA, shuttles between the nucleus and cytoplasm and promotes the nuclear export of viral transcripts. In the present study, we show that ORF 57 shuttles between the nucleus and cytoplasm in a CRM-1 (chromosomal region maintenance 1)-independent manner. ORF 57 interacts with the mRNA export factor REF (RNA export factor) and two other components of the exon junction complex, Y14 and Magoh. The association of ORF 57 with REF stimulates recruitment of the cellular mRNA export factor TAP (Tip-associated protein), and HVS infection triggers the relocalization of REF and TAP from the nuclear speckles to several large clumps within the cell. Using a dominant-negative form of TAP and RNA interference to deplete TAP, we show that it is essential for bulk mRNA export in mammalian cells and is required for ORF 57-mediated viral RNA export. Furthermore, we show that the disruption of TAP reduces viral replication. These results indicate that HVS utilizes ORF 57 to recruit components of the exon junction complex and subsequently TAP to promote viral RNA export through the cellular mRNA export pathway.
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Key Words
- chromosomal region maintenance 1 (crm-1)
- exon junction complex
- herpesvirus
- mrna export
- open reading frame 57 (orf 57)
- tip-associated protein (tap)
- cmv, cytomegalovirus
- crm-1, chromosomal region maintenance 1
- cte, constitutive transport element
- ejc, exon junction complex
- fish, fluorescence in situ hybridization
- gb, glycoprotein b
- gfp, green fluorescent protein
- gst, glutathione s-transferase
- hek-293t cells, human embryonic kidney 293t cells
- hsv, herpes simplex virus
- hvs, herpesvirus saimiri
- kshv, kaposi's sarcoma associated herpesvirus
- lmb, leptomycin b
- moi, multiplicity of infection
- ref, rna export factor
- mref2-1, murine ref2-1
- nes, nuclear export signal
- nmd, nonsense-mediated decay
- omk cells, owl monkey kidney cells
- orf 57, open reading frame 57
- rnai, rna interference
- rnps1, rna-binding protein prevalent during s phase
- rrm, rna recognition motif
- tap, tip-associated protein
- trex complex, transcription and export complex
- yfp, yellow fluorescent protein
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Affiliation(s)
- Ben J. L. Williams
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - James R. Boyne
- †School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, U.K
| | - Delyth J. Goodwin
- †School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, U.K
| | - Louise Roaden
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - Guillaume M. Hautbergue
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - Stuart A. Wilson
- *Department of Biomolecular Sciences, University of Manchester Institute of Science and Technology, Manchester M60 1QD, U.K
| | - Adrian Whitehouse
- †School of Biochemistry and Microbiology, University of Leeds, Leeds LS2 9JT, U.K
- ‡Molecular and Cellular Biology Research Group, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K
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Custódio N, Carvalho C, Condado I, Antoniou M, Blencowe BJ, Carmo-Fonseca M. In vivo recruitment of exon junction complex proteins to transcription sites in mammalian cell nuclei. RNA 2004; 10:622-33. [PMID: 15037772 PMCID: PMC1370553 DOI: 10.1261/rna.5258504] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Studies over the past years indicate that there is extensive coupling between nuclear export of mRNA and pre-mRNA processing. Here, we visualized the distribution of exon junction complex (EJC) proteins and RNA export factors relative to sites of abundant pre-mRNA synthesis in the nucleus. We analyzed both HeLa cells infected with adenovirus and murine erythroleukemia (MEL) cells stably transfected with the human beta-globin gene. Using in situ hybridization and confocal microscopy, we observe accumulation of EJC proteins (REF/Aly, Y14, SRm160, UAP56, RNPS1, and Magoh) and core spliceosome components (U snRNPs) at sites of transcription. This suggests that EJC proteins bind stably to pre-mRNA cotranscriptionally. No concentration of the export factors NXF1/TAP, p15, and Dbp5 was detected on nascent transcripts, arguing that in mammalian cells these proteins bind the mRNA shortly before or after release from the sites of transcription. These results also suggest that binding of EJC proteins to the mRNA is not sufficient to recruit TAP-p15, consistent with recent findings showing that the EJC does not play a crucial role in mRNA export. Contrasting to the results obtained in MEL cells expressing normal human beta-globin transcripts, mutant pre-mRNAs defective in splicing and 3'end processing do not colocalize with SRm160, REF, UAP56, or Sm proteins. This shows that the accumulation of EJC proteins at transcription sites requires efficient processing of the nascent pre-mRNAs, arguing that transcription per se is not sufficient for the stable assembly of the EJC.
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Affiliation(s)
- Noélia Custódio
- Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Lisbon 1649-028, Portugal
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Chan CC, Dostie J, Diem MD, Feng W, Mann M, Rappsilber J, Dreyfuss G. eIF4A3 is a novel component of the exon junction complex. RNA 2004; 10:200-9. [PMID: 14730019 PMCID: PMC1370532 DOI: 10.1261/rna.5230104] [Citation(s) in RCA: 195] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2003] [Accepted: 11/19/2003] [Indexed: 05/19/2023]
Abstract
The exon junction complex (EJC) is a protein complex that assembles near exon-exon junctions of mRNAs as a result of splicing. EJC proteins play important roles in postsplicing events including mRNA export, cytoplasmic localization, and nonsense-mediated decay. Recent evidence suggests that mRNA translation is also influenced by the splicing history of the transcript. Here we identify eIF4A3, a DEAD-box RNA helicase and a member of the eIF4A family of translation initiation factors, as a novel component of the EJC. We show that eIF4A3 associates preferentially with nuclear complexes containing the EJC proteins magoh and Y14. Furthermore, eIF4A3, but not the highly related eIF4A1 or eIF4A2, preferentially associates with spliced mRNA. In vitro splicing and mapping experiments demonstrate that eIF4A3 binds mRNAs at the position of the EJC. Using monoclonal antibodies, we show that eIF4A3 is found in the nucleus whereas eIF4A1 and eIF4A2 are found in the cytoplasm. Thus, eIF4A3 likely provides a splicing-dependent influence on the translation of mRNAs.
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Affiliation(s)
- Chia C Chan
- Howard Hughes Medical Institute and Department of Biochemistry & Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148, USA
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Reichert VL, Le Hir H, Jurica MS, Moore MJ. 5' exon interactions within the human spliceosome establish a framework for exon junction complex structure and assembly. Genes Dev 2002; 16:2778-91. [PMID: 12414731 PMCID: PMC187475 DOI: 10.1101/gad.1030602] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
A general consequence of pre-mRNA splicing is the stable deposition of several proteins 20-24 nucleotides (nt) upstream of exon-exon junctions on spliced mRNAs. This exon junction complex (EJC) contains factors involved in mRNA export, cytoplasmic localization, and nonsense-mediated mRNA decay. Here we probed the mechanism and timing of EJC assembly. Over the course of splicing, the 5' exon is subject to numerous dynamic protein-RNA interactions involving at least nine distinct polypeptides. Within the fully assembled spliceosome, these interactions afford protection to the last 25-27 nt of the 5' exon intermediate. Coincident with exon ligation, interactions at the 3' end of the 5' exon disappear, and new species associate with position -24. Mass spectrometry and Western blotting of purified H, C, and mRNP complexes revealed that at least one EJC component, REF/Aly, can interact with pre-mRNA prior to spliceosome assembly, whereas Y14, Magoh, RNPS1, UAP56, and SRm160 are found in intermediate-containing spliceosomes. Upon exon ligation, association of RNPS1, UAP56, and SRm160 is destabilized. In contrast, REF/Aly, Y14, and Magoh remain stably bound to spliced mRNA, indicating that these three proteins are components of the EJC core.
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Affiliation(s)
- Vienna L Reichert
- Howard Hughes Medical Institute, Department of Biochemistry, Brandeis University, Massachusetts 02454, USA
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