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Bensaude O, Barbosa I, Morillo L, Dikstein R, Le Hir H. Exon-junction complex association with stalled ribosomes and slow translation-independent disassembly. Nat Commun 2024; 15:4209. [PMID: 38760352 PMCID: PMC11101648 DOI: 10.1038/s41467-024-48371-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2023] [Accepted: 04/29/2024] [Indexed: 05/19/2024] Open
Abstract
Exon junction complexes are deposited at exon-exon junctions during splicing. They are primarily known to activate non-sense mediated degradation of transcripts harbouring premature stop codons before the last intron. According to a popular model, exon-junction complexes accompany mRNAs to the cytoplasm where the first translating ribosome pushes them out. However, they are also removed by uncharacterized, translation-independent mechanisms. Little is known about kinetic and transcript specificity of these processes. Here we tag core subunits of exon-junction complexes with complementary split nanoluciferase fragments to obtain sensitive and quantitative assays for complex formation. Unexpectedly, exon-junction complexes form large stable mRNPs containing stalled ribosomes. Complex assembly and disassembly rates are determined after an arrest in transcription and/or translation. 85% of newly deposited exon-junction complexes are disassembled by a translation-dependent mechanism. However as this process is much faster than the translation-independent one, only 30% of the exon-junction complexes present in cells at steady state require translation for disassembly. Deep RNA sequencing shows a bias of exon-junction complex bound transcripts towards microtubule and centrosome coding ones and demonstrate that the lifetimes of exon-junction complexes are transcript-specific. This study provides a dynamic vision of exon-junction complexes and uncovers their unexpected stable association with ribosomes.
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Affiliation(s)
- Olivier Bensaude
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, PSL Research University, Paris, France.
| | - Isabelle Barbosa
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, PSL Research University, Paris, France
| | - Lucia Morillo
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, PSL Research University, Paris, France
| | - Rivka Dikstein
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot, Israel
| | - Hervé Le Hir
- Institut de Biologie de l'Ecole Normale Supérieure (IBENS), Ecole Normale Supérieure, CNRS, INSERM, PSL Research University, Paris, France.
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2
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Das R, Panigrahi GK. Messenger RNA Surveillance: Current Understanding, Regulatory Mechanisms, and Future Implications. Mol Biotechnol 2024:10.1007/s12033-024-01062-4. [PMID: 38411790 DOI: 10.1007/s12033-024-01062-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 01/02/2024] [Indexed: 02/28/2024]
Abstract
Nonsense-mediated mRNA decay (NMD) is an evolutionarily conserved surveillance mechanism in eukaryotes primarily deployed to ensure RNA quality control by eliminating aberrant transcripts and also involved in modulating the expression of several physiological transcripts. NMD, the mRNA surveillance pathway, is a major form of gene regulation in eukaryotes. NMD serves as one of the most significant quality control mechanisms as it primarily scans the newly synthesized transcripts and differentiates the aberrant and non-aberrant transcripts. The synthesis of truncated proteins is restricted, which would otherwise lead to cellular dysfunctions. The up-frameshift factors (UPFs) play a central role in executing the NMD event, largely by recognizing and recruiting multiple protein factors that result in the decay of non-physiological mRNAs. NMD exhibits astounding variability in its ability across eukaryotes in an array of pathological and physiological contexts. The detailed understanding of NMD and the underlying molecular mechanisms remains blurred. This review outlines our current understanding of NMD, in regulating multifaceted cellular events during development and disease. It also attempts to identify unanswered questions that deserve further investigation.
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Affiliation(s)
- Rutupurna Das
- Department of Zoology, School of Applied Sciences, Centurion University of Technology and Management, Jatni, Khordha, Odisha, India
| | - Gagan Kumar Panigrahi
- Department of Zoology, School of Applied Sciences, Centurion University of Technology and Management, Jatni, Khordha, Odisha, India.
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3
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Carrard J, Lejeune F. Nonsense-mediated mRNA decay, a simplified view of a complex mechanism. BMB Rep 2023; 56:625-632. [PMID: 38052423 PMCID: PMC10761751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/31/2023] [Accepted: 11/17/2023] [Indexed: 12/07/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is both a quality control mechanism and a gene regulation pathway. It has been studied for more than 30 years, with an accumulation of many mechanistic details that have often led to debate and hence to different models of NMD activation, particularly in higher eukaryotes. Two models seem to be opposed, since the first requires intervention of the exon junction complex (EJC) to recruit NMD factors downstream of the premature termination codon (PTC), whereas the second involves an EJC-independent mechanism in which NMD factors concentrate in the 3'UTR to initiate NMD in the presence of a PTC. In this review we describe both models, giving recent molecular details and providing experimental arguments supporting one or the other model. In the end it is certainly possible to imagine that these two mechanisms co-exist, rather than viewing them as mutually exclusive. [BMB Reports 2023; 56(12): 625-632].
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Affiliation(s)
- Julie Carrard
- Univ. Lille, CNRS, Inserm, UMR9020-U1277 - CANTHER - Cancer Heterogeneity Plasticity and Resistance to Therapies, Lille F-59000, France
| | - Fabrice Lejeune
- Univ. Lille, CNRS, Inserm, UMR9020-U1277 - CANTHER - Cancer Heterogeneity Plasticity and Resistance to Therapies, Lille F-59000, France
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4
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Chang J, Shin MK, Park J, Hwang HJ, Locker N, Ahn J, Kim D, Baek D, Park Y, Lee Y, Boo SH, Kim HI, Kim YK. An interaction between eIF4A3 and eIF3g drives the internal initiation of translation. Nucleic Acids Res 2023; 51:10950-10969. [PMID: 37811880 PMCID: PMC10639049 DOI: 10.1093/nar/gkad763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2022] [Revised: 08/30/2023] [Accepted: 09/08/2023] [Indexed: 10/10/2023] Open
Abstract
An RNA structure or modified RNA sequences can provide a platform for ribosome loading and internal translation initiation. The functional significance of internal translation has recently been highlighted by the discovery that a subset of circular RNAs (circRNAs) is internally translated. However, the molecular mechanisms underlying the internal initiation of translation in circRNAs remain unclear. Here, we identify eIF3g (a subunit of eIF3 complex) as a binding partner of eIF4A3, a core component of the exon-junction complex (EJC) that is deposited onto spliced mRNAs and plays multiple roles in the regulation of gene expression. The direct interaction between eIF4A3-eIF3g serves as a molecular linker between the eIF4A3 and eIF3 complex, thereby facilitating internal ribosomal entry. Protein synthesis from in vitro-synthesized circRNA demonstrates eIF4A3-driven internal translation, which relies on the eIF4A3-eIF3g interaction. Furthermore, our transcriptome-wide analysis shows that efficient polysomal association of endogenous circRNAs requires eIF4A3. Notably, a subset of endogenous circRNAs can express a full-length intact protein, such as β-catenin, in an eIF4A3-dependent manner. Collectively, our results expand the understanding of the protein-coding potential of the human transcriptome, including circRNAs.
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Affiliation(s)
- Jeeyoon Chang
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Min-Kyung Shin
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Joori Park
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Hyun Jung Hwang
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Nicolas Locker
- Department of Microbial and Cellular Sciences, University of Surrey, Guildford GU2 7HX, UK
| | - Junhak Ahn
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Doyeon Kim
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Daehyun Baek
- School of Biological Sciences, Seoul National University, Seoul 08826, Republic of Korea
| | - Yeonkyoung Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Yujin Lee
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Sung Ho Boo
- Division of Life Sciences, Korea University, Seoul 02841, Republic of Korea
| | - Hyeong-In Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Yoon Ki Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
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5
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Sun L, Mailliot J, Schaffitzel C. Nonsense-Mediated mRNA Decay Factor Functions in Human Health and Disease. Biomedicines 2023; 11:722. [PMID: 36979701 PMCID: PMC10045457 DOI: 10.3390/biomedicines11030722] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/21/2023] [Accepted: 02/22/2023] [Indexed: 03/06/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a cellular surveillance mechanism that degrades mRNAs with a premature stop codon, avoiding the synthesis of C-terminally truncated proteins. In addition to faulty mRNAs, NMD recognises ~10% of endogenous transcripts in human cells and downregulates their expression. The up-frameshift proteins are core NMD factors and are conserved from yeast to human in structure and function. In mammals, NMD diversified into different pathways that target different mRNAs employing additional NMD factors. Here, we review our current understanding of molecular mechanisms and cellular roles of NMD pathways and the involvement of more specialised NMD factors. We describe the consequences of mutations in NMD factors leading to neurodevelopmental diseases, and the role of NMD in cancer. We highlight strategies of RNA viruses to evade recognition and decay by the NMD machinery.
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Affiliation(s)
- Lingling Sun
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Justine Mailliot
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
| | - Christiane Schaffitzel
- School of Biochemistry, University of Bristol, University Walk, Bristol BS8 1TD, UK
- Bristol Engineering Biology Centre BrisEngBio, 24 Tyndall Ave, Bristol BS8 1TQ, UK
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Temporal-iCLIP captures co-transcriptional RNA-protein interactions. Nat Commun 2023; 14:696. [PMID: 36755023 PMCID: PMC9908952 DOI: 10.1038/s41467-023-36345-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 01/27/2023] [Indexed: 02/10/2023] Open
Abstract
Dynamic RNA-protein interactions govern the co-transcriptional packaging of RNA polymerase II (RNAPII)-derived transcripts. Yet, our current understanding of this process in vivo primarily stems from steady state analysis. To remedy this, we here conduct temporal-iCLIP (tiCLIP), combining RNAPII transcriptional synchronisation with UV cross-linking of RNA-protein complexes at serial timepoints. We apply tiCLIP to the RNA export adaptor, ALYREF; a component of the Nuclear Exosome Targeting (NEXT) complex, RBM7; and the nuclear cap binding complex (CBC). Regardless of function, all tested factors interact with nascent RNA as it exits RNAPII. Moreover, we demonstrate that the two transesterification steps of pre-mRNA splicing temporally separate ALYREF and RBM7 binding to splicing intermediates, and that exon-exon junction density drives RNA 5'end binding of ALYREF. Finally, we identify underappreciated steps in snoRNA 3'end processing performed by RBM7. Altogether, our data provide a temporal view of RNA-protein interactions during the early phases of transcription.
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7
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Nonsense-Mediated mRNA Decay as a Mediator of Tumorigenesis. Genes (Basel) 2023; 14:genes14020357. [PMID: 36833284 PMCID: PMC9956241 DOI: 10.3390/genes14020357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 01/23/2023] [Accepted: 01/26/2023] [Indexed: 02/03/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is an evolutionarily conserved and well-characterized biological mechanism that ensures the fidelity and regulation of gene expression. Initially, NMD was described as a cellular surveillance or quality control process to promote selective recognition and rapid degradation of erroneous transcripts harboring a premature translation-termination codon (PTC). As estimated, one-third of mutated and disease-causing mRNAs were reported to be targeted and degraded by NMD, suggesting the significance of this intricate mechanism in maintaining cellular integrity. It was later revealed that NMD also elicits down-regulation of many endogenous mRNAs without mutations (~10% of the human transcriptome). Therefore, NMD modulates gene expression to evade the generation of aberrant truncated proteins with detrimental functions, compromised activities, or dominant-negative effects, as well as by controlling the abundance of endogenous mRNAs. By regulating gene expression, NMD promotes diverse biological functions during development and differentiation, and facilitates cellular responses to adaptation, physiological changes, stresses, environmental insults, etc. Mutations or alterations (such as abnormal expression, degradation, post-translational modification, etc.) that impair the function or expression of proteins associated with the NMD pathway can be deleterious to cells and may cause pathological consequences, as implicated in developmental and intellectual disabilities, genetic defects, and cancer. Growing evidence in past decades has highlighted NMD as a critical driver of tumorigenesis. Advances in sequencing technologies provided the opportunity to identify many NMD substrate mRNAs in tumor samples compared to matched normal tissues. Interestingly, many of these changes are tumor-specific and are often fine-tuned in a tumor-specific manner, suggesting the complex regulation of NMD in cancer. Tumor cells differentially exploit NMD for survival benefits. Some tumors promote NMD to degrade a subset of mRNAs, such as those encoding tumor suppressors, stress response proteins, signaling proteins, RNA binding proteins, splicing factors, and immunogenic neoantigens. In contrast, some tumors suppress NMD to facilitate the expression of oncoproteins or other proteins beneficial for tumor growth and progression. In this review, we discuss how NMD is regulated as a critical mediator of oncogenesis to promote the development and progression of tumor cells. Understanding how NMD affects tumorigenesis differentially will pave the way for the development of more effective and less toxic, targeted therapeutic opportunities in the era of personalized medicine.
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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: 61] [Impact Index Per Article: 61.0] [Reference Citation Analysis] [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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9
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V M DD, Sivaramakrishnan V, Arvind Kumar K. Structural systems biology approach delineate the functional implications of SNPs in exon junction complex interaction network. J Biomol Struct Dyn 2023; 41:11969-11986. [PMID: 36617892 DOI: 10.1080/07391102.2022.2164355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 12/26/2022] [Indexed: 01/10/2023]
Abstract
In eukaryotes, transcripts that carry premature termination codons (PTC) leading to truncated proteins are degraded by the Nonsense Mediated Decay (NMD) machinery. Missense and nonsense Single Nucleotide Polymorphisms (SNPs) in proteins belonging to Exon junction complex (EJC) and up-frameshift protein (UPF) will compromise NMD leading to the accumulation of truncated proteins in various diseases. The EJC and UPF which are involved in NMD is a good model system to study the effect of SNPs at a system level. Despite the availability of crystal structures, computational tools, and data on mutational and deletion studies, with functional implications, an integrated effort to understand the impact of SNPs at the systems level is lacking. To study the functional consequences of missense SNPs, sequence-based techniques like SIFT and PolyPhen which classify SNPs as deleterious or non-deleterious and structure-based methods like FoldX which calculate the Delta Delta G, (ddGs, ∆∆G) are used. Using FoldX, the ddG for mutations with experimentally validated functional effects is calculated and compared with those calculated for SNPs in the same protein-protein interaction interface. Further, a model is conceived to explain the functional implications of SNPs based on the effects observed for known mutants. The results are visualized in a network format. The effects of nonsense mutations are discerned by comparing with deletion mutation studies and loss of interaction in the crystal structure. The present work not only integrates genomics, proteomics, and classical genetics with 'Structural Biology' but also helps to integrate it into a 'systems-level functional network'.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Datta Darshan V M
- Disease Biology Lab, Department of Biosciences, Sri Sathya Sai Institute of Higher Learning, Prasanthi Nilayam, Anantapur, Andhra Pradesh, India
| | - Venketesh Sivaramakrishnan
- Disease Biology Lab, Department of Biosciences, Sri Sathya Sai Institute of Higher Learning, Prasanthi Nilayam, Anantapur, Andhra Pradesh, India
| | - K Arvind Kumar
- Disease Biology Lab, Department of Biosciences, Sri Sathya Sai Institute of Higher Learning, Prasanthi Nilayam, Anantapur, Andhra Pradesh, India
- Department of Physiology and Biophysics, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
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10
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Embree CM, Abu-Alhasan R, Singh G. Features and factors that dictate if terminating ribosomes cause or counteract nonsense-mediated mRNA decay. J Biol Chem 2022; 298:102592. [PMID: 36244451 PMCID: PMC9661723 DOI: 10.1016/j.jbc.2022.102592] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 10/07/2022] [Accepted: 10/10/2022] [Indexed: 11/13/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a quality control pathway in eukaryotes that continuously monitors mRNA transcripts to ensure truncated polypeptides are not produced. The expression of many normal mRNAs that encode full-length polypeptides is also regulated by this pathway. Such transcript surveillance by NMD is intimately linked to translation termination. When a ribosome terminates translation at a normal termination codon, NMD is not activated, and mRNA can undergo repeated rounds of translation. On the other hand, when translation termination is deemed abnormal, such as that on a premature termination codon, it leads to a series of poorly understood events involving the NMD pathway, which destabilizes the transcript. In this review, we summarize our current understanding of how the NMD machinery interfaces with the translation termination factors to initiate NMD. We also discuss a variety of cis-acting sequence contexts and trans-acting factors that can cause readthrough, ribosome reinitiation, or ribosome frameshifting at stop codons predicted to induce NMD. These alternative outcomes can lead to the ribosome translating downstream of such stop codons and hence the transcript escaping NMD. NMD escape via these mechanisms can have wide-ranging implications on human health, from being exploited by viruses to hijack host cell systems to being harnessed as potential therapeutic possibilities to treat genetic diseases.
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Affiliation(s)
- Caleb M Embree
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, USA; Center for RNA Biology, The Ohio State University, Columbus, Ohio USA
| | - Rabab Abu-Alhasan
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, USA; Center for RNA Biology, The Ohio State University, Columbus, Ohio USA
| | - Guramrit Singh
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio, USA; Center for RNA Biology, The Ohio State University, Columbus, Ohio USA.
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Martin H, Rupkey J, Asthana S, Yoon J, Patel S, Mott J, Pei Z, Mao Y. Diverse Roles of the Exon Junction Complex Factors in the Cell Cycle, Cancer, and Neurodevelopmental Disorders-Potential for Therapeutic Targeting. Int J Mol Sci 2022; 23:ijms231810375. [PMID: 36142288 PMCID: PMC9499366 DOI: 10.3390/ijms231810375] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Revised: 09/01/2022] [Accepted: 09/05/2022] [Indexed: 12/04/2022] Open
Abstract
The exon junction complex (EJC) plays a crucial role in regulating gene expression at the levels of alternative splicing, translation, mRNA localization, and nonsense-mediated decay (NMD). The EJC is comprised of three core proteins: RNA-binding motif 8A (RBM8A), Mago homolog (MAGOH), eukaryotic initiation factor 4A3 (eIF4A3), and a peripheral EJC factor, metastatic lymph node 51 (MLN51), in addition to other peripheral factors whose structural integration is activity-dependent. The physiological and mechanistic roles of the EJC in contribution to molecular, cellular, and organismal level function continue to be explored for potential insights into genetic or pathological dysfunction. The EJC’s specific role in the cell cycle and its implications in cancer and neurodevelopmental disorders prompt enhanced investigation of the EJC as a potential target for these diseases. In this review, we highlight the current understanding of the EJC’s position in the cell cycle, its relation to cancer and developmental diseases, and potential avenues for therapeutic targeting.
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Affiliation(s)
- Hannah Martin
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
| | - Julian Rupkey
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
| | - Shravan Asthana
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
- Feinberg School of Medicine, Northwestern University, 303 East Superior Street, Chicago, IL 60611, USA
| | - Joy Yoon
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
| | - Shray Patel
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
| | - Jennifer Mott
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
| | - Zifei Pei
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
| | - Yingwei Mao
- Department of Biology, Pennsylvania State University, University Park, State College, PA 16802, USA
- Correspondence:
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12
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No-nonsense: insights into the functional interplay of nonsense-mediated mRNA decay factors. Biochem J 2022; 479:973-993. [PMID: 35551602 PMCID: PMC9162471 DOI: 10.1042/bcj20210556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2022] [Revised: 04/10/2022] [Accepted: 04/12/2022] [Indexed: 11/22/2022]
Abstract
Nonsense-mediated messenger RNA decay (NMD) represents one of the main surveillance pathways used by eukaryotic cells to control the quality and abundance of mRNAs and to degrade viral RNA. NMD recognises mRNAs with a premature termination codon (PTC) and targets them to decay. Markers for a mRNA with a PTC, and thus NMD, are a long a 3′-untranslated region and the presence of an exon-junction complex (EJC) downstream of the stop codon. Here, we review our structural understanding of mammalian NMD factors and their functional interplay leading to a branched network of different interconnected but specialised mRNA decay pathways. We discuss recent insights into the potential impact of EJC composition on NMD pathway choice. We highlight the coexistence and function of different isoforms of up-frameshift protein 1 (UPF1) with an emphasis of their role at the endoplasmic reticulum and during stress, and the role of the paralogs UPF3B and UPF3A, underscoring that gene regulation by mammalian NMD is tightly controlled and context-dependent being conditional on developmental stage, tissue and cell types.
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13
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The Physiological Roles of the Exon Junction Complex in Development and Diseases. Cells 2022; 11:cells11071192. [PMID: 35406756 PMCID: PMC8997533 DOI: 10.3390/cells11071192] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/19/2022] [Accepted: 03/24/2022] [Indexed: 01/12/2023] Open
Abstract
The exon junction complex (EJC) becomes an increasingly important regulator of early gene expression in the central nervous system (CNS) and other tissues. The EJC is comprised of three core proteins: RNA-binding motif 8A (RBM8A), Mago homolog (MAGOH), eukaryotic initiation factor 4A3 (EIF4A3), and a peripheral EJC factor, metastatic lymph node 51 (MLN51), together with various auxiliary factors. The EJC is assembled specifically at exon-exon junctions on mRNAs, hence the name of the complex. The EJC regulates multiple levels of gene expression, from splicing to translation and mRNA degradation. The functional roles of the EJC have been established as crucial to the normal progress of embryonic and neurological development, with wide ranging implications on molecular, cellular, and organism level function. Dysfunction of the EJC has been implicated in multiple developmental and neurological diseases. In this review, we discuss recent progress on the EJC’s physiological roles.
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14
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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] [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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15
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The MAGOH paralogs - MAGOH, MAGOHB and their multiple isoforms. GENE REPORTS 2021. [DOI: 10.1016/j.genrep.2021.101214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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16
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Ye J, She X, Liu Z, He Z, Gao X, Lu L, Liang R, Lin Y. Eukaryotic Initiation Factor 4A-3: A Review of Its Physiological Role and Involvement in Oncogenesis. Front Oncol 2021; 11:712045. [PMID: 34458150 PMCID: PMC8386015 DOI: 10.3389/fonc.2021.712045] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 07/27/2021] [Indexed: 12/30/2022] Open
Abstract
EIF4A3, a member of the DEAD-box protein family, is a nuclear matrix protein and a core component of the exon junction complex (EJC). Under physiological conditions, EIF4A3 participates in post-transcriptional gene regulation by promoting EJC control of precursor mRNA splicing, thus influencing nonsense-mediated mRNA decay. In addition, EIF4A3 maintains the expression of significant selenoproteins, including phospholipid hydroperoxide glutathione peroxidase and thioredoxin reductase 1. Several recent studies have shown that EIF4A3 promotes tumor growth in multiple human cancers such as glioblastoma, hepatocellular carcinoma, pancreatic cancer, and ovarian cancer. Molecular biology studies also showed that EIF4A3 is recruited by long non-coding RNAs to regulate the expression of certain proteins in tumors. However, its tumor-related functions and underlying mechanisms are not well understood. Here, we review the physiological role of EIF4A3 and the potential association between EIF4A3 overexpression and tumorigenesis. We also evaluate the protein's potential utility as a diagnosis biomarker, therapeutic target, and prognosis indicator, hoping to provide new ideas for future research.
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Affiliation(s)
- Jiazhou Ye
- Guangxi Medical University Cancer Hospital, Nanning, China
| | | | - Ziyu Liu
- Guangxi Medical University, Nanning, China
| | - Ziqin He
- Guangxi Medical University, Nanning, China
| | - Xing Gao
- Guangxi Medical University Cancer Hospital, Nanning, China
| | - Lu Lu
- Guangxi Medical University Cancer Hospital, Nanning, China
| | - Rong Liang
- Guangxi Medical University Cancer Hospital, Nanning, China
| | - Yan Lin
- Guangxi Medical University Cancer Hospital, Nanning, China
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17
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Otani Y, Fujita KI, Kameyama T, Mayeda A. The Exon Junction Complex Core Represses Cancer-Specific Mature mRNA Re-splicing: A Potential Key Role in Terminating Splicing. Int J Mol Sci 2021; 22:ijms22126519. [PMID: 34204574 PMCID: PMC8234774 DOI: 10.3390/ijms22126519] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 06/08/2021] [Indexed: 02/08/2023] Open
Abstract
Using TSG101 pre-mRNA, we previously discovered cancer-specific re-splicing of mature mRNA that generates aberrant transcripts/proteins. The fact that mRNA is aberrantly re-spliced in various cancer cells implies there must be an important mechanism to prevent deleterious re-splicing on the spliced mRNA in normal cells. We thus postulated that mRNA re-splicing is controlled by specific repressors, and we searched for repressor candidates by siRNA-based screening for mRNA re-splicing activity. We found that knock-down of EIF4A3, which is a core component of the exon junction complex (EJC), significantly promoted mRNA re-splicing. Remarkably, we could recapitulate cancer-specific mRNA re-splicing in normal cells by knock-down of any of the core EJC proteins, EIF4A3, MAGOH, or RBM8A (Y14), implicating the EJC core as the repressor of mRNA re-splicing often observed in cancer cells. We propose that the EJC core is a critical mRNA quality control factor to prevent over-splicing of mature mRNA.
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Affiliation(s)
- Yuta Otani
- Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake 470-1192, Aichi, Japan; (Y.O.); (K.-i.F.)
- Laboratories of Discovery Research, Nippon Shinyaku Co., Ltd., Kyoto 601-8550, Kyoto, Japan
| | - Ken-ichi Fujita
- Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake 470-1192, Aichi, Japan; (Y.O.); (K.-i.F.)
| | - Toshiki Kameyama
- Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake 470-1192, Aichi, Japan; (Y.O.); (K.-i.F.)
- Department of Physiology, School of Medicine, Fujita Health University, Toyoake 470-1192, Aichi, Japan
- Correspondence: (T.K.); (A.M.)
| | - Akila Mayeda
- Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake 470-1192, Aichi, Japan; (Y.O.); (K.-i.F.)
- Correspondence: (T.K.); (A.M.)
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18
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Biology of the mRNA Splicing Machinery and Its Dysregulation in Cancer Providing Therapeutic Opportunities. Int J Mol Sci 2021; 22:ijms22105110. [PMID: 34065983 PMCID: PMC8150589 DOI: 10.3390/ijms22105110] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/07/2021] [Accepted: 05/07/2021] [Indexed: 12/13/2022] Open
Abstract
Dysregulation of messenger RNA (mRNA) processing—in particular mRNA splicing—is a hallmark of cancer. Compared to normal cells, cancer cells frequently present aberrant mRNA splicing, which promotes cancer progression and treatment resistance. This hallmark provides opportunities for developing new targeted cancer treatments. Splicing of precursor mRNA into mature mRNA is executed by a dynamic complex of proteins and small RNAs called the spliceosome. Spliceosomes are part of the supraspliceosome, a macromolecular structure where all co-transcriptional mRNA processing activities in the cell nucleus are coordinated. Here we review the biology of the mRNA splicing machinery in the context of other mRNA processing activities in the supraspliceosome and present current knowledge of its dysregulation in lung cancer. In addition, we review investigations to discover therapeutic targets in the spliceosome and give an overview of inhibitors and modulators of the mRNA splicing process identified so far. Together, this provides insight into the value of targeting the spliceosome as a possible new treatment for lung cancer.
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19
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Wang B, Rong X, Zhou Y, Liu Y, Sun J, Zhao B, Deng B, Lu L, Lu L, Li Y, Zhou J. Eukaryotic initiation factor 4A3 inhibits Wnt/β-catenin signaling and regulates axis formation in zebrafish embryos. Development 2021; 148:261699. [PMID: 33914867 DOI: 10.1242/dev.198101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 03/25/2021] [Indexed: 12/31/2022]
Abstract
A key step in the activation of canonical Wnt signaling is the interaction between β-catenin and Tcf/Lefs that forms the transcription activation complex and facilitates the expression of target genes. Eukaryotic initiation factor 4A3 (EIF4A3) is an ATP-dependent DEAD box-family RNA helicase and acts as a core subunit of the exon junction complex (EJC) to control a series of RNA post-transcriptional processes. In this study, we uncover that EIF4A3 functions as a Wnt inhibitor by interfering with the formation of β-catenin/Tcf transcription activation complex. As Wnt stimulation increases, accumulated β-catenin displaces EIF4A3 from a transcriptional complex with Tcf/Lef, allowing the active complex to facilitate the expression of target genes. In zebrafish embryos, eif4a3 depletion inhibited the development of the dorsal organizer and pattern formation of the anterior neuroectoderm by increasing Wnt/β-catenin signaling. Conversely, overexpression of eif4a3 decreased Wnt/β-catenin signaling and inhibited the formation of the dorsal organizer before gastrulation. Our results reveal previously unreported roles of EIF4A3 in the inhibition of Wnt signaling and the regulation of embryonic development in zebrafish.
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Affiliation(s)
- Bo Wang
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Xiaozhi Rong
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266003, China
| | - Yumei Zhou
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Yunzhang Liu
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Jiqin Sun
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Beibei Zhao
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Bei Deng
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Lei Lu
- Model Animal Research Center of Nanjing University and MOE Key Laboratory of Model Animals for Disease Study, 12 Xuefu Road, Pukou High-Tech Zone, Nanjing 210061, China
| | - Ling Lu
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China
| | - Yun Li
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266003, China
| | - Jianfeng Zhou
- Key Laboratory of Marine Drugs (Ocean University of China), Chinese Ministry of Education, and School of Medicine and Pharmacy, Ocean University of China, 5 Yushan Road, Qingdao 266003, China.,Laboratory for Marine Drugs and Bioproducts, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266003, China
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20
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Dou Y, Barbosa I, Jiang H, Iasillo C, Molloy KR, Schulze WM, Cusack S, Schmid M, Le Hir H, LaCava J, Jensen TH. NCBP3 positively impacts mRNA biogenesis. Nucleic Acids Res 2020; 48:10413-10427. [PMID: 32960271 PMCID: PMC7544205 DOI: 10.1093/nar/gkaa744] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Revised: 08/19/2020] [Accepted: 08/26/2020] [Indexed: 12/26/2022] Open
Abstract
The nuclear Cap-Binding Complex (CBC), consisting of Nuclear Cap-Binding Protein 1 (NCBP1) and 2 (NCBP2), associates with the nascent 5′cap of RNA polymerase II transcripts and impacts RNA fate decisions. Recently, the C17orf85 protein, also called NCBP3, was suggested to form an alternative CBC by replacing NCBP2. However, applying protein–protein interaction screening of NCBP1, 2 and 3, we find that the interaction profile of NCBP3 is distinct. Whereas NCBP1 and 2 identify known CBC interactors, NCBP3 primarily interacts with components of the Exon Junction Complex (EJC) and the TRanscription and EXport (TREX) complex. NCBP3-EJC association in vitro and in vivo requires EJC core integrity and the in vivo RNA binding profiles of EJC and NCBP3 overlap. We further show that NCBP3 competes with the RNA degradation factor ZC3H18 for binding CBC-bound transcripts, and that NCBP3 positively impacts the nuclear export of polyadenylated RNAs and the expression of large multi-exonic transcripts. Collectively, our results place NCBP3 with the EJC and TREX complexes in supporting mRNA expression.
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Affiliation(s)
- Yuhui Dou
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, Aarhus 8000, Denmark
| | - Isabelle Barbosa
- Institut de Biologie de l'ENS (IBENS), Département de biologie, École normale supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - Hua Jiang
- Laboratory of Cellular and Structural Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Claudia Iasillo
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, Aarhus 8000, Denmark
| | - Kelly R Molloy
- Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
| | - Wiebke Manuela Schulze
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, CS 90181, Grenoble Cedex 9 38042, France
| | - Stephen Cusack
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, CS 90181, Grenoble Cedex 9 38042, France
| | - Manfred Schmid
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, Aarhus 8000, Denmark
| | - Hervé Le Hir
- Institut de Biologie de l'ENS (IBENS), Département de biologie, École normale supérieure, CNRS, INSERM, Université PSL, 75005 Paris, France
| | - John LaCava
- Laboratory of Cellular and Structural Biology, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.,European Research Institute for the Biology of Ageing, University Medical Center Groningen, Groningen 9713 AV, Netherlands
| | - Torben Heick Jensen
- Department of Molecular Biology and Genetics, Aarhus University, C.F. Møllers Allé 3, Aarhus 8000, Denmark
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21
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Abstract
Viruses have evolved in tandem with the organisms that they infect. Afflictions of the plant and animal kingdoms with viral infections have forced the host organism to evolve new or exploit existing systems to develop the countermeasures needed to offset viral insults. As one example, nonsense-mediated mRNA decay, a cellular quality-control mechanism ensuring the translational fidelity of mRNA transcripts, has been used to restrict virus replication in both plants and animals. In response, viruses have developed a slew of means to disrupt or become insensitive to NMD, providing researchers with potential new reagents that can be used to more fully understand the NMD mechanism.
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Affiliation(s)
- Maximilian Wei-Lin Popp
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
- Center for RNA Biology, University of Rochester, Rochester, New York 14642, USA
| | - Hana Cho
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
- Center for RNA Biology, University of Rochester, Rochester, New York 14642, USA
| | - Lynne E Maquat
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
- Center for RNA Biology, University of Rochester, Rochester, New York 14642, USA
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22
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Abstract
DEAD box RNA helicases regulate diverse facets of RNA biology. Proteins of this family carry out essential cellular functions, and emerging literature is revealing additional roles in immune defense. Using RNA interference screening, we identified an evolutionarily conserved antiviral role for the helicase DDX56 against the alphavirus Sindbis virus (SINV), a mosquito-transmitted pathogen that infects humans. Depletion of DDX56 enhanced infection in Drosophila and human cells. Furthermore, we found that DDX56 also controls the emerging alphavirus chikungunya virus (CHIKV) through an interferon-independent mechanism. Using cross-linking immunoprecipitation (CLIP-Seq), we identified a predicted stem-loop on the viral genomic RNA bound by DDX56. Mechanistically, we found that DDX56 levels increase in the cytoplasm during CHIKV infection. In the cytoplasm, DDX56 impacts the earliest step in the viral replication cycle by binding and destabilizing the incoming viral genomic RNA, thereby attenuating infection. Thus, DDX56 is a conserved antiviral RNA binding protein that controls alphavirus infection.IMPORTANCE Arthropod-borne viruses are diverse pathogens and include the emerging virus chikungunya virus, which is associated with human disease. Through genetic screening, we found that the conserved RNA binding protein DDX56 is antiviral against chikungunya virus in insects and humans. DDX56 relocalizes from the nucleus to the cytoplasm, where it binds to a stem-loop in the viral genome and destabilizes incoming genomes. Thus, DDX56 is an evolutionarily conserved antiviral factor that controls alphavirus infection.
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23
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Gerbracht JV, Boehm V, Britto-Borges T, Kallabis S, Wiederstein JL, Ciriello S, Aschemeier DU, Krüger M, Frese CK, Altmüller J, Dieterich C, Gehring NH. CASC3 promotes transcriptome-wide activation of nonsense-mediated decay by the exon junction complex. Nucleic Acids Res 2020; 48:8626-8644. [PMID: 32621609 PMCID: PMC7470949 DOI: 10.1093/nar/gkaa564] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 05/20/2020] [Accepted: 07/01/2020] [Indexed: 01/08/2023] Open
Abstract
The exon junction complex (EJC) is an essential constituent and regulator of spliced messenger ribonucleoprotein particles (mRNPs) in metazoans. As a core component of the EJC, CASC3 was described to be pivotal for EJC-dependent nuclear and cytoplasmic processes. However, recent evidence suggests that CASC3 functions differently from other EJC core proteins. Here, we have established human CASC3 knockout cell lines to elucidate the cellular role of CASC3. In the knockout cells, overall EJC composition and EJC-dependent splicing are unchanged. A transcriptome-wide analysis reveals that hundreds of mRNA isoforms targeted by nonsense-mediated decay (NMD) are upregulated. Mechanistically, recruiting CASC3 to reporter mRNAs by direct tethering or via binding to the EJC stimulates mRNA decay and endonucleolytic cleavage at the termination codon. Building on existing EJC-NMD models, we propose that CASC3 equips the EJC with the persisting ability to communicate with the NMD machinery in the cytoplasm. Collectively, our results characterize CASC3 as a peripheral EJC protein that tailors the transcriptome by promoting the degradation of EJC-dependent NMD substrates.
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Affiliation(s)
| | - Volker Boehm
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany
| | - Thiago Britto-Borges
- Section of Bioinformatics and Systems Cardiology, Department of Internal Medicine III and Klaus Tschira Institute for Integrative Computational Cardiology, University of Heidelberg, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Partner site Heidelberg/Mannheim, 69120 Heidelberg, Germany
| | - Sebastian Kallabis
- CECAD Research Center, University of Cologne, Joseph-Stelzmann-Str. 26, 50931 Cologne, Germany
| | - Janica L Wiederstein
- CECAD Research Center, University of Cologne, Joseph-Stelzmann-Str. 26, 50931 Cologne, Germany
| | - Simona Ciriello
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany
| | | | - Marcus Krüger
- CECAD Research Center, University of Cologne, Joseph-Stelzmann-Str. 26, 50931 Cologne, Germany
| | - Christian K Frese
- CECAD Research Center, University of Cologne, Joseph-Stelzmann-Str. 26, 50931 Cologne, Germany
| | - Janine Altmüller
- Cologne Center for Genomics (CCG), University of Cologne, 50931 Cologne, Germany.,Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50937 Cologne, Germany
| | - Christoph Dieterich
- Section of Bioinformatics and Systems Cardiology, Department of Internal Medicine III and Klaus Tschira Institute for Integrative Computational Cardiology, University of Heidelberg, 69120 Heidelberg, Germany.,DZHK (German Centre for Cardiovascular Research), Partner site Heidelberg/Mannheim, 69120 Heidelberg, Germany
| | - Niels H Gehring
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany.,Center for Molecular Medicine Cologne (CMMC), University of Cologne, 50937 Cologne, Germany
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24
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The Branched Nature of the Nonsense-Mediated mRNA Decay Pathway. Trends Genet 2020; 37:143-159. [PMID: 33008628 DOI: 10.1016/j.tig.2020.08.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/11/2020] [Accepted: 08/18/2020] [Indexed: 12/16/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) is a conserved translation-coupled quality control mechanism in all eukaryotes that regulates the expression of a significant fraction of both the aberrant and normal transcriptomes. In vertebrates, NMD has become an essential process owing to expansion of the diversity of NMD-regulated transcripts, particularly during various developmental processes. Surprisingly, however, some core NMD factors that are essential for NMD in simpler organisms appear to be dispensable for vertebrate NMD. At the same time, numerous NMD enhancers and suppressors have been identified in multicellular organisms including vertebrates. Collectively, the available data suggest that vertebrate NMD is a complex, branched pathway wherein individual branches regulate specific mRNA subsets to fulfill distinct physiological functions.
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25
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Rahman MA, Lin KT, Bradley RK, Abdel-Wahab O, Krainer AR. Recurrent SRSF2 mutations in MDS affect both splicing and NMD. Genes Dev 2020; 34:413-427. [PMID: 32001512 PMCID: PMC7050488 DOI: 10.1101/gad.332270.119] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Accepted: 12/20/2019] [Indexed: 12/23/2022]
Abstract
Oncogenic mutations in the RNA splicing factors SRSF2, SF3B1, and U2AF1 are the most frequent class of mutations in myelodysplastic syndromes and are also common in clonal hematopoiesis, acute myeloid leukemia, chronic lymphocytic leukemia, and a variety of solid tumors. They cause genome-wide splicing alterations that affect important regulators of hematopoiesis. Several mRNA isoforms promoted by the various splicing factor mutants comprise a premature termination codon (PTC) and are therefore potential targets of nonsense-mediated mRNA decay (NMD). In light of the mechanistic relationship between splicing and NMD, we sought evidence for a specific role of mutant SRSF2 in NMD. We show that SRSF2 Pro95 hot spot mutations elicit enhanced mRNA decay, which is dependent on sequence-specific RNA binding and splicing. SRSF2 mutants enhance the deposition of exon junction complexes (EJCs) downstream from the PTC through RNA-mediated molecular interactions. This architecture then favors the association of key NMD factors to elicit mRNA decay. Gene-specific blocking of EJC deposition by antisense oligonucleotides circumvents aberrant NMD promoted by mutant SRSF2, restoring the expression of PTC-containing transcript. Our study uncovered critical effects of SRSF2 mutants in hematologic malignancies, reflecting the regulation at multiple levels of RNA metabolism, from splicing to decay.
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Affiliation(s)
| | - Kuan-Ting Lin
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
| | - Robert K Bradley
- Computational Biology Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.,Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA
| | - Omar Abdel-Wahab
- Memorial Sloan Kettering Cancer Center, New York, New York 10065, USA
| | - Adrian R Krainer
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York 11724, USA
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26
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Aznarez I, Nomakuchi TT, Tetenbaum-Novatt J, Rahman MA, Fregoso O, Rees H, Krainer AR. Mechanism of Nonsense-Mediated mRNA Decay Stimulation by Splicing Factor SRSF1. Cell Rep 2019; 23:2186-2198. [PMID: 29768215 PMCID: PMC5999336 DOI: 10.1016/j.celrep.2018.04.039] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 02/20/2018] [Accepted: 04/06/2018] [Indexed: 11/25/2022] Open
Abstract
The splicing factor SRSF1 promotes nonsense-mediated mRNA decay (NMD), a quality control mechanism that degrades mRNAs with premature termination codons (PTCs). Here we show that transcript-bound SRSF1 increases the binding of NMD factor UPF1 to mRNAs while in, or associated with, the nucleus, bypassing UPF2 recruitment and promoting NMD. SRSF1 promotes NMD when positioned downstream of a PTC, which resembles the mode of action of exon junction complex (EJC) and NMD factors. Moreover, splicing and/or EJC deposition increase the effect of SRSF1 on NMD. Lastly, SRSF1 enhances NMD of PTC-containing endogenous transcripts that result from various events. Our findings reveal an alternative mechanism for UPF1 recruitment, uncovering an additional connection between splicing and NMD. SRSF1’s role in the mRNA’s journey from splicing to decay has broad implications for gene expression regulation and genetic diseases.
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Affiliation(s)
- Isabel Aznarez
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | | | | | | | - Oliver Fregoso
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Holly Rees
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA
| | - Adrian R Krainer
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
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27
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Bartkowska K, Tepper B, Turlejski K, Djavadian RL. Roles of the exon junction complex components in the central nervous system: a mini review. Rev Neurosci 2019; 29:817-824. [PMID: 29791316 DOI: 10.1515/revneuro-2017-0113] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 03/22/2018] [Indexed: 01/02/2023]
Abstract
The exon junction complex (EJC) consists of four core proteins: Magoh, RNA-binding motif 8A (Rbm8a, also known as Y14), eukaryotic initiation factor 4A3 (eIF4A3, also known as DDX48), and metastatic lymph node 51 (MLN51, also known as Casc3 or Barentsz), which are involved in the regulation of many processes occurring between gene transcription and protein translation. Its main role is to assemble into spliceosomes at the exon-exon junction of mRNA during splicing. It is, therefore, a range of functions concerning post-splicing events such as mRNA translocation, translation, and nonsense-mediated mRNA decay (NMD). Apart from this, proteins of the EJC control the splicing of specific pre-mRNAs, for example, splicing of the mapk transcript. Recent studies support essential functions of EJC proteins in oocytes and, after fertilization, in all stages of zygote development, as well as the growth of the embryo, including the development of the nervous system. During the development of the central nervous system (CNS), the EJC controls mitosis, regulating both symmetric and asymmetric cell divisions. Reduced levels of EJC components cause microcephaly. In the adult brain, Y14 and eIF4A3 appear to be involved in synaptic plasticity and in learning and memory. In this review, we focus on the involvement of EJC components in brain development and its functioning under normal conditions.
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Affiliation(s)
- Katarzyna Bartkowska
- Department of Molecular and Cellular Biology, Nencki Institute of Experimental Biology Polish Academy of Sciences, Warsaw, Poland
| | - Beata Tepper
- Department of Molecular and Cellular Biology, Nencki Institute of Experimental Biology Polish Academy of Sciences, Warsaw, Poland
| | - Kris Turlejski
- Faculty of Biology and Environmental Sciences, Cardinal Stefan Wyszynski University, Warsaw, Poland
| | - Ruzanna L Djavadian
- Department of Molecular and Cellular Biology, Nencki Institute of Experimental Biology Polish Academy of Sciences, Warsaw 02-093, Poland
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28
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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 INTERDISCIPLINARY REVIEWS-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] [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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29
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Mazloomian A, Araki S, Ohori M, El-Naggar AM, Yap D, Bashashati A, Nakao S, Sorensen PH, Nakanishi A, Shah S, Aparicio S. Pharmacological systems analysis defines EIF4A3 functions in cell-cycle and RNA stress granule formation. Commun Biol 2019; 2:165. [PMID: 31069274 PMCID: PMC6499833 DOI: 10.1038/s42003-019-0391-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 03/11/2019] [Indexed: 12/13/2022] Open
Abstract
The RNA helicase EIF4A3 regulates the exon junction complex and nonsense-mediated mRNA decay functions in RNA transcript processing. However, a transcriptome-wide network definition of these functions has been lacking, in part due to the lack of suitable pharmacological inhibitors. Here we employ short-duration graded EIF4A3 inhibition using small molecule allosteric inhibitors to define the transcriptome-wide dependencies of EIF4A3. We thus define conserved cellular functions, such as cell cycle control, that are EIF4A3 dependent. We show that EIF4A3-dependent splicing reactions have a distinct genome-wide pattern of associated RNA-binding protein motifs. We also uncover an unanticipated role of EIF4A3 in the biology of RNA stress granules, which sequester and silence the translation of most mRNAs under stress conditions and are implicated in cell survival and tumour progression. We show that stress granule induction and maintenance is suppressed on the inhibition of EIF4A3, in part through EIF4A3-associated regulation of G3BP1 and TIA1 scaffold protein expression.
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Affiliation(s)
- Alborz Mazloomian
- Department of Molecular Oncology, BC Cancer, part of the Provincial Health Services Authority, 675 West 10th Avenue, Vancouver, BC V5Z 1L3 Canada
- Department of Pathology and Laboratory Medicine, G227-2211 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 2B5 Canada
| | - Shinsuke Araki
- Research Department, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555 Japan
| | - Momoko Ohori
- Research Department, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555 Japan
| | - Amal M. El-Naggar
- Department of Molecular Oncology, BC Cancer, part of the Provincial Health Services Authority, 675 West 10th Avenue, Vancouver, BC V5Z 1L3 Canada
- Department of Pathology and Laboratory Medicine, G227-2211 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 2B5 Canada
- Department of Pathology, Faculty of Medicine, Menoufia University, Menoufia Governorate, Egypt
| | - Damian Yap
- Department of Molecular Oncology, BC Cancer, part of the Provincial Health Services Authority, 675 West 10th Avenue, Vancouver, BC V5Z 1L3 Canada
- Department of Pathology and Laboratory Medicine, G227-2211 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 2B5 Canada
| | - Ali Bashashati
- Department of Molecular Oncology, BC Cancer, part of the Provincial Health Services Authority, 675 West 10th Avenue, Vancouver, BC V5Z 1L3 Canada
- Department of Pathology and Laboratory Medicine, G227-2211 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 2B5 Canada
| | - Shoichi Nakao
- Research Department, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555 Japan
| | - Poul H. Sorensen
- Department of Molecular Oncology, BC Cancer, part of the Provincial Health Services Authority, 675 West 10th Avenue, Vancouver, BC V5Z 1L3 Canada
- Department of Pathology and Laboratory Medicine, G227-2211 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 2B5 Canada
| | - Atsushi Nakanishi
- Research Department, Takeda Pharmaceutical Company Limited, 26-1, Muraoka-Higashi 2-chome, Fujisawa, Kanagawa 251-8555 Japan
| | - Sohrab Shah
- Department of Molecular Oncology, BC Cancer, part of the Provincial Health Services Authority, 675 West 10th Avenue, Vancouver, BC V5Z 1L3 Canada
- Department of Pathology and Laboratory Medicine, G227-2211 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 2B5 Canada
- Department of Epidemiology & Biostatistics, Memorial Sloan Kettering Cancer Center, 417 E68th St, New York, NY 10065 USA
| | - Samuel Aparicio
- Department of Molecular Oncology, BC Cancer, part of the Provincial Health Services Authority, 675 West 10th Avenue, Vancouver, BC V5Z 1L3 Canada
- Department of Pathology and Laboratory Medicine, G227-2211 Wesbrook Mall, University of British Columbia, Vancouver, BC V6T 2B5 Canada
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30
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Identification of antiviral roles for the exon-junction complex and nonsense-mediated decay in flaviviral infection. Nat Microbiol 2019; 4:985-995. [PMID: 30833725 PMCID: PMC6533143 DOI: 10.1038/s41564-019-0375-z] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Accepted: 01/18/2019] [Indexed: 12/31/2022]
Abstract
West Nile virus (WNV) is an emerging mosquito-borne flavivirus, related to dengue virus and Zika virus. To gain insight into host pathways involved in WNV infection, we performed a systematic affinity-tag purification mass spectrometry (AP-MS) study to identify 259 WNV-interacting human proteins. RNAi screening revealed 26 genes that both interact with WNV proteins and influence WNV infection. We found that WNV, dengue and Zika virus capsids interact with a conserved subset of proteins that impact infection. These include the exon-junction complex (EJC) recycling factor, PYM1, which is antiviral against all three viruses. The EJC has roles in nonsense-mediated decay (NMD), and we found that both the EJC and NMD are antiviral and the EJC protein RBM8A directly binds WNV RNA. To counteract this, flavivirus infection inhibits NMD and the capsid-PYM1 interaction interferes with EJC protein function and localization. Depletion of PYM1 attenuates RBM8A binding to viral RNA, suggesting that WNV sequesters PYM1 to protect viral RNA from decay. Together, these data suggest a complex interplay between the virus and host in regulating NMD and the EJC.
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31
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Gordo G, Rodriguez-Laguna L, Agra N, Mendez P, Feito M, Lapunzina P, Lopez-Gutierrez JC, Martinez-Glez V. Constitutional mosaicism in RASA1
-related capillary malformation-arteriovenous malformation. Clin Genet 2019; 95:516-519. [DOI: 10.1111/cge.13499] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 12/20/2018] [Accepted: 12/21/2018] [Indexed: 12/31/2022]
Affiliation(s)
- Gema Gordo
- Vascular Malformations Section; Institute of Medical and Molecular Genetics, INGEMM-IdiPAZ, Hospital Universitario La Paz; Madrid Spain
| | - Lara Rodriguez-Laguna
- Vascular Malformations Section; Institute of Medical and Molecular Genetics, INGEMM-IdiPAZ, Hospital Universitario La Paz; Madrid Spain
| | - Noelia Agra
- Vascular Malformations Section; Institute of Medical and Molecular Genetics, INGEMM-IdiPAZ, Hospital Universitario La Paz; Madrid Spain
| | - Pilar Mendez
- Unidad de Genética, Servicio de Inmunología y Genética; Complejo Hospitalario Universitario de Badajoz; Badajoz Spain
| | - Marta Feito
- Department of Dermatology; Hospital Universitario La Paz; Madrid Spain
| | - Pablo Lapunzina
- Clinical Genetics Section; Institute of Medical and Molecular Genetics, INGEMM-IdiPAZ, Hospital Universitario La Paz; Madrid Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER); ISCIII; Madrid Spain
| | | | - Victor Martinez-Glez
- Vascular Malformations Section; Institute of Medical and Molecular Genetics, INGEMM-IdiPAZ, Hospital Universitario La Paz; Madrid Spain
- Clinical Genetics Section; Institute of Medical and Molecular Genetics, INGEMM-IdiPAZ, Hospital Universitario La Paz; Madrid Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER); ISCIII; Madrid Spain
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32
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Zhou Z, Chen Y, Jin M, He J, Guli A, Yan C, Ding S. Comprehensive Analysis of Lysine Acetylome Reveals a Site-Specific Pattern in Rapamycin-Induced Autophagy. J Proteome Res 2019; 18:865-877. [PMID: 30592415 DOI: 10.1021/acs.jproteome.8b00533] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Protein acetylation reportedly acts as a key regulator of autophagy. However, up to now, the relationship between acetylome and autophagy has remained unclear. Here stable isotope labeling of amino acids in cell culture and high-throughput quantitative mass spectrometry were used to perform an acetylome analysis of rapamycin-induced autophagy in vitro. Our data revealed that 2135 sites were quantified on 1081 proteins. During autophagy, 421 sites were significantly regulated on 296 proteins, with 80.8% of sites downregulated and 19.2% upregulated. Motif enrichment analysis revealed five main motifs. Most of the downregulated sites conformed to the classical functional motif of p300/CBP [G-AcK]. Furthermore, acetylation targeted proteins involved mainly in ribosomes, spliceosomes, and AcCoA-related metabolic process. In-depth analysis indicated that most of the acetylation sites were in the critical domain, were functional sites, or could change their enzymatic activity by acetylation, highlighting the importance of site-specific acetylation patterns. Subsequently, we demonstrated that K1549 of p300 was also a functional site that could regulate the autophagic process in vitro. In conclusion, our data reveal a deacetylation-preponderant profile with autophagy. The specificity of the related motifs and the identification of site-specific acetylation patterns will assist searches for potential targets or subsequent mechanism-focused studies to elucidate site-specific protein networks in autophagy.
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Affiliation(s)
- Zhuo Zhou
- The National Education Base for Basic Medical Sciences , Zhejiang University School of Medicine , 866 Yuhangtang Road , Hangzhou 310058 , Zhejiang Province , China
| | - Yu Chen
- The National Education Base for Basic Medical Sciences , Zhejiang University School of Medicine , 866 Yuhangtang Road , Hangzhou 310058 , Zhejiang Province , China
| | - Mengqi Jin
- The National Education Base for Basic Medical Sciences , Zhejiang University School of Medicine , 866 Yuhangtang Road , Hangzhou 310058 , Zhejiang Province , China
| | - Jianqin He
- State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, The First Affiliated Hospital , Zhejiang University School of Medicine , 79 Qingchun Road , Hangzhou 310003 , Zhejiang Province , China
| | - Ayiding Guli
- The National Education Base for Basic Medical Sciences , Zhejiang University School of Medicine , 866 Yuhangtang Road , Hangzhou 310058 , Zhejiang Province , China
| | - Chunlan Yan
- Department of Biophysics, Key Laboratory of Medical Neurobiology, Ministry of Health of China , Zhejiang University School of Medicine , 866 Yuhangtang Road , Hangzhou 310058 , Zhejiang Province , China
| | - Shiping Ding
- The National Education Base for Basic Medical Sciences , Zhejiang University School of Medicine , 866 Yuhangtang Road , Hangzhou 310058 , Zhejiang Province , China
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33
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Gong P, Li J, He C. Exon junction complex (EJC) core genes play multiple developmental roles in Physalis floridana. PLANT MOLECULAR BIOLOGY 2018; 98:545-563. [PMID: 30426309 PMCID: PMC6280879 DOI: 10.1007/s11103-018-0795-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Accepted: 11/07/2018] [Indexed: 06/09/2023]
Abstract
KEY MESSAGE Molecular and functional characterization of four gene families of the Physalis exon junction complex (EJC) core improved our understanding of the evolution and function of EJC core genes in plants. The exon junction complex (EJC) plays significant roles in posttranscriptional regulation of genes in eukaryotes. However, its developmental roles in plants are poorly known. We characterized four EJC core genes from Physalis floridana that were named PFMAGO, PFY14, PFeIF4AIII and PFBTZ. They shared a similar phylogenetic topology and were expressed in all examined organs. PFMAGO, PFY14 and PFeIF4AIII were localized in both the nucleus and cytoplasm while PFBTZ was mainly localized in the cytoplasm. No protein homodimerization was observed, but they could form heterodimers excluding the PFY14-PFBTZ heterodimerization. Virus-induced gene silencing (VIGS) of PFMAGO or PFY14 aborted pollen development and resulted in low plant survival due to a leaf-blight-like phenotype in the shoot apex. Carpel functionality was also impaired in the PFY14 knockdowns, whereas pollen maturation was uniquely affected in PFBTZ-VIGS plants. Once PFeIF4AIII was strongly downregulated, plant survival was reduced via a decomposing root collar after flowering and Chinese lantern morphology was distorted. The expression of Physalis orthologous genes in the DYT1-TDF1-AMS-bHLH91 regulatory cascade that is associated with pollen maturation was significantly downregulated in PFMAGO-, PFY14- and PFBTZ-VIGS flowers. Intron-retention in the transcripts of P. floridana dysfunctional tapetum1 (PFDYT1) occurred in these mutated flowers. Additionally, the expression level of WRKY genes in defense-related pathways in the shoot apex of PFMAGO- or PFY14-VIGS plants and in the root collar of PFeIF4AIII-VIGS plants was significantly downregulated. Taken together, the Physalis EJC core genes play multiple roles including a conserved role in male fertility and newly discovered roles in Chinese lantern development, carpel functionality and defense-related processes. These data increase our understanding of the evolution and functions of EJC core genes in plants.
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Affiliation(s)
- Pichang Gong
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
| | - Jing Li
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chaoying He
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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34
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Roberti D, Conforti R, Giugliano T, Brogna B, Tartaglione I, Casale M, Piluso G, Perrotta S. A Novel 12q13.2-q13.3 Microdeletion Syndrome With Combined Features of Diamond Blackfan Anemia, Pierre Robin Sequence and Klippel Feil Deformity. Front Genet 2018; 9:549. [PMID: 30524470 PMCID: PMC6262175 DOI: 10.3389/fgene.2018.00549] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 10/26/2018] [Indexed: 11/21/2022] Open
Abstract
Diamond-Blackfan anemia (DBA) is a rare congenital erythroid aplasia with a highly heterogeneous genetic background; it usually occurs in infancy. Approximately 30–40% of patients have other associated congenital anomalies; in particular, facial anomalies, such as cleft palate, are part of about 10% of the DBA clinical presentations. Pierre Robin sequence (PRS) is a heterogeneous condition, defined by the presence of the triad of glossoptosis, micrognathia and cleft palate; it occurs in 1/8500 to 1/14,000 births. Klippel Feil (KF) syndrome is a complex of both osseous and visceral anomalies, characterized mainly by congenital development defects of the cervical spine. We describe the case of a 22-years-old woman affected by DBA, carrying a de novo deletion about 500 Kb-long at 12q13.2-q13.3 that included RPS26 and, at least, others 25 flanking genes. The patient showed craniofacial anomalies due to PRS and suffered for KF deformities (type II). Computed Tomography study of cranio-cervical junction (CCJ) drew out severe bone malformations and congenital anomalies as atlanto-occipital assimilation (AOA), arcuate foramen and occipito-condylar hyperplasia. Foramen magnum was severely reduced. Atlanto-axial instability (AAI) was linked to atlanto-occipital assimilation, congenital vertebral fusion and occipito-condyle bone hyperplasia. Basilar invagination and platybasia were ruled out on CT and Magnetic Resonance Imaging (MRI) studies. Furthermore, the temporal Bone CT study showed anomalies of external auditory canals, absent mastoid pneumatization, chronic middle ear otitis and abnormal course of the facial nerve bones canal. The described phenotype might be related to the peculiar deletion affecting the patient, highlighting that genes involved in the in the breakdown of extracellular matrix (MMP19), in cell cycle regulation (CDK2), vesicular trafficking (RAB5B), in ribonucleoprotein complexes formation (ZC3H10) and muscles function (MYL6 and MYL6B) could be potentially related to bone-developmental disorders. Moreover, it points out that multiple associated ribosomal deficits might play a role in DBA-related phenotypes, considering the simultaneous deletion of three of them in the index case (RPS26, PA2G4 and RPL41), and it confirms the association among SLC39A5 functional disruption and severe myopia. This report highlights the need for a careful genetic evaluation and a detailed phenotype-genotype correlation in each complex malformative syndrome.
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Affiliation(s)
- Domenico Roberti
- Department of Woman, Child and General and Specialized Surgery, University of Campania "L. Vanvitelli" Naples, Italy
| | - Renata Conforti
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy
| | - Teresa Giugliano
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy
| | - Barbara Brogna
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy
| | - Immacolata Tartaglione
- Department of Woman, Child and General and Specialized Surgery, University of Campania "L. Vanvitelli" Naples, Italy
| | - Maddalena Casale
- Department of Woman, Child and General and Specialized Surgery, University of Campania "L. Vanvitelli" Naples, Italy
| | - Giulio Piluso
- Department of Precision Medicine, University of Campania "L. Vanvitelli", Naples, Italy
| | - Silverio Perrotta
- Department of Woman, Child and General and Specialized Surgery, University of Campania "L. Vanvitelli" Naples, Italy
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35
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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: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [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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36
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Boehm V, Britto-Borges T, Steckelberg AL, Singh KK, Gerbracht JV, Gueney E, Blazquez L, Altmüller J, Dieterich C, Gehring NH. Exon Junction Complexes Suppress Spurious Splice Sites to Safeguard Transcriptome Integrity. Mol Cell 2018; 72:482-495.e7. [DOI: 10.1016/j.molcel.2018.08.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2018] [Revised: 07/24/2018] [Accepted: 08/20/2018] [Indexed: 12/14/2022]
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37
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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: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [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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38
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Karamyshev AL, Karamysheva ZN. Lost in Translation: Ribosome-Associated mRNA and Protein Quality Controls. Front Genet 2018; 9:431. [PMID: 30337940 PMCID: PMC6180196 DOI: 10.3389/fgene.2018.00431] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 09/11/2018] [Indexed: 12/15/2022] Open
Abstract
Aberrant, misfolded, and mislocalized proteins are often toxic to cells and result in many human diseases. All proteins and their mRNA templates are subject to quality control. There are several distinct mechanisms that control the quality of mRNAs and proteins during translation at the ribosome. mRNA quality control systems, nonsense-mediated decay, non-stop decay, and no-go decay detect premature stop codons, the absence of a natural stop codon, and stalled ribosomes in translation, respectively, and degrade their mRNAs. Defective truncated polypeptide nascent chains generated from faulty mRNAs are degraded by ribosome-associated protein quality control pathways. Regulation of aberrant protein production, a novel pathway, senses aberrant proteins by monitoring the status of nascent chain interactions during translation and triggers degradation of their mRNA. Here, we review the current progress in understanding of the molecular mechanisms of mRNA and protein quality controls at the ribosome during translation.
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Affiliation(s)
- Andrey L Karamyshev
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Zemfira N Karamysheva
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, United States
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39
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The splicing of tiny introns of Paramecium is controlled by MAGO. Gene 2018; 663:101-109. [PMID: 29653229 DOI: 10.1016/j.gene.2018.04.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Revised: 03/27/2018] [Accepted: 04/04/2018] [Indexed: 11/22/2022]
Abstract
The exon junction complex (EJC) is a key element of the splicing machinery. The EJC core is composed of eIF4A3, MAGO, Y14 and MLN51. Few accessory proteins, such as CWC22 or UPF3, bind transiently to the EJC. The EJC has been implicated in the control of the splicing of long introns. To ascertain whether the EJC controls the splicing of short introns, we used Paramecium tetraurelia as a model organism, since it has thousands of very tiny introns. To elucidate whether EJC affects intron splicing in P. tetraurelia, we searched for EJC protein-coding genes, and silenced those genes coding for eIF4A3, MAGO and CWC22. We found that P. tetraurelia likely assembles an active EJC with only three of the core proteins, since MLN51 is lacking. Silencing of eIF4A3 or CWC22 genes, but not that of MAGO, caused lethality. Silencing of the MAGO gene caused either an increase, decrease, or no change in intron retention levels of some intron-containing mRNAs used as reporters. We suggest that a fine-tuning expression of EJC genes is required for steady intron removal in P. tetraurelia. Taking into consideration our results and those published by others, we conclude that the EJC controls splicing independently of the intron size.
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40
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Bannerman BP, Kramer S, Dorrell RG, Carrington M. Multispecies reconstructions uncover widespread conservation, and lineage-specific elaborations in eukaryotic mRNA metabolism. PLoS One 2018; 13:e0192633. [PMID: 29561870 PMCID: PMC5862402 DOI: 10.1371/journal.pone.0192633] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 01/26/2018] [Indexed: 12/01/2022] Open
Abstract
The degree of conservation and evolution of cytoplasmic mRNA metabolism pathways across the eukaryotes remains incompletely resolved. In this study, we describe a comprehensive genome and transcriptome-wide analysis of proteins involved in mRNA maturation, translation, and mRNA decay across representative organisms from the six eukaryotic super-groups. We demonstrate that eukaryotes share common pathways for mRNA metabolism that were almost certainly present in the last eukaryotic common ancestor, and show for the first time a correlation between intron density and a selective absence of some Exon Junction Complex (EJC) components in eukaryotes. In addition, we identify pathways that have diversified in individual lineages, with a specific focus on the unique gene gains and losses in members of the Excavata and SAR groups that contribute to their unique gene expression pathways compared to other organisms.
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Affiliation(s)
| | - Susanne Kramer
- Biozentrum, Lehrstuhl für Zell-und Entwicklungsbiologie, Universität Würzburg, Am Hubland, Würzburg, Germany
| | - Richard G. Dorrell
- Institute of Biology, École Normale Supérieure, PSL Research University, Paris, France
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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41
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Baird TD, Cheng KCC, Chen YC, Buehler E, Martin SE, Inglese J, Hogg JR. ICE1 promotes the link between splicing and nonsense-mediated mRNA decay. eLife 2018. [PMID: 29528287 PMCID: PMC5896957 DOI: 10.7554/elife.33178] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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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42
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The exon junction complex: structural insights into a faithful companion of mammalian mRNPs. Biochem Soc Trans 2018; 46:153-161. [PMID: 29351963 DOI: 10.1042/bst20170059] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 12/13/2017] [Accepted: 12/18/2017] [Indexed: 12/21/2022]
Abstract
During splicing, the exon junction complex (EJC) is deposited upstream of exon-exon boundaries. The EJC and its peripheral bound proteins play an essential role in mediating mRNA export, translation and turnover. However, the exact sequence of EJC assembly and the involved factors during splicing remain elusive. Recently published structures of the human C* spliceosome clarified the position of the EJC at this phase of splicing and have given insight into previously unidentified interactions between the EJC and spliceosomal proteins. Here, these new observations are presented and the significance for EJC assembly is discussed. Furthermore, the vast landscape of EJC interacting proteins and their manifold functions are described. Finally, the factors involved in EJC disassembly and recycling are recapitulated. This review aims to integrate structural, biochemical and physiological data to obtain a comprehensive picture of EJC components during the lifetime of the EJC.
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43
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C-terminal short arginine/serine repeat sequence-dependent regulation of Y14 (RBM8A) localization. Sci Rep 2018; 8:612. [PMID: 29330450 PMCID: PMC5766523 DOI: 10.1038/s41598-017-18765-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 12/15/2017] [Indexed: 01/01/2023] Open
Abstract
Y14 (RBM8A) is an RNA recognition motif-containing protein that forms heterodimers with MAGOH and serves as a core factor of the RNA surveillance machinery for the exon junction complex (EJC). The role of the Y14 C-terminal serine/arginine (RS) repeat-containing region, which has been reported to undergo modifications such as phosphorylation and methylation, has not been sufficiently investigated. Thus, we aimed to explore the functional significance of the Y14 C-terminal region. Deletion or dephosphorylation mimic mutants of the C-terminal region showed a shift in localization from the nucleoplasmic region; in addition, the C-terminal RS repeat-containing sequence itself exhibited the potential for nucleolar localization. Additionally, the regulation of Y14 localization by the C-terminal region was further found to be exquisitely controlled by MAGOH binding. Cumulatively, our findings, which demonstrated that Y14 localization is regulated not only by the previously reported N-terminal localization signal but also by the C-terminal RS repeat-containing region through phosphorylation and MAGOH binding to Y14, provide new insights for the mechanism of localization of short RS repeat-containing proteins.
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44
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Gupta P, Li YR. Upf proteins: highly conserved factors involved in nonsense mRNA mediated decay. Mol Biol Rep 2017; 45:39-55. [PMID: 29282598 DOI: 10.1007/s11033-017-4139-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 12/14/2017] [Indexed: 11/28/2022]
Abstract
Over 10% of genetic diseases are caused by mutations that introduce a premature termination codon in protein-coding mRNA. Nonsense-mediated mRNA decay (NMD) is an essential cellular pathway that degrades these mRNAs to prevent the accumulation of harmful partial protein products. NMD machinery is also increasingly appreciated to play a role in other essential cellular functions, including telomere homeostasis and the regulation of normal mRNA turnover, and is misregulated in numerous cancers. Hence, understanding and designing therapeutics targeting NMD is an important goal in biomedical science. The central regulator of NMD, the Upf1 protein, interacts with translation termination factors and contextual factors to initiate NMD specifically on mRNAs containing PTCs. The molecular details of how these contextual factors affect Upf1 function remain poorly understood. Here, we review plausible models for the NMD pathway and the evidence for the variety of roles NMD machinery may play in different cellular processes.
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Affiliation(s)
- Puneet Gupta
- Harvard College, Harvard University, Cambridge, MA, 02138, USA.,School of Arts and Sciences, St. Bonaventure University, St. Bonaventure, NY, 14778, USA
| | - Yan-Ruide Li
- Harvard Medical School, Harvard University, Boston, MA, 02115, USA. .,College of Life Sciences, Zhejiang University, 866 Yu Hang Tang Road, Hangzhou, 310058, China.
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45
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Martinez-Nunez RT, Wallace A, Coyne D, Jansson L, Rush M, Ennajdaoui H, Katzman S, Bailey J, Deinhardt K, Sanchez-Elsner T, Sanford JR. Modulation of nonsense mediated decay by rapamycin. Nucleic Acids Res 2017; 45:3448-3459. [PMID: 27899591 PMCID: PMC5389481 DOI: 10.1093/nar/gkw1109] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 10/28/2016] [Indexed: 01/24/2023] Open
Abstract
Rapamycin is a naturally occurring macrolide whose target is at the core of nutrient and stress regulation in a wide range of species. Despite well-established roles as an inhibitor of cap-dependent mRNA translation, relatively little is known about its effects on other modes of RNA processing. Here, we characterize the landscape of rapamycin-induced post-transcriptional gene regulation. Transcriptome analysis of rapamycin-treated cells reveals genome-wide changes in alternative mRNA splicing and pronounced changes in NMD-sensitive isoforms. We demonstrate that despite well-documented attenuation of cap-dependent mRNA translation, rapamycin can augment NMD of certain transcripts. Rapamycin-treatment significantly reduces the levels of both endogenous and exogenous Premature Termination Codon (PTC)-containing mRNA isoforms and its effects are dose-, UPF1- and 4EBP-dependent. The PTC-containing SRSF6 transcript exhibits a shorter half-life upon rapamycin-treatment as compared to the non-PTC isoform. Rapamycin-treatment also causes depletion of PTC-containing mRNA isoforms from polyribosomes, underscoring the functional relationship between translation and NMD. Enhanced NMD activity also correlates with an enrichment of the nuclear Cap Binding Complex (CBC) in rapamycin-treated cells. Our data demonstrate that rapamycin modulates global RNA homeostasis by NMD.
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Affiliation(s)
- Rocio T Martinez-Nunez
- University of California Santa Cruz, Department of Molecular, Cellular and Developmental Biology, Santa Cruz, CA 95064, USA.,Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | - Andrew Wallace
- University of California Santa Cruz, Department of Molecular, Cellular and Developmental Biology, Santa Cruz, CA 95064, USA
| | - Doyle Coyne
- University of California Santa Cruz, Department of Molecular, Cellular and Developmental Biology, Santa Cruz, CA 95064, USA
| | - Linnea Jansson
- University of California Santa Cruz, Department of Molecular, Cellular and Developmental Biology, Santa Cruz, CA 95064, USA
| | - Miles Rush
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | - Hanane Ennajdaoui
- University of California Santa Cruz, Department of Molecular, Cellular and Developmental Biology, Santa Cruz, CA 95064, USA
| | - Sol Katzman
- Center for Biomolecular Science and Engineering, University of California Santa Cruz, 1156 High Street, Santa Cruz, CA 95060, USA
| | - Joanne Bailey
- Centre for Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Katrin Deinhardt
- Centre for Biological Sciences, Faculty of Natural and Environmental Sciences, University of Southampton, Southampton SO17 1BJ, UK
| | - Tilman Sanchez-Elsner
- Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, UK
| | - Jeremy R Sanford
- University of California Santa Cruz, Department of Molecular, Cellular and Developmental Biology, Santa Cruz, CA 95064, USA
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46
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Ottens F, Boehm V, Sibley CR, Ule J, Gehring NH. Transcript-specific characteristics determine the contribution of endo- and exonucleolytic decay pathways during the degradation of nonsense-mediated decay substrates. RNA (NEW YORK, N.Y.) 2017; 23:1224-1236. [PMID: 28461625 PMCID: PMC5513067 DOI: 10.1261/rna.059659.116] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 04/17/2017] [Indexed: 06/07/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) controls gene expression by eliminating mRNAs with premature or aberrant translation termination. Degradation of NMD substrates is initiated by the central NMD factor UPF1, which recruits the endonuclease SMG6 and the deadenylation-promoting SMG5/7 complex. The extent to which SMG5/7 and SMG6 contribute to the degradation of individual substrates and their regulation by UPF1 remains elusive. Here we map transcriptome-wide sites of SMG6-mediated endocleavage via 3' fragment capture and degradome sequencing. This reveals that endogenous transcripts can have NMD-eliciting features at various positions, including upstream open reading frames (uORFs), premature termination codons (PTCs), and long 3' UTRs. We find that NMD substrates with PTCs undergo constitutive SMG6-dependent endocleavage, rather than SMG7-dependent exonucleolytic decay. In contrast, the turnover of NMD substrates containing uORFs and long 3' UTRs involves both SMG6- and SMG7-dependent endo- and exonucleolytic decay, respectively. This suggests that the extent to which SMG6 and SMG7 degrade NMD substrates is determined by the mRNA architecture.
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Affiliation(s)
- Franziska Ottens
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany
| | - Volker Boehm
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany
| | - Christopher R Sibley
- Division of Brain Sciences, Imperial College London, London W12 0NN, United Kingdom
| | - Jernej Ule
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, United Kingdom
| | - Niels H Gehring
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany
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47
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da Costa PJ, Menezes J, Romão L. The role of alternative splicing coupled to nonsense-mediated mRNA decay in human disease. Int J Biochem Cell Biol 2017; 91:168-175. [PMID: 28743674 DOI: 10.1016/j.biocel.2017.07.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2017] [Revised: 07/15/2017] [Accepted: 07/18/2017] [Indexed: 12/29/2022]
Abstract
Alternative pre-mRNA splicing (AS) affects gene expression as it generates proteome diversity. Nonsense-mediated mRNA decay (NMD) is a surveillance pathway that recognizes and selectively degrades mRNAs carrying premature translation-termination codons (PTCs), preventing the production of truncated proteins that could result in disease. Several studies have also implicated NMD in the regulation of steady-state levels of physiological mRNAs. In addition, it is known that several regulated AS events do not lead to generation of protein products, as they lead to transcripts that carry PTCs and thus, they are committed to NMD. Indeed, an estimated one-third of naturally occurring, alternatively spliced mRNAs is targeted for NMD, being AS coupled to NMD (AS-NMD) an efficient strategy to regulate gene expression. In this review, we will focus on how AS mechanism operates and how can be coupled to NMD to fine-tune gene expression levels. Furthermore, we will demonstrate the physiological significance of the interplay among AS and NMD in human disease, such as cancer and neurological disorders. The understanding of how AS-NMD orchestrates expression of vital genes is of utmost importance for the advance in diagnosis, prognosis and treatment of many human disorders.
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Affiliation(s)
- Paulo J da Costa
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Lisbon, Portugal; Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Juliane Menezes
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Lisbon, Portugal; Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Luísa Romão
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Lisbon, Portugal; Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.
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48
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Shaul O. How introns enhance gene expression. Int J Biochem Cell Biol 2017; 91:145-155. [PMID: 28673892 DOI: 10.1016/j.biocel.2017.06.016] [Citation(s) in RCA: 223] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2017] [Revised: 06/26/2017] [Accepted: 06/30/2017] [Indexed: 01/18/2023]
Abstract
In many eukaryotes, including mammals, plants, yeast, and insects, introns can increase gene expression without functioning as a binding site for transcription factors. This phenomenon was termed 'intron-mediated enhancement'. Introns can increase transcript levels by affecting the rate of transcription, nuclear export, and transcript stability. Moreover, introns can also increase the efficiency of mRNA translation. This review discusses the current knowledge about these processes. The role of splicing in IME and the significance of intron position relative to the sites of transcription and translation initiation are elaborated. Particular emphasis is placed on the question why different introns, present at the same location of the same genes and spliced at a similar high efficiency, can have very different impacts on expression - from almost no effect to considerable stimulation. This situation can be at least partly accounted for by the identification of splicing-unrelated intronic elements with a special ability to enhance mRNA accumulation or translational efficiency. The many factors that could lead to the large variation observed between the impact of introns in different genes and experimental systems are highlighted. It is suggested that there is no sole, definite answer to the question "how do introns enhance gene expression". Rather, each intron-gene combination might undergo its own unique mixture of processes that lead to the perceptible outcome.
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Affiliation(s)
- Orit Shaul
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
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49
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Nabih A, Sobotka JA, Wu MZ, Wedeles CJ, Claycomb JM. Examining the intersection between splicing, nuclear export and small RNA pathways. Biochim Biophys Acta Gen Subj 2017; 1861:2948-2955. [PMID: 28578161 DOI: 10.1016/j.bbagen.2017.05.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 05/25/2017] [Accepted: 05/29/2017] [Indexed: 01/06/2023]
Abstract
BACKGROUND Nuclear Argonaute/small RNA pathways in a variety of eukaryotic species are generally known to regulate gene expression via chromatin modulation and transcription attenuation in a process known as transcriptional gene silencing (TGS). However, recent data, including genetic screens, phylogenetic profiling, and molecular mechanistic studies, also point to a novel and emerging intersection between the splicing and nuclear export machinery with nuclear Argonaute/small RNA pathways in many organisms. SCOPE OF REVIEW In this review, we summarize the field's current understanding regarding the relationship between splicing, export and small RNA pathways, and consider the biological implications for coordinated regulation of transcripts by these pathways. We also address the importance and available approaches for understanding the RNA regulatory logic generated by the intersection of these particular pathways in the context of synthetic biology. MAJOR CONCLUSIONS The interactions between various eukaryotic RNA regulatory pathways, particularly splicing, nuclear export and small RNA pathways provide a type of combinatorial code that informs the identity ("self" versus "non-self") and dictates the fate of each transcript in a cell. Although the molecular mechanisms for how splicing and nuclear export impact small RNA pathways are not entirely clear at this early stage, the links between these pathways are widespread across eukaryotic phyla. GENERAL SIGNIFICANCE The link between splicing, nuclear export, and small RNA pathways is emerging and establishes a new frontier for understanding the combinatorial logic of gene regulation across species that could someday be harnessed for therapeutic, biotechnology and agricultural applications. This article is part of a Special Issue entitled "Biochemistry of Synthetic Biology - Recent Developments" Guest Editor: Dr. Ilka Heinemann and Dr. Patrick O'Donoghue.
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Affiliation(s)
- Amena Nabih
- Dept. of Molecular Genetics, University of Toronto, Canada
| | | | - Monica Z Wu
- Dept. of Molecular Genetics, University of Toronto, Canada
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50
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Carvalho T, Martins S, Rino J, Marinho S, Carmo-Fonseca M. Pharmacological inhibition of the spliceosome subunit SF3b triggers exon junction complex-independent nonsense-mediated decay. J Cell Sci 2017; 130:1519-1531. [PMID: 28302904 DOI: 10.1242/jcs.202200] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Accepted: 03/06/2017] [Indexed: 12/12/2022] Open
Abstract
Spliceostatin A, meayamycin, and pladienolide B are small molecules that target the SF3b subunit of the spliceosomal U2 small nuclear ribonucleoprotein (snRNP). These compounds are attracting much attention as tools to manipulate splicing and for use as potential anti-cancer drugs. We investigated the effects of these inhibitors on mRNA transport and stability in human cells. Upon splicing inhibition, unspliced pre-mRNAs accumulated in the nucleus, particularly within enlarged nuclear speckles. However, a small fraction of the pre-mRNA molecules were exported to the cytoplasm. We identified the export adaptor ALYREF as being associated with intron-containing transcripts and show its requirement for the nucleo-cytoplasmic transport of unspliced pre-mRNA. In contrast, the exon junction complex (EJC) core protein eIF4AIII failed to form a stable complex with intron-containing transcripts. Despite the absence of EJC, unspliced transcripts in the cytoplasm were degraded by nonsense-mediated decay (NMD), suggesting that unspliced transcripts are degraded by an EJC-independent NMD pathway. Collectively, our results indicate that although blocking the function of SF3b elicits a massive accumulation of unspliced pre-mRNAs in the nucleus, intron-containing transcripts can still bind the ALYREF export factor and be transported to the cytoplasm, where they trigger an alternative NMD pathway.
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Affiliation(s)
- Teresa Carvalho
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Sandra Martins
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - José Rino
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Sérgio Marinho
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
| | - Maria Carmo-Fonseca
- Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa 1649-028, Portugal
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