101
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Fanourgakis G, Lesche M, Akpinar M, Dahl A, Jessberger R. Chromatoid Body Protein TDRD6 Supports Long 3' UTR Triggered Nonsense Mediated mRNA Decay. PLoS Genet 2016; 12:e1005857. [PMID: 27149095 PMCID: PMC4858158 DOI: 10.1371/journal.pgen.1005857] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 01/20/2016] [Indexed: 02/08/2023] Open
Abstract
Chromatoid bodies (CBs) are spermiogenesis-specific organelles of largely unknown function. CBs harbor various RNA species, RNA-associated proteins and proteins of the tudor domain family like TDRD6, which is required for a proper CB architecture. Proteome analysis of purified CBs revealed components of the nonsense-mediated mRNA decay (NMD) machinery including UPF1. TDRD6 is essential for UPF1 localization to CBs, for UPF1-UPF2 and UPF1-MVH interactions. Upon removal of TDRD6, the association of several mRNAs with UPF1 and UPF2 is disturbed, and the long 3’ UTR-stimulated but not the downstream exon-exon junction triggered pathway of NMD is impaired. Reduced association of the long 3’ UTR mRNAs with UPF1 and UPF2 correlates with increased stability and enhanced translational activity. Thus, we identified TDRD6 within CBs as required for mRNA degradation, specifically the extended 3’ UTR-triggered NMD pathway, and provide evidence for the requirement of NMD in spermiogenesis. This function depends on TDRD6-promoted assembly of mRNA and decay enzymes in CBs. Tudor-domain containing protein 6 (TDRD6) is a central component of the chromatoid body (CB) in male germ cells. Chromatoid bodies, which are present in spermatids, contain RNA and protein, are not enclosed by membranes, and typically reside close to the nucleus. Without TDRD6, a much distorted CB structure is observed, and this work asked for the functional contribution of TDRD6 to spermatids. We found that TDRD6 is required for localization of an RNA degradation machinery to the CB. This so-called nonsense mediated decay (NMD) machinery, known from somatic cells, destroys mRNAs that feature premature stop codons. Absence of TDRD6 significantly impairs one specific mechanism of NMD, which depends on long 3’ untranslated regions of the transcripts. Thus, the CB component TDRD6 acts in the assembly of the NMD machinery in the CB.
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Affiliation(s)
- Grigorios Fanourgakis
- Institute of Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Mathias Lesche
- Deep Sequencing Group SFB 655, Biotechnology Center, Technische Universität Dresden, Dresden, Germany
| | - Müge Akpinar
- Institute of Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
| | - Andreas Dahl
- Deep Sequencing Group SFB 655, Biotechnology Center, Technische Universität Dresden, Dresden, Germany
| | - Rolf Jessberger
- Institute of Physiological Chemistry, Medical Faculty Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- * E-mail:
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102
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Ottens F, Gehring NH. Physiological and pathophysiological role of nonsense-mediated mRNA decay. Pflugers Arch 2016; 468:1013-28. [PMID: 27138169 DOI: 10.1007/s00424-016-1826-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 04/07/2016] [Accepted: 04/18/2016] [Indexed: 12/27/2022]
Abstract
Nonsense-mediated messenger RNA (mRNA) decay (NMD) is a quality control mechanism that degrades irregular or faulty mRNAs. NMD mainly degrades mRNAs, which contain a premature termination codon (PTC) and therefore encode a truncated protein. Furthermore, NMD alters the expression of different types of cellular mRNAs, the so-called endogenous NMD substrates. In this review, we focus on the impact of NMD on cellular and molecular physiology. We specify key classes of NMD substrates and provide a detailed overview of the physiological function of gene regulation by NMD. We also describe different mechanisms of NMD substrate degradation and how the regulation of the NMD machinery affects cellular physiology. Finally, we outline the physiological functions of central NMD factors.
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Affiliation(s)
- Franziska Ottens
- Institute for Genetics, University of Cologne, Zuelpicher Str. 47a, 50674, Cologne, Germany
| | - Niels H Gehring
- Institute for Genetics, University of Cologne, Zuelpicher Str. 47a, 50674, Cologne, Germany.
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103
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Ganguly K, Giddaluru J, August A, Khan N. Post-transcriptional Regulation of Immunological Responses through Riboclustering. Front Immunol 2016; 7:161. [PMID: 27199986 PMCID: PMC4850162 DOI: 10.3389/fimmu.2016.00161] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 04/15/2016] [Indexed: 12/22/2022] Open
Abstract
Immunological programing of immune cells varies in response to changing environmental signals. This process is facilitated by modifiers that regulate the translational fate of mRNAs encoding various immune mediators, including cytokines and chemokines, which in turn determine the rapid activation, tolerance, and plasticity of the immune system. RNA-binding proteins (RBPs) recruited by the specific sequence elements in mRNA transcripts are one such modifiers. These RBPs form RBP-RNA complexes known as "riboclusters." These riboclusters serve as RNA sorting machinery, where depending upon the composition of the ribocluster, translation, degradation, or storage of mRNA is controlled. Recent findings suggest that this regulation of mRNA homeostasis is critical for controlling the immune response. Here, we present the current knowledge of the ribocluster-mediated post-transcriptional regulation of immune mediators and highlight recent findings regarding their implications for the pathogenesis of acute or chronic inflammatory diseases.
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Affiliation(s)
- Koelina Ganguly
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad , Hyderabad , India
| | - Jeevan Giddaluru
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad , Hyderabad , India
| | - Avery August
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University , New York, NY , USA
| | - Nooruddin Khan
- Department of Biotechnology and Bioinformatics, School of Life Sciences, University of Hyderabad , Hyderabad , India
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104
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Takei S, Togo-Ohno M, Suzuki Y, Kuroyanagi H. Evolutionarily conserved autoregulation of alternative pre-mRNA splicing by ribosomal protein L10a. Nucleic Acids Res 2016; 44:5585-5596. [PMID: 26961311 PMCID: PMC4937301 DOI: 10.1093/nar/gkw152] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Alternative splicing of pre-mRNAs can regulate expression of protein-coding genes by generating unproductive mRNAs rapidly degraded by nonsense-mediated mRNA decay (NMD). Many of the genes directly regulated by alternative splicing coupled with NMD (AS-NMD) are related to RNA metabolism, but the repertoire of genes regulated by AS-NMD in vivo is to be determined. Here, we analyzed transcriptome data of wild-type and NMD-defective mutant strains of the nematode worm Caenorhabditis elegans and demonstrate that eight of the 82 cytoplasmic ribosomal protein (rp) genes generate unproductively spliced mRNAs. Knockdown of any of the eight rp genes exerted a dynamic and compensatory effect on alternative splicing of its own transcript and inverse effects on that of the other rp genes. A large subunit protein L10a, termed RPL-1 in nematodes, directly and specifically binds to an evolutionarily conserved 39-nt stretch termed L10ARE between the two alternative 5′ splice sites in its own pre-mRNA to switch the splice site choice. Furthermore, L10ARE-mediated splicing autoregulation of the L10a-coding gene is conserved in vertebrates. These results indicate that L10a is an evolutionarily conserved splicing regulator and that homeostasis of a subset of the rp genes are regulated at the level of pre-mRNA splicing in vivo.
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Affiliation(s)
- Satomi Takei
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Marina Togo-Ohno
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Yutaka Suzuki
- Department of Medical Genome Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Hidehito Kuroyanagi
- Laboratory of Gene Expression, Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
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105
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Nelson JO, Moore KA, Chapin A, Hollien J, Metzstein MM. Degradation of Gadd45 mRNA by nonsense-mediated decay is essential for viability. eLife 2016; 5:e12876. [PMID: 26952209 PMCID: PMC4848089 DOI: 10.7554/elife.12876] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 03/08/2016] [Indexed: 12/22/2022] Open
Abstract
The nonsense-mediated mRNA decay (NMD) pathway functions to degrade both abnormal and wild-type mRNAs. NMD is essential for viability in most organisms, but the molecular basis for this requirement is unknown. Here we show that a single, conserved NMD target, the mRNA coding for the stress response factor growth arrest and DNA-damage inducible 45 (GADD45) can account for lethality in Drosophila lacking core NMD genes. Moreover, depletion of Gadd45 in mammalian cells rescues the cell survival defects associated with NMD knockdown. Our findings demonstrate that degradation of Gadd45 mRNA is the essential NMD function and, surprisingly, that the surveillance of abnormal mRNAs by this pathway is not necessarily required for viability.
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Affiliation(s)
- Jonathan O Nelson
- Department of Human Genetics, University of Utah, Salt Lake City, United States
| | - Kristin A Moore
- Department of Biology, University of Utah, Salt Lake City, United States
- Center for Cell and Genome Sciences, University of Utah, Salt Lake City, United States
| | - Alex Chapin
- Department of Human Genetics, University of Utah, Salt Lake City, United States
| | - Julie Hollien
- Department of Biology, University of Utah, Salt Lake City, United States
- Center for Cell and Genome Sciences, University of Utah, Salt Lake City, United States
| | - Mark M Metzstein
- Department of Human Genetics, University of Utah, Salt Lake City, United States
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106
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Hug N, Longman D, Cáceres JF. Mechanism and regulation of the nonsense-mediated decay pathway. Nucleic Acids Res 2016; 44:1483-95. [PMID: 26773057 PMCID: PMC4770240 DOI: 10.1093/nar/gkw010] [Citation(s) in RCA: 322] [Impact Index Per Article: 40.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 12/31/2015] [Indexed: 12/11/2022] Open
Abstract
The Nonsense-mediated mRNA decay (NMD) pathway selectively degrades mRNAs harboring premature termination codons (PTCs) but also regulates the abundance of a large number of cellular RNAs. The central role of NMD in the control of gene expression requires the existence of buffering mechanisms that tightly regulate the magnitude of this pathway. Here, we will focus on the mechanism of NMD with an emphasis on the role of RNA helicases in the transition from NMD complexes that recognize a PTC to those that promote mRNA decay. We will also review recent strategies aimed at uncovering novel trans-acting factors and their functional role in the NMD pathway. Finally, we will describe recent progress in the study of the physiological role of the NMD response.
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Affiliation(s)
- Nele Hug
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK
| | - Dasa Longman
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK
| | - Javier F Cáceres
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Edinburgh, EH4 2XU, UK
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107
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Ge Z, Quek BL, Beemon KL, Hogg JR. Polypyrimidine tract binding protein 1 protects mRNAs from recognition by the nonsense-mediated mRNA decay pathway. eLife 2016; 5. [PMID: 26744779 PMCID: PMC4764554 DOI: 10.7554/elife.11155] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Accepted: 01/07/2016] [Indexed: 12/26/2022] Open
Abstract
The nonsense-mediated mRNA decay (NMD) pathway degrades mRNAs containing long 3'UTRs to perform dual roles in mRNA quality control and gene expression regulation. However, expansion of vertebrate 3'UTR functions has required a physical expansion of 3'UTR lengths, complicating the process of detecting nonsense mutations. We show that the polypyrimidine tract binding protein 1 (PTBP1) shields specific retroviral and cellular transcripts from NMD. When bound near a stop codon, PTBP1 blocks the NMD protein UPF1 from binding 3'UTRs. PTBP1 can thus mark specific stop codons as genuine, preserving both the ability of NMD to accurately detect aberrant mRNAs and the capacity of long 3'UTRs to regulate gene expression. Illustrating the wide scope of this mechanism, we use RNA-seq and transcriptome-wide analysis of PTBP1 binding sites to show that many human mRNAs are protected by PTBP1 and that PTBP1 enrichment near stop codons correlates with 3'UTR length and resistance to NMD. DOI:http://dx.doi.org/10.7554/eLife.11155.001 Genes are used as templates to create molecules of messenger RNA (mRNA) that contain all the information needed to make a protein. This information begins with a 'start site' and ends with a 'stop site.' The regions of the mRNA outside of the start and stop sites are called untranslated regions. Not all mRNAs are correctly made, and cells combat this problem by detecting and destroying faulty mRNAs before they are translated into protein. One way cells do this is by recognizing and destroying mRNAs that include long untranslated regions, which can indicate that the mRNA might have a stop site too early in its sequence. A key problem with this mechanism, however, is that long untranslated regions also serve important roles in the cell: for example, by determining where and when mRNA molecules are read to make protein. How then do mRNAs with long but important untranslated regions escape detection and degradation? Ge et al. have now investigated this question using an approach that allows a 'handle' to be attached to particular RNA molecules. This allows the RNA and any proteins bound to it to be purified away from all other RNAs and proteins in the cell, and the proteins can then be identified by a technique called mass spectrometry. Ge at al. found that mRNAs can recruit a protein called PTBP1 to part of the RNA sequence near the stop site. This prevents an RNA decay protein recognizing and triggering the degradation of the mRNA, even if the mRNA has a long untranslated region. Thus, PTBP1 plays a crucial role in protecting human RNAs with long untranslated regions from destruction by the nonsense-mediated decay pathway. Some viral RNAs are also able to evade decay, and so Ge et al. hypothesize that the virus stole this method for maintaining its RNAs from host cells. A future goal is to understand whether this system works the same way in all cell types or protects different RNAs in different cells. DOI:http://dx.doi.org/10.7554/eLife.11155.002
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Affiliation(s)
- Zhiyun Ge
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, United States
| | - Bao Lin Quek
- Department of Biology, Johns Hopkins University, Baltimore, United States
| | - Karen L Beemon
- Department of Biology, Johns Hopkins University, Baltimore, 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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108
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Srour N, Chemin G, Tinguely A, Ashi MO, Oruc Z, Péron S, Sirac C, Cogné M, Delpy L. A plasma cell differentiation quality control ablates B cell clones with biallelic Ig rearrangements and truncated Ig production. J Exp Med 2015; 213:109-22. [PMID: 26666261 PMCID: PMC4710196 DOI: 10.1084/jem.20131511] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 11/12/2015] [Indexed: 01/26/2023] Open
Abstract
Aberrantly rearranged immunoglobulin (Ig) alleles are frequent. They are usually considered sterile and innocuous as a result of nonsense-mediated mRNA decay. However, alternative splicing can yield internally deleted proteins from such nonproductively V(D)J-rearranged loci. We show that nonsense codons from variable (V) Igκ exons promote exon-skipping and synthesis of V domain-less κ light chains (ΔV-κLCs). Unexpectedly, such ΔV-κLCs inhibit plasma cell (PC) differentiation. Accordingly, in wild-type mice, rearrangements encoding ΔV-κLCs are rare in PCs, but frequent in B cells. Likewise, enforcing expression of ΔV-κLCs impaired PC differentiation and antibody responses without disturbing germinal center reactions. In addition, PCs expressing ΔV-κLCs synthesize low levels of Ig and are mostly found among short-lived plasmablasts. ΔV-κLCs have intrinsic toxic effects in PCs unrelated to Ig assembly, but mediated by ER stress-associated apoptosis, making PCs producing ΔV-κLCs highly sensitive to proteasome inhibitors. Altogether, these findings demonstrate a quality control checkpoint blunting terminal PC differentiation by eliminating those cells expressing nonfunctionally rearranged Igκ alleles. This truncated Ig exclusion (TIE) checkpoint ablates PC clones with ΔV-κLCs production and exacerbated ER stress response. The TIE checkpoint thus mediates selection of long-lived PCs with limited ER stress supporting high Ig secretion, but with a cost in terms of antigen-independent narrowing of the repertoire.
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Affiliation(s)
- Nivine Srour
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
| | - Guillaume Chemin
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
| | - Aurélien Tinguely
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
| | - Mohamad Omar Ashi
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
| | - Zéliha Oruc
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
| | - Sophie Péron
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
| | - Christophe Sirac
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
| | - Michel Cogné
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France Institut Universitaire de France, Université de Limoges, 87000 Limoges, France
| | - Laurent Delpy
- Centre National de la Recherche Scientifique UMR 7276, Université de Limoges, 87000 Limoges, France
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109
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Fatscher T, Boehm V, Gehring NH. Mechanism, factors, and physiological role of nonsense-mediated mRNA decay. Cell Mol Life Sci 2015; 72:4523-44. [PMID: 26283621 PMCID: PMC11113733 DOI: 10.1007/s00018-015-2017-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Revised: 07/10/2015] [Accepted: 08/06/2015] [Indexed: 02/04/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) is a translation-dependent, multistep process that degrades irregular or faulty messenger RNAs (mRNAs). NMD mainly targets mRNAs with a truncated open reading frame (ORF) due to premature termination codons (PTCs). In addition, NMD also regulates the expression of different types of endogenous mRNA substrates. A multitude of factors are involved in the tight regulation of the NMD mechanism. In this review, we focus on the molecular mechanism of mammalian NMD. Based on the published data, we discuss the involvement of translation termination in NMD initiation. Furthermore, we provide a detailed overview of the core NMD machinery, as well as several peripheral NMD factors, and discuss their function. Finally, we present an overview of diseases associated with NMD factor mutations and summarize the current state of treatment for genetic disorders caused by nonsense mutations.
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Affiliation(s)
- Tobias Fatscher
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Volker Boehm
- Institute for Genetics, University of Cologne, Cologne, Germany
| | - Niels H Gehring
- Institute for Genetics, University of Cologne, Cologne, Germany.
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110
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Affiliation(s)
- Justin J.-L. Wong
- Gene and Stem Cell Therapy Program, Centenary Institute; Royal Prince Alfred Hospital; Camperdown Australia
- Sydney Medical School; University of Sydney; Camperdown Australia
| | - Amy Y. M. Au
- Gene and Stem Cell Therapy Program, Centenary Institute; Royal Prince Alfred Hospital; Camperdown Australia
- Sydney Medical School; University of Sydney; Camperdown Australia
| | - William Ritchie
- Gene and Stem Cell Therapy Program, Centenary Institute; Royal Prince Alfred Hospital; Camperdown Australia
- Sydney Medical School; University of Sydney; Camperdown Australia
- Department of Bioinformatics, Centenary Institute; Royal Prince Alfred Hospital; Camperdown Australia
| | - John E. J. Rasko
- Gene and Stem Cell Therapy Program, Centenary Institute; Royal Prince Alfred Hospital; Camperdown Australia
- Sydney Medical School; University of Sydney; Camperdown Australia
- Cell and Molecular Therapies; Royal Prince Alfred Hospital; Camperdown Australia
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111
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He F, Jacobson A. Nonsense-Mediated mRNA Decay: Degradation of Defective Transcripts Is Only Part of the Story. Annu Rev Genet 2015; 49:339-66. [PMID: 26436458 DOI: 10.1146/annurev-genet-112414-054639] [Citation(s) in RCA: 190] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) is a eukaryotic surveillance mechanism that monitors cytoplasmic mRNA translation and targets mRNAs undergoing premature translation termination for rapid degradation. From yeasts to humans, activation of NMD requires the function of the three conserved Upf factors: Upf1, Upf2, and Upf3. Here, we summarize the progress in our understanding of the molecular mechanisms of NMD in several model systems and discuss recent experiments that address the roles of Upf1, the principal regulator of NMD, in the initial targeting and final degradation of NMD-susceptible mRNAs. We propose a unified model for NMD in which the Upf factors provide several functions during premature termination, including the stimulation of release factor activity and the dissociation and recycling of ribosomal subunits. In this model, the ultimate degradation of the mRNA is the last step in a complex premature termination process.
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Affiliation(s)
- Feng He
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts 01655; ,
| | - Allan Jacobson
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts 01655; ,
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112
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Mocquet V, Durand S, Jalinot P. How Retroviruses Escape the Nonsense-Mediated mRNA Decay. AIDS Res Hum Retroviruses 2015; 31:948-58. [PMID: 26066561 DOI: 10.1089/aid.2014.0326] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Many posttranscriptional processes are known to regulate gene expression and some of them can act as an antiviral barrier. The nonsense-mediated mRNA decay (NMD) was first identified as an mRNA quality control pathway that triggers rapid decay of mRNA containing premature stop codons due to mutations. NMD is now considered as a general posttranscriptional regulation pathway controlling the expression of a large set of cellular genes. In addition to premature stop codons, many other features including alternative splicing, 5' uORF, long 3' UTR, selenocystein codons, and frameshift are able to promote NMD. Interestingly, many viral mRNAs exhibit some of these features suggesting that virus expression and replication might be sensitive to NMD. Several studies, including recent ones, have shown that this is the case for retroviruses; however, it also appears that retroviruses have developed strategies to overcome NMD in order to protect their genome and ensure a true expression of their genes. As a consequence of NMD inhibition, these viruses also affect the expression of host genes that are prone to NMD, and therefore can potentially trigger pathological effects on infected cells. Here, we review recent studies supporting this newly uncovered function of the NMD pathway as a defense barrier that viruses must overcome in order to replicate.
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Affiliation(s)
- Vincent Mocquet
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique , Ecole Normale Supérieure, Lyon, France
| | - Sebastien Durand
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique , Ecole Normale Supérieure, Lyon, France
| | - Pierre Jalinot
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique , Ecole Normale Supérieure, Lyon, France
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113
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Lykke-Andersen S, Jensen TH. Nonsense-mediated mRNA decay: an intricate machinery that shapes transcriptomes. Nat Rev Mol Cell Biol 2015; 16:665-77. [PMID: 26397022 DOI: 10.1038/nrm4063] [Citation(s) in RCA: 522] [Impact Index Per Article: 58.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) is probably the best characterized eukaryotic RNA degradation pathway. Through intricate steps, a set of NMD factors recognize and degrade mRNAs with translation termination codons that are positioned in abnormal contexts. However, NMD is not only part of a general cellular quality control system that prevents the production of aberrant proteins. Mammalian cells also depend on NMD to dynamically adjust their transcriptomes and their proteomes to varying physiological conditions. In this Review, we discuss how NMD targets mRNAs, the types of mRNAs that are targeted, and the roles of NMD in cellular stress, differentiation and maturation processes.
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Affiliation(s)
- Søren Lykke-Andersen
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
| | - Torben Heick Jensen
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology and Genetics, Aarhus University, DK-8000 Aarhus, Denmark
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114
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Proudhon C, Hao B, Raviram R, Chaumeil J, Skok JA. Long-Range Regulation of V(D)J Recombination. Adv Immunol 2015; 128:123-82. [PMID: 26477367 DOI: 10.1016/bs.ai.2015.07.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Given their essential role in adaptive immunity, antigen receptor loci have been the focus of analysis for many years and are among a handful of the most well-studied genes in the genome. Their investigation led initially to a detailed knowledge of linear structure and characterization of regulatory elements that confer control of their rearrangement and expression. However, advances in DNA FISH and imaging combined with new molecular approaches that interrogate chromosome conformation have led to a growing appreciation that linear structure is only one aspect of gene regulation and in more recent years, the focus has switched to analyzing the impact of locus conformation and nuclear organization on control of recombination. Despite decades of work and intense effort from numerous labs, we are still left with an incomplete picture of how the assembly of antigen receptor loci is regulated. This chapter summarizes our advances to date and points to areas that need further investigation.
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Affiliation(s)
- Charlotte Proudhon
- Department of Pathology, New York University School of Medicine, New York, USA
| | - Bingtao Hao
- Department of Pathology, New York University School of Medicine, New York, USA
| | - Ramya Raviram
- Department of Pathology, New York University School of Medicine, New York, USA
| | - Julie Chaumeil
- Institut Curie, CNRS UMR3215, INSERM U934, Paris, France
| | - Jane A Skok
- Department of Pathology, New York University School of Medicine, New York, USA.
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115
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Zou D, McSweeney C, Sebastian A, Reynolds DJ, Dong F, Zhou Y, Deng D, Wang Y, Liu L, Zhu J, Zou J, Shi Y, Albert I, Mao Y. A critical role of RBM8a in proliferation and differentiation of embryonic neural progenitors. Neural Dev 2015; 10:18. [PMID: 26094033 PMCID: PMC4479087 DOI: 10.1186/s13064-015-0045-7] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 06/17/2015] [Indexed: 02/04/2023] Open
Abstract
Background Nonsense mediated mRNA decay (NMD) is an RNA surveillance mechanism that controls RNA stability and ensures the speedy degradation of erroneous and unnecessary transcripts. This mechanism depends on several core factors in the exon junction complex (EJC), eIF4A3, RBM8a, Magoh, and BTZ, as well as peripheral factors to distinguish premature stop codons (PTCs) from normal stop codons in transcripts. Recently, emerging evidence has indicated that NMD factors are associated with neurodevelopmental disorders such as autism spectrum disorder (ASD) and intellectual disability (ID). However, the mechanism in which these factors control embryonic brain development is not clear. Result We found that RBM8a is critical for proliferation and differentiation in cortical neural progenitor cells (NPCs). RBM8a is highly expressed in the subventricular zone (SVZ) of the early embryonic cortex, suggesting that RBM8a may play a role in regulating NPCs. RBM8a overexpression stimulates embryonic NPC proliferation and suppresses neuronal differentiation. Conversely, knockdown of RBM8a in the neocortex reduces NPC proliferation and promotes premature neuronal differentiation. Moreover, overexpression of RBM8a suppresses cell cycle exit and keeps cortical NPCs in a proliferative state. To uncover the underlying mechanisms of this phenotype, genome-wide RNAseq was used to identify potential downstream genes of RBM8a in the brain, which have been implicated in autism and neurodevelopmental disorders. Interestingly, autism and schizophrenia risk genes are highly represented in downstream transcripts of RBM8a. In addition, RBM8a regulates multiple alternative splicing genes and NMD targets that are implicated in ASD. Taken together, this data suggests a novel role of RBM8a in the regulation of neurodevelopment. Conclusions Our studies provide some insight into causes of mental illnesses and will facilitate the development of new therapeutic strategies for neurodevelopmental illnesses. Electronic supplementary material The online version of this article (doi:10.1186/s13064-015-0045-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Donghua Zou
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Province, 530021, China. .,Department of Geriatrics, The 303 Hospital of Chinese People's Liberation Army, Nanning, Guangxi Province, 530021, China. .,Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Colleen McSweeney
- Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Aswathy Sebastian
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Derrick James Reynolds
- Department of Microbiology & Molecular Genetics School of Medicine, University of California, Irvine, CA, 92697, USA.
| | - Fengping Dong
- Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Yijing Zhou
- Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Dazhi Deng
- Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA. .,Department of Emergency, Guangxi Zhuang Autonomous Region People's Hospital, Nanning, Guangxi Province, 530021, China.
| | - Yonggang Wang
- Department of Neurology, School of Medicine, Renji Hospital, Shanghai Jiaotong University, Shanghai, 200127, China.
| | - Long Liu
- Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA. .,Department of Chemistry and Biology, College of Science, National University of Defense Technology, Changsha, 410073, China.
| | - Jun Zhu
- Systems Biology Center, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD, 20892, USA.
| | - Jizhong Zou
- Center for Molecular Medicine, National Heart, Lung, and Blood Institute, NIH, Bethesda, MD, 20892, USA.
| | - Yongsheng Shi
- Department of Microbiology & Molecular Genetics School of Medicine, University of California, Irvine, CA, 92697, USA.
| | - Istvan Albert
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA, 16802, USA.
| | - Yingwei Mao
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, Nanning, Guangxi Province, 530021, China. .,Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA.
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116
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Gloggnitzer J, Akimcheva S, Srinivasan A, Kusenda B, Riehs N, Stampfl H, Bautor J, Dekrout B, Jonak C, Jiménez-Gómez JM, Parker JE, Riha K. Nonsense-mediated mRNA decay modulates immune receptor levels to regulate plant antibacterial defense. Cell Host Microbe 2015; 16:376-90. [PMID: 25211079 DOI: 10.1016/j.chom.2014.08.010] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 07/29/2014] [Accepted: 08/24/2014] [Indexed: 12/15/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) is a conserved eukaryotic RNA surveillance mechanism that degrades aberrant mRNAs. NMD impairment in Arabidopsis is linked to constitutive immune response activation and enhanced antibacterial resistance, but the underlying mechanisms are unknown. Here we show that NMD contributes to innate immunity in Arabidopsis by controlling the turnover of numerous TIR domain-containing, nucleotide-binding, leucine-rich repeat (TNL) immune receptor-encoding mRNAs. Autoimmunity resulting from NMD impairment depends on TNL signaling pathway components and can be triggered through deregulation of a single TNL gene, RPS6. Bacterial infection of plants causes host-programmed inhibition of NMD, leading to stabilization of NMD-regulated TNL transcripts. Conversely, constitutive NMD activity prevents TNL stabilization and impairs plant defense, demonstrating that host-regulated NMD contributes to disease resistance. Thus, NMD shapes plant innate immunity by controlling the threshold for activation of TNL resistance pathways.
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Affiliation(s)
- Jiradet Gloggnitzer
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria.
| | - Svetlana Akimcheva
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Arunkumar Srinivasan
- Department of Plant Breeding and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Branislav Kusenda
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Nina Riehs
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Hansjörg Stampfl
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Jaqueline Bautor
- Department of Plant-Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Bettina Dekrout
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - Claudia Jonak
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria
| | - José M Jiménez-Gómez
- Department of Plant Breeding and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany; Institut Jean-Pierre Bourgin, UMR1318, INRA-AgroParisTech, 78000 Versailles, France
| | - Jane E Parker
- Department of Plant-Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Karel Riha
- Gregor Mendel Institute, Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr.-Bohr-Gasse 3, 1030 Vienna, Austria; CEITEC, Masaryk University, Kamenice 753/5, 625 00 Brno, Czech Republic.
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117
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Linder B, Fischer U, Gehring NH. mRNA metabolism and neuronal disease. FEBS Lett 2015; 589:1598-606. [DOI: 10.1016/j.febslet.2015.04.052] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 04/26/2015] [Accepted: 04/27/2015] [Indexed: 12/12/2022]
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118
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Wang X, Gregory-Evans CY. Nonsense suppression therapies in ocular genetic diseases. Cell Mol Life Sci 2015; 72:1931-8. [PMID: 25651836 PMCID: PMC11113309 DOI: 10.1007/s00018-015-1843-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 12/23/2014] [Accepted: 01/23/2015] [Indexed: 12/24/2022]
Abstract
Premature termination codons (PTCs) are caused by nonsense mutations and this leads to either degradation of the mutant mRNA template by nonsense-mediated decay (NMD) or the production of a non-functional, truncated polypeptide. PTCs contribute significantly to inherited human diseases including ocular disorders. Nonsense suppression therapy allows readthrough of PTCs, thereby rescuing the production of a full-length functional protein. In this review, we highlight the mechanisms that are involved in discriminating normal translation termination from premature termination codons; the current understanding of nonsense-mediated mRNA decay models (NMD); the association and crosstalk between PTC and the underlying dynamic NMD process; and the suppression therapies that have been employed in nonsense-medicated ocular disease models. Defining the mechanistic complexity of PTC and NMD will be important to improve treatments of the numerous genetic disorders caused by PTC mutations.
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Affiliation(s)
- Xia Wang
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC, V5Z 3N9, Canada,
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119
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Toma KG, Rebbapragada I, Durand S, Lykke-Andersen J. Identification of elements in human long 3' UTRs that inhibit nonsense-mediated decay. RNA (NEW YORK, N.Y.) 2015; 21:887-97. [PMID: 25805855 PMCID: PMC4408796 DOI: 10.1261/rna.048637.114] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 01/05/2015] [Indexed: 05/18/2023]
Abstract
The nonsense-mediated mRNA decay (NMD) pathway serves an important role in gene expression by targeting aberrant mRNAs that have acquired premature termination codons (PTCs) as well as a subset of normally processed endogenous mRNAs. One determinant for the targeting of mRNAs by NMD is the occurrence of translation termination distal to the poly(A) tail. Yet, a large subset of naturally occurring mRNAs contain long 3' UTRs, many of which, according to global studies, are insensitive to NMD. This raises the possibility that such mRNAs have evolved mechanisms for NMD evasion. Here, we analyzed a set of human long 3' UTR mRNAs and found that many are indeed resistant to NMD. By dissecting the 3' UTR of one such mRNA, TRAM1 mRNA, we identified a cis element located within the first 200 nt that inhibits NMD when positioned in downstream proximity of the translation termination codon and is sufficient for repressing NMD of a heterologous reporter mRNA. Investigation of other NMD-evading long 3' UTR mRNAs revealed a subset that, similar to TRAM1 mRNA, contains NMD-inhibiting cis elements in the first 200 nt. A smaller subset of long 3' UTR mRNAs evades NMD by a different mechanism that appears to be independent of a termination-proximal cis element. Our study suggests that different mechanisms have evolved to ensure NMD evasion of human mRNAs with long 3' UTRs.
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Affiliation(s)
- Kalodiah G Toma
- Division of Biological Sciences, University of California San Diego, La Jolla, California 92093, USA
| | - Indrani Rebbapragada
- Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
| | - Sébastien Durand
- Division of Biological Sciences, University of California San Diego, La Jolla, California 92093, USA Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
| | - Jens Lykke-Andersen
- Division of Biological Sciences, University of California San Diego, La Jolla, California 92093, USA Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
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120
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Tummala H, Walne A, Collopy L, Cardoso S, de la Fuente J, Lawson S, Powell J, Cooper N, Foster A, Mohammed S, Plagnol V, Vulliamy T, Dokal I. Poly(A)-specific ribonuclease deficiency impacts telomere biology and causes dyskeratosis congenita. J Clin Invest 2015; 125:2151-60. [PMID: 25893599 DOI: 10.1172/jci78963] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Accepted: 02/12/2015] [Indexed: 11/17/2022] Open
Abstract
Dyskeratosis congenita (DC) and related syndromes are inherited, life-threatening bone marrow (BM) failure disorders, and approximately 40% of cases are currently uncharacterized at the genetic level. Here, using whole exome sequencing (WES), we have identified biallelic mutations in the gene encoding poly(A)-specific ribonuclease (PARN) in 3 families with individuals exhibiting severe DC. PARN is an extensively characterized exonuclease with deadenylation activity that controls mRNA stability in part and therefore regulates expression of a large number of genes. The DC-associated mutations identified affect key domains within the protein, and evaluation of patient cells revealed reduced deadenylation activity. This deadenylation deficiency caused an early DNA damage response in terms of nuclear p53 regulation, cell-cycle arrest, and reduced cell viability upon UV treatment. Individuals with biallelic PARN mutations and PARN-depleted cells exhibited reduced RNA levels for several key genes that are associated with telomere biology, specifically TERC, DKC1, RTEL1, and TERF1. Moreover, PARN-deficient cells also possessed critically short telomeres. Collectively, these results identify a role for PARN in telomere maintenance and demonstrate that it is a disease-causing gene in a subset of patients with severe DC.
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121
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Chuang TW, Lee KM, Tarn WY. Function and pathological implications of exon junction complex factor Y14. Biomolecules 2015; 5:343-55. [PMID: 25866920 PMCID: PMC4496676 DOI: 10.3390/biom5020343] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 03/31/2015] [Accepted: 04/01/2015] [Indexed: 01/01/2023] Open
Abstract
Eukaryotic mRNA biogenesis involves a series of interconnected steps, including nuclear pre-mRNA processing, mRNA export, and surveillance. The exon-junction complex (EJC) is deposited on newly spliced mRNAs and coordinates several downstream steps of mRNA biogenesis. The EJC core protein, Y14, functions with its partners in nonsense-mediated mRNA decay and translational enhancement. Y14 plays additional roles in mRNA metabolism, some of which are independent of the EJC, and it is also involved in other cellular processes. Genetic mutations or aberrant expression of Y14 results in physiological abnormality and may cause disease. Therefore, it is important to understand the various functions of Y14 and its physiological and pathological roles.
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Affiliation(s)
- Tzu-Wei Chuang
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Kou-Ming Lee
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
| | - Woan-Yuh Tarn
- Institute of Biomedical Sciences, Academia Sinica, Taipei 115, Taiwan.
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122
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Smith JE, Baker KE. Nonsense-mediated RNA decay--a switch and dial for regulating gene expression. Bioessays 2015; 37:612-23. [PMID: 25820233 DOI: 10.1002/bies.201500007] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Nonsense-mediated RNA decay (NMD) represents an established quality control checkpoint for gene expression that protects cells from consequences of gene mutations and errors during RNA biogenesis that lead to premature termination during translation. Characterization of NMD-sensitive transcriptomes has revealed, however, that NMD targets not only aberrant transcripts but also a broad array of mRNA isoforms expressed from many endogenous genes. NMD is thus emerging as a master regulator that drives both fine and coarse adjustments in steady-state RNA levels in the cell. Importantly, while NMD activity is subject to autoregulation as a means to maintain homeostasis, modulation of the pathway by external cues provides a means to reprogram gene expression and drive important biological processes. Finally, the unanticipated observation that transcripts predicted to lack protein-coding capacity are also sensitive to this translation-dependent surveillance mechanism implicates NMD in regulating RNA function in new and diverse ways.
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Affiliation(s)
- Jenna E Smith
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH, USA
| | - Kristian E Baker
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH, USA
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123
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Degtiar E, Fridman A, Gottlieb D, Vexler K, Berezin I, Farhi R, Golani L, Shaul O. The feedback control of UPF3 is crucial for RNA surveillance in plants. Nucleic Acids Res 2015; 43:4219-35. [PMID: 25820429 PMCID: PMC4417159 DOI: 10.1093/nar/gkv237] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 03/06/2015] [Indexed: 11/24/2022] Open
Abstract
Nonsense-mediated-decay (NMD) is a eukaryotic RNA surveillance mechanism that controls the levels of both aberrant and normal transcripts. The regulation of this process is not well understood. The Arabidopsis NMD factor UPF3 is regulated by a negative feedback-loop that targets its own transcript for NMD. We investigated the functional significance of this control for the overall regulation of NMD in Arabidopsis. For this, we tested the ability of NMD-sensitive and -insensitive forms of UPF3, expressed under the control of UPF3 promoter, to complement NMD functionality in NMD-mutant plants and investigated their impact in wild-type (WT) plants. The sensitivity of UPF3 transcript to NMD was essential for efficient complementation of NMD in upf3 mutants. Upregulated UPF3 expression in WT plants resulted in over-degradation of certain transcripts and inhibited degradation of other transcripts. Our results demonstrate that, in contrast to mammalian cells, a delicate balance of UPF3 transcript levels by its feedback loop and by restriction of its transcription, are crucial for proper NMD regulation in Arabidopsis. Interestingly, the levels of many small-nucleolar-RNAs (snoRNAs) were decreased in upf1 and upf3 mutants and increased upon enhanced UPF3 expression. This suggests that proper snoRNA homeostasis in Arabidopsis depends on the integrity of the NMD pathway.
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Affiliation(s)
- Evgeniya Degtiar
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Adi Fridman
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Dror Gottlieb
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Karina Vexler
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Irina Berezin
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Ronit Farhi
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Linoy Golani
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
| | - Orit Shaul
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel
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124
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Karam R, Lou CH, Kroeger H, Huang L, Lin JH, Wilkinson MF. The unfolded protein response is shaped by the NMD pathway. EMBO Rep 2015; 16:599-609. [PMID: 25807986 DOI: 10.15252/embr.201439696] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 02/24/2015] [Indexed: 12/15/2022] Open
Abstract
Endoplasmic reticulum (ER) stress induces the unfolded protein response (UPR), an essential adaptive intracellular pathway that relieves the stress. Although the UPR is an evolutionarily conserved and beneficial pathway, its chronic activation contributes to the pathogenesis of a wide variety of human disorders. The fidelity of UPR activation must thus be tightly regulated to prevent inappropriate signaling. The nonsense-mediated RNA decay (NMD) pathway has long been known to function in RNA quality control, rapidly degrading aberrant mRNAs, and has been suggested to regulate subsets of normal mRNAs. Here, we report that the NMD pathway regulates the UPR. NMD increases the threshold for triggering the UPR in vitro and in vivo, thereby preventing UPR activation in response to normally innocuous levels of ER stress. NMD also promotes the timely termination of the UPR. We demonstrate that NMD directly targets the mRNAs encoding several UPR components, including the highly conserved UPR sensor, IRE1α, whose NMD-dependent degradation partly underpins this process. Our work not only sheds light on UPR regulation, but demonstrates the physiological relevance of NMD's ability to regulate normal mRNAs.
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Affiliation(s)
- Rachid Karam
- Department of Reproductive Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Chih-Hong Lou
- Department of Reproductive Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Heike Kroeger
- Department of Pathology, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Lulu Huang
- Department of Reproductive Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Jonathan H Lin
- Department of Pathology, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Miles F Wilkinson
- Department of Reproductive Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA Institute of Genomic Medicine, University of California San Diego, La Jolla, CA, USA
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125
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Li T, Shi Y, Wang P, Guachalla LM, Sun B, Joerss T, Chen YS, Groth M, Krueger A, Platzer M, Yang YG, Rudolph KL, Wang ZQ. Smg6/Est1 licenses embryonic stem cell differentiation via nonsense-mediated mRNA decay. EMBO J 2015; 34:1630-47. [PMID: 25770585 PMCID: PMC4475398 DOI: 10.15252/embj.201489947] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 02/18/2015] [Indexed: 12/12/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a post-transcriptional mechanism that targets aberrant transcripts and regulates the cellular RNA reservoir. Genetic modulation in vertebrates suggests that NMD is critical for cellular and tissue homeostasis, although the underlying mechanism remains elusive. Here, we generate knockout mice lacking Smg6/Est1, a key nuclease in NMD and a telomerase cofactor. While the complete loss of Smg6 causes mouse lethality at the blastocyst stage, inducible deletion of Smg6 is compatible with embryonic stem cell (ESC) proliferation despite the absence of telomere maintenance and functional NMD. Differentiation of Smg6-deficient ESCs is blocked due to sustained expression of pluripotency genes, normally repressed by NMD, and forced down-regulation of one such target, c-Myc, relieves the differentiation block. Smg6-null embryonic fibroblasts are viable as well, but are refractory to cellular reprograming into induced pluripotent stem cells (iPSCs). Finally, depletion of all major NMD factors compromises ESC differentiation, thus identifying NMD as a licensing factor for the switch of cell identity in the process of stem cell differentiation and somatic cell reprograming.
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Affiliation(s)
- Tangliang Li
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Yue Shi
- Disease Genomics and Individualized Medicine Laboratory, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Pei Wang
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Luis Miguel Guachalla
- Institute of Molecular Medicine and Max-Planck-Research Department of Stem Cell Aging, University of Ulm, Ulm, Germany
| | - Baofa Sun
- Disease Genomics and Individualized Medicine Laboratory, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Tjard Joerss
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Yu-Sheng Chen
- Disease Genomics and Individualized Medicine Laboratory, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Marco Groth
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Anja Krueger
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Matthias Platzer
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany
| | - Yun-Gui Yang
- Disease Genomics and Individualized Medicine Laboratory, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, China
| | - Karl Lenhard Rudolph
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany Institute of Molecular Medicine and Max-Planck-Research Department of Stem Cell Aging, University of Ulm, Ulm, Germany
| | - Zhao-Qi Wang
- Leibniz Institute for Age Research - Fritz Lipmann Institute (FLI), Jena, Germany Faculty of Biology and Pharmacy, Friedrich-Schiller University of Jena, Jena, Germany
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126
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Lykke-Andersen S, Chen Y, Ardal BR, Lilje B, Waage J, Sandelin A, Jensen TH. Human nonsense-mediated RNA decay initiates widely by endonucleolysis and targets snoRNA host genes. Genes Dev 2015; 28:2498-517. [PMID: 25403180 PMCID: PMC4233243 DOI: 10.1101/gad.246538.114] [Citation(s) in RCA: 131] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Eukaryotic RNAs with premature termination codons (PTCs) are eliminated by nonsense-mediated decay (NMD). Lykke-Andersen et al. discover that SMG6-catalyzed endonucleolysis widely initiates the degradation of human nonsense RNAs, whereas decapping is used to a lesser extent. A large proportion of genes hosting snoRNAs in their introns produce considerable amounts of NMD-sensitive splice variants, indicating that these RNAs are merely by-products of a primary snoRNA production process. Eukaryotic RNAs with premature termination codons (PTCs) are eliminated by nonsense-mediated decay (NMD). While human nonsense RNA degradation can be initiated either by an endonucleolytic cleavage event near the PTC or through decapping, the individual contribution of these activities on endogenous substrates has remained unresolved. Here we used concurrent transcriptome-wide identification of NMD substrates and their 5′–3′ decay intermediates to establish that SMG6-catalyzed endonucleolysis widely initiates the degradation of human nonsense RNAs, whereas decapping is used to a lesser extent. We also show that a large proportion of genes hosting snoRNAs in their introns produce considerable amounts of NMD-sensitive splice variants, indicating that these RNAs are merely by-products of a primary snoRNA production process. Additionally, transcripts from genes encoding multiple snoRNAs often yield alternative transcript isoforms that allow for differential expression of individual coencoded snoRNAs. Based on our findings, we hypothesize that snoRNA host genes need to be highly transcribed to accommodate high levels of snoRNA production and that the expression of individual snoRNAs and their cognate spliced RNA can be uncoupled via alternative splicing and NMD.
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Affiliation(s)
- Søren Lykke-Andersen
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology and Genetics, Aarhus University, Aarhus DK-8000, Denmark
| | - Yun Chen
- The Bioinformatics Centre, Department of Biology and Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Britt R Ardal
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology and Genetics, Aarhus University, Aarhus DK-8000, Denmark
| | - Berit Lilje
- The Bioinformatics Centre, Department of Biology and Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Johannes Waage
- The Bioinformatics Centre, Department of Biology and Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Albin Sandelin
- The Bioinformatics Centre, Department of Biology and Biotech Research and Innovation Centre, University of Copenhagen, Copenhagen DK-2200, Denmark
| | - Torben Heick Jensen
- Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology and Genetics, Aarhus University, Aarhus DK-8000, Denmark
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127
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Abstract
Jeremy and Jeffrey Wilusz discuss the accompanying study by Lykke-Andersen et al. on the contribution of SMG6-catalyzed endonucleolytic cleavage to nonsense-mediated RNA decay and its role in snoRNA biogenesis. Production of multiple functional RNAs from a single primary transcript is an extremely efficient use of genetic information, although it complicates the ability of the cell to independently regulate the production of each RNA. For the case of small nucleolar RNAs (snoRNAs) encoded within introns of mRNA genes, Lykke-Andersen and colleagues (pp. 2498–2517) demonstrated that alternative splicing and the SMG6 endonuclease of the nonsense-mediated RNA decay pathway are key regulators that control which RNAs accumulate.
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Affiliation(s)
- Jeremy E Wilusz
- Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA;
| | - Jeffrey Wilusz
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado 80523, USA
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128
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Chen FC. Alternative RNA structure-coupled gene regulations in tumorigenesis. Int J Mol Sci 2014; 16:452-75. [PMID: 25551597 PMCID: PMC4307256 DOI: 10.3390/ijms16010452] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 12/16/2014] [Indexed: 12/11/2022] Open
Abstract
Alternative RNA structures (ARSs), or alternative transcript isoforms, are critical for regulating cellular phenotypes in humans. In addition to generating functionally diverse protein isoforms from a single gene, ARS can alter the sequence contents of 5'/3' untranslated regions (UTRs) and intronic regions, thus also affecting the regulatory effects of these regions. ARS may introduce premature stop codon(s) into a transcript, and render the transcript susceptible to nonsense-mediated decay, which in turn can influence the overall gene expression level. Meanwhile, ARS can regulate the presence/absence of upstream open reading frames and microRNA targeting sites in 5'UTRs and 3'UTRs, respectively, thus affecting translational efficiencies and protein expression levels. Furthermore, since ARS may alter exon-intron structures, it can influence the biogenesis of intronic microRNAs and indirectly affect the expression of the target genes of these microRNAs. The connections between ARS and multiple regulatory mechanisms underline the importance of ARS in determining cell fate. Accumulating evidence indicates that ARS-coupled regulations play important roles in tumorigenesis. Here I will review our current knowledge in this field, and discuss potential future directions.
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Affiliation(s)
- Feng-Chi Chen
- Institute of Population Health Sciences, National Health Research Institutes, Miaoli County 350, Taiwan.
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129
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Bao J, Tang C, Yuan S, Porse BT, Yan W. UPF2, a nonsense-mediated mRNA decay factor, is required for prepubertal Sertoli cell development and male fertility by ensuring fidelity of the transcriptome. Development 2014; 142:352-62. [PMID: 25503407 DOI: 10.1242/dev.115642] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) represents a highly conserved RNA surveillance mechanism through which mRNA transcripts bearing premature termination codons (PTCs) are selectively degraded to maintain transcriptomic fidelity in the cell. Numerous in vitro studies have demonstrated the importance of the NMD pathway; however, evidence supporting its physiological necessity has only just started to emerge. Here, we report that ablation of Upf2, which encodes a core NMD factor, in murine embryonic Sertoli cells (SCs) leads to severe testicular atrophy and male sterility owing to rapid depletion of both SCs and germ cells during prepubertal testicular development. RNA-Seq and bioinformatic analyses revealed impaired transcriptomic homeostasis in SC-specific Upf2 knockout testes, characterized by an accumulation of PTC-containing transcripts and the transcriptome-wide dysregulation of genes encoding splicing factors and key proteins essential for SC fate control. Our data demonstrate an essential role of UPF2-mediated NMD in prepubertal SC development and male fertility.
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Affiliation(s)
- Jianqiang Bao
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, 1664 North Virginia Street, MS575, Reno, NV 89557, USA
| | - Chong Tang
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, 1664 North Virginia Street, MS575, Reno, NV 89557, USA
| | - Shuiqiao Yuan
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, 1664 North Virginia Street, MS575, Reno, NV 89557, USA
| | - Bo T Porse
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Jagtvej 124, Copenhagen, DK-2200, Denmark Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Jagtvej 124, Copenhagen, DK-2200, Denmark Danish Stem Cell Centre (DanStem), Faculty of Health Sciences, University of Copenhagen, Ole Maaløes Vej 5, Copenhagen N DK2200, Denmark
| | - Wei Yan
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, 1664 North Virginia Street, MS575, Reno, NV 89557, USA
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130
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Celik A, Kervestin S, Jacobson A. NMD: At the crossroads between translation termination and ribosome recycling. Biochimie 2014; 114:2-9. [PMID: 25446649 DOI: 10.1016/j.biochi.2014.10.027] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 10/27/2014] [Indexed: 10/24/2022]
Abstract
Nonsense-mediated mRNA decay (NMD) is one of three regulatory mechanisms that monitor the cytoplasm for aberrant mRNAs. NMD is usually triggered by premature translation termination codons that arise from mutations, transcription errors, or inefficient splicing, but which also occur in transcripts with alternately spliced isoforms or upstream open reading frames, or in the context of long 3'-UTRs. This surveillance pathway requires detection of the nonsense codon by the eukaryotic release factors (eRF1 and eRF3) and the activities of the Upf proteins, but the exact mechanism by which a nonsense codon is recognized as premature, and the individual roles of the Upf proteins, are poorly understood. In this review, we highlight important differences between premature and normal termination. Based on our current understanding of normal termination and ribosome recycling, we propose a similar mechanism for premature termination events that includes a role for the Upf proteins. In this model, the Upf proteins not only target the mRNA and nascent peptide for degradation, but also assume the role of recycling factors and rescue a ribosome stalled at a premature nonsense codon. The ATPase and helicase activities of Upf1, with the help of Upf2 and Upf3, are thus thought to be the catalytic force in ribosome subunit dissociation and ribosome recycling at an otherwise poorly dissociable termination event. While this model is somewhat speculative, it provides a unified vision for current data and a direction for future research.
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Affiliation(s)
- Alper Celik
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01655-0122, USA
| | - Stephanie Kervestin
- CNRS FRE3630 Associated with Université Diderot, Sorbonne Paris Cité, Institut de Biologie Physico-Chimique, 75005 Paris, France
| | - Allan Jacobson
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, 368 Plantation Street, Worcester, MA 01655-0122, USA.
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131
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Joncourt R, Eberle AB, Rufener SC, Mühlemann O. Eukaryotic initiation factor 4G suppresses nonsense-mediated mRNA decay by two genetically separable mechanisms. PLoS One 2014; 9:e104391. [PMID: 25148142 PMCID: PMC4141738 DOI: 10.1371/journal.pone.0104391] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 07/08/2014] [Indexed: 11/19/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD), which is best known for degrading mRNAs with premature termination codons (PTCs), is thought to be triggered by aberrant translation termination at stop codons located in an environment of the mRNP that is devoid of signals necessary for proper termination. In mammals, the cytoplasmic poly(A)-binding protein 1 (PABPC1) has been reported to promote correct termination and therewith antagonize NMD by interacting with the eukaryotic release factors 1 (eRF1) and 3 (eRF3). Using tethering assays in which proteins of interest are recruited as MS2 fusions to a NMD reporter transcript, we show that the three N-terminal RNA recognition motifs (RRMs) of PABPC1 are sufficient to antagonize NMD, while the eRF3-interacting C-terminal domain is dispensable. The RRM1-3 portion of PABPC1 interacts with eukaryotic initiation factor 4G (eIF4G) and tethering of eIF4G to the NMD reporter also suppresses NMD. We identified the interactions of the eIF4G N-terminus with PABPC1 and the eIF4G core domain with eIF3 as two genetically separable features that independently enable tethered eIF4G to inhibit NMD. Collectively, our results reveal a function of PABPC1, eIF4G and eIF3 in translation termination and NMD suppression, and they provide additional evidence for a tight coupling between translation termination and initiation.
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Affiliation(s)
- Raphael Joncourt
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Andrea B. Eberle
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
| | - Simone C. Rufener
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Oliver Mühlemann
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
- * E-mail:
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132
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Carpenter S, Ricci EP, Mercier BC, Moore MJ, Fitzgerald KA. Post-transcriptional regulation of gene expression in innate immunity. Nat Rev Immunol 2014; 14:361-76. [PMID: 24854588 DOI: 10.1038/nri3682] [Citation(s) in RCA: 268] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Innate immune responses combat infectious microorganisms by inducing inflammatory responses, antimicrobial pathways and adaptive immunity. Multiple genes within each of these functional categories are coordinately and temporally regulated in response to distinct external stimuli. The substantial potential of these responses to drive pathological inflammation and tissue damage highlights the need for rigorous control of these responses. Although transcriptional control of inflammatory gene expression has been studied extensively, the importance of post-transcriptional regulation of these processes is less well defined. In this Review, we discuss the regulatory mechanisms that occur at the level of mRNA splicing, mRNA polyadenylation, mRNA stability and protein translation, and that have instrumental roles in controlling both the magnitude and duration of the inflammatory response.
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Affiliation(s)
- Susan Carpenter
- 1] Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2]
| | - Emiliano P Ricci
- 1] Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2]
| | - Blandine C Mercier
- 1] Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2]
| | - Melissa J Moore
- Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Katherine A Fitzgerald
- 1] Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2] Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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133
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Kafasla P, Skliris A, Kontoyiannis DL. Post-transcriptional coordination of immunological responses by RNA-binding proteins. Nat Immunol 2014; 15:492-502. [PMID: 24840980 DOI: 10.1038/ni.2884] [Citation(s) in RCA: 141] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Accepted: 04/01/2014] [Indexed: 12/22/2022]
Abstract
Immunological reactions are propelled by ever-changing signals that alter the translational ability of the RNA in the cells involved. Such alterations are considered to be consequential modifications in the transcriptomic decoding of the genetic blueprint. The identification of RNA-binding protein (RBP) assemblies engaged in the coordinative regulation of state-specific RNAs indicates alternative and exclusive means for determining the activation, plasticity and tolerance of cells of the immune system. Here we review current knowledge about RBP-regulated post-transcriptional events involved in the reactivity of cells of the immune system and the importance of their alteration during chronic inflammatory pathology and autoimmunity.
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Affiliation(s)
- Panagiota Kafasla
- Division of Immunology, Biomedical Sciences Research Center "Alexander Fleming", Vari, Greece
| | - Antonis Skliris
- Division of Immunology, Biomedical Sciences Research Center "Alexander Fleming", Vari, Greece
| | - Dimitris L Kontoyiannis
- Division of Immunology, Biomedical Sciences Research Center "Alexander Fleming", Vari, Greece
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134
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Turner M, Galloway A, Vigorito E. Noncoding RNA and its associated proteins as regulatory elements of the immune system. Nat Immunol 2014; 15:484-91. [PMID: 24840979 DOI: 10.1038/ni.2887] [Citation(s) in RCA: 144] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 04/01/2014] [Indexed: 12/11/2022]
Abstract
The rapid changes in gene expression that accompany developmental transitions, stress responses and proliferation are controlled by signal-mediated coordination of transcriptional and post-transcriptional mechanisms. In recent years, understanding of the mechanics of these processes and the contexts in which they are employed during hematopoiesis and immune challenge has increased. An important aspect of this progress is recognition of the importance of RNA-binding proteins and noncoding RNAs. These have roles in the development and function of the immune system and in pathogen life cycles, and they represent an important aspect of intracellular immunity.
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Affiliation(s)
- Martin Turner
- Laboratory of Lymphocyte Signalling and Development, The Babraham Institute, Babraham Research Campus, Cambridge, UK
| | - Alison Galloway
- Laboratory of Lymphocyte Signalling and Development, The Babraham Institute, Babraham Research Campus, Cambridge, UK
| | - Elena Vigorito
- Laboratory of Lymphocyte Signalling and Development, The Babraham Institute, Babraham Research Campus, Cambridge, UK
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135
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Regulation of natural mRNAs by the nonsense-mediated mRNA decay pathway. EUKARYOTIC CELL 2014; 13:1126-35. [PMID: 25038084 DOI: 10.1128/ec.00090-14] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The nonsense-mediated mRNA decay (NMD) pathway is a specialized mRNA degradation pathway that degrades select mRNAs. This pathway is conserved in all eukaryotes examined so far, and it triggers the degradation of mRNAs that prematurely terminate translation. Originally identified as a pathway that degrades mRNAs with premature termination codons as a result of errors during transcription, splicing, or damage to the mRNA, NMD is now also recognized as a pathway that degrades some natural mRNAs. The degradation of natural mRNAs by NMD has been identified in multiple eukaryotes, including Saccharomyces cerevisiae, Drosophila melanogaster, Arabidopsis thaliana, and humans. S. cerevisiae is used extensively as a model to study natural mRNA regulation by NMD. Inactivation of the NMD pathway in S. cerevisiae affects approximately 10% of the transcriptome. Similar percentages of natural mRNAs in the D. melanogaster and human transcriptomes are also sensitive to the pathway, indicating that NMD is important for the regulation of gene expression in multiple organisms. NMD can either directly or indirectly regulate the decay rate of natural mRNAs. Direct NMD targets possess NMD-inducing features. This minireview focuses on the regulation of natural mRNAs by the NMD pathway, as well as the features demonstrated to target these mRNAs for decay by the pathway in S. cerevisiae. We also compare NMD-targeting features identified in S. cerevisiae with known NMD-targeting features in other eukaryotic organisms.
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136
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Abstract
Nonsense suppression therapy encompasses approaches aimed at suppressing translation termination at in-frame premature termination codons (PTCs, also known as nonsense mutations) to restore deficient protein function. In this review, we examine the current status of PTC suppression as a therapy for genetic diseases caused by nonsense mutations. We discuss what is currently known about the mechanism of PTC suppression as well as therapeutic approaches under development to suppress PTCs. The approaches considered include readthrough drugs, suppressor tRNAs, PTC pseudouridylation, and inhibition of nonsense-mediated mRNA decay. We also discuss the barriers that currently limit the clinical application of nonsense suppression therapy and suggest how some of these difficulties may be overcome. Finally, we consider how PTC suppression may play a role in the clinical treatment of genetic diseases caused by nonsense mutations.
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Affiliation(s)
- Kim M Keeling
- Department of Microbiology and Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham, Birmingham, Alabama 35294; , , ,
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137
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Kawashima T, Douglass S, Gabunilas J, Pellegrini M, Chanfreau GF. Widespread use of non-productive alternative splice sites in Saccharomyces cerevisiae. PLoS Genet 2014; 10:e1004249. [PMID: 24722551 PMCID: PMC3983031 DOI: 10.1371/journal.pgen.1004249] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 02/04/2014] [Indexed: 01/22/2023] Open
Abstract
Saccharomyces cerevisiae has been used as a model system to investigate the mechanisms of pre-mRNA splicing but only a few examples of alternative splice site usage have been described in this organism. Using RNA-Seq analysis of nonsense-mediated mRNA decay (NMD) mutant strains, we show that many S. cerevisiae intron-containing genes exhibit usage of alternative splice sites, but many transcripts generated by splicing at these sites are non-functional because they introduce premature termination codons, leading to degradation by NMD. Analysis of splicing mutants combined with NMD inactivation revealed the role of specific splicing factors in governing the use of these alternative splice sites and identified novel functions for Prp17p in enhancing the use of branchpoint-proximal upstream 3′ splice sites and for Prp18p in suppressing the usage of a non-canonical AUG 3′-splice site in GCR1. The use of non-productive alternative splice sites can be increased in stress conditions in a promoter-dependent manner, contributing to the down-regulation of genes during stress. These results show that alternative splicing is frequent in S. cerevisiae but masked by RNA degradation and that the use of alternative splice sites in this organism is mostly aimed at controlling transcript levels rather than increasing proteome diversity. Accurate gene expression requires the transfer of gene information from DNA to RNA. When DNA is transcribed into RNA, part of the RNA needs to be removed (spliced) to generate a proper copy of the genetic information. This process needs to be very accurate to preserve the genetic information that will be transferred into proteins. Our study shows that in baker's yeast, the splicing process does not always produce the correctly spliced products, as RNA splicing events frequently utilize incorrect splice sites. However, these deficient RNA molecules are eliminated from cells by a quality control mechanism to preserve the integrity of the genetic information. However, incorrect splicing is not useless, as it can be used to regulate the quantity of RNA that is generated.
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Affiliation(s)
- Tadashi Kawashima
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, UCLA, Los Angeles, California, United States of America
| | - Stephen Douglass
- Bioinformatics Interdepartmental Program, UCLA, Los Angeles, California, United States of America
| | - Jason Gabunilas
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, UCLA, Los Angeles, California, United States of America
| | - Matteo Pellegrini
- Department of Molecular, Cellular and Developmental Biology, UCLA, Los Angeles, California, United States of America
| | - Guillaume F. Chanfreau
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, UCLA, Los Angeles, California, United States of America
- * E-mail:
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138
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Distinctive properties of identical twins' TCR repertoires revealed by high-throughput sequencing. Proc Natl Acad Sci U S A 2014; 111:5980-5. [PMID: 24711416 DOI: 10.1073/pnas.1319389111] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Adaptive immunity in humans is provided by hypervariable Ig-like molecules on the surface of B and T cells. The final set of these molecules in each organism is formed under the influence of two forces: individual genetic traits and the environment, which includes the diverse spectra of alien and self-antigens. Here we assess the impact of individual genetic factors on the formation of the adaptive immunity by analyzing the T-cell receptor (TCR) repertoires of three pairs of monozygous twins by next-generation sequencing. Surprisingly, we found that an overlap between the TCR repertoires of monozygous twins is similar to an overlap between the TCR repertoires of nonrelated individuals. However, the number of identical complementary determining region 3 sequences in two individuals is significantly increased for twin pairs in the fraction of highly abundant TCR molecules, which is enriched by the antigen-experienced T cells. We found that the initial recruitment of particular TCR V genes for recombination and subsequent selection in the thymus is strictly determined by individual genetic factors. J genes of TCRs are selected randomly for recombination; however, the subsequent selection in the thymus gives preference to some α but not β J segments. These findings provide a deeper insight into the mechanism of TCR repertoire generation.
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139
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Martin L, Grigoryan A, Wang D, Wang J, Breda L, Rivella S, Cardozo T, Gardner LB. Identification and characterization of small molecules that inhibit nonsense-mediated RNA decay and suppress nonsense p53 mutations. Cancer Res 2014; 74:3104-13. [PMID: 24662918 DOI: 10.1158/0008-5472.can-13-2235] [Citation(s) in RCA: 95] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Many of the gene mutations found in genetic disorders, including cancer, result in premature termination codons (PTC) and the rapid degradation of their mRNAs by nonsense-mediated RNA decay (NMD). We used virtual library screening, targeting a pocket in the SMG7 protein, a key component of the NMD mechanism, to identify compounds that disrupt the SMG7-UPF1 complex and inhibit NMD. Several of these compounds upregulated NMD-targeted mRNAs at nanomolar concentrations, with minimal toxicity in cell-based assays. As expected, pharmacologic NMD inhibition disrupted SMG7-UPF1 interactions. When used in cells with PTC-mutated p53, pharmacologic NMD inhibition combined with a PTC "read-through" drug led to restoration of full-length p53 protein, upregulation of p53 downstream transcripts, and cell death. These studies serve as proof-of-concept that pharmacologic NMD inhibitors can restore mRNA integrity in the presence of PTC and can be used as part of a strategy to restore full-length protein in a variety of genetic diseases.
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Affiliation(s)
- Leenus Martin
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
| | - Arsen Grigoryan
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
| | - Ding Wang
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
| | - Jinhua Wang
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
| | - Laura Breda
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
| | - Stefano Rivella
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
| | - Timothy Cardozo
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
| | - Lawrence B Gardner
- Authors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New YorkAuthors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New YorkAuthors' Affiliations: Departments of Medicine, Biochemistry and Molecular Pharmacology; The NYU Cancer Institute, New York University School of Medicine; and Departments of Pediatrics and Cell and Biology Development, Weill Cornell School of Medicine, New York, New York
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140
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In vivo determination of direct targets of the nonsense-mediated decay pathway in Drosophila. G3-GENES GENOMES GENETICS 2014; 4:485-96. [PMID: 24429422 PMCID: PMC3962487 DOI: 10.1534/g3.113.009357] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Nonsense-mediated messenger RNA (mRNA) decay (NMD) is a mRNA degradation pathway that regulates a significant portion of the transcriptome. The expression levels of numerous genes are known to be altered in NMD mutants, but it is not known which of these transcripts is a direct pathway target. Here, we present the first genome-wide analysis of direct NMD targeting in an intact animal. By using rapid reactivation of the NMD pathway in a Drosophila melanogaster NMD mutant and globally monitoring of changes in mRNA expression levels, we can distinguish between primary and secondary effects of NMD on gene expression. Using this procedure, we identified 168 candidate direct NMD targets in vivo. Remarkably, we found that 81% of direct target genes do not show increased expression levels in an NMD mutant, presumably due to feedback regulation. Because most previous studies have used up-regulation of mRNA expression as the only means to identify NMD-regulated transcripts, our results provide new directions for understanding the roles of the NMD pathway in endogenous gene regulation during animal development and physiology. For instance, we show clearly that direct target genes have longer 3′ untranslated regions compared with nontargets, suggesting long 3′ untranslated regions target mRNAs for NMD in vivo. In addition, we investigated the role of NMD in suppressing transcriptional noise and found that although the transposable element Copia is up-regulated in NMD mutants, this effect appears to be indirect.
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141
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Lou CH, Shao A, Shum EY, Espinoza JL, Huang L, Karam R, Wilkinson MF. Posttranscriptional control of the stem cell and neurogenic programs by the nonsense-mediated RNA decay pathway. Cell Rep 2014; 6:748-64. [PMID: 24529710 DOI: 10.1016/j.celrep.2014.01.028] [Citation(s) in RCA: 112] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 12/11/2013] [Accepted: 01/21/2014] [Indexed: 11/19/2022] Open
Abstract
The mechanisms dictating whether a cell proliferates or differentiates have undergone intense scrutiny, but they remain poorly understood. Here, we report that UPF1, a central component in the nonsense-mediated RNA decay (NMD) pathway, plays a key role in this decision by promoting the proliferative, undifferentiated cell state. UPF1 acts, in part, by destabilizing the NMD substrate encoding the TGF-β inhibitor SMAD7 and stimulating TGF-β signaling. UPF1 also promotes the decay of mRNAs encoding many other proteins that oppose the proliferative, undifferentiated cell state. Neural differentiation is triggered when NMD is downregulated by neurally expressed microRNAs (miRNAs). This UPF1-miRNA circuitry is highly conserved and harbors negative feedback loops that act as a molecular switch. Our results suggest that the NMD pathway collaborates with the TGF-β signaling pathway to lock in the stem-like state, a cellular state that is stably reversed when neural differentiation signals that induce NMD-repressive miRNAs are received.
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Affiliation(s)
- Chih H Lou
- Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA
| | - Ada Shao
- Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA
| | - Eleen Y Shum
- Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA
| | - Josh L Espinoza
- Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA
| | - Lulu Huang
- Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA
| | - Rachid Karam
- Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA
| | - Miles F Wilkinson
- Department of Reproductive Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA; Institute of Genomic Medicine, University of California, San Diego, La Jolla, CA 92093-0695, USA.
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142
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Ishigaki Y, Nakamura Y, Tatsuno T, Hashimoto M, Shimasaki T, Iwabuchi K, Tomosugi N. Depletion of RNA-binding protein RBM8A (Y14) causes cell cycle deficiency and apoptosis in human cells. Exp Biol Med (Maywood) 2014; 238:889-97. [PMID: 23970407 DOI: 10.1177/1535370213494646] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RBM8A (Y14) contains an RNA-binding motif and forms a tight heterodimer with Magoh. The heterodimer is known to be a member of the exon junction complex that forms on mRNA before export and it is required for mRNA metabolism processes such as splicing, mRNA export and nonsense-mediated mRNA decay. Recently, deficient cellular proliferation has been observed in RBM8A- or Magoh-depleted cells. These results prompted us to study the role of RBM8A in cell cycle progression of human tumour cells. The depletion of RBM8A in A549 cells resulted in poor cell survival and the accumulation of mitotic cells. After release from G1/S arrest induced by a double thymidine block, the RBM8A-silenced cells could not proceed to the next G1 phase beyond G2/M phase. Finally, the sub-G1 population increased and the apoptosis markers caspases 3/7 were activated. Silenced cells exhibited an increased frequency of multipolar or monopolar centrosomes, which may have caused the observed deficiency in cell cycle progression. Finally, silencing of either RBM8A or Magoh resulted in mutual downregulation of the other protein. These results illustrate that the RBM8A-Magoh mRNA binding complex is required for M phase progression and both proteins may be novel targets for anticancer therapy.
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Affiliation(s)
- Yasuhito Ishigaki
- Division of Advanced Medicine, Medical Research Institute, Kanazawa Medical University, Uchinada-machi, Kahoku-gun 920-0293, Japan
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143
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Hasemann MS, Lauridsen FKB, Waage J, Jakobsen JS, Frank AK, Schuster MB, Rapin N, Bagger FO, Hoppe PS, Schroeder T, Porse BT. C/EBPα is required for long-term self-renewal and lineage priming of hematopoietic stem cells and for the maintenance of epigenetic configurations in multipotent progenitors. PLoS Genet 2014; 10:e1004079. [PMID: 24415956 PMCID: PMC3886906 DOI: 10.1371/journal.pgen.1004079] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 11/19/2013] [Indexed: 12/29/2022] Open
Abstract
Transcription factors are key regulators of hematopoietic stem cells (HSCs) and act through their ability to bind DNA and impact on gene transcription. Their functions are interpreted in the complex landscape of chromatin, but current knowledge on how this is achieved is very limited. C/EBPα is an important transcriptional regulator of hematopoiesis, but its potential functions in HSCs have remained elusive. Here we report that C/EBPα serves to protect adult HSCs from apoptosis and to maintain their quiescent state. Consequently, deletion of Cebpa is associated with loss of self-renewal and HSC exhaustion. By combining gene expression analysis with genome-wide assessment of C/EBPα binding and epigenetic configurations, we show that C/EBPα acts to modulate the epigenetic states of genes belonging to molecular pathways important for HSC function. Moreover, our data suggest that C/EBPα acts as a priming factor at the HSC level where it actively promotes myeloid differentiation and counteracts lymphoid lineage choice. Taken together, our results show that C/EBPα is a key regulator of HSC biology, which influences the epigenetic landscape of HSCs in order to balance different cell fate options. Hematopoietic stem cells (HSCs) are required for the lifelong generation of blood cells. To fulfill this requirement HSCs carefully balance cell fate decisions such as self-renewal, differentiation, quiescence, proliferation and death. These features are regulated in part by transcription factors, which act by controlling the expression of genes important for the functional properties of HSCs. C/EBPα is a well-known inducer of myeloid differentiation. It is lowly expressed in HSCs and its potential function in these cells has been extensively debated. Here, we demonstrate that Cebpa deletion impacts on HSC self-renewal, differentiation, quiescence and survival. Through gene expression and ChIP-seq analyses of stem and progenitor cell-enriched cell populations, we further show that C/EBPα binds to regulatory regions of genes that are induced during granulocytic differentiation, suggesting that C/EBPα acts to prime HSCs for differentiation along the myeloid lineage. Finally, we demonstrate that C/EBPα loss leads to epigenetic changes at genes central to HSC biology, which implies that it may act to recruit chromatin writers/erasers through mechanisms that remain to be characterized. In conclusion, our work identifies C/EBPα as a central hub for HSC function and highlights how a single transcription factor may coordinate several HSC fate options.
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Affiliation(s)
- Marie S. Hasemann
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Felicia K. B. Lauridsen
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Johannes Waage
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- The Bioinformatic Centre, Department of Biology, Faculty of Natural Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Janus S. Jakobsen
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anne-Katrine Frank
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Mikkel B. Schuster
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nicolas Rapin
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- The Bioinformatic Centre, Department of Biology, Faculty of Natural Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Frederik O. Bagger
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- The Bioinformatic Centre, Department of Biology, Faculty of Natural Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Philipp S. Hoppe
- Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
| | - Timm Schroeder
- Department of Biosystems Science and Engineering, ETH Zurich, Basel, Switzerland
| | - Bo T. Porse
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- Biotech Research and Innovation Center (BRIC), University of Copenhagen, Copenhagen, Denmark
- Danish Stem Cell Centre (DanStem) Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark
- The Bioinformatic Centre, Department of Biology, Faculty of Natural Sciences, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
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144
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Howard A, Rogers AN. Role of translation initiation factor 4G in lifespan regulation and age-related health. Ageing Res Rev 2014; 13:115-24. [PMID: 24394551 DOI: 10.1016/j.arr.2013.12.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Revised: 12/18/2013] [Accepted: 12/23/2013] [Indexed: 01/04/2023]
Abstract
Inhibiting expression of eukaryotic translation initiation factor 4G (eIF4G) arrests normal development but extends lifespan when suppressed during adulthood. In addition to reducing overall translation, inhibition alters the stoichiometry of mRNA translation in favor of genes important for responding to stress and against those associated with growth and reproduction in C. elegans. In humans, aberrant expression of eIF4G is associated with certain forms of cancer and neurodegeneration. Here we review what is known about the roles of eIF4G in molecular, cellular, and organismal contexts. Also discussed are the gaps in understanding of this factor, particularly with regard to the roles of specific forms of expression in individual tissues and the importance of understanding eIF4G for development of potential therapeutic applications.
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145
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Crotty Alexander LE, Marsh BJ, Timmer AM, Lin AE, Zainabadi K, Czopik A, Guarente L, Nizet V. Myeloid cell sirtuin-1 expression does not alter host immune responses to Gram-negative endotoxemia or Gram-positive bacterial infection. PLoS One 2013; 8:e84481. [PMID: 24386389 PMCID: PMC3873454 DOI: 10.1371/journal.pone.0084481] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 11/14/2013] [Indexed: 11/20/2022] Open
Abstract
The role of sirtuin-1 (SIRT1) in innate immunity, and in particular the influence of SIRT1 on antimicrobial defense against infection, has yet to be reported but is important to define since SIRT1 inhibitors are being investigated as therapeutic agents in the treatment of cancer, Huntington’s disease, and autoimmune diseases. Given the therapeutic potential of SIRT1 suppression, we sought to characterize the role of SIRT1 in host defense. Utilizing both pharmacologic methods and a genetic knockout, we demonstrate that SIRT1 expression has little influence on macrophage and neutrophil antimicrobial functions. Myeloid SIRT1 expression does not change mortality in gram-negative toxin-induced shock or gram-positive bacteremia, suggesting that therapeutic suppression of SIRT1 may be done safely without suppression of myeloid cell-specific immune responses to severe bacterial infections.
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Affiliation(s)
- Laura E Crotty Alexander
- Pulmonary Critical Care Section, Veterans Affairs San Diego Healthcare System, San Diego, California, United States of America ; Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Brenda J Marsh
- Pulmonary Critical Care Section, Veterans Affairs San Diego Healthcare System, San Diego, California, United States of America ; Department of Medicine, University of California San Diego, San Diego, California, United States of America
| | - Anjuli M Timmer
- Department of Pediatrics, University of California San Diego, San Diego, California, United States of America
| | - Ann E Lin
- Department of Pediatrics, University of California San Diego, San Diego, California, United States of America
| | - Kayvan Zainabadi
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Agnieszka Czopik
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Leonard Guarente
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Victor Nizet
- Department of Pediatrics, University of California San Diego, San Diego, California, United States of America ; Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, San Diego, California, United States of America
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146
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Ohlsson E, Hasemann MS, Willer A, Lauridsen FKB, Rapin N, Jendholm J, Porse BT. Initiation of MLL-rearranged AML is dependent on C/EBPα. ACTA ACUST UNITED AC 2013; 211:5-13. [PMID: 24367003 PMCID: PMC3892979 DOI: 10.1084/jem.20130932] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
C/EBPα collaborates with MLL-ENL to activate a group of genes that, together with Hoxa9 and Meis1, are responsible for the early events that transforms normal hematopoietic cells into leukemic cells MLL-fusion proteins are potent inducers of oncogenic transformation, and their expression is considered to be the main oncogenic driving force in ∼10% of human acute myeloid leukemia (AML) patients. These oncogenic fusion proteins are responsible for the initiation of a downstream transcriptional program leading to the expression of factors such as MEIS1 and HOXA9, which in turn can replace MLL-fusion proteins in overexpression experiments. To what extent MLL fusion proteins act on their own during tumor initiation, or if they collaborate with other transcriptional regulators, is unclear. Here, we have compared gene expression profiles from human MLL-rearranged AML to normal progenitors and identified the myeloid tumor suppressor C/EBPα as a putative collaborator in MLL-rearranged AML. Interestingly, we find that deletion of Cebpa rendered murine hematopoietic progenitors completely resistant to MLL-ENL–induced leukemic transformation, whereas C/EBPα was dispensable in already established AMLs. Furthermore, we show that Cebpa-deficient granulocytic-monocytic progenitors were equally resistant to transformation and that C/EBPα collaborates with MLL-ENL in the induction of a transcriptional program, which is also apparent in human AML. Thus, our studies demonstrate a key role of C/EBPα in MLL fusion–driven transformation and find that it sharply demarcates tumor initiation and maintenance.
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Affiliation(s)
- Ewa Ohlsson
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences; 2 Biotech Research and Innovation Center (BRIC); 3 Danish Stem Cell Centre (DanStem) Faculty of Health Sciences; 4 The Bioinformatic Centre, Department of Biology, Faculty of Natural Sciences, University of Copenhagen, 2200 Copenhagen, Denmark
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147
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Ge Y, Porse BT. The functional consequences of intron retention: alternative splicing coupled to NMD as a regulator of gene expression. Bioessays 2013; 36:236-43. [PMID: 24352796 DOI: 10.1002/bies.201300156] [Citation(s) in RCA: 133] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The explosion in sequencing technologies has provided us with an instrument to describe mammalian transcriptomes at unprecedented depths. This has revealed that alternative splicing is used extensively not only to generate protein diversity, but also as a means to regulate gene expression post-transcriptionally. Intron retention (IR) is overwhelmingly perceived as an aberrant splicing event with little or no functional consequence. However, recent work has now shown that IR is used to regulate a specific differentiation event within the haematopoietic system by coupling it to nonsense-mediated mRNA decay (NMD). Here, we highlight how IR and, more broadly, alternative splicing coupled to NMD (AS-NMD) can be used to regulate gene expression and how this is deregulated in disease. We suggest that the importance of AS-NMD is not restricted to the haematopoietic system but that it plays a prominent role in other normal and aberrant biological settings.
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Affiliation(s)
- Ying Ge
- The Finsen Laboratory, Rigshospitalet, Faculty of Health Sciences, University of Copenhagen, Denmark; Biotech Research and Innovation Centre (BRIC), University of Copenhagen, Copenhagen, Denmark; Danish Stem Cell Centre (DanStem), Faculty of Health Sciences, University of Copenhagen, Denmark
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148
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Nonsense-mediated mRNA decay: inter-individual variability and human disease. Neurosci Biobehav Rev 2013; 46 Pt 2:175-86. [PMID: 24239855 DOI: 10.1016/j.neubiorev.2013.10.016] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 10/29/2013] [Accepted: 10/30/2013] [Indexed: 01/09/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) is a regulatory pathway that functions to degrade transcripts containing premature termination codons (PTCs) and to maintain normal transcriptome homeostasis. Nonsense and frameshift mutations that generate PTCs cause approximately one-third of all known human genetic diseases and thus NMD has a potentially important role in human disease. In genetic disorders in which the affected genes carry PTC-generating mutations, NMD acts as a double-edge sword. While it can benefit the patient by degrading PTC-containing mRNAs that encode detrimental, dominant-negative truncated proteins, it can also make the disease worse when a PTC-containing mRNA is degraded that encodes a mutant but still functional protein. There is evidence that the magnitude of NMD varies between individuals, which, in turn, has been shown to correlate with both clinical presentations and the patients' responses to drugs that promote read-through of PTCs. In this review, we examine the evidence supporting the existence of inter-individual variability in NMD efficiency and discuss the genetic factors that underlie this variability. We propose that inter-individual variability in NMD efficiency is a common phenomenon in human populations and that an individual's NMD efficiency should be taken into consideration when testing, developing, and making therapeutic decisions for diseases caused by genes harboring PTCs.
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149
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Zhao X, Nogawa A, Matsunaga T, Takegami T, Nakagawa H, Ishigaki Y. Proteasome inhibitors and knockdown of SMG1 cause accumulation of Upf1 and Upf2 in human cells. Int J Oncol 2013; 44:222-8. [PMID: 24173962 DOI: 10.3892/ijo.2013.2149] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2013] [Accepted: 09/23/2013] [Indexed: 11/06/2022] Open
Abstract
The ubiquitin-proteasome system (UPS) is one of the most promising anticancer drug targets of the century. However, the involved molecular mechanisms are still unclear. The nonsense-mediated mRNA decay (NMD) pathway is a highly conserved pathway which degrades nonsense mutation‑containing mRNA selectively and efficiently. In this pathway, the SMG1-Upf1-eRF (SURF) complex binds to Upf2 on the exon junction complex and finally causes degradation of nonsense-containing mRNA. To reveal the relationship between the UPS and NMD pathways, we analyzed the effects of proteasome inhibitors on Upf1 and Upf2. The data showed that treatment with proteasome inhibitors caused the accumulation of the Upf1 and Upf2 proteins in A549 cells. In addition, we found that knockdown of SMG1 also caused the upregulation of Upf1 and Upf2 proteins, which was confirmed by different target sequences of siRNA. SMG1 and UPS appear to participate in different pathways of the degradation of Upf1 and Upf2, since simultaneous treatment with both of them caused additive effects. This study demonstrated the quantitative regulation of Upf1 and Upf2 proteins by UPS and SMG1.
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Affiliation(s)
- Xia Zhao
- Institute of Pathology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, P.R. China
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150
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Yuan J, Muljo SA. Exploring the RNA world in hematopoietic cells through the lens of RNA-binding proteins. Immunol Rev 2013; 253:290-303. [PMID: 23550653 DOI: 10.1111/imr.12048] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The discovery of microRNAs has renewed interest in posttranscriptional modes of regulation, fueling an emerging view of a rich RNA world within our cells that deserves further exploration. Much work has gone into elucidating genetic regulatory networks that orchestrate gene expression programs and direct cell fate decisions in the hematopoietic system. However, the focus has been to elucidate signaling pathways and transcriptional programs. To bring us one step closer to reverse engineering the molecular logic of cellular differentiation, it will be necessary to map posttranscriptional circuits as well and integrate them in the context of existing network models. In this regard, RNA-binding proteins (RBPs) may rival transcription factors as important regulators of cell fates and represent a tractable opportunity to connect the RNA world to the proteome. ChIP-seq has greatly facilitated genome-wide localization of DNA-binding proteins, helping us to understand genomic regulation at a systems level. Similarly, technological advances such as CLIP-seq allow transcriptome-wide mapping of RBP binding sites, aiding us to unravel posttranscriptional networks. Here, we review RBP-mediated posttranscriptional regulation, paying special attention to findings relevant to the immune system. As a prime example, we highlight the RBP Lin28B, which acts as a heterochronic switch between fetal and adult lymphopoiesis.
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Affiliation(s)
- Joan Yuan
- Integrative Immunobiology Unit, Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1892, USA
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