1
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Carrard J, Lejeune F. Nonsense-mediated mRNA decay, a simplified view of a complex mechanism. BMB Rep 2023; 56:625-632. [PMID: 38052423 PMCID: PMC10761751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/31/2023] [Accepted: 11/17/2023] [Indexed: 12/07/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is both a quality control mechanism and a gene regulation pathway. It has been studied for more than 30 years, with an accumulation of many mechanistic details that have often led to debate and hence to different models of NMD activation, particularly in higher eukaryotes. Two models seem to be opposed, since the first requires intervention of the exon junction complex (EJC) to recruit NMD factors downstream of the premature termination codon (PTC), whereas the second involves an EJC-independent mechanism in which NMD factors concentrate in the 3'UTR to initiate NMD in the presence of a PTC. In this review we describe both models, giving recent molecular details and providing experimental arguments supporting one or the other model. In the end it is certainly possible to imagine that these two mechanisms co-exist, rather than viewing them as mutually exclusive. [BMB Reports 2023; 56(12): 625-632].
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Affiliation(s)
- Julie Carrard
- Univ. Lille, CNRS, Inserm, UMR9020-U1277 - CANTHER - Cancer Heterogeneity Plasticity and Resistance to Therapies, Lille F-59000, France
| | - Fabrice Lejeune
- Univ. Lille, CNRS, Inserm, UMR9020-U1277 - CANTHER - Cancer Heterogeneity Plasticity and Resistance to Therapies, Lille F-59000, France
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2
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Tan K, Stupack DG, Wilkinson MF. Nonsense-mediated RNA decay: an emerging modulator of malignancy. Nat Rev Cancer 2022; 22:437-451. [PMID: 35624152 PMCID: PMC11009036 DOI: 10.1038/s41568-022-00481-2] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 04/19/2022] [Indexed: 12/11/2022]
Abstract
Nonsense-mediated RNA decay (NMD) is a highly conserved RNA turnover pathway that selectively degrades RNAs harbouring truncating mutations that prematurely terminate translation, including nonsense, frameshift and some splice-site mutations. Recent studies show that NMD shapes the mutational landscape of tumours by selecting for mutations that tend to downregulate the expression of tumour suppressor genes but not oncogenes. This suggests that NMD can benefit tumours, a notion further supported by the finding that mRNAs encoding immunogenic neoantigen peptides are typically targeted for decay by NMD. Together, this raises the possibility that NMD-inhibitory therapy could be of therapeutic benefit against many tumour types, including those with a high load of neoantigen-generating mutations. Complicating this scenario is the evidence that NMD can also be detrimental for many tumour types, and consequently tumours often have perturbed NMD. NMD may suppress tumour generation and progression by degrading subsets of specific normal mRNAs, including those encoding stress-response proteins, signalling factors and other proteins beneficial for tumours, as well as pro-tumour non-coding RNAs. Together, these findings suggest that NMD-modulatory therapy has the potential to provide widespread therapeutic benefit against diverse tumour types. However, whether NMD should be stimulated or repressed requires careful analysis of the tumour to be treated.
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Affiliation(s)
- Kun Tan
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Diego, La Jolla, CA, USA
| | - Dwayne G Stupack
- Department of Obstetrics, Gynecology, and Reproductive Sciences, University of California, San Diego, La Jolla, CA, USA.
- UCSD Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA.
| | - Miles F Wilkinson
- Department of Obstetrics, Gynecology, and Reproductive Sciences, 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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3
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Udy DB, Bradley RK. Nonsense-mediated mRNA decay uses complementary mechanisms to suppress mRNA and protein accumulation. Life Sci Alliance 2022; 5:e202101217. [PMID: 34880103 PMCID: PMC8711849 DOI: 10.26508/lsa.202101217] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 12/13/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is an essential, highly conserved quality control pathway that detects and degrades mRNAs containing premature termination codons. Although the essentiality of NMD is frequently ascribed to its prevention of truncated protein accumulation, the extent to which NMD actually suppresses proteins encoded by NMD-sensitive transcripts is less well-understood than NMD-mediated suppression of mRNA. Here, we describe a reporter system that permits accurate quantification of both mRNA and protein levels via stable integration of paired reporters encoding NMD-sensitive and NMD-insensitive transcripts into the AAVS1 safe harbor loci in human cells. We use this system to demonstrate that NMD suppresses proteins encoded by NMD-sensitive transcripts by up to eightfold more than the mRNA itself. Our data indicate that NMD limits the accumulation of proteins encoded by NMD substrates by mechanisms beyond mRNA degradation, such that even when NMD-sensitive mRNAs escape destruction, their encoded proteins are still effectively suppressed.
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Affiliation(s)
- Dylan B Udy
- Computational Biology Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Molecular and Cellular Biology Graduate Program, University of Washington, Seattle, WA, USA
| | - Robert K Bradley
- Computational Biology Program, Public Health Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, WA, USA
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4
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Williams DL, Sikora VM, Hammer MA, Amin S, Brinjikji T, Brumley EK, Burrows CJ, Carrillo PM, Cromer K, Edwards SJ, Emri O, Fergle D, Jenkins MJ, Kaushik K, Maydan DD, Woodard W, Clowney EJ. May the Odds Be Ever in Your Favor: Non-deterministic Mechanisms Diversifying Cell Surface Molecule Expression. Front Cell Dev Biol 2022; 9:720798. [PMID: 35087825 PMCID: PMC8787164 DOI: 10.3389/fcell.2021.720798] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 11/24/2021] [Indexed: 12/30/2022] Open
Abstract
How does the information in the genome program the functions of the wide variety of cells in the body? While the development of biological organisms appears to follow an explicit set of genomic instructions to generate the same outcome each time, many biological mechanisms harness molecular noise to produce variable outcomes. Non-deterministic variation is frequently observed in the diversification of cell surface molecules that give cells their functional properties, and is observed across eukaryotic clades, from single-celled protozoans to mammals. This is particularly evident in immune systems, where random recombination produces millions of antibodies from only a few genes; in nervous systems, where stochastic mechanisms vary the sensory receptors and synaptic matching molecules produced by different neurons; and in microbial antigenic variation. These systems employ overlapping molecular strategies including allelic exclusion, gene silencing by constitutive heterochromatin, targeted double-strand breaks, and competition for limiting enhancers. Here, we describe and compare five stochastic molecular mechanisms that produce variety in pathogen coat proteins and in the cell surface receptors of animal immune and neuronal cells, with an emphasis on the utility of non-deterministic variation.
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Affiliation(s)
- Donnell L. Williams
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
| | - Veronica Maria Sikora
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Max A. Hammer
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Sayali Amin
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Taema Brinjikji
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Emily K. Brumley
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Connor J. Burrows
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Paola Michelle Carrillo
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Kirin Cromer
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Summer J. Edwards
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Olivia Emri
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Daniel Fergle
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - M. Jamal Jenkins
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
| | - Krishangi Kaushik
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Daniella D. Maydan
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - Wrenn Woodard
- MCDB 464 – Cellular Diversity in the Immune and Nervous Systems, University of Michigan, Ann Arbor, MI, United States
| | - E. Josephine Clowney
- Department of Molecular, Cellular and Developmental Biology, The University of Michigan, Ann Arbor, MI, United States
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5
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Eberle AB, Mühlemann O. Tethered Function Assays to Elucidate the Role of RNA-Binding Proteins. Methods Mol Biol 2022; 2537:285-306. [PMID: 35895271 DOI: 10.1007/978-1-0716-2521-7_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The fate of each RNA molecule is strongly determined by RNA-binding proteins (RBPs) which accompany transcripts from its synthesis to its degradation. To elucidate the effect of a specific RBP on bound RNA, it can be artificially recruited to a specific site on a reporter mRNA that can be followed by a variety of methods. In this so-called tethering assay, the protein of interest (POI) is fused to the coat protein of the MS2 bacteriophage and expressed in your favorite cells together with a reporter gene containing MS2 binding sites. The MS2 binding sites are recognized by the MS2 coat protein (MS2CP) with high affinity and specificity and by doing so, the POI is tethered to the reporter RNA. Here, we describe how with the help of this assay the human cytoplasmic poly(A) binding protein is recruited to a mini-μ RNA reporter, thereby influencing the stability of the reporter transcript.
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Affiliation(s)
- Andrea B Eberle
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland
| | - Oliver Mühlemann
- Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland.
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6
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Mikocziova I, Peres A, Gidoni M, Greiff V, Yaari G, Sollid LM. Germline polymorphisms and alternative splicing of human immunoglobulin light chain genes. iScience 2021; 24:103192. [PMID: 34693229 PMCID: PMC8517844 DOI: 10.1016/j.isci.2021.103192] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 07/17/2021] [Accepted: 09/27/2021] [Indexed: 10/25/2022] Open
Abstract
Inference of germline polymorphisms in immunoglobulin genes from B cell receptor repertoires is complicated by somatic hypermutations, sequencing/PCR errors, and by varying length of reference alleles. The light chain inference is particularly challenging owing to large gene duplications and absence of D genes. We analyzed the light chain cDNA sequences from naïve B cell receptor repertoires from 100 individuals. We optimized light chain allele inference by tweaking parameters of the TIgGER functions, extending the germline reference sequences, and establishing mismatch frequency patterns at polymorphic positions to filter out false-positive candidates. We identified 48 previously unreported variants of light chain variable genes. We selected 14 variants for validation and successfully validated 11 by Sanger sequencing. Clustering of light chain 5'UTR, L-PART1, and L-PART2 revealed partial intron retention in 11 kappa and 9 lambda V alleles. Our results provide insight into germline variation in human light chain immunoglobulin loci.
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Affiliation(s)
- Ivana Mikocziova
- K.G. Jebsen Centre for Coeliac Disease Research, Institute of Clinical Medicine, University of Oslo, 0372 Oslo, Norway
- Department of Immunology, Oslo University Hospital, 0372 Oslo, Norway
| | - Ayelet Peres
- Faculty of Engineering, Bar Ilan University, Ramat Gan 5290002, Israel
- Bar Ilan Institute of Nanotechnologies and Advanced Materials, Bar Ilan University, Ramat Gan 5290002, Israel
| | - Moriah Gidoni
- Faculty of Engineering, Bar Ilan University, Ramat Gan 5290002, Israel
| | - Victor Greiff
- Department of Immunology, Oslo University Hospital, 0372 Oslo, Norway
| | - Gur Yaari
- Faculty of Engineering, Bar Ilan University, Ramat Gan 5290002, Israel
- Bar Ilan Institute of Nanotechnologies and Advanced Materials, Bar Ilan University, Ramat Gan 5290002, Israel
| | - Ludvig M. Sollid
- K.G. Jebsen Centre for Coeliac Disease Research, Institute of Clinical Medicine, University of Oslo, 0372 Oslo, Norway
- Department of Immunology, Oslo University Hospital, 0372 Oslo, Norway
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7
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García-Moreno JF, Romão L. Perspective in Alternative Splicing Coupled to Nonsense-Mediated mRNA Decay. Int J Mol Sci 2020; 21:ijms21249424. [PMID: 33321981 PMCID: PMC7764535 DOI: 10.3390/ijms21249424] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 12/03/2020] [Accepted: 12/07/2020] [Indexed: 12/19/2022] Open
Abstract
Alternative splicing (AS) of precursor mRNA (pre-mRNA) is a cellular post-transcriptional process that generates protein isoform diversity. Nonsense-mediated RNA decay (NMD) is an mRNA surveillance pathway that recognizes and selectively degrades transcripts containing premature translation-termination codons (PTCs), thereby preventing the production of truncated proteins. Nevertheless, NMD also fine-tunes the gene expression of physiological mRNAs encoding full-length proteins. Interestingly, around one third of all AS events results in PTC-containing transcripts that undergo NMD. Numerous studies have reported a coordinated action between AS and NMD, in order to regulate the expression of several genes, especially those coding for RNA-binding proteins (RBPs). This coupling of AS to NMD (AS-NMD) is considered a gene expression tool that controls the ratio of productive to unproductive mRNA isoforms, ultimately degrading PTC-containing non-functional mRNAs. In this review, we focus on the mechanisms underlying AS-NMD, and how this regulatory process is able to control the homeostatic expression of numerous RBPs, including splicing factors, through auto- and cross-regulatory feedback loops. Furthermore, we discuss the importance of AS-NMD in the regulation of biological processes, such as cell differentiation. Finally, we analyze interesting recent data on the relevance of AS-NMD to human health, covering its potential roles in cancer and other disorders.
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Affiliation(s)
- Juan F. García-Moreno
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal;
- Faculty of Science, BioISI—Biosystems and Integrative Sciences Institute, University of Lisboa, 1749-016 Lisboa, Portugal
| | - Luísa Romão
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal;
- Faculty of Science, BioISI—Biosystems and Integrative Sciences Institute, University of Lisboa, 1749-016 Lisboa, Portugal
- Correspondence: ; Tel.: +351-217-508-155
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8
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Abstract
Immunoglobulin heavy chain checkpoint (IgHCC) is a critical step during early B cell development. The role of immunoglobulin heavy chain (IgHC) at this step is well established. However, with the expanding knowledge of RNA in regulating central biological processes, there could be a noncoding contribution of IgHC mRNA (IgHR) in controlling the IgHCC. Here, we generated a novel mouse model that enabled us to determine a potential role of IgHR in the IgHCC, independent of IgHC signaling. Our data indicate that IgHR has no role in IgHCC and the latter is predominantly controlled by IgHC, as proposed earlier. Furthermore, this study highlights the sensitivity of progenitor B cells to low amounts of IgHC. Development of progenitor B cells (ProB cells) into precursor B cells (PreB cells) is dictated by immunoglobulin heavy chain checkpoint (IgHCC), where the IgHC encoded by a productively rearranged Igh allele assembles into a PreB cell receptor complex (PreBCR) to generate signals to initiate this transition and suppressing antigen receptor gene recombination, ensuring that only one productive Igh allele is expressed, a phenomenon known as Igh allelic exclusion. In contrast to a productively rearranged Igh allele, the Igh messenger RNA (mRNA) (IgHR) from a nonproductively rearranged Igh allele is degraded by nonsense-mediated decay (NMD). This fact prohibited firm conclusions regarding the contribution of stable IgHR to the molecular and developmental changes associated with the IgHCC. This point was addressed by generating the IghTer5H∆TM mouse model from IghTer5H mice having a premature termination codon at position +5 in leader exon of IghTer5H allele. This prohibited NMD, and the lack of a transmembrane region (∆TM) prevented the formation of any signaling-competent PreBCR complexes that may arise as a result of read-through translation across premature Ter5 stop codon. A highly sensitive sandwich Western blot revealed read-through translation of IghTer5H message, indicating that previous conclusions regarding a role of IgHR in establishing allelic exclusion requires further exploration. As determined by RNA sequencing (RNA-Seq), this low amount of IgHC sufficed to initiate PreB cell markers normally associated with PreBCR signaling. In contrast, the IghTer5H∆TM knock-in allele, which generated stable IgHR but no detectable IgHC, failed to induce PreB development. Our data indicate that the IgHCC is controlled at the level of IgHC and not IgHR expression.
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9
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Annibaldis G, Domanski M, Dreos R, Contu L, Carl S, Kläy N, Mühlemann O. Readthrough of stop codons under limiting ABCE1 concentration involves frameshifting and inhibits nonsense-mediated mRNA decay. Nucleic Acids Res 2020; 48:10259-10279. [PMID: 32941650 PMCID: PMC7544199 DOI: 10.1093/nar/gkaa758] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 08/28/2020] [Accepted: 09/09/2020] [Indexed: 12/11/2022] Open
Abstract
To gain insight into the mechanistic link between translation termination and nonsense-mediated mRNA decay (NMD), we depleted the ribosome recycling factor ABCE1 in human cells, resulting in an upregulation of NMD-sensitive mRNAs. Suppression of NMD on these mRNAs occurs prior to their SMG6-mediated endonucleolytic cleavage. ABCE1 depletion caused ribosome stalling at termination codons (TCs) and increased ribosome occupancy in 3′ UTRs, implying enhanced TC readthrough. ABCE1 knockdown indeed increased the rate of readthrough and continuation of translation in different reading frames, providing a possible explanation for the observed NMD inhibition, since enhanced readthrough displaces NMD activating proteins from the 3′ UTR. Our results indicate that stalling at TCs triggers ribosome collisions and activates ribosome quality control. Collectively, we show that improper translation termination can lead to readthrough of the TC, presumably due to ribosome collisions pushing the stalled ribosomes into the 3′ UTR, where it can resume translation in-frame as well as out-of-frame.
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Affiliation(s)
- Giuditta Annibaldis
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Mittelstrasse 43, CH-3012 Bern, Switzerland
| | - Michal Domanski
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - René Dreos
- Center for Integrative Genomics, University of Lausanne, CH-1015 Lausanne, Switzerland
| | - Lara Contu
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, Mittelstrasse 43, CH-3012 Bern, Switzerland
| | - Sarah Carl
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland
| | - Nina Kläy
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
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10
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Mechanisms and Regulation of Nonsense-Mediated mRNA Decay and Nonsense-Associated Altered Splicing in Lymphocytes. Int J Mol Sci 2020; 21:ijms21041335. [PMID: 32079193 PMCID: PMC7072976 DOI: 10.3390/ijms21041335] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 02/12/2020] [Accepted: 02/13/2020] [Indexed: 12/11/2022] Open
Abstract
The presence of premature termination codons (PTCs) in transcripts is dangerous for the cell as they encode potentially deleterious truncated proteins that can act with dominant-negative or gain-of-function effects. To avoid the synthesis of these shortened polypeptides, several RNA surveillance systems can be activated to decrease the level of PTC-containing mRNAs. Nonsense-mediated mRNA decay (NMD) ensures an accelerated degradation of mRNAs harboring PTCs by using several key NMD factors such as up-frameshift (UPF) proteins. Another pathway called nonsense-associated altered splicing (NAS) upregulates transcripts that have skipped disturbing PTCs by alternative splicing. Thus, these RNA quality control processes eliminate abnormal PTC-containing mRNAs from the cells by using positive and negative responses. In this review, we describe the general mechanisms of NMD and NAS and their respective involvement in the decay of aberrant immunoglobulin and TCR transcripts in lymphocytes.
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11
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Lambert JM, Srour N, Delpy L. The Yin and Yang of RNA surveillance in B lymphocytes and antibody-secreting plasma cells. BMB Rep 2019. [PMID: 31619318 PMCID: PMC6941761 DOI: 10.5483/bmbrep.2019.52.12.232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The random V(D)J recombination process ensures the diversity of the primary immunoglobulin (Ig) repertoire. In two thirds of cases, imprecise recombination between variable (V), diversity (D), and joining (J) segments induces a frameshift in the open reading frame that leads to the appearance of premature termination codons (PTCs). Thus, many B lineage cells harbour biallelic V(D)J-rearrangements of Ig heavy or light chain genes, with a productively-recombined allele encoding the functional Ig chain and a nonproductive allele potentially encoding truncated Ig polypeptides. Since the pattern of Ig gene expression is mostly biallelic, transcription initiated from nonproductive Ig alleles generates considerable amounts of primary transcripts with out-of-frame V(D)J junctions. How RNA surveillance pathways cooperate to control the noise from nonproductive Ig genes will be discussed in this review, focusing on the benefits of nonsense-mediated mRNA decay (NMD) activation during B-cell development and detrimental effects of nonsense-associated altered splicing (NAS) in terminally differentiated plasma cells.
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Affiliation(s)
- Jean-Marie Lambert
- UMR CNRS 7276 - INSERM 1268 - Université de Limoges, Centre de Biologie et de Recherche en Santé, 2 rue du Dr Marcland, Limoges F-87025, France
| | - Nivine Srour
- UMR CNRS 7276 - INSERM 1268 - Université de Limoges, Centre de Biologie et de Recherche en Santé, 2 rue du Dr Marcland, Limoges F-87025, France
| | - Laurent Delpy
- UMR CNRS 7276 - INSERM 1268 - Université de Limoges, Centre de Biologie et de Recherche en Santé, 2 rue du Dr Marcland, Limoges F-87025, France
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12
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Weinstein-Marom H, Hendel L, Laron EA, Sharabi-Nov A, Margalit A, Gross G. MHC-I presentation of peptides derived from intact protein products of the pioneer round of translation. FASEB J 2019; 33:11458-11468. [PMID: 31343935 DOI: 10.1096/fj.201802717rrr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Among the earliest protein products of most cellular genes are those synthesized during the pioneer round of translation (PRT), a key step in nonsense-mediated mRNA decay (NMD) that allows scanning of new transcripts for the presence of a premature termination codon (PTC). It has been demonstrated that at least some PRT degradation products can be targeted to major histocompatibility (MHC)-I presentation. To gain new insight into this putative PRT-to-MHC-I route, we have assembled 2 pairs of reporter genes so that the 2 genes in each pair encode an identical fusion protein between a model antigenic peptide and enhanced green fluorescent protein (EGFP), one of which harbors a PTC. We expressed these genes in different mouse and human cell lines and confirmed enhanced NMD activity for the PTC(+) gene in each pair by monitoring the effect of cycloheximide on the level of the respective mRNA. We then exploited several strategies for establishing the ratio between level of peptide presentation and total amount of protein product. We consistently observed significantly higher ratios for the PTC(+) mRNAs compared with the PTC(-) ones, pointing to correlation between the turnover of otherwise identical proteins and the fate of their template mRNA. Using confocal microscopy, we showed a clear link between NMD, the presence of misfolded EGFP polypeptides, and enhanced MHC-I peptide presentation. Altogether, these findings imply that identical full-length gene products differing only in 3' noncoding sequences can be differentially degraded and targeted to the MHC-I presentation pathway, suggesting a more general role for the PRT in establishing the MHC-I peptidome.-Weinstein-Marom, H., Hendel, L., Laron, E. A., Sharabi-Nov, A., Margalit, A., Gross, G. MHC-I presentation of peptides derived from intact protein products of the pioneer round of translation.
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Affiliation(s)
- Hadas Weinstein-Marom
- Laboratory of Immunology, MIGAL-Galilee Research Institute, Kiryat Shmona, Israel.,Tel-Hai College, Upper Galilee, Israel.,Inter-Faculty Biotechnology Program, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Liron Hendel
- Laboratory of Immunology, MIGAL-Galilee Research Institute, Kiryat Shmona, Israel.,Tel-Hai College, Upper Galilee, Israel
| | - Efrat Avigad Laron
- Laboratory of Immunology, MIGAL-Galilee Research Institute, Kiryat Shmona, Israel.,Tel-Hai College, Upper Galilee, Israel
| | | | - Alon Margalit
- Laboratory of Immunology, MIGAL-Galilee Research Institute, Kiryat Shmona, Israel.,Tel-Hai College, Upper Galilee, Israel
| | - Gideon Gross
- Laboratory of Immunology, MIGAL-Galilee Research Institute, Kiryat Shmona, Israel.,Tel-Hai College, Upper Galilee, Israel
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13
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Mizuguchi T, Nakashima M, Kato M, Okamoto N, Kurahashi H, Ekhilevitch N, Shiina M, Nishimura G, Shibata T, Matsuo M, Ikeda T, Ogata K, Tsuchida N, Mitsuhashi S, Miyatake S, Takata A, Miyake N, Hata K, Kaname T, Matsubara Y, Saitsu H, Matsumoto N. Loss-of-function and gain-of-function mutations in PPP3CA cause two distinct disorders. Hum Mol Genet 2019; 27:1421-1433. [PMID: 29432562 DOI: 10.1093/hmg/ddy052] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 02/05/2018] [Indexed: 02/07/2023] Open
Abstract
Calcineurin is a calcium (Ca2+)/calmodulin-regulated protein phosphatase that mediates Ca2+-dependent signal transduction. Here, we report six heterozygous mutations in a gene encoding the alpha isoform of the calcineurin catalytic subunit (PPP3CA). Notably, mutations were observed in different functional domains: in addition to three catalytic domain mutations, two missense mutations were found in the auto-inhibitory (AI) domain. One additional frameshift insertion that caused premature termination was also identified. Detailed clinical evaluation of the six individuals revealed clinically unexpected consequences of the PPP3CA mutations. First, the catalytic domain mutations and frameshift mutation were consistently found in patients with nonsyndromic early onset epileptic encephalopathy. In contrast, the AI domain mutations were associated with multiple congenital abnormalities including craniofacial dysmorphism, arthrogryposis and short stature. In addition, one individual showed severe skeletal developmental defects, namely, severe craniosynostosis and gracile bones (severe bone slenderness and perinatal fractures). Using a yeast model system, we showed that the catalytic and AI domain mutations visibly result in decreased and increased calcineurin signaling, respectively. These findings indicate that different functional effects of PPP3CA mutations are associated with two distinct disorders and suggest that functional approaches using a simple cellular system provide a tool for resolving complex genotype-phenotype correlations.
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Affiliation(s)
- Takeshi Mizuguchi
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Mitsuko Nakashima
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Mitsuhiro Kato
- Department of Pediatrics, Showa University School of Medicine, Tokyo 142-8666, Japan
| | - Nobuhiko Okamoto
- Department of Medical Genetics, Osaka Women's and Children's Hospital, Osaka 594-1101, Japan
| | - Hirokazu Kurahashi
- Department of Pediatrics, Aichi Medical University, Aichi 480-1195, Japan
| | - Nina Ekhilevitch
- The Genetics Institute, Rambam Health Care Campus, Haifa 3109601, Israel
| | - Masaaki Shiina
- Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Gen Nishimura
- Center for Intractable Diseases, Saitama Medical University Hospital, Saitama 350-0495, Japan
| | - Takashi Shibata
- Department of Child Neurology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700-8558, Japan
| | - Muneaki Matsuo
- Department of Pediatrics, Saga University Faculty of Medicine, Saga 849-8501, Japan
| | - Tae Ikeda
- Department of Pediatric Neurology, Osaka Women's and Children's Hospital, Osaka 594-1101, Japan
| | - Kazuhiro Ogata
- Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Naomi Tsuchida
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Satomi Mitsuhashi
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Satoko Miyatake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan.,Clinical Genetics Department, Yokohama City University Hospital, Yokohama 236-0004, Japan
| | - Atsushi Takata
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Kenichiro Hata
- Department of Maternal-Fetal Biology, National Research Institute for Child Health and Development, Tokyo 157-8535, Japan
| | - Tadashi Kaname
- Department of Genome Medicine, National Center for Child Health and Development, Tokyo 157-8535, Japan
| | - Yoichi Matsubara
- Department of Medical Genetics, Tohoku University School of Medicine, Sendai 980-8574, Japan.,National Research Institute for Child Health and Development, Tokyo 157-8535, Japan
| | - Hirotomo Saitsu
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
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14
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Nicholson P, Gkratsou A, Josi C, Colombo M, Mühlemann O. Dissecting the functions of SMG5, SMG7, and PNRC2 in nonsense-mediated mRNA decay of human cells. RNA (NEW YORK, N.Y.) 2018; 24:557-573. [PMID: 29348139 PMCID: PMC5855955 DOI: 10.1261/rna.063719.117] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 01/08/2018] [Indexed: 05/04/2023]
Abstract
The term "nonsense-mediated mRNA decay" (NMD) originally described the degradation of mRNAs with premature translation-termination codons (PTCs), but its meaning has recently been extended to be a translation-dependent post-transcriptional regulator of gene expression affecting 3%-10% of all mRNAs. The degradation of NMD target mRNAs involves both exonucleolytic and endonucleolytic pathways in mammalian cells. While the latter is mediated by the endonuclease SMG6, the former pathway has been reported to require a complex of SMG5-SMG7 or SMG5-PNRC2 binding to UPF1. However, the existence, dominance, and mechanistic details of these exonucleolytic pathways are divisive. Therefore, we have investigated the possible exonucleolytic modes of mRNA decay in NMD by examining the roles of UPF1, SMG5, SMG7, and PNRC2 using a combination of functional assays and interaction mapping. Confirming previous work, we detected an interaction between SMG5 and SMG7 and also a functional need for this complex in NMD. In contrast, we found no evidence for the existence of a physical or functional interaction between SMG5 and PNRC2. Instead, we show that UPF1 interacts with PNRC2 and that it triggers 5'-3' exonucleolytic decay of reporter transcripts in tethering assays. PNRC2 interacts mainly with decapping factors and its knockdown does not affect the RNA levels of NMD reporters. We conclude that PNRC2 is probably an important mRNA decapping factor but that it does not appear to be required for NMD.
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Affiliation(s)
- Pamela Nicholson
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland
| | - Asimina Gkratsou
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern 3012, Switzerland
| | - Christoph Josi
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern 3012, Switzerland
| | - Martino Colombo
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern 3012, Switzerland
| | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland
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15
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HTLV-1 Tax plugs and freezes UPF1 helicase leading to nonsense-mediated mRNA decay inhibition. Nat Commun 2018; 9:431. [PMID: 29382845 PMCID: PMC5789848 DOI: 10.1038/s41467-017-02793-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2017] [Accepted: 12/28/2017] [Indexed: 12/19/2022] Open
Abstract
Up-Frameshift Suppressor 1 Homolog (UPF1) is a key factor for nonsense-mediated mRNA decay (NMD), a cellular process that can actively degrade mRNAs. Here, we study NMD inhibition during infection by human T-cell lymphotropic virus type I (HTLV-1) and characterise the influence of the retroviral Tax factor on UPF1 activity. Tax interacts with the central helicase core domain of UPF1 and might plug the RNA channel of UPF1, reducing its affinity for nucleic acids. Furthermore, using a single-molecule approach, we show that the sequential interaction of Tax with a RNA-bound UPF1 freezes UPF1: this latter is less sensitive to the presence of ATP and shows translocation defects, highlighting the importance of this feature for NMD. These mechanistic insights reveal how HTLV-1 hijacks the central component of NMD to ensure expression of its own genome. UPF1 is a central protein in nonsense-mediated mRNA decay (NMD), but contribution of its RNA processivity to NMD is unclear. Here, the authors show how the retroviral Tax protein interacts with and inhibits UPF1, and demonstrate that UPF1’s translocase activity contributes to NMD.
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16
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Reber S, Mechtersheimer J, Nasif S, Benitez JA, Colombo M, Domanski M, Jutzi D, Hedlund E, Ruepp MD. CRISPR-Trap: a clean approach for the generation of gene knockouts and gene replacements in human cells. Mol Biol Cell 2017; 29:75-83. [PMID: 29167381 PMCID: PMC5909934 DOI: 10.1091/mbc.e17-05-0288] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Revised: 10/27/2017] [Accepted: 11/16/2017] [Indexed: 01/08/2023] Open
Abstract
CRISPR/Cas9-based genome editing offers the possibility to knock out almost any gene of interest in an affordable and simple manner. The most common strategy is the introduction of a frameshift into the open reading frame (ORF) of the target gene which truncates the coding sequence (CDS) and targets the corresponding transcript for degradation by nonsense-mediated mRNA decay (NMD). However, we show that transcripts containing premature termination codons (PTCs) are not always degraded efficiently and can generate C-terminally truncated proteins which might have residual or dominant negative functions. Therefore, we recommend an alternative approach for knocking out genes, which combines CRISPR/Cas9 with gene traps (CRISPR-Trap) and is applicable to ∼50% of all spliced human protein-coding genes and a large subset of lncRNAs. CRISPR-Trap completely prevents the expression of the ORF and avoids expression of C-terminal truncated proteins. We demonstrate the feasibility of CRISPR-Trap by utilizing it to knock out several genes in different human cell lines. Finally, we also show that this approach can be used to efficiently generate gene replacements allowing for modulation of protein levels for otherwise lethal knockouts (KOs). Thus, CRISPR-Trap offers several advantages over conventional KO approaches and allows for generation of clean CRISPR/Cas9-based KOs.
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Affiliation(s)
- Stefan Reber
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - Jonas Mechtersheimer
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - Sofia Nasif
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland
| | | | - Martino Colombo
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - Michal Domanski
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland
| | - Daniel Jutzi
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland.,Graduate School for Cellular and Biomedical Sciences, University of Bern, CH-3012 Bern, Switzerland
| | - Eva Hedlund
- Department of Neuroscience, Karolinska Institutet,171 77 Stockholm, Sweden
| | - Marc-David Ruepp
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland
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17
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The rules and impact of nonsense-mediated mRNA decay in human cancers. Nat Genet 2016; 48:1112-8. [PMID: 27618451 PMCID: PMC5045715 DOI: 10.1038/ng.3664] [Citation(s) in RCA: 284] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Accepted: 08/11/2016] [Indexed: 12/19/2022]
Abstract
Premature termination codons (PTCs) cause a large proportion of inherited human genetic diseases. PTC-containing transcripts can be degraded by an mRNA surveillance pathway termed nonsense-mediated mRNA decay (NMD). However, the efficiency of NMD varies; it is inefficient when a PTC is located downstream of the last exon junction complex (EJC). We used matched exome and transcriptome data from 9,769 human tumors to systematically elucidate the rules of NMD targeting in human cells. An integrated model incorporating multiple rules beyond the canonical EJC model explains approximately three-quarters of the non-random variance in NMD efficiency across thousands of PTCs. We also show that dosage compensation may mask the effects of NMD. Applying the NMD model identifies signatures of both positive and negative selection on NMD-triggering mutations in human tumors and provides a classification of tumor suppressor genes.
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18
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Nicholson P, Josi C, Kurosawa H, Yamashita A, Mühlemann O. A novel phosphorylation-independent interaction between SMG6 and UPF1 is essential for human NMD. Nucleic Acids Res 2014; 42:9217-35. [PMID: 25053839 PMCID: PMC4132754 DOI: 10.1093/nar/gku645] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Eukaryotic mRNAs with premature translation-termination codons (PTCs) are recognized and eliminated by nonsense-mediated mRNA decay (NMD). NMD substrates can be degraded by different routes that all require phosphorylated UPF1 (P-UPF1) as a starting point. The endonuclease SMG6, which cleaves mRNA near the PTC, is one of the three known NMD factors thought to be recruited to nonsense mRNAs via an interaction with P-UPF1, leading to eventual mRNA degradation. By artificial tethering of SMG6 and mutants thereof to a reporter mRNA combined with knockdowns of various NMD factors, we demonstrate that besides its endonucleolytic activity, SMG6 also requires UPF1 and SMG1 to reduce reporter mRNA levels. Using in vivo and in vitro approaches, we further document that SMG6 and the unique stalk region of the UPF1 helicase domain, along with a contribution from the SQ domain, form a novel interaction and we also show that this region of the UPF1 helicase domain is critical for SMG6 function and NMD. Our results show that this interaction is required for NMD and for the capability of tethered SMG6 to degrade its bound RNA, suggesting that it contributes to the intricate regulation of UPF1 and SMG6 enzymatic activities.
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Affiliation(s)
- Pamela Nicholson
- Department of Chemistry and Biochemistry, University of Berne, Berne, CH-3012, Switzerland
| | - Christoph Josi
- Department of Chemistry and Biochemistry, University of Berne, Berne, CH-3012, Switzerland
| | - Hitomi Kurosawa
- Department of Microbiology, Yokohama City University, School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan
| | - Akio Yamashita
- Department of Microbiology, Yokohama City University, School of Medicine, 3-9, Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan
| | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Berne, Berne, CH-3012, Switzerland
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19
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Flury V, Restuccia U, Bachi A, Mühlemann O. Characterization of phosphorylation- and RNA-dependent UPF1 interactors by quantitative proteomics. J Proteome Res 2014; 13:3038-53. [PMID: 24762188 DOI: 10.1021/pr5002143] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Human up-frameshift 1 (UPF1) is an ATP-dependent RNA helicase and phosphoprotein implicated in several biological processes but is best known for its key function in nonsense-mediated mRNA decay (NMD). Here we employed a combination of stable isotope labeling of amino acids in cell culture experiments to determine by quantitative proteomics UPF1 interactors. We used this approach to distinguish between RNA-mediated and protein-mediated UPF1 interactors and to determine proteins that preferentially bind the hypo- or the hyper-phosphorylated form of UPF1. Confirming and expanding previous studies, we identified the eukaryotic initiation factor 3 (eIF3) as a prominent protein-mediated interactor of UPF1. However, unlike previously reported, eIF3 binds to UPF1 independently of UPF1's phosphorylation state. Furthermore, our data revealed many nucleus-associated RNA-binding proteins that preferentially associate with hyper-phosphorylated UPF1 in an RNase-sensitive manner, suggesting that UPF1 gets recruited to mRNA and becomes phosphorylated before being exported to the cytoplasm as part of the mRNP.
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Affiliation(s)
- Valentin Flury
- Department of Chemistry and Biochemistry, University of Bern , Freiestr. 3, Bern 3012, Switzerland
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20
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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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21
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Translation-dependent displacement of UPF1 from coding sequences causes its enrichment in 3' UTRs. Nat Struct Mol Biol 2013; 20:936-43. [PMID: 23832275 DOI: 10.1038/nsmb.2635] [Citation(s) in RCA: 128] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 06/20/2013] [Indexed: 12/28/2022]
Abstract
Recruitment of the UPF1 nonsense-mediated mRNA decay (NMD) factor to target mRNAs was initially proposed to occur through interaction with release factors at terminating ribosomes. However, recently emerging evidence points toward translation-independent interaction with the 3' untranslated region (UTR) of mRNAs. We mapped transcriptome-wide UPF1-binding sites by individual-nucleotide-resolution UV cross-linking and immunoprecipitation in human cells and found that UPF1 preferentially associated with 3' UTRs in translationally active cells but underwent significant redistribution toward coding regions (CDS) upon translation inhibition, thus indicating that UPF1 binds RNA before translation and gets displaced from the CDS by translating ribosomes. Corroborated by RNA immunoprecipitation and by UPF1 cross-linking to long noncoding RNAs, our evidence for translation-independent UPF1-RNA interaction suggests that the triggering of NMD occurs after UPF1 binding to mRNA, presumably through activation of RNA-bound UPF1 by aberrant translation termination.
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22
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Fang Y, Bateman JF, Mercer JF, Lamandé SR. Nonsense-mediated mRNA decay of collagen -emerging complexity in RNA surveillance mechanisms. J Cell Sci 2013; 126:2551-60. [PMID: 23729740 DOI: 10.1242/jcs.120220] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is an evolutionarily conserved mRNA surveillance system that degrades mRNA transcripts that harbour a premature translation-termination codon (PTC), thus reducing the synthesis of truncated proteins that would otherwise have deleterious effects. Although extensive research has identified a conserved repertoire of NMD factors, these studies have been performed with a restricted set of genes and gene constructs with relatively few exons. As a consequence, NMD mechanisms are poorly understood for genes with large 3' terminal exons, and the applicability of the current models to large multi-exon genes is not clear. In this Commentary, we present an overview of the current understanding of NMD and discuss how analysis of nonsense mutations in the collagen gene family has provided new mechanistic insights into this process. Although NMD of the collagen genes with numerous small exons is consistent with the widely accepted exon-junction complex (EJC)-dependent model, the degradation of Col10a1 transcripts with nonsense mutations cannot be explained by any of the current NMD models. Col10a1 NMD might represent a fail-safe mechanism for genes that have large 3' terminal exons. Defining the mechanistic complexity of NMD is important to allow us to understand the pathophysiology of the numerous genetic disorders caused by PTC mutations.
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Affiliation(s)
- Yiwen Fang
- Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville 3052, Australia
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23
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Moreno AB, Martínez de Alba AE, Bardou F, Crespi MD, Vaucheret H, Maizel A, Mallory AC. Cytoplasmic and nuclear quality control and turnover of single-stranded RNA modulate post-transcriptional gene silencing in plants. Nucleic Acids Res 2013; 41:4699-708. [PMID: 23482394 PMCID: PMC3632135 DOI: 10.1093/nar/gkt152] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Eukaryotic RNA quality control (RQC) uses both endonucleolytic and exonucleolytic degradation to eliminate dysfunctional RNAs. In addition, endogenous and exogenous RNAs are degraded through post-transcriptional gene silencing (PTGS), which is triggered by the production of double-stranded (ds)RNAs and proceeds through short-interfering (si)RNA-directed ARGONAUTE-mediated endonucleolytic cleavage. Compromising cytoplasmic or nuclear 5'-3' exoribonuclease function enhances sense-transgene (S)-PTGS in Arabidopsis, suggesting that these pathways compete for similar RNA substrates. Here, we show that impairing nonsense-mediated decay, deadenylation or exosome activity enhanced S-PTGS, which requires host RNA-dependent RNA polymerase 6 (RDR6/SGS2/SDE1) and SUPPRESSOR OF GENE SILENCING 3 (SGS3) for the transformation of single-stranded RNA into dsRNA to trigger PTGS. However, these RQC mutations had no effect on inverted-repeat-PTGS, which directly produces hairpin dsRNA through transcription. Moreover, we show that these RQC factors are nuclear and cytoplasmic and are found in two RNA degradation foci in the cytoplasm: siRNA-bodies and processing-bodies. We propose a model of single-stranded RNA tug-of-war between RQC and S-PTGS that ensures the correct partitioning of RNA substrates among these RNA degradation pathways.
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Affiliation(s)
- Ana Beatriz Moreno
- Institut des Sciences du Végétal, CNRS UPR 2355, SPS Saclay Plant Sciences, 91198 Gif-sur-Yvette, France
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24
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Nicholson P, Joncourt R, Mühlemann O. Analysis of nonsense-mediated mRNA decay in mammalian cells. CURRENT PROTOCOLS IN CELL BIOLOGY 2012; Chapter 27:Unit27.4. [PMID: 22733442 DOI: 10.1002/0471143030.cb2704s55] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The nonsense-mediated mRNA decay (NMD) pathway acts to selectively identify and degrade mRNAs that contain a premature translation termination codon (PTC), and hence reduce the accumulation of potentially toxic truncated proteins. NMD is one of the best studied mRNA quality-control mechanisms in eukaryotes, and it has become clear during recent years that many physiological mRNAs are also NMD substrates, signifying a role for NMD beyond mRNA quality control as a translation-dependent post-transcriptional regulator of gene expression. Despite a great deal of scientific research for over twenty years, the process of NMD is far from being fully understood with regard to its physiological relevance to the cell, the molecular mechanisms that underpin this pathway, all of the factors that are involved, and the exact cellular locations of NMD. This unit details some of the fundamental RNA based approaches taken to examine aspects of NMD, such as creating PTC+ reporter genes, knocking down key NMD factors via RNAi, elucidating the important functions of NMD factors by complementation assays or Tethered Function Assays, and measuring RNA levels by reverse-transcription quantitative PCR.
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25
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CLIP-seq of eIF4AIII reveals transcriptome-wide mapping of the human exon junction complex. Nat Struct Mol Biol 2012; 19:1124-31. [PMID: 23085716 DOI: 10.1038/nsmb.2420] [Citation(s) in RCA: 149] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2012] [Accepted: 09/21/2012] [Indexed: 12/14/2022]
Abstract
The exon junction complex (EJC) is a central effector of the fate of mRNAs, linking nuclear processing to mRNA transport, translation and surveillance. However, little is known about its transcriptome-wide targets. We used cross-linking and immunoprecipitation methods coupled to high-throughput sequencing (CLIP-seq) in human cells to identify the binding sites of the DEAD-box helicase eIF4AIII, an EJC core component. CLIP reads form peaks that are located mainly in spliced mRNAs. Most expressed exons harbor peaks either in the canonical EJC region, located ~24 nucleotides upstream of exonic junctions, or in other noncanonical regions. Notably, both of these types of peaks are preferentially associated with unstructured and purine-rich sequences containing the motif GAAGA, which is a potential binding site for EJC-associated factors. Therefore, EJC positions vary spatially and quantitatively between exons. This transcriptome-wide mapping of human eIF4AIII reveals unanticipated aspects of the EJC and broadens its potential impact on post-transcriptional regulation.
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26
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Christie M, Brosnan CA, Rothnagel JA, Carroll BJ. RNA decay and RNA silencing in plants: competition or collaboration? FRONTIERS IN PLANT SCIENCE 2011; 2:99. [PMID: 22639621 PMCID: PMC3355627 DOI: 10.3389/fpls.2011.00099] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 11/30/2011] [Indexed: 05/25/2023]
Abstract
Initiation of RNA polymerase II transcription signals the beginning of a series of physically and functionally coupled pre-mRNA processing events that transform an RNA transcript into a highly structured, mature ribonucleoprotein complex. With such a complexity of co-transcriptional processes comes the need to identify and degrade improperly processed transcripts. Quality control of mRNA expression primarily involves exonucleolytic degradation of aberrant RNAs. RNA silencing, on the other hand, tends to be viewed separately as a pathway that primarily functions in regulating endogenous gene expression and in genome defense against transposons and viruses. Here, we review current knowledge of these pathways as they exist in plants and draw parallels to similar pathways in other eukaryotes. We then highlight some unexplored overlaps that exist between the RNA silencing and RNA decay pathways of plants, as evidenced by their shared RNA substrates and shared genetic requirements.
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Affiliation(s)
- Michael Christie
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
| | - Christopher A. Brosnan
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
| | - Joseph A. Rothnagel
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
| | - Bernard J. Carroll
- School of Chemistry and Molecular Biosciences, The University of QueenslandBrisbane, QLD, Australia
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27
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de Turris V, Nicholson P, Orozco RZ, Singer RH, Mühlemann O. Cotranscriptional effect of a premature termination codon revealed by live-cell imaging. RNA (NEW YORK, N.Y.) 2011; 17:2094-107. [PMID: 22028363 PMCID: PMC3222123 DOI: 10.1261/rna.02918111] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 08/30/2011] [Indexed: 05/29/2023]
Abstract
Aberrant mRNAs with premature translation termination codons (PTCs) are recognized and eliminated by the nonsense-mediated mRNA decay (NMD) pathway in eukaryotes. We employed a novel live-cell imaging approach to investigate the kinetics of mRNA synthesis and release at the transcription site of PTC-containing (PTC+) and PTC-free (PTC-) immunoglobulin-μ reporter genes. Fluorescence recovery after photobleaching (FRAP) and photoconversion analyses revealed that PTC+ transcripts are specifically retained at the transcription site. Remarkably, the retained PTC+ transcripts are mainly unspliced, and this RNA retention is dependent upon two important NMD factors, UPF1 and SMG6, since their depletion led to the release of the PTC+ transcripts. Finally, ChIP analysis showed a physical association of UPF1 and SMG6 with both the PTC+ and the PTC- reporter genes in vivo. Collectively, our data support a mechanism for regulation of PTC+ transcripts at the transcription site.
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Affiliation(s)
| | - Pamela Nicholson
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland
| | | | | | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland
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Yepiskoposyan H, Aeschimann F, Nilsson D, Okoniewski M, Mühlemann O. Autoregulation of the nonsense-mediated mRNA decay pathway in human cells. RNA (NEW YORK, N.Y.) 2011; 17:2108-18. [PMID: 22028362 PMCID: PMC3222124 DOI: 10.1261/rna.030247.111] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Nonsense-mediated mRNA decay (NMD) is traditionally portrayed as a quality-control mechanism that degrades mRNAs with truncated open reading frames (ORFs). However, it is meanwhile clear that NMD also contributes to the post-transcriptional gene regulation of numerous physiological mRNAs. To identify endogenous NMD substrate mRNAs and analyze the features that render them sensitive to NMD, we performed transcriptome profiling of human cells depleted of the NMD factors UPF1, SMG6, or SMG7. It revealed that mRNAs up-regulated by NMD abrogation had a greater median 3'-UTR length compared with that of the human mRNAome and were also enriched for 3'-UTR introns and uORFs. Intriguingly, most mRNAs coding for NMD factors were among the NMD-sensitive transcripts, implying that the NMD process is autoregulated. These mRNAs all possess long 3' UTRs, and some of them harbor uORFs. Using reporter gene assays, we demonstrated that the long 3' UTRs of UPF1, SMG5, and SMG7 mRNAs are the main NMD-inducing features of these mRNAs, suggesting that long 3' UTRs might be a frequent trigger of NMD.
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Affiliation(s)
- Hasmik Yepiskoposyan
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Florian Aeschimann
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
| | - Daniel Nilsson
- Science for Life Laboratory, Clinical Genetics Unit L5:03, Karolinska University Hospital, Solna 171 76, Stockholm, Sweden
| | - Michal Okoniewski
- Functional Genomics Center, University of Zurich and Swiss Federal Institute of Technology, 8057 Zurich, Switzerland
| | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
- Corresponding author.E-mail .
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29
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Cross talk between immunoglobulin heavy-chain transcription and RNA surveillance during B cell development. Mol Cell Biol 2011; 32:107-17. [PMID: 22037763 DOI: 10.1128/mcb.06138-11] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Immunoglobulin (Ig) genes naturally acquire frequent premature termination codons during the error-prone V(D)J recombination process. Although B cell differentiation is linked to the expression of productive Ig alleles, the transcriptional status of nonfunctionally recombined alleles remains unclear. Here, we tracked transcription and posttranscriptional regulation for both Ig heavy-chain (IgH) alleles in mice carrying a nonfunctional knock-in allele. We show that productively and nonproductively VDJ-rearranged alleles are transcribed throughout B cell development, carry similar active chromatin marks, and even display equivalent RNA polymerase II (RNAPII) loading after B cell stimulation. Hence, these results challenge the idea that the repositioning of one allele to heterochromatin could promote the silencing of nonproductive alleles. Interestingly, the efficiency of downstream RNA surveillance mechanisms fluctuates according to B cell activation and terminal differentiation: unspliced nonfunctional transcripts accumulate in primary B cells, while B cell activation promotes IgH transcription, RNA splicing, and nonsense-mediated mRNA decay (NMD). Altogether, IgH transcription and RNA splicing rates determine by which RNA surveillance mechanisms a B cell can get rid of nonproductive IgH mRNAs.
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30
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Ly JP, Onay T, Sison K, Sivaskandarajah G, Sabbisetti V, Li L, Bonventre JV, Flenniken A, Paragas N, Barasch JM, Adamson SL, Osborne L, Rossant J, Schnermann J, Quaggin SE. The Sweet Pee model for Sglt2 mutation. J Am Soc Nephrol 2011; 22:113-23. [PMID: 21209254 DOI: 10.1681/asn.2010080888] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Inhibiting renal glucose transport is a potential pharmacologic approach to treat diabetes. The renal tubular sodium-glucose transporter 2 (SGLT2) reabsorbs approximately 90% of the filtered glucose load. An animal model with sglt2 dysfunction could provide information regarding the potential long-term safety and efficacy of SGLT2 inhibitors, which are currently under clinical investigation. Here, we describe Sweet Pee, a mouse model that carries a nonsense mutation in the Slc5a2 gene, which results in the loss of sglt2 protein function. The phenotype of Sweet Pee mutants was remarkably similar to patients with mutations in the Scl5a2 gene. The Sweet Pee mutants had improved glucose tolerance, higher urinary excretion of calcium and magnesium, and growth retardation. Renal physiologic studies demonstrated a prominent distal osmotic diuresis without enhanced natriuresis. Sweet Pee mutants did not exhibit increased KIM-1 or NGAL, markers of acute tubular injury. After induction of diabetes, Sweet Pee mice had better overall glycemic control than wild-type control mice, but had a higher risk for infection and an increased mortality rate (70% in homozygous mutants versus 10% in controls at 20 weeks). In summary, the Sweet Pee model allows study of the long-term benefits and risks associated with inhibition of SGLT2 for the management of diabetes. Our model suggests that inhibiting SGLT2 may improve glucose control but may confer increased risks for infection, malnutrition, volume contraction, and mortality.
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Affiliation(s)
- Joseph P Ly
- The Samuel Lunenfeld Research Institute, TCP Building, Room 5-1015-2, 25 Orde Street, Toronto, Ontario M5T 3H7, Canada
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31
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Makarov R, Steiner B, Gucev Z, Tasic V, Wieacker P, Wieland I. The impact of CFNS-causing EFNB1 mutations on ephrin-B1 function. BMC MEDICAL GENETICS 2010; 11:98. [PMID: 20565770 PMCID: PMC2901216 DOI: 10.1186/1471-2350-11-98] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 06/17/2010] [Indexed: 02/02/2023]
Abstract
Background Mutations of EFNB1 cause the X-linked malformation syndrome craniofrontonasal syndrome (CFNS). CFNS is characterized by an unusual phenotypic pattern of inheritance, because it affects heterozygous females more severely than hemizygous males. This sex-dependent inheritance has been explained by random X-inactivation in heterozygous females and the consequences of cellular interference of wild type and mutant EFNB1-expressing cell populations. EFNB1 encodes the transmembrane protein ephrin-B1, that forms bi-directional signalling complexes with Eph receptor tyrosine kinases expressed on complementary cells. Here, we studied the effects of patient-derived EFNB1 mutations predicted to give rise to truncated ephrin-B1 protein or to disturb Eph/ephrin-B1 reverse ephrin-B1 signalling. Five mutations are investigated in this work: nonsense mutation c.196C > T/p.R66X, frameshift mutation c.614_615delCT, splice-site mutation c.406 + 2T > C and two missense mutations p.P54L and p.T111I. Both missense mutations are located in the extracellular ephrin domain involved in Eph-ephrin-B1 recognition and higher order complex formation. Methods Nonsense mutation c.196C > T/p.R66X, frameshift mutation c.614_615delCT and splice-site mutation c.406+2T > C were detected in the primary patient fibroblasts by direct sequencing of the DNA and were further analysed by RT-PCR and Western blot analyses. The impact of missense mutations p.P54L and p.T111I on cell behaviour and reverse ephrin-B1 cell signalling was analysed in a cell culture model using NIH 3T3 fibroblasts. These cells were transfected with the constructs generated by in vitro site-directed mutagenesis. Investigation of missense mutations was performed using the Western blot analysis and time-lapse microscopy. Results and Discussion Nonsense mutation c.196C > T/p.R66X and frameshift mutation c.614_615delCT escape nonsense-mediated RNA decay (NMD), splice-site mutation c.406+2T > C results in either retention of intron 2 or activation of a cryptic splice site in exon 2. However, c.614_615delCT and c.406+2T > C mutations were found to be not compatible with production of a soluble ephrin-B1 protein. Protein expression of the p.R66X mutation was predicted unlikely but has not been investigated. Ectopic expression of p.P54L ephrin-B1 resists Eph-receptor mediated cell cluster formation in tissue culture and intracellular ephrin-B1 Tyr324 and Tyr329 phosphorylation. Cells expressing p.T111I protein show similar responses as wild type expressing cells, however, phosphorylation of Tyr324 and Tyr329 is reduced. Conclusions Pathogenic mechanisms in CFNS manifestation include impaired ephrin-B1 signalling combined with cellular interference.
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Affiliation(s)
- Roman Makarov
- Institut für Humangenetik, Universitätsklinikum, Otto-von-Guericke-Universität, Magdeburg, Germany
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32
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Tsakiridis A, Tzouanacou E, Rahman A, Colby D, Axton R, Chambers I, Wilson V, Forrester L, Brickman JM. Expression-independent gene trap vectors for random and targeted mutagenesis in embryonic stem cells. Nucleic Acids Res 2009; 37:e129. [PMID: 19692586 PMCID: PMC2770648 DOI: 10.1093/nar/gkp640] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 07/13/2009] [Accepted: 07/17/2009] [Indexed: 12/04/2022] Open
Abstract
Promoterless gene trap vectors have been widely used for high-efficiency gene targeting and random mutagenesis in embryonic stem (ES) cells. Unfortunately, such vectors are only effective for genes expressed in ES cells and this has prompted the development of expression-independent vectors. These polyadenylation (poly A) trap vectors employ a splice donor to capture an endogenous gene's polyadenylation sequence and provide transcript stability. However, the spectrum of mutations generated by these vectors appears largely restricted to the last intron of target loci due to nonsense-mediated mRNA decay (NMD) making them unsuitable for gene targeting applications. Here, we present novel poly A trap vectors that overcome the effect of NMD and also employ RNA instability sequences to improve splicing efficiency. The set of random insertions generated with these vectors show a significantly reduced insertional bias and the vectors can be targeted directly to a 5' intron. We also show that this relative positional independence is linked to the human beta-actin promoter and is most likely a result of its transcriptional activity in ES cells. Taken together our data indicate that these vectors are an effective tool for insertional mutagenesis that can be used for either gene trapping or gene targeting.
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Affiliation(s)
- Anestis Tsakiridis
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Elena Tzouanacou
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Afifah Rahman
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Douglas Colby
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Richard Axton
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Ian Chambers
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Valerie Wilson
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Lesley Forrester
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
| | - Joshua M. Brickman
- MRC Centre for Regenerative Medicine, Institute for Stem Cell Research, School of Biological Sciences, University of Edinburgh, King's Buildings, West Mains Road and MRC Centre for Regenerative Medicine, Queens Medical Research Institute, University of Edinburgh, 47 Little France Crescent, Edinburgh, UK
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Kim SH, Koroleva OA, Lewandowska D, Pendle AF, Clark GP, Simpson CG, Shaw PJ, Brown JWS. Aberrant mRNA transcripts and the nonsense-mediated decay proteins UPF2 and UPF3 are enriched in the Arabidopsis nucleolus. THE PLANT CELL 2009; 21:2045-57. [PMID: 19602621 PMCID: PMC2729600 DOI: 10.1105/tpc.109.067736] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Revised: 06/10/2009] [Accepted: 06/24/2009] [Indexed: 05/19/2023]
Abstract
The eukaryotic nucleolus is multifunctional and involved in the metabolism and assembly of many different RNAs and ribonucleoprotein particles as well as in cellular functions, such as cell division and transcriptional silencing in plants. We previously showed that Arabidopsis thaliana exon junction complex proteins associate with the nucleolus, suggesting a role for the nucleolus in mRNA production. Here, we report that the plant nucleolus contains mRNAs, including fully spliced, aberrantly spliced, and single exon gene transcripts. Aberrant mRNAs are much more abundant in nucleolar fractions, while fully spliced products are more abundant in nucleoplasmic fractions. The majority of the aberrant transcripts contain premature termination codons and have characteristics of nonsense-mediated decay (NMD) substrates. A direct link between NMD and the nucleolus is shown by increased levels of the same aberrant transcripts in both the nucleolus and in Up-frameshift (upf) mutants impaired in NMD. In addition, the NMD factors UPF3 and UPF2 localize to the nucleolus, suggesting that the Arabidopsis nucleolus is therefore involved in identifying aberrant mRNAs and NMD.
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Affiliation(s)
- Sang Hyon Kim
- Genetics Programme, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, Scotland, United Kingdom
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Belessi C, Stamatopoulos K, Hadzidimitriou A, Hatzi K, Smilevska T, Stavroyianni N, Marantidou F, Paterakis G, Fassas A, Anagnostopoulos A, Laoutaris N. Analysis of expressed and non-expressed IGK locus rearrangements in chronic lymphocytic leukemia. Mol Med 2009; 11:52-8. [PMID: 16622520 PMCID: PMC1449522 DOI: 10.2119/2005-00044.belessi] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2005] [Accepted: 03/05/2006] [Indexed: 11/06/2022] Open
Abstract
Immunoglobulin kappa (IGK) locus rearrangements were analyzed in parallel on cDNA/genomic DNA in 188 kappa- and 103 lambda-chronic lymphocytic leukemia (CLL) cases. IGKV-KDE and IGKJ-C-intron-KDE rearrangements were also analyzed on genomic DNA. In kappa-CLL, only 3 of 188 cases carried double in-frame IGKV-J transcripts: in such cases, the possibility that leukemic cells expressed more than one kappa chain cannot be excluded. Twenty-eight kappa-CLL cases also carried nonexpressed (nontranscribed and/or out-of-frame) IGKV-J rearrangements. Taking IGKV-J, IGKV-KDE, and IGKJ-C-intron-KDE rearrangements together, 38% of kappa-CLL cases carried biallelic IGK locus rearrangements. In lambda-CLL, 69 IGKV-J rearrangements were detected in 64 of 103 cases (62%); 24 rearrangements (38.2%) were in-frame. Four cases carried in-frame IGKV-J transcripts but retained monotypic light-chain expression, suggesting posttranscriptional regulation of allelic exclusion. In all, taking IGKV-J, IGKV-KDE, and IGKJ-C-intron-KDE rearrangements together, 97% of lambda-CLL cases had at least 1 rearranged IGK allele, in keeping with normal cells. IG repertoire comparisons in kappa- versus lambda-CLL revealed that CLL precursor cells tried many rearrangements on the same IGK allele before they became lambda producers. Thirteen of 28 and 26 of 69 non-expressed sequences in, respectively, kappa- or lambda-CLL had < 100% homology to germline. This finding might be considered as evidence for secondary rearrangements occurring after the onset of somatic hypermutation, at least in some cases. The inactivation of potentially functional IGKV-J joints by secondary rearrangements indicates active receptor editing in CLL and provides further evidence for the role of antigen in CLL immunopathogenesis.
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MESH Headings
- Adult
- Aged
- Amino Acid Sequence
- Cells, Cultured
- Female
- Gene Expression Regulation, Neoplastic/immunology
- Gene Rearrangement, B-Lymphocyte/immunology
- Humans
- Immunoglobulin Joining Region/biosynthesis
- Immunoglobulin Joining Region/genetics
- Immunoglobulin Variable Region/biosynthesis
- Immunoglobulin Variable Region/genetics
- Immunoglobulin kappa-Chains/biosynthesis
- Immunoglobulin kappa-Chains/genetics
- Immunoglobulin kappa-Chains/metabolism
- Immunoglobulin lambda-Chains/biosynthesis
- Immunoglobulin lambda-Chains/genetics
- Immunoglobulin lambda-Chains/metabolism
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/immunology
- Male
- Middle Aged
- Molecular Sequence Data
- RNA Editing/immunology
- Receptors, Antigen, B-Cell/genetics
- Recombination, Genetic/immunology
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Eberle AB, Herrmann K, Jäck HM, Mühlemann O. Equal transcription rates of productively and nonproductively rearranged immunoglobulin mu heavy chain alleles in a pro-B cell line. RNA (NEW YORK, N.Y.) 2009; 15:1021-1028. [PMID: 19363217 PMCID: PMC2685528 DOI: 10.1261/rna.1516409] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Accepted: 02/24/2009] [Indexed: 05/27/2023]
Abstract
During B cell maturation, immunoglobulin (Ig) genes frequently acquire premature translation-termination codons (PTCs) as a result of the somatic rearrangement of V, D, and J gene segments. However, it is essential for a B lymphocyte to produce only one kind of antibody and therefore to ensure that the heavy and light chain polypeptides are expressed exclusively from the corresponding functional alleles, whereas no protein is made from the nonproductively rearranged alleles. At the post-transcriptional level, a well-studied mRNA quality control mechanism, termed nonsense-mediated mRNA decay (NMD), recognizes and degrades PTC-containing mRNAs in a translation-dependent manner. In addition, transcriptional silencing of PTC-containing Ig-mu and Ig-gamma heavy chain reporter genes was observed in HeLa cells. To investigate the silencing of nonproductively rearranged Ig genes in a more physiological context, we analyzed a monoclonal line of immortalized murine pro-B cells harboring one productively (PTC-) and one nonproductively (PTC+) rearranged Ig-mu heavy chain allele. We show that the steady-state abundance of PTC+ mRNA was approximately 40-fold lower when compared to that of the PTC- mRNA. However, both the PTC+ and PTC- allele seemed to be equally well transcribed since the abundances of PTC+ and PTC- pre-mRNA were very similar and chromatin immunoprecipitations revealed comparable occupancy of RNA polymerase II and acetylated histone H3 on both alleles. Altogether, we found no evidence for transcriptional silencing of the PTC+ allele in this pro-B cell line; hence, the efficient down-regulation of the PTC+ Ig-mu mRNA results entirely from NMD.
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Affiliation(s)
- Andrea B Eberle
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
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36
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Two molecular pathways (NMD and ERAD) contribute to a genetic epilepsy associated with the GABA(A) receptor GABRA1 PTC mutation, 975delC, S326fs328X. J Neurosci 2009; 29:2833-44. [PMID: 19261879 DOI: 10.1523/jneurosci.4512-08.2009] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Approximately one-third of human genetic diseases are caused by premature translation-termination codon (PTC)-generating mutations. These mutations in sodium channel and GABA(A) receptor genes have been associated with idiopathic generalized epilepsies, but the cellular consequences of the PTCs on the mutant channel subunit biogenesis and function are unknown. The PTCs could result in translation of a truncated subunit, or more likely, trigger mRNA degradation through nonsense-mediated mRNA decay (NMD), thus preventing or reducing production of mutant subunit at the transcriptional level. The GABA(A) receptor alpha1 subunit mutation, 975delC, S326fs328X, is an autosomal dominant mutation associated with childhood absence epilepsy that generates a PTC in exon 8 of the 9 exon GABRA1 gene that is 74 bp upstream of intron 8. Using an intron 8-inclusion minigene that supports NMD, we demonstrated that mutant mRNA was substantially reduced, but not absent. Loss of mutant transcripts was blocked by ribosome inhibition or by silencing the NMD-essential gene hUPF-1. In both neurons and non-neuronal cells, the PTC caused substantial loss of mutant alpha1(S326fs328X) subunit mRNA through NMD with a minor portion of the mRNA escaping NMD and producing a mutant protein. The translated mutant protein had reduced stability due to endoplasmic reticulum associated degradation (ERAD) and had enhanced association with molecular chaperones. This study suggests that loss of mRNA due to activation of NMD and activation of ERAD by the mutant protein may contribute to epileptogenesis. The molecular mechanisms outlined here delineate a model for the pathogenesis of many PTC-generating mutations.
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Abstract
Nonsense-mediated mRNA decay (NMD) is a translation-coupled mechanism that eliminates mRNAs containing premature translation-termination codons (PTCs). In mammalian cells, NMD is also linked to pre-mRNA splicing, as in many instances strong mRNA reduction occurs only when the PTC is located upstream of an intron. It is proposed that in these systems, the exon junction complex (EJC) mediates the link between splicing and NMD. Recent studies have questioned the role of splicing and the EJC in initiating NMD. Instead, they put forward a general and evolutionarily conserved mechanism in which the main regulator of NMD is the distance between a PTC and the poly(A) tail of an mRNA. Here we discuss the limitations of the new NMD model and the EJC concept; we argue that neither satisfactorily accounts for all of the available data and offer a new model to test in future studies.
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Affiliation(s)
- Saverio Brogna
- University of Birmingham, School of Biosciences, Edgbaston, Birmingham B15 2TT, UK.
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38
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Eberle AB, Lykke-Andersen S, Mühlemann O, Jensen TH. SMG6 promotes endonucleolytic cleavage of nonsense mRNA in human cells. Nat Struct Mol Biol 2008; 16:49-55. [PMID: 19060897 DOI: 10.1038/nsmb.1530] [Citation(s) in RCA: 296] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2008] [Accepted: 11/18/2008] [Indexed: 11/09/2022]
Abstract
From yeast to humans, mRNAs harboring premature termination codons (PTCs) are recognized and degraded by nonsense-mediated mRNA decay (NMD). However, degradation mechanisms of NMD have been suggested to differ between species. In Drosophila melanogaster, NMD is initiated by endonucleolysis near the PTC, whereas in yeast and human cells the current view posits that NMD occurs by exonucleolysis from one or both RNA termini. Here we report that degradation of human nonsense mRNAs can be initiated by PTC-proximal endonucleolytic cleavage. We identify the metazoan-specific NMD factor SMG6 as the responsible endonuclease by demonstrating that mutation of conserved residues in its nuclease domain--the C-terminal PIN motif--abolishes endonucleolysis in vivo and in vitro. Our data lead to a revised mechanistic model for degradation of nonsense mRNA in human cells and suggest that endonucleolytic cleavage is a conserved feature in metazoan NMD.
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Affiliation(s)
- Andrea B Eberle
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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Abstract
Among the different cellular surveillance mechanisms that ensure accurate gene expression, nonsense-mediated mRNA decay rapidly degrades mRNAs harbouring PTCs (premature translation-termination codons) and thereby prevents the accumulation of potentially deleterious proteins with C-terminal truncations. In the present article, I review recent data from yeast, fluitflies, nematode worms and human cells and endeavour to merge these results into a unified model for recognition of nonsense mRNA. According to this model, the distinction between translation termination at PTCs and at 'normal' termination codons relies on the physical distance between the terminating ribosome and PABP [poly(A)-binding protein]. Correct translation termination is promoted by a PABP-mediated signal to the terminating ribosome, whereas the absence of this signal leads to the assembly of an mRNA decay-promoting protein complex including the conserved NMD factors UPF (up-frameshift) 1-3.
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40
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Posttranscriptional gene regulation by spatial rearrangement of the 3' untranslated region. PLoS Biol 2008; 6:e92. [PMID: 18447580 PMCID: PMC2689704 DOI: 10.1371/journal.pbio.0060092] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Accepted: 03/04/2008] [Indexed: 12/23/2022] Open
Abstract
Translation termination at premature termination codons (PTCs) triggers degradation of the aberrant mRNA, but the mechanism by which a termination event is defined as premature is still unclear. Here we show that the physical distance between the termination codon and the poly(A)-binding protein PABPC1 is a crucial determinant for PTC recognition in human cells. “Normal” termination codons can trigger nonsense-mediated mRNA decay (NMD) when this distance is extended; and vice versa, NMD can be suppressed by folding the poly(A) tail into proximity of a PTC or by tethering of PABPC1 nearby a PTC, indicating an evolutionarily conserved function of PABPC1 in promoting correct translation termination and antagonizing activation of NMD. Most importantly, our results demonstrate that spatial rearrangements of the 3′ untranslated region can modulate the NMD pathway and thereby provide a novel mechanism for posttranscriptional gene regulation. Correct expression of the genetic information is essential for life, and several quality control systems have evolved to ensure accurate protein synthesis. One of these processes, termed nonsense-mediated mRNA decay (NMD), detects inappropriate termination of mRNA translation at premature termination codons (PTCs) and triggers degradation of the aberrant mRNA. Although the occurrence of NMD is well documented in yeast, worms, flies, mammals, and plants, the mechanism by which a termination event is defined as premature is still unclear, and different models have been proposed for different species. For mammals, the current prevailing view is that a termination codon is identified as premature and elicits NMD when it is located upstream of the 3′-most exon junction complex. However, well-documented examples of NMD triggered by PTCs in the last exon challenge this “mammalian NMD model.” Here we show that the physical distance between the termination codon and the poly(A)-binding protein PABPC1 is a crucial determinant for PTC recognition in human cells, indicating an evolutionarily conserved function of PABPC1 in promoting correct translation termination and antagonizing activation of NMD. Most importantly, our results demonstrate that spatial rearrangements of the 3′ untranslated region can modulate the NMD pathway and thereby provide a novel, translation-dependent mechanism for posttranscriptional gene regulation. The physical distance to the poly(A) tail is a crucial determinant to define a termination codon as premature in human cells. This indicates evolutionary conservation of the basic mechanism of nonsense-mediated mRNA decay and provides a novel mechanism for translation-dependent posttranscriptional gene regulation.
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41
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Neu-Yilik G, Kulozik AE. NMD: multitasking between mRNA surveillance and modulation of gene expression. ADVANCES IN GENETICS 2008; 62:185-243. [PMID: 19010255 DOI: 10.1016/s0065-2660(08)00604-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Gene expression is a highly specific and regulated multilayer process with a plethora of interconnections as well as safeguard and feedback mechanisms. Messenger RNA, long neglected as a mere subcarrier of genetic information, is more recently recognized as a linchpin of regulation and control of gene expression. Moreover, the awareness of not only proteins but also mRNA as a modulator of genetic disorders has vastly increased in recent years. Nonsense-mediated mRNA decay (NMD) is a posttranscriptional surveillance mechanism that uses an intricate network of nuclear and cytoplasmic processes to eliminate mRNAs, containing premature termination codons. It thus helps limit the synthesis of potentially harmful truncated proteins. However, recent results suggest functions of NMD that go far beyond this role and affect the expression of wild-type genes and the modulation of whole pathways. In both respects--the elimination of faulty transcripts and the regulation of error-free mRNAs--NMD has many medical implications. Therefore, it has earned increasing interest from researchers of all fields of the life sciences. In the following text, we (1) present current knowledge about the NMD mechanism and its targets, (2) define its relevance in the regulation of important biochemical pathways, (3) explore its medical significance and the prospects of therapeutic interventions, and (4) discuss additional functions of NMD effectors, some of which may be networked to NMD. The main focus of this chapter lies on mammalian NMD and resorts to the features and factors of NMD in other organisms if these help to complete or illuminate the picture.
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Affiliation(s)
- Gabriele Neu-Yilik
- Department for Pediatric Oncology, Hematology and Immunology, University Hospital Heidelberg and Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 156, 69120 Heidelberg, Germany
| | - Andreas E Kulozik
- Department for Pediatric Oncology, Hematology and Immunology, University Hospital Heidelberg and Molecular Medicine Partnership Unit, University of Heidelberg and European Molecular Biology Laboratory, Im Neuenheimer Feld 156, 69120 Heidelberg, Germany
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42
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Matsuda D, Sato H, Maquat LE. Chapter 9. Studying nonsense-mediated mRNA decay in mammalian cells. Methods Enzymol 2008; 449:177-201. [PMID: 19215759 DOI: 10.1016/s0076-6879(08)02409-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Nonsense-mediated decay (NMD) in eukaryotic cells largely functions as a quality control mechanism by degrading faulty mRNAs that terminate translation prematurely. In recent years it has become evident that NMD also eliminates a subset of naturally occurring mRNA during proper gene expression. The mechanism of NMD in mammalian cells can be distinguished from the mechanism in, for example, Saccharomyces cerevisiae or Caenorhabditis elegans, by its apparent restriction to newly synthesized mRNA during a pioneer round of translation. This dependence can be explained by the need for at least one exon-exon junction complex (EJC) that is deposited on newly synthesized mRNA during the process of pre-mRNA splicing. Additionally, mammalian-cell NMD is promoted by the cap-binding protein heterodimer CBP80/20 that also typifies newly synthesized mRNA. When translation terminates sufficiently upstream of an EJC, the NMD factor Up-frameshift (Upf)1 is thought to join the stable EJC constituent NMD factors Upf2 and Upf3 or Upf3X (also called Upf3a or Upf3b, respectively), and undergo phosphorylation. Phosphorylation appears to trigger translational repression and mRNA decay. Although there are established rules for what generally defines an NMD target in mammalian cells, as with any rule there are exceptions and, thus, the need to experimentally verify individual mRNAs as bona fide targets of NMD. This chapter provides guidelines and protocols for how to define NMD targets using cultured mammalian cells.
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Affiliation(s)
- Daiki Matsuda
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York, USA
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43
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Isken O, Maquat LE. Quality control of eukaryotic mRNA: safeguarding cells from abnormal mRNA function. Genes Dev 2007; 21:1833-56. [PMID: 17671086 DOI: 10.1101/gad.1566807] [Citation(s) in RCA: 433] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Cells routinely make mistakes. Some mistakes are encoded by the genome and may manifest as inherited or acquired diseases. Other mistakes occur because metabolic processes can be intrinsically inefficient or inaccurate. Consequently, cells have developed mechanisms to minimize the damage that would result if mistakes went unchecked. Here, we provide an overview of three quality control mechanisms--nonsense-mediated mRNA decay, nonstop mRNA decay, and no-go mRNA decay. Each surveys mRNAs during translation and degrades those mRNAs that direct aberrant protein synthesis. Along with other types of quality control that occur during the complex processes of mRNA biogenesis, these mRNA surveillance mechanisms help to ensure the integrity of protein-encoding gene expression.
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Affiliation(s)
- Olaf Isken
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry, University of Rochester, Rochester, New York 14642, USA
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44
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Hori K, Watanabe Y. Context analysis of termination codons in mRNA that are recognized by plant NMD. PLANT & CELL PHYSIOLOGY 2007; 48:1072-8. [PMID: 17567637 DOI: 10.1093/pcp/pcm075] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The nonsense-mediated mRNA decay (NMD) system is an RNA surveillance system that degrades mRNAs possessing premature translation termination codons (PTCs). Although NMD factors are well conserved in eukaryotes, it is speculated that the contexts of those termination codons that are subject to NMD are different depending on the organism. Context analysis of termination codons that are recognized by the plant NMD system would clarify NMD target mRNAs in plants, and contribute to our understanding of its biological relevance in plants. In the present study we analyzed the positions of termination codons that were recognized as PTCs using an Agrobacterium transient expression assay, i.e. the accumulation of a series of plant mRNAs with nonsense mutations in different contexts was tested in plants. The results indicated that termination codons that are located distant from the mRNA 3' termini or >50 nucleotides upstream of the 3'-most exon-exon junction are recognized as substrates for NMD.
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Affiliation(s)
- Koichi Hori
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo, 153-8902 Japan
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45
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Stalder L, Mühlemann O. Transcriptional silencing of nonsense codon-containing immunoglobulin micro genes requires translation of its mRNA. J Biol Chem 2007; 282:16079-85. [PMID: 17428806 DOI: 10.1074/jbc.m610595200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotes have evolved quality control mechanisms that prevent the expression of genes in which the protein coding potential is crippled by the presence of a premature translation-termination codon (PTC). In addition to nonsense-mediated mRNA decay (NMD), a well documented posttranscriptional consequence of the presence of a PTC in an mRNA, we recently reported the transcriptional silencing of PTC-containing immunoglobulin (Ig) mu and gamma minigenes when they are stably integrated into the genome of HeLa cells. Here we demonstrate that this transcriptional silencing of PTC-containing Ig-mu constructs requires active translation of the cognate mRNA, as it is not observed under conditions where translation of the PTC-containing mRNA is inhibited through an iron-responsive element in the 5'-untranslated region. Furthermore, RNA interference-mediated depletion of the essential NMD factor Upf1 not only abolishes NMD but also reduces the extent of nonsense-mediated transcriptional gene silencing (NMTGS). Collectively, our data indicate that NMTGS and NMD are linked, relying on the same mechanism for PTC recognition, and that the NMTGS pathway branches from the NMD pathway at a step after Upf1 function.
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Affiliation(s)
- Lukas Stalder
- Institute of Cell Biology, University of Berne, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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46
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Chan WK, Huang L, Gudikote JP, Chang YF, Imam JS, MacLean JA, Wilkinson MF. An alternative branch of the nonsense-mediated decay pathway. EMBO J 2007; 26:1820-30. [PMID: 17363904 PMCID: PMC1847659 DOI: 10.1038/sj.emboj.7601628] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Accepted: 02/05/2007] [Indexed: 11/08/2022] Open
Abstract
The T-cell receptor (TCR) locus undergoes programmed rearrangements that frequently generate premature termination codons (PTCs). The PTC-bearing transcripts derived from such nonproductively rearranged genes are dramatically downregulated by the nonsense-mediated decay (NMD) pathway. Here, we show that depletion of the NMD factor UPF3b does not impair TCRbeta NMD, thereby distinguishing it from classical NMD. Depletion of the related factor UPF3a, by itself or in combination with UPF3b, also has no effect on TCRbeta NMD. Mapping experiments revealed the identity of TCRbeta sequences that elicit a switch to UPF3b dependence. This regulation is not a peculiarity of TCRbeta, as we identified many wild-type genes, including one essential for NMD, that transcribe NMD-targeted mRNAs whose downregulation is little or not affected by UPF3a and UPF3b depletion. We propose that we have uncovered an alternative branch of the NMD pathway that not only degrades aberrant mRNAs but also regulates normal mRNAs, including one that participates in a negative feedback loop controlling the magnitude of NMD.
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MESH Headings
- Animals
- Clone Cells
- Codon, Nonsense/genetics
- Codon, Nonsense/metabolism
- Gene Expression Regulation
- HeLa Cells
- Humans
- Introns/genetics
- Mice
- RNA Helicases
- RNA Stability
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Small Interfering/metabolism
- RNA-Binding Proteins/metabolism
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Receptors, Antigen, T-Cell, alpha-beta/metabolism
- Sequence Deletion
- Trans-Activators/metabolism
- VDJ Exons/genetics
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Affiliation(s)
- Wai-Kin Chan
- Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Lulu Huang
- Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Jayanthi P Gudikote
- Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Yao-Fu Chang
- Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - J Saadi Imam
- Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - James A MacLean
- Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Miles F Wilkinson
- Department of Biochemistry and Molecular Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Department of Biochemistry and Molecular Biology, Unit 1000, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030, USA. Tel.: +1 713 563 3215; Fax: +1 713 563 3375; E-mail:
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47
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Behm-Ansmant I, Gatfield D, Rehwinkel J, Hilgers V, Izaurralde E. A conserved role for cytoplasmic poly(A)-binding protein 1 (PABPC1) in nonsense-mediated mRNA decay. EMBO J 2007; 26:1591-601. [PMID: 17318186 PMCID: PMC1829367 DOI: 10.1038/sj.emboj.7601588] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2006] [Accepted: 01/12/2007] [Indexed: 01/01/2023] Open
Abstract
The nonsense-mediated mRNA decay (NMD) pathway degrades mRNAs with premature translation termination codons (PTCs). The mechanisms by which PTCs and natural stop codons are discriminated remain unclear. We show that the position of stops relative to the poly(A) tail (and thus of PABPC1) is a critical determinant for PTC definition in Drosophila melanogaster. Indeed, tethering of PABPC1 downstream of a PTC abolishes NMD. Conversely, natural stops trigger NMD when the length of the 3' UTR is increased. However, many endogenous transcripts with exceptionally long 3' UTRs escape NMD, suggesting that the increase in 3' UTR length has co-evolved with the acquisition of features that suppress NMD. We provide evidence for the existence of 3' UTRs conferring immunity to NMD. We also show that PABPC1 binding is sufficient for PTC recognition, regardless of cleavage or polyadenylation. The role of PABPC1 in NMD must go beyond that of providing positional information for PTC definition, because its depletion suppresses NMD under conditions in which translation efficiency is not affected. These findings reveal a conserved role for PABPC1 in mRNA surveillance.
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Affiliation(s)
| | | | | | | | - Elisa Izaurralde
- Max-Planck-Institute for Developmental Biology, Tübingen, Germany
- EMBL, Heidelberg, Germany
- Max-Planck-Institute for Developmental Biology, Spemannstrasse 35, Tübingen 72076, Germany. Tel.: +49 7071 601 1350; Fax: +49 7071 601 1353; E-mail:
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48
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Belessi CJ, Davi FB, Stamatopoulos KE, Degano M, Andreou TM, Moreno C, Merle-Béral H, Crespo M, Laoutaris NP, Montserrat E, Caligaris-Cappio F, Anagnostopoulos AZ, Ghia P. IGHV gene insertions and deletions in chronic lymphocytic leukemia: "CLL-biased" deletions in a subset of cases with stereotyped receptors. Eur J Immunol 2006; 36:1963-74. [PMID: 16783849 DOI: 10.1002/eji.200535751] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Nucleotide insertions/duplications or deletions in immunoglobulin heavy chain genes have been found in 24/760 patients (3.15%) with chronic lymphocytic leukemia (CLL). In 21/24 cases, the inserted/duplicated or lost nucleotides occurred in multiples of 3; therefore, the original reading frame was maintained and a potentially intact receptor was coded. The pattern and location of insertions/duplications or deletions in CLL and their restriction to mutated IGHV rearranged genes strongly suggests that they resulted from somatic hypermutation. Their incidence in CLL is consistent with previous reports in normal, auto-reactive and neoplastic human B cells, thus seemingly indicating that these modifications generally arise without any particular disease-specific associations. A striking exception to this rule was identified in CLL IGHV3-21-expressing cases: one amino acid was deleted from the CDR2 region in 16/63 (25.4%) mutated CLL IGHV3-21 sequences (including public database-derived IGHV3-21 CLL cases + the present series) vs. only 2/257 (0.78%) public database-derived mutated non-CLL IGHV3-21 sequences; 15/16 CLL IGHV3-21 sequences carrying this deletion belonged to a subset with unique, shared HCDR3 and light chain CDR3 motifs. This finding further supports the idea of selective antigenic pressures playing a pathogenetic role in some CLL cases.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Complementarity Determining Regions/genetics
- Gene Deletion
- Gene Rearrangement, B-Lymphocyte, Heavy Chain
- Humans
- Immunoglobulin Heavy Chains/genetics
- Immunoglobulin Variable Region/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/immunology
- Molecular Sequence Data
- Mutagenesis, Insertional
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, T-Cell/genetics
- Somatic Hypermutation, Immunoglobulin
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49
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Bühler M, Steiner S, Mohn F, Paillusson A, Mühlemann O. EJC-independent degradation of nonsense immunoglobulin-mu mRNA depends on 3' UTR length. Nat Struct Mol Biol 2006; 13:462-4. [PMID: 16622410 DOI: 10.1038/nsmb1081] [Citation(s) in RCA: 203] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2005] [Accepted: 03/06/2006] [Indexed: 11/09/2022]
Abstract
Inconsistent with prevailing models for nonsense-mediated mRNA decay (NMD) in mammals, the mRNA levels of immunoglobulin-mu (Ig-mu) genes with premature termination codons (PTCs) in the penultimate exon are still reduced by NMD when the intron furthest downstream is deleted. As in yeast, this exon junction complex-independent NMD of Ig-mu mRNAs depends on the distance between the termination codon and the poly(A) tail and suggests an evolutionarily conserved mode of PTC recognition.
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Affiliation(s)
- Marc Bühler
- Institute of Cell Biology, University of Bern, Baltzerstrasse 4, CH-3012 Bern, Switzerland
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50
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Yamanegi K, Tang S, Zheng ZM. Kaposi's sarcoma-associated herpesvirus K8beta is derived from a spliced intermediate of K8 pre-mRNA and antagonizes K8alpha (K-bZIP) to induce p21 and p53 and blocks K8alpha-CDK2 interaction. J Virol 2006; 79:14207-21. [PMID: 16254356 PMCID: PMC1280184 DOI: 10.1128/jvi.79.22.14207-14221.2005] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is a lymphotropic DNA tumor virus that induces Kaposi's sarcoma and AIDS-related primary effusion lymphoma. KSHV open reading frame 50 and K8 genes in early viral lytic infection express, respectively, a tricistronic and a bicistronic pre-mRNA, which undergo alternative splicing to create two major spliced mRNA isoforms, alpha and beta, by inclusion (beta) or exclusion (alpha) of an intron at nucleotides 75563 to 75645. This intron contains some suboptimal features, which cause the intron 5' splice site (ss) to interact weakly with U1 snRNA and the 3' ss to bind a U2 auxiliary factor, U2AF, with low affinity. Optimization of this intron in K8 (K8 intron 2) promoted the interaction of the 5' ss with U1 and the 3' ss with U2AF, resulting in a substantial increase in intron splicing. Splicing of K8 intron 2 has also been shown to be stimulated by the splicing of a downstream intron. This was confirmed by the insertion of a human beta-globin intron into the K8beta exon 3-exon 4 splice junction, which promoted splicing of K8beta intron 2 and conversion of the K8beta mRNA to the K8alpha mRNA that encodes a K-bZIP protein. Intron 2 contains a premature termination codon, yet the K8beta mRNA is insensitive to nonsense-mediated mRNA decay, suggesting that the truncated K8beta protein may have a biological function. Indeed, although the truncated K8beta protein is missing only a C-terminal leucine zipper domain from the K-bZIP, its expression antagonizes the ability of the K-bZIP to induce p53 and p21 and blocks K-bZIP-CDK2 interaction through interfering K8alpha mRNA production.
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Affiliation(s)
- Koji Yamanegi
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-1868, USA
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