1
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Gibbs VJ, Lin YH, Ghuge AA, Anderson RA, Schiemann AH, Conaglen L, Sansom BJM, da Silva RC, Sattlegger E. GCN2 in Viral Defence and the Subversive Tactics Employed by Viruses. J Mol Biol 2024; 436:168594. [PMID: 38724002 DOI: 10.1016/j.jmb.2024.168594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 05/01/2024] [Accepted: 05/01/2024] [Indexed: 06/10/2024]
Abstract
The recent SARS-CoV-2 pandemic and associated COVID19 disease illustrates the important role of viral defence mechanisms in ensuring survival and recovery of the host or patient. Viruses absolutely depend on the host's protein synthesis machinery to replicate, meaning that impeding translation is a powerful way to counteract viruses. One major approach used by cells to obstruct protein synthesis is to phosphorylate the alpha subunit of eukaryotic translation initiation factor 2 (eIF2α). Mammals possess four different eIF2α-kinases: PKR, HRI, PEK/PERK, and GCN2. While PKR is currently considered the principal eIF2α-kinase involved in viral defence, the other eIF2α-kinases have also been found to play significant roles. Unsurprisingly, viruses have developed mechanisms to counteract the actions of eIF2α-kinases, or even to exploit them to their benefit. While some of these virulence factors are specific to one eIF2α-kinase, such as GCN2, others target all eIF2α-kinases. This review critically evaluates the current knowledge of viral mechanisms targeting the eIF2α-kinase GCN2. A detailed and in-depth understanding of the molecular mechanisms by which viruses evade host defence mechanisms will help to inform the development of powerful anti-viral measures.
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Affiliation(s)
- Victoria J Gibbs
- School of Food Technology and Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Yu H Lin
- School of Food Technology and Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Aditi A Ghuge
- School of Food Technology and Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Reuben A Anderson
- School of Food Technology and Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Anja H Schiemann
- School of Food Technology and Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Layla Conaglen
- School of Food Technology and Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Bianca J M Sansom
- School of Natural Sciences, Massey University, Auckland, New Zealand
| | - Richard C da Silva
- School of Natural Sciences, Massey University, Auckland, New Zealand; Genome Biology and Epigenetics, Department of Biology, Utrecht University, Utrecht, the Netherlands
| | - Evelyn Sattlegger
- School of Food Technology and Natural Sciences, Massey University, Palmerston North, New Zealand; School of Natural Sciences, Massey University, Auckland, New Zealand; Maurice Wilkins Centre for Molecular BioDiscovery, Palmerston North, New Zealand.
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2
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Tseng YJ, Krans A, Malik I, Deng X, Yildirim E, Ovunc S, Tank EH, Jansen-West K, Kaufhold R, Gomez N, Sher R, Petrucelli L, Barmada S, Todd P. Ribosomal quality control factors inhibit repeat-associated non-AUG translation from GC-rich repeats. Nucleic Acids Res 2024; 52:5928-5949. [PMID: 38412259 PMCID: PMC11162809 DOI: 10.1093/nar/gkae137] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 02/05/2024] [Accepted: 02/19/2024] [Indexed: 02/29/2024] Open
Abstract
A GGGGCC (G4C2) hexanucleotide repeat expansion in C9ORF72 causes amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD), while a CGG trinucleotide repeat expansion in FMR1 leads to the neurodegenerative disorder Fragile X-associated tremor/ataxia syndrome (FXTAS). These GC-rich repeats form RNA secondary structures that support repeat-associated non-AUG (RAN) translation of toxic proteins that contribute to disease pathogenesis. Here we assessed whether these same repeats might trigger stalling and interfere with translational elongation. We find that depletion of ribosome-associated quality control (RQC) factors NEMF, LTN1 and ANKZF1 markedly boost RAN translation product accumulation from both G4C2 and CGG repeats while overexpression of these factors reduces RAN production in both reporter assays and C9ALS/FTD patient iPSC-derived neurons. We also detected partially made products from both G4C2 and CGG repeats whose abundance increased with RQC factor depletion. Repeat RNA sequence, rather than amino acid content, is central to the impact of RQC factor depletion on RAN translation-suggesting a role for RNA secondary structure in these processes. Together, these findings suggest that ribosomal stalling and RQC pathway activation during RAN translation inhibits the generation of toxic RAN products. We propose augmenting RQC activity as a therapeutic strategy in GC-rich repeat expansion disorders.
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Affiliation(s)
- Yi-Ju Tseng
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
- Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI 48109, USA
| | - Indranil Malik
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Biotechnology, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, 502284 Telangana, India
| | - Xiexiong Deng
- Department of Molecular, Cellular and Developmental Biology, Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Evrim Yildirim
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Sinem Ovunc
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Elizabeth M H Tank
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Karen Jansen-West
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Ross Kaufhold
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
- Medical Scientist Training Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nicolas B Gomez
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
- Medical Scientist Training Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Roger Sher
- Department of Neurobiology and Behavior & Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY 11794, USA
| | | | - Sami J Barmada
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI 48109, USA
- Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI 48109, USA
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3
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Brito Querido J, Díaz-López I, Ramakrishnan V. The molecular basis of translation initiation and its regulation in eukaryotes. Nat Rev Mol Cell Biol 2024; 25:168-186. [PMID: 38052923 DOI: 10.1038/s41580-023-00624-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2023] [Indexed: 12/07/2023]
Abstract
The regulation of gene expression is fundamental for life. Whereas the role of transcriptional regulation of gene expression has been studied for several decades, it has been clear over the past two decades that post-transcriptional regulation of gene expression, of which translation regulation is a major part, can be equally important. Translation can be divided into four main stages: initiation, elongation, termination and ribosome recycling. Translation is controlled mainly during its initiation, a process which culminates in a ribosome positioned with an initiator tRNA over the start codon and, thus, ready to begin elongation of the protein chain. mRNA translation has emerged as a powerful tool for the development of innovative therapies, yet the detailed mechanisms underlying the complex process of initiation remain unclear. Recent studies in yeast and mammals have started to shed light on some previously unclear aspects of this process. In this Review, we discuss the current state of knowledge on eukaryotic translation initiation and its regulation in health and disease. Specifically, we focus on recent advances in understanding the processes involved in assembling the 43S pre-initiation complex and its recruitment by the cap-binding complex eukaryotic translation initiation factor 4F (eIF4F) at the 5' end of mRNA. In addition, we discuss recent insights into ribosome scanning along the 5' untranslated region of mRNA and selection of the start codon, which culminates in joining of the 60S large subunit and formation of the 80S initiation complex.
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Affiliation(s)
- Jailson Brito Querido
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Irene Díaz-López
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
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4
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Gotoh S, Mori K, Fujino Y, Kawabe Y, Yamashita T, Omi T, Nagata K, Tagami S, Nagai Y, Ikeda M. eIF5 stimulates the CUG initiation of RAN translation of poly-GA dipeptide repeat protein (DPR) in C9orf72 FTLD/ALS. J Biol Chem 2024; 300:105703. [PMID: 38301895 PMCID: PMC10904283 DOI: 10.1016/j.jbc.2024.105703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 01/20/2024] [Accepted: 01/23/2024] [Indexed: 02/03/2024] Open
Abstract
Tandem GGGGCC repeat expansion in C9orf72 is a genetic cause of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Transcribed repeats are translated into dipeptide repeat proteins via repeat-associated non-AUG (RAN) translation. However, the regulatory mechanism of RAN translation remains unclear. Here, we reveal a GTPase-activating protein, eukaryotic initiation factor 5 (eIF5), which allosterically facilitates the conversion of eIF2-bound GTP into GDP upon start codon recognition, as a novel modifier of C9orf72 RAN translation. Compared to global translation, eIF5, but not its inactive mutants, preferentially stimulates poly-GA RAN translation. RAN translation is increased during integrated stress response, but the stimulatory effect of eIF5 on poly-GA RAN translation was additive to the increase of RAN translation during integrated stress response, with no further increase in phosphorylated eIF2α. Moreover, an alteration of the CUG near cognate codon to CCG or AUG in the poly-GA reading frame abolished the stimulatory effects, indicating that eIF5 primarily acts through the CUG-dependent initiation. Lastly, in a Drosophila model of C9orf72 FTLD/ALS that expresses GGGGCC repeats in the eye, knockdown of endogenous eIF5 by two independent RNAi strains significantly reduced poly-GA expressions, confirming in vivo effect of eIF5 on poly-GA RAN translation. Together, eIF5 stimulates the CUG initiation of poly-GA RAN translation in cellular and Drosophila disease models of C9orf72 FTLD/ALS.
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Affiliation(s)
- Shiho Gotoh
- Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Kohji Mori
- Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan.
| | - Yuzo Fujino
- Department of Neurology, Kindai University Faculty of Medicine, Osaka-Sayama, Japan; Department of Neurology, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Yuya Kawabe
- Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Tomoko Yamashita
- Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Tsubasa Omi
- Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Kenichi Nagata
- Department of Precision Medicine for Dementia, Osaka University Graduate School of Medicine, Suita, Japan
| | - Shinji Tagami
- Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
| | - Yoshitaka Nagai
- Department of Neurology, Kindai University Faculty of Medicine, Osaka-Sayama, Japan
| | - Manabu Ikeda
- Department of Psychiatry, Osaka University Graduate School of Medicine, Suita, Japan
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5
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Grove DJ, Russell PJ, Kearse MG. To initiate or not to initiate: A critical assessment of eIF2A, eIF2D, and MCT-1·DENR to deliver initiator tRNA to ribosomes. WILEY INTERDISCIPLINARY REVIEWS. RNA 2024; 15:e1833. [PMID: 38433101 PMCID: PMC11260288 DOI: 10.1002/wrna.1833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/15/2024] [Accepted: 01/17/2024] [Indexed: 03/05/2024]
Abstract
Selection of the correct start codon is critical for high-fidelity protein synthesis. In eukaryotes, this is typically governed by a multitude of initiation factors (eIFs), including eIF2·GTP that directly delivers the initiator tRNA (Met-tRNAi Met ) to the P site of the ribosome. However, numerous reports, some dating back to the early 1970s, have described other initiation factors having high affinity for the initiator tRNA and the ability of delivering it to the ribosome, which has provided a foundation for further work demonstrating non-canonical initiation mechanisms using alternative initiation factors. Here we provide a critical analysis of current understanding of eIF2A, eIF2D, and the MCT-1·DENR dimer, the evidence surrounding their ability to initiate translation, their implications in human disease, and lay out important key questions for the field. This article is categorized under: RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes Translation > Mechanisms Translation > Regulation.
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Affiliation(s)
- Daisy J. Grove
- The Ohio State Biochemistry Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | - Paul J. Russell
- The Ohio State Biochemistry Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
- The Cellular, Molecular, Biochemical Sciences Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
| | - Michael G. Kearse
- The Ohio State Biochemistry Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
- The Cellular, Molecular, Biochemical Sciences Program, Department of Biological Chemistry, Center for RNA Biology, The Ohio State University, Columbus, Ohio, USA
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6
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Ito H, Machida K, Hasumi M, Ueyama M, Nagai Y, Imataka H, Taguchi H. Reconstitution of C9orf72 GGGGCC repeat-associated non-AUG translation with purified human translation factors. Sci Rep 2023; 13:22826. [PMID: 38129650 PMCID: PMC10739749 DOI: 10.1038/s41598-023-50188-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Accepted: 12/16/2023] [Indexed: 12/23/2023] Open
Abstract
Nucleotide repeat expansion of GGGGCC (G4C2) in the non-coding region of C9orf72 is the most common genetic cause underlying amyotrophic lateral sclerosis and frontotemporal dementia. Transcripts harboring this repeat expansion undergo the translation of dipeptide repeats via a non-canonical process known as repeat-associated non-AUG (RAN) translation. In order to ascertain the essential components required for RAN translation, we successfully recapitulated G4C2-RAN translation using an in vitro reconstituted translation system comprising human factors, namely the human PURE system. Our findings conclusively demonstrate that the presence of fundamental translation factors is sufficient to mediate the elongation from the G4C2 repeat. Furthermore, the initiation mechanism proceeded in a 5' cap-dependent manner, independent of eIF2A or eIF2D. In contrast to cell lysate-mediated RAN translation, where longer G4C2 repeats enhanced translation, we discovered that the expansion of the G4C2 repeats inhibited translation elongation using the human PURE system. These results suggest that the repeat RNA itself functions as a repressor of RAN translation. Taken together, our utilization of a reconstituted RAN translation system employing minimal factors represents a distinctive and potent approach for elucidating the intricacies underlying RAN translation mechanism.
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Grants
- JPMJFS2112 Japan Science and Technology Agency
- JP26116002 Ministry of Education, Culture, Sports, Science and Technology
- JP18H03984 Ministry of Education, Culture, Sports, Science and Technology
- JP21H04763 Ministry of Education, Culture, Sports, Science and Technology
- JP20H05925 Ministry of Education, Culture, Sports, Science and Technology
- 2019-25 Mitsubishi Foundation
- 2019 Uehara Memorial Foundation
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Affiliation(s)
- Hayato Ito
- School of Life Science and Technology, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan
| | - Kodai Machida
- Graduate School of Engineering, University of Hyogo, Shosha, 2167, Himeji, Hyogo, 671-2280, Japan
| | - Mayuka Hasumi
- School of Life Science and Technology, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan
| | - Morio Ueyama
- Department of Neurology, Faculty of Medicine, Kindai University, Ohonohigashi 377-2, Osaka-Sayama, 589-8511, Japan
| | - Yoshitaka Nagai
- Department of Neurology, Faculty of Medicine, Kindai University, Ohonohigashi 377-2, Osaka-Sayama, 589-8511, Japan
| | - Hiroaki Imataka
- Graduate School of Engineering, University of Hyogo, Shosha, 2167, Himeji, Hyogo, 671-2280, Japan
| | - Hideki Taguchi
- School of Life Science and Technology, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan.
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, S2-19, Nagatsuta 4259, Midori-ku, Yokohama, 226-8501, Japan.
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7
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Ferguson ME, Eyles RP, Garcia-Oliveira AL, Kapinga F, Masumba EA, Amuge T, Bredeson JV, Rokhsar DS, Lyons JB, Shah T, Rounsley S, Mkamilo G. Candidate genes for field resistance to cassava brown streak disease revealed through the analysis of multiple data sources. FRONTIERS IN PLANT SCIENCE 2023; 14:1270963. [PMID: 38023930 PMCID: PMC10655247 DOI: 10.3389/fpls.2023.1270963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 10/09/2023] [Indexed: 12/01/2023]
Abstract
Cassava (Manihot esculenta Crantz) is a food and industrial storage root crop with substantial potential to contribute to managing risk associated with climate change due to its inherent resilience and in providing a biodegradable option in manufacturing. In Africa, cassava production is challenged by two viral diseases, cassava brown streak disease (CBSD) and cassava mosaic disease. Here we detect quantitative trait loci (QTL) associated with CBSD in a biparental mapping population of a Tanzanian landrace, Nachinyaya and AR37-80, phenotyped in two locations over three years. The purpose was to use the information to ultimately facilitate either marker-assisted selection or adjust weightings in genomic selection to increase the efficiency of breeding. Results from this study were considered in relation to those from four other biparental populations, of similar genetic backgrounds, that were phenotyped and genotyped simultaneously. Further, we investigated the co-localization of QTL for CBSD resistance across populations and the genetic relationships of parents based on whole genome sequence information. Two QTL on chromosome 4 for resistance to CBSD foliar symptoms and one on each of chromosomes 11 and 18 for root necrosis were of interest. Of significance within the candidate genes underlying the QTL on chromosome 4 are Phenylalanine ammonia-lyase (PAL) and Cinnamoyl-CoA reductase (CCR) genes and three PEPR1-related kinases associated with the lignin pathway. In addition, a CCR gene was also underlying the root necrosis-resistant QTL on chromosome 11. Upregulation of key genes in the cassava lignification pathway from an earlier transcriptome study, including PAL and CCR, in a CBSD-resistant landrace compared to a susceptible landrace suggests a higher level of basal lignin deposition in the CBSD-resistant landrace. Earlier RNAscope® in situ hybridisation imaging experiments demonstrate that cassava brown streak virus (CBSV) is restricted to phloem vessels in CBSV-resistant varieties, and phloem unloading for replication in mesophyll cells is prevented. The results provide evidence for the involvement of the lignin pathway. In addition, five eukaryotic initiation factor (eIF) genes associated with plant virus resistance were found within the priority QTL regions.
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Affiliation(s)
- Morag E. Ferguson
- Cassava Breeding, International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
| | - Rodney P. Eyles
- Cassava Breeding, International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
| | | | - Fortunus Kapinga
- Cassava Breeding, International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
- Cassava Breeding, Naliendele Agricultural Research Institute, Mtwara, Tanzania
| | - Esther A. Masumba
- Cassava Breeding, International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
- Cassava Breeding, Sugarcane Research Institute, Kibaha, Tanzania
| | - Teddy Amuge
- Cassava Breeding, International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
- Cassava Breeding, National Crops Resources Research Institute (NaCRRI), Namulonge, Uganda
| | - Jessen V. Bredeson
- Molecular and Cell Biology Department, University of California, Berkeley, Berkeley, CA, United States
| | - Daniel S. Rokhsar
- Molecular and Cell Biology Department, University of California, Berkeley, Berkeley, CA, United States
| | - Jessica B. Lyons
- Molecular and Cell Biology Department, University of California, Berkeley, Berkeley, CA, United States
| | - Trushar Shah
- Bioinformatics, International Institute of Tropical Agriculture (IITA), Nairobi, Kenya
| | - Steve Rounsley
- Seeds & Traits R&D, Dow AgroSciences, Indianapolis, IN, United States
| | - Geoffrey Mkamilo
- Cassava Breeding, Naliendele Agricultural Research Institute, Mtwara, Tanzania
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8
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Grove DJ, Levine DJ, Kearse MG. Increased levels of eIF2A inhibit translation by sequestering 40S ribosomal subunits. Nucleic Acids Res 2023; 51:9983-10000. [PMID: 37602404 PMCID: PMC10570035 DOI: 10.1093/nar/gkad683] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2022] [Revised: 08/03/2023] [Accepted: 08/09/2023] [Indexed: 08/22/2023] Open
Abstract
eIF2A was the first eukaryotic initiator tRNA carrier discovered but its exact function has remained enigmatic. Uncharacteristic of translation initiation factors, eIF2A is reported to be non-cytosolic in multiple human cancer cell lines. Attempts to study eIF2A mechanistically have been limited by the inability to achieve high yield of soluble recombinant protein. Here, we developed a purification paradigm that yields ∼360-fold and ∼6000-fold more recombinant human eIF2A from Escherichia coli and insect cells, respectively, than previous reports. Using a mammalian in vitro translation system, we found that increased levels of recombinant human eIF2A inhibit translation of multiple reporter mRNAs, including those that are translated by cognate and near-cognate start codons, and does so prior to start codon recognition. eIF2A also inhibited translation directed by all four types of cap-independent viral IRESs, including the CrPV IGR IRES that does not require initiation factors or initiator tRNA, suggesting excess eIF2A sequesters 40S subunits. Supplementation with additional 40S subunits prevented eIF2A-mediated inhibition and pull-down assays demonstrated direct binding between recombinant eIF2A and purified 40S subunits. These data support a model that eIF2A must be kept away from the translation machinery to avoid sequestering 40S ribosomal subunits.
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Affiliation(s)
- Daisy J Grove
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
- Department of Biological Chemistry and Pharmacology, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Daniel J Levine
- Department of Biological Chemistry and Pharmacology, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
| | - Michael G Kearse
- The Ohio State Biochemistry Program, The Ohio State University, Columbus, OH 43210, USA
- Department of Biological Chemistry and Pharmacology, Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA
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9
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Sonobe Y, Lee S, Krishnan G, Gu Y, Kwon DY, Gao FB, Roos RP, Kratsios P. Translation of dipeptide repeat proteins in C9ORF72 ALS/FTD through unique and redundant AUG initiation codons. eLife 2023; 12:e83189. [PMID: 37675986 PMCID: PMC10541178 DOI: 10.7554/elife.83189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 09/06/2023] [Indexed: 09/08/2023] Open
Abstract
A hexanucleotide repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). A hallmark of ALS/FTD pathology is the presence of dipeptide repeat (DPR) proteins, produced from both sense GGGGCC (poly-GA, poly-GP, poly-GR) and antisense CCCCGG (poly-PR, poly-PG, poly-PA) transcripts. Translation of sense DPRs, such as poly-GA and poly-GR, depends on non-canonical (non-AUG) initiation codons. Here, we provide evidence for canonical AUG-dependent translation of two antisense DPRs, poly-PR and poly-PG. A single AUG is required for synthesis of poly-PR, one of the most toxic DPRs. Unexpectedly, we found redundancy between three AUG codons necessary for poly-PG translation. Further, the eukaryotic translation initiation factor 2D (EIF2D), which was previously implicated in sense DPR synthesis, is not required for AUG-dependent poly-PR or poly-PG translation, suggesting that distinct translation initiation factors control DPR synthesis from sense and antisense transcripts. Our findings on DPR synthesis from the C9ORF72 locus may be broadly applicable to many other nucleotide repeat expansion disorders.
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Affiliation(s)
- Yoshifumi Sonobe
- University of Chicago Medical CenterChicagoUnited States
- Department of Neurology, University of Chicago Medical CenterChicagoUnited States
- Neuroscience Institute, University of ChicagoChicagoUnited States
| | - Soojin Lee
- RNA Therapeutics Institute, University of Massachusetts Chan Medical SchoolWorcesterUnited States
- Department of Neurology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Gopinath Krishnan
- RNA Therapeutics Institute, University of Massachusetts Chan Medical SchoolWorcesterUnited States
- Department of Neurology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Yuanzheng Gu
- Neuromuscular & Movement Disorders, BiogenCambridgeUnited States
| | - Deborah Y Kwon
- Neuromuscular & Movement Disorders, BiogenCambridgeUnited States
| | - Fen-Biao Gao
- RNA Therapeutics Institute, University of Massachusetts Chan Medical SchoolWorcesterUnited States
- Department of Neurology, University of Massachusetts Chan Medical SchoolWorcesterUnited States
| | - Raymond P Roos
- University of Chicago Medical CenterChicagoUnited States
- Department of Neurology, University of Chicago Medical CenterChicagoUnited States
- Neuroscience Institute, University of ChicagoChicagoUnited States
| | - Paschalis Kratsios
- Neuroscience Institute, University of ChicagoChicagoUnited States
- Department of Neurobiology, University of ChicagoChicagoUnited States
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10
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Malik I, Tseng YJ, Wieland CM, Green KM, Zheng K, Calleja K, Todd PK. Dissecting the roles of EIF4G homologs reveals DAP5 as a modifier of CGG repeat-associated toxicity in a Drosophila model of FXTAS. Neurobiol Dis 2023; 184:106212. [PMID: 37352983 PMCID: PMC11149892 DOI: 10.1016/j.nbd.2023.106212] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Revised: 06/19/2023] [Accepted: 06/21/2023] [Indexed: 06/25/2023] Open
Abstract
Neurodegeneration in Fragile X-associated tremor/ataxia syndrome (FXTAS) is caused by a CGG trinucleotide repeat expansion in the 5' UTR of FMR1. Expanded CGG repeat RNAs form stable secondary structures, which in turn support repeat-associated non-AUG (RAN) translation to produce toxic peptides. The parameters that impact RAN translation initiation efficiency are not well understood. Here we used a Drosophila melanogaster model of FXTAS to evaluate the role of the eIF4G family of eukaryotic translation initiation factors (EIF4G1, EIF4GII and EIF4G2/DAP5) in modulating RAN translation and CGG repeat-associated toxicity. DAP5 knockdown robustly suppressed CGG repeat-associated toxicity and inhibited RAN translation. Furthermore, knockdown of initiation factors that preferentially associate with DAP5 (such as EIF2β, EIF3F and EIF3G) also selectively suppressed CGG repeat-induced eye degeneration. In mammalian cellular reporter assays, DAP5 knockdown exhibited modest and cell-type specific effects on RAN translation. Taken together, these data support a role for DAP5 in CGG repeat associated toxicity possibly through modulation of RAN translation.
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Affiliation(s)
- Indranil Malik
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Yi-Ju Tseng
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA; Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Clare M Wieland
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA; Neuroscience Graduate Program, University of Michigan, Ann Arbor, MI, USA
| | - Katelyn M Green
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Kristina Zheng
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Katyanne Calleja
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA
| | - Peter K Todd
- Department of Neurology, University of Michigan, Ann Arbor, MI, USA; Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI, USA.
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Tseng YJ, Malik I, Deng X, Krans A, Jansen-West K, Tank EM, Gomez NB, Sher R, Petrucelli L, Barmada SJ, Todd PK. Ribosomal quality control factors inhibit repeat-associated non-AUG translation from GC-rich repeats. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.07.544135. [PMID: 37333274 PMCID: PMC10274811 DOI: 10.1101/2023.06.07.544135] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
A GGGGCC (G4C2) hexanucleotide repeat expansion in C9ORF72 causes amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD), while a CGG trinucleotide repeat expansion in FMR1 leads to the neurodegenerative disorder Fragile X-associated tremor/ataxia syndrome (FXTAS). These GC-rich repeats form RNA secondary structures that support repeat-associated non-AUG (RAN) translation of toxic proteins that contribute to disease pathogenesis. Here we assessed whether these same repeats might trigger stalling and interfere with translational elongation. We find that depletion of ribosome-associated quality control (RQC) factors NEMF, LTN1, and ANKZF1 markedly boost RAN translation product accumulation from both G4C2 and CGG repeats while overexpression of these factors reduces RAN production in both reporter cell lines and C9ALS/FTD patient iPSC-derived neurons. We also detected partially made products from both G4C2 and CGG repeats whose abundance increased with RQC factor depletion. Repeat RNA sequence, rather than amino acid content, is central to the impact of RQC factor depletion on RAN translation - suggesting a role for RNA secondary structure in these processes. Together, these findings suggest that ribosomal stalling and RQC pathway activation during RAN translation elongation inhibits the generation of toxic RAN products. We propose augmenting RQC activity as a therapeutic strategy in GC-rich repeat expansion disorders.
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Affiliation(s)
- Yi-Ju Tseng
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Indranil Malik
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Xiexiong Deng
- Department of Molecular, Cellular and Developmental Biology, Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Amy Krans
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA
- Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI, 48109, USA
| | - Karen Jansen-West
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL, 32224, USA
| | | | - Nicolas B. Gomez
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, 48109, USA
- Medical Scientist Training Program, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Roger Sher
- Department of Neurobiology and Behavior & Center for Nervous System Disorders, Stony Brook University, Stony Brook, NY, 11794, USA
| | | | - Sami J. Barmada
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Peter K. Todd
- Cellular and Molecular Biology Graduate Program, University of Michigan, Ann Arbor, MI, 48109, USA
- Department of Neurology, University of Michigan, Ann Arbor, MI, 48109, USA
- Ann Arbor Veterans Administration Healthcare, Ann Arbor, MI, 48109, USA
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Van't Spijker HM, Almeida S. How villains are made: The translation of dipeptide repeat proteins in C9ORF72-ALS/FTD. Gene 2023; 858:147167. [PMID: 36621656 PMCID: PMC9928902 DOI: 10.1016/j.gene.2023.147167] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 01/03/2023] [Indexed: 01/07/2023]
Abstract
A hexanucleotide repeat expansion in the C9ORF72 gene is the most common genetic alteration associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). These neurodegenerative diseases share genetic, clinical and pathological features. The mutation in C9ORF72 appears to drive pathogenesis through a combination of loss of C9ORF72 normal function and gain of toxic effects due to the repeat expansion, which result in aggregation prone expanded RNAs and dipeptide repeat (DPR) proteins. Studies in cellular and animal models indicate that the DPR proteins are the more toxic species. Thus, a large body of research has focused on identifying the cellular pathways most directly impacted by these toxic proteins, with the goal of characterizing disease pathogenesis and nominating potential targets for therapeutic development. The preventative block of the production of the toxic proteins before they can cause harm is a second strategy of intense focus. Despite the considerable amount of effort dedicated to this prophylactic approach, it is still unclear how the DPR proteins are synthesized from RNAs harboring repeat expansions. In this review, we summarize our current knowledge of the specific protein translation mechanisms shown to account for the synthesis of DPR proteins. We will then discuss how enhanced understanding of the composition of these toxic effectors could help in refining disease mechanisms, and paving the way to identify and design effective prophylactic therapies for C9ORF72 ALS-FTD.
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Affiliation(s)
- Heleen M Van't Spijker
- Program in Molecular Medicine, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA
| | - Sandra Almeida
- Department of Neurology, University of Massachusetts Chan Medical School, Worcester, MA 01605, USA.
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Kim H, Aponte-Diaz D, Sotoudegan MS, Shengjuler D, Arnold JJ, Cameron CE. The enterovirus genome can be translated in an IRES-independent manner that requires the initiation factors eIF2A/eIF2D. PLoS Biol 2023; 21:e3001693. [PMID: 36689548 PMCID: PMC9894558 DOI: 10.1371/journal.pbio.3001693] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Revised: 02/02/2023] [Accepted: 01/04/2023] [Indexed: 01/24/2023] Open
Abstract
RNA recombination in positive-strand RNA viruses is a molecular-genetic process, which permits the greatest evolution of the genome and may be essential to stabilizing the genome from the deleterious consequences of accumulated mutations. Enteroviruses represent a useful system to elucidate the details of this process. On the biochemical level, it is known that RNA recombination is catalyzed by the viral RNA-dependent RNA polymerase using a template-switching mechanism. For this mechanism to function in cells, the recombining genomes must be located in the same subcellular compartment. How a viral genome is trafficked to the site of genome replication and recombination, which is membrane associated and isolated from the cytoplasm, is not known. We hypothesized that genome translation was essential for colocalization of genomes for recombination. We show that complete inactivation of internal ribosome entry site (IRES)-mediated translation of a donor enteroviral genome enhanced recombination instead of impairing it. Recombination did not occur by a nonreplicative mechanism. Rather, sufficient translation of the nonstructural region of the genome occurred to support subsequent steps required for recombination. The noncanonical translation initiation factors, eIF2A and eIF2D, were required for IRES-independent translation. Our results support an eIF2A/eIF2D-dependent mechanism under conditions in which the eIF2-dependent mechanism is inactive. Detection of an IRES-independent mechanism for translation of the enterovirus genome provides an explanation for a variety of debated observations, including nonreplicative recombination and persistence of enteroviral RNA lacking an IRES. The existence of an eIF2A/eIF2D-dependent mechanism in enteroviruses predicts the existence of similar mechanisms in other viruses.
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Affiliation(s)
- Hyejeong Kim
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - David Aponte-Diaz
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Mohamad S. Sotoudegan
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | | | - Jamie J. Arnold
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
| | - Craig E. Cameron
- Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill, North Carolina, United States of America
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