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Desroches Altamirano C, Kang MK, Jordan MA, Borianne T, Dilmen I, Gnädig M, von Appen A, Honigmann A, Franzmann TM, Alberti S. eIF4F is a thermo-sensing regulatory node in the translational heat shock response. Mol Cell 2024; 84:1727-1741.e12. [PMID: 38547866 DOI: 10.1016/j.molcel.2024.02.038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 12/18/2023] [Accepted: 02/29/2024] [Indexed: 05/05/2024]
Abstract
Heat-shocked cells prioritize the translation of heat shock (HS) mRNAs, but the underlying mechanism is unclear. We report that HS in budding yeast induces the disassembly of the eIF4F complex, where eIF4G and eIF4E assemble into translationally arrested mRNA ribonucleoprotein particles (mRNPs) and HS granules (HSGs), whereas eIF4A promotes HS translation. Using in vitro reconstitution biochemistry, we show that a conformational rearrangement of the thermo-sensing eIF4A-binding domain of eIF4G dissociates eIF4A and promotes the assembly with mRNA into HS-mRNPs, which recruit additional translation factors, including Pab1p and eIF4E, to form multi-component condensates. Using extracts and cellular experiments, we demonstrate that HS-mRNPs and condensates repress the translation of associated mRNA and deplete translation factors that are required for housekeeping translation, whereas HS mRNAs can be efficiently translated by eIF4A. We conclude that the eIF4F complex is a thermo-sensing node that regulates translation during HS.
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Affiliation(s)
- Christine Desroches Altamirano
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Moo-Koo Kang
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Mareike A Jordan
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Tom Borianne
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Irem Dilmen
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Maren Gnädig
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Alexander von Appen
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Alf Honigmann
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Titus M Franzmann
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany
| | - Simon Alberti
- Biotechnology Center (BIOTEC), Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, Tatzberg 47/49, 01307 Dresden, Germany.
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2
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Villa N, Fraser CS. Human eukaryotic initiation factor 4G directly binds the 40S ribosomal subunit to promote efficient translation. J Biol Chem 2024; 300:107242. [PMID: 38569933 PMCID: PMC11063902 DOI: 10.1016/j.jbc.2024.107242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 03/15/2024] [Accepted: 03/19/2024] [Indexed: 04/05/2024] Open
Abstract
Messenger RNA (mRNA) recruitment to the 40S ribosomal subunit is mediated by eukaryotic initiation factor 4F (eIF4F). This complex includes three subunits: eIF4E (m7G cap-binding protein), eIF4A (DEAD-box helicase), and eIF4G. Mammalian eIF4G is a scaffold that coordinates the activities of eIF4E and eIF4A and provides a bridge to connect the mRNA and 40S ribosomal subunit through its interaction with eIF3. While the roles of many eIF4G binding domains are relatively clear, the precise function of RNA binding by eIF4G remains to be elucidated. In this work, we used an eIF4G-dependent translation assay to reveal that the RNA binding domain (eIF4G-RBD; amino acids 682-720) stimulates translation. This stimulating activity is observed when eIF4G is independently tethered to an internal region of the mRNA, suggesting that the eIF4G-RBD promotes translation by a mechanism that is independent of the m7G cap and mRNA tethering. Using a kinetic helicase assay, we show that the eIF4G-RBD has a minimal effect on eIF4A helicase activity, demonstrating that the eIF4G-RBD is not required to coordinate eIF4F-dependent duplex unwinding. Unexpectedly, native gel electrophoresis and fluorescence polarization assays reveal a previously unidentified direct interaction between eIF4G and the 40S subunit. Using binding assays, our data show that this 40S subunit interaction is separate from the previously characterized interaction between eIF4G and eIF3. Thus, our work reveals how eIF4F can bind to the 40S subunit using eIF3-dependent and eIF3-independent binding domains to promote translation initiation.
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Affiliation(s)
- Nancy Villa
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California, USA
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California, USA.
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3
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O'Sullivan MH, Fraser CS. Monitoring RNA restructuring in a human cell-free extract reveals eIF4A-dependent and eIF4A-independent unwinding activity. J Biol Chem 2023:104936. [PMID: 37331603 PMCID: PMC10362145 DOI: 10.1016/j.jbc.2023.104936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 06/12/2023] [Accepted: 06/14/2023] [Indexed: 06/20/2023] Open
Abstract
The canonical DEAD-box helicase, eIF4A, unwinds 5' UTR secondary structures to promote mRNA translation initiation. Growing evidence has indicated that other helicases, such as DHX29 and DDX3/ded1p, also function to promote the scanning of the 40S subunit on highly structured mRNAs. It is unknown how the relative contributions of eIF4A and other helicases regulate duplex unwinding on an mRNA to promote initiation. Here, we have adapted a real-time fluorescent duplex unwinding assay to monitor precisely helicase activity in the 5' UTR of a reporter mRNA that can be translated in a cell-free extract in parallel. We monitored the rate of 5' UTR-dependent duplex unwinding in the absence or presence of an eIF4A inhibitor (Hippuristanol), a dominant negative eIF4A (eIF4A-R362Q), or a mutant eIF4E (eIF4E-W73L) that can bind the m7G cap but not eIF4G. Our experiments reveal that the duplex unwinding activity in the cell-free extract is roughly evenly split between eIF4A-dependent and eIF4A-independent mechanisms. Importantly, we show that the robust eIF4A-independent duplex unwinding is not sufficient for translation. We also show that the m7G cap structure, and not the poly(A) tail, is the primary mRNA modification responsible for promoting duplex unwinding in our cell-free extract system. Overall, the fluorescent duplex unwinding assay provides a precise method to investigate how eIF4A-dependent and eIF4A-independent helicase activity regulates translation initiation in cell-free extracts. We anticipate that potential small molecule inhibitors could be tested for helicase inhibition using this duplex unwinding assay.
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Affiliation(s)
- Mattie H O'Sullivan
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616.
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4
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Grindheim AK, Patil SS, Nebigil CG, Désaubry L, Vedeler A. The flavagline FL3 interferes with the association of Annexin A2 with the eIF4F initiation complex and transiently stimulates the translation of annexin A2 mRNA. Front Cell Dev Biol 2023; 11:1094941. [PMID: 37250892 PMCID: PMC10214161 DOI: 10.3389/fcell.2023.1094941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 04/28/2023] [Indexed: 05/31/2023] Open
Abstract
Introduction: Annexin A2 (AnxA2) plays a critical role in cell transformation, immune response, and resistance to cancer therapy. Besides functioning as a calcium- and lipidbinding protein, AnxA2 also acts as an mRNA-binding protein, for instance, by interacting with regulatory regions of specific cytoskeleton-associated mRNAs. Methods and Results: Nanomolar concentrations of FL3, an inhibitor of the translation factor eIF4A, transiently increases the expression of AnxA2 in PC12 cells and stimulates shortterm transcription/translation of anxA2 mRNA in the rabbit reticulocyte lysate. AnxA2 regulates the translation of its cognate mRNA by a feed-back mechanism, which can partly be relieved by FL3. Results obtained using the holdup chromatographic retention assay results suggest that AnxA2 interacts transiently with eIF4E (possibly eIF4G) and PABP in an RNA-independent manner while cap pulldown experiments indicate a more stable RNA-dependent interaction. Short-term (2 h) treatment of PC12 cells with FL3 increases the amount of eIF4A in cap pulldown complexes of total lysates, but not of the cytoskeletal fraction. AnxA2 is only present in cap analogue-purified initiation complexes from the cytoskeletal fraction and not total lysates confirming that AnxA2 binds to a specific subpopulation of mRNAs. Discussion: Thus, AnxA2 interacts with PABP1 and subunits of the initiation complex eIF4F, explaining its inhibitory effect on translation by preventing the formation of the full eIF4F complex. This interaction appears to be modulated by FL3. These novel findings shed light on the regulation of translation by AnxA2 and contribute to a better understanding of the mechanism of action of eIF4A inhibitors.
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Affiliation(s)
- Ann Kari Grindheim
- Department of Biomedicine, Faculty of Medicine, University of Bergen, Bergen, Norway
| | - Sudarshan S. Patil
- Department of Biomedicine, Faculty of Medicine, University of Bergen, Bergen, Norway
| | - Canan G. Nebigil
- Regenerative Nanomedicine Laboratory (UMR1260), Faculty of Medicine, FMTS, INSERM-University of Strasbourg, Strasbourg, France
| | - Laurent Désaubry
- Regenerative Nanomedicine Laboratory (UMR1260), Faculty of Medicine, FMTS, INSERM-University of Strasbourg, Strasbourg, France
| | - Anni Vedeler
- Department of Biomedicine, Faculty of Medicine, University of Bergen, Bergen, Norway
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5
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Abstract
The eukaryotic initiation factor 4G2 (eIF4G2, DAP5, Nat1, p97) was discovered in 1997. Over the past two decades, dozens of papers have presented contradictory data on eIF4G2 function. Since its identification, eIF4G2 has been assumed to participate in noncanonical translation initiation mechanisms, but recent results indicate that it can be involved in scanning as well. In particular, eIF4G2 provides leaky scanning through some upstream open reading frames (uORFs), which are typical for long 5' UTRs of mRNAs from higher eukaryotes. It is likely the protein can also help the ribosome overcome other impediments during scanning of the 5' UTRs of animal mRNAs. This may explain the need for eIF4G2 in higher eukaryotes, as many mRNAs that encode regulatory proteins have rather long and highly structured 5' UTRs. Additionally, they often bind to various proteins, which also hamper the movement of scanning ribosomes. This review discusses the suggested mechanisms of eIF4G2 action, denotes obscure or inconsistent results, and proposes ways to uncover other fundamental mechanisms in which this important protein factor may be involved in higher eukaryotes.
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Affiliation(s)
- Ekaterina D Shestakova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119234, Russia
| | - Victoria V Smirnova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - Ivan N Shatsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - Ilya M Terenin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
- Sirius University of Science and Technology, Sochi 354349, Russia
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6
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Pelletier J, Sonenberg N. Therapeutic targeting of eukaryotic initiation factor (eIF) 4E. Biochem Soc Trans 2023; 51:113-24. [PMID: 36661272 DOI: 10.1042/BST20220285] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 01/06/2023] [Accepted: 01/10/2023] [Indexed: 01/21/2023]
Abstract
Fundamental studies unraveled the role of eukaryotic initiation factor (eIF) 4E in mRNA translation and its control. Under physiological conditions, regulation of translation by eIF4E is essential to cellular homeostasis. Under stress, gene flow information is parsed by eIF4E to support adaptive mechanisms that favor cell survival. Dysregulated eIF4E activity fuels tumor formation and progression and modulates response to therapy. Thus, there has been heightened interest in understanding eIF4E function in controlling gene expression as well as developing strategies to block its activity to treat disease.
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Feng Y, Grotegut S, Jovanovic P, Gandin V, Olson SH, Murad R, Beall A, Colayco S, De-Jesus P, Chanda S, English BP, Singer RH, Jackson M, Topisirovic I, Ronai ZA. Inhibition of coronavirus HCoV-OC43 by targeting the eIF4F complex. Front Pharmacol 2022; 13:1029093. [PMID: 36532738 PMCID: PMC9751428 DOI: 10.3389/fphar.2022.1029093] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 11/08/2022] [Indexed: 12/05/2022] Open
Abstract
The translation initiation complex 4F (eIF4F) is a rate-limiting factor in protein synthesis. Alterations in eIF4F activity are linked to several diseases, including cancer and infectious diseases. To this end, coronaviruses require eIF4F complex activity to produce proteins essential for their life cycle. Efforts to target coronaviruses by abrogating translation have been largely limited to repurposing existing eIF4F complex inhibitors. Here, we report the results of a high throughput screen to identify small molecules that disrupt eIF4F complex formation and inhibit coronavirus RNA and protein levels. Of 338,000 small molecules screened for inhibition of the eIF4F-driven, CAP-dependent translation, we identified SBI-1232 and two structurally related analogs, SBI-5844 and SBI-0498, that inhibit human coronavirus OC43 (HCoV-OC43; OC43) with minimal cell toxicity. Notably, gene expression changes after OC43 infection of Vero E6 or A549 cells were effectively reverted upon treatment with SBI-5844 or SBI-0498. Moreover, SBI-5844 or SBI-0498 treatment effectively impeded the eIF4F complex assembly, with concomitant inhibition of newly synthesized OC43 nucleocapsid protein and OC43 RNA and protein levels. Overall, we identify SBI-5844 and SBI-0498 as small molecules targeting the eIF4F complex that may limit coronavirus transcripts and proteins, thereby representing a basis for developing novel therapeutic modalities against coronaviruses.
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Affiliation(s)
- Yongmei Feng
- Cancer Center at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Stefan Grotegut
- Conrad Prebys Center for Chemical Genomics at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Predrag Jovanovic
- Lady Davis Institute, SMBD Jewish General Hospital, Gerald Bronfman Department of Oncology and Division of Experimental Medicine, McGill University, Montreal, QC, Canada
| | - Valentina Gandin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, United States
| | - Steven H. Olson
- Conrad Prebys Center for Chemical Genomics at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Rabi Murad
- Cancer Center at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Anne Beall
- Immunology and Infectious Disease Center at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Sharon Colayco
- Immunology and Infectious Disease Center at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Paul De-Jesus
- Immunology and Infectious Disease Center at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Sumit Chanda
- Immunology and Infectious Disease Center at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Brian P. English
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, United States
| | - Robert H. Singer
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, United States
| | - Michael Jackson
- Conrad Prebys Center for Chemical Genomics at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States
| | - Ivan Topisirovic
- Lady Davis Institute, SMBD Jewish General Hospital, Gerald Bronfman Department of Oncology and Division of Experimental Medicine, McGill University, Montreal, QC, Canada
| | - Ze’ev A. Ronai
- Cancer Center at Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, United States,*Correspondence: Ze’ev A. Ronai,
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8
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Izidoro MS, Sokabe M, Villa N, Merrick WC, Fraser CS. Human eukaryotic initiation factor 4E (eIF4E) and the nucleotide-bound state of eIF4A regulate eIF4F binding to RNA. J Biol Chem 2022; 298:102368. [PMID: 35963437 PMCID: PMC9483636 DOI: 10.1016/j.jbc.2022.102368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 08/05/2022] [Accepted: 08/09/2022] [Indexed: 11/30/2022] Open
Abstract
During translation initiation, the underlying mechanism by which the eukaryotic initiation factor (eIF) 4E, eIF4A, and eIF4G components of eIF4F coordinate their binding activities to regulate eIF4F binding to mRNA is poorly defined. Here, we used fluorescence anisotropy to generate thermodynamic and kinetic frameworks for the interaction of uncapped RNA with human eIF4F. We demonstrate that eIF4E binding to an autoinhibitory domain in eIF4G generates a high-affinity binding conformation of the eIF4F complex for RNA. In addition, we show that the nucleotide-bound state of the eIF4A component further regulates uncapped RNA binding by eIF4F, with a four-fold decrease in the equilibrium dissociation constant observed in the presence versus the absence of ATP. Monitoring uncapped RNA dissociation in real time reveals that ATP reduces the dissociation rate constant of RNA for eIF4F by ∼4-orders of magnitude. Thus, release of ATP from eIF4A places eIF4F in a dynamic state that has very fast association and dissociation rates from RNA. Monitoring the kinetic framework for eIF4A binding to eIF4G revealed two different rate constants that likely reflect two conformational states of the eIF4F complex. Furthermore, we determined that the eIF4G autoinhibitory domain promotes a more stable, less dynamic, eIF4A-binding state, which is overcome by eIF4E binding. Overall, our data support a model whereby eIF4E binding to eIF4G/4A stabilizes a high-affinity RNA-binding state of eIF4F and enables eIF4A to adopt a more dynamic interaction with eIF4G. This dynamic conformation may contribute to the ability of eIF4F to rapidly bind and release mRNA during scanning.
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Affiliation(s)
- Mario Servulo Izidoro
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616
| | - Nancy Villa
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616
| | - William C Merrick
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616.
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9
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Condé L, Allatif O, Ohlmann T, de Breyne S. Translation of SARS-CoV-2 gRNA Is Extremely Efficient and Competitive despite a High Degree of Secondary Structures and the Presence of an uORF. Viruses 2022; 14:1505. [PMID: 35891485 PMCID: PMC9322171 DOI: 10.3390/v14071505] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 07/06/2022] [Accepted: 07/07/2022] [Indexed: 12/15/2022] Open
Abstract
The SARS-CoV-2 infection generates up to nine different sub-genomic mRNAs (sgRNAs), in addition to the genomic RNA (gRNA). The 5'UTR of each viral mRNA shares the first 75 nucleotides (nt.) at their 5'end, called the leader, but differentiates by a variable sequence (0 to 190 nt. long) that follows the leader. As a result, each viral mRNA has its own specific 5'UTR in term of length, RNA structure, uORF and Kozak context; each one of these characteristics could affect mRNA expression. In this study, we have measured and compared translational efficiency of each of the ten viral transcripts. Our data show that most of them are very efficiently translated in all translational systems tested. Surprisingly, the gRNA 5'UTR, which is the longest and the most structured, was also the most efficient to initiate translation. This property is conserved in the 5'UTR of SARS-CoV-1 but not in MERS-CoV strain, mainly due to the regulation imposed by the uORF. Interestingly, the translation initiation mechanism on the SARS-CoV-2 gRNA 5'UTR requires the cap structure and the components of the eIF4F complex but showed no dependence in the presence of the poly(A) tail in vitro. Our data strongly suggest that translation initiation on SARS-CoV-2 mRNAs occurs via an unusual cap-dependent mechanism.
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Affiliation(s)
| | | | - Théophile Ohlmann
- CIRI, Centre International de Recherche en Infectiologie, (Team Ohlmann), Univ Lyon, Inserm U1111, Université Claude Bernard Lyon 1, CNRS UMR5308, ENS de Lyon, F-69007 Lyon, France; (L.C.); (O.A.)
| | - Sylvain de Breyne
- CIRI, Centre International de Recherche en Infectiologie, (Team Ohlmann), Univ Lyon, Inserm U1111, Université Claude Bernard Lyon 1, CNRS UMR5308, ENS de Lyon, F-69007 Lyon, France; (L.C.); (O.A.)
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10
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Biziaev NS, Egorova TV, Alkalaeva EZ. [Dynamics of Eukaryotic mRNA Structure during Translation]. Mol Biol (Mosk) 2022; 56:451-464. [PMID: 35621099 DOI: 10.31857/s002689842203003x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 12/07/2021] [Indexed: 06/15/2023]
Abstract
Currently, there is no single concept of the optimal spatial structure of mRNA during translation. It is known that many proteins, associated with the 5' end of mRNA, interact with proteins associated with the 3' end. Moreover, this interaction often affects the activity of these proteins. It is possible within the same mRNA molecule only when the mRNA forms a circular structure in which its ends are spatially close. Discovery of such proteins, in the 90s of the 20th century, made it possible to formulate the closed-loop mRNA structure hypothesis, in which it is assumed that the ends of translationally active mRNA are fixed next to each other due to the interaction of proteins and (or) RNA. However, later it was shown that a closed-loop structure is not always necessary for translation. Moreover, some authors have proposed a model according to which the translating mRNA, on the contrary, should be unfolded into a linear structure. Thus, the spatial structure of the translating mRNA does not have to be universal for all mRNA and can change dynamically, which affects its functional activity. In this review, we have summarized a variety of experimental data and concepts on the relationship between the spatial structure of mRNA and its translational activity.
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Affiliation(s)
- N S Biziaev
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991 Russia
| | - T V Egorova
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991 Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Moscow, 119991 Russia
| | - E Z Alkalaeva
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991 Russia
- Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Moscow, 119991 Russia
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11
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Maracci C, Motta S, Romagnoli A, Costantino M, Perego P, Di Marino D. The mTOR/4E-BP1/eIF4E signalling pathway as source of cancer drug targets. Curr Med Chem 2022; 29:3501-3529. [PMID: 35209811 DOI: 10.2174/0929867329666220224112042] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 12/23/2021] [Accepted: 01/01/2022] [Indexed: 11/22/2022]
Abstract
The mechanistic/mammalian target of rapamycin (mTOR) is the crucial hub of signalling pathways that regulate essential steps in the cell life cycle. Once incorporated in the mTORC1 complex, mTOR phosphorylates the eukaryotic initiation factor 4E (eIF4E)- binding protein 1 (4E-BP1), which then releases eIF4E. When not bound to 4E-BPs, eIF4E recognizes the mRNA 5'-cap structure and, together with eIF4A and eIF4G, it forms the eIF4F complex that recruits the ribosome on the mRNA. Under normal conditions, the cellular concentration of eIF4E is very low, making eIF4E the limiting factor in the initiation of protein synthesis. The vast majority of cancer types are characterized by the simultaneous deregulation of the mTOR/4E-BP1 signaling pathway and upregulation of eIF4E, which lead to an increased expression of cancer-promoting genes and deregulated cellular growth. Over the last decades, a growing number of selective inhibitors of the mTOR/4E-BP1/eIF4E pathway have been discovered or designed. Several inhibitors with encouraging preclinical results have been tested in clinical trials. This review summarizes the most recent research on drug development against mTOR, 4E-BP1 and eIF4E, describing the design rationale and the available structural and functional data on the most promising compounds.
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Affiliation(s)
- Cristina Maracci
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy
| | - Stefano Motta
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
- Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
| | - Alice Romagnoli
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy
| | - Matteo Costantino
- Molecular Pharmacology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Paola Perego
- Molecular Pharmacology Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy
| | - Daniele Di Marino
- Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy
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12
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Xu X, Ahmed T, Wang L, Cao X, Zhang Z, Wang M, Lv Y, Kanwal S, Tariq M, Lin R, Zhang H, Huang Y, Peng H, Lin D, Shi X, Geng D, Liu B, Zhang X, Yi W, Qin Y, Esteban MA, Qin B. The mTORC1- eIF4F axis controls paused pluripotency. EMBO Rep 2022; 23:e53081. [PMID: 34866316 PMCID: PMC8811634 DOI: 10.15252/embr.202153081] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 11/01/2021] [Accepted: 11/16/2021] [Indexed: 02/05/2023] Open
Abstract
Mouse embryonic stem cells (mESCs) can self-renew indefinitely and maintain pluripotency. Inhibition of mechanistic target of rapamycin (mTOR) by the kinase inhibitor INK128 is known to induce paused pluripotency in mESCs cultured with traditional serum/LIF medium (SL), but the underlying mechanisms remain unclear. In this study, we demonstrate that mTOR complex 1 (mTORC1) but not complex 2 (mTORC2) mediates mTOR inhibition-induced paused pluripotency in cells grown in both SL and 2iL medium (GSK3 and MEK inhibitors and LIF). We also show that mTORC1 regulates self-renewal in both conditions mainly through eIF4F-mediated translation initiation that targets mRNAs of both cytosolic and mitochondrial ribosome subunits. Moreover, inhibition of mitochondrial translation is sufficient to induce paused pluripotency. Interestingly, eIF4F also regulates maintenance of pluripotency in an mTORC1-independent but MEK/ERK-dependent manner in SL, indicating that translation of pluripotency genes is controlled differently in SL and 2iL. Our study reveals a detailed picture of how mTOR governs self-renewal in mESCs and uncovers a context-dependent function of eIF4F in pluripotency regulation.
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Affiliation(s)
- Xueting Xu
- School of Life SciencesUniversity of Science and Technology of ChinaHefeiChina,CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina
| | - Tanveer Ahmed
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina
| | - Lulu Wang
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina
| | - Xintao Cao
- Key Laboratory of RNA BiologyInstitute of BiophysicsChinese Academy of SciencesBeijingChina
| | - Zeyu Zhang
- Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory)GuangzhouChina
| | - Ming Wang
- Guangdong Key Laboratory of Genome Stability and Human Disease PreventionDepartment of Biochemistry & Molecular BiologyShenzhen University Health Science CenterShenzhenChina
| | - Yuan Lv
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,University of Chinese Academy of SciencesBeijingChina,Laboratory of Integrative BiologyGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina
| | - Shahzina Kanwal
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Integrative BiologyGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina
| | - Muqddas Tariq
- Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory)GuangzhouChina
| | - Runxia Lin
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,University of Chinese Academy of SciencesBeijingChina
| | - Hui Zhang
- Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory)GuangzhouChina
| | - Yinghua Huang
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina
| | - Hao Peng
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,University of Chinese Academy of SciencesBeijingChina
| | - Danni Lin
- School of Life SciencesUniversity of Science and Technology of ChinaHefeiChina,CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina
| | - Xue Shi
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,University of Chinese Academy of SciencesBeijingChina
| | - Didi Geng
- MOE Key Laboratory of Biosystems Homeostasis & ProtectionCollege of Life SciencesZhejiang UniversityHangzhouChina
| | - Baohua Liu
- Guangdong Key Laboratory of Genome Stability and Human Disease PreventionDepartment of Biochemistry & Molecular BiologyShenzhen University Health Science CenterShenzhenChina
| | - Xiaofei Zhang
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory)GuangzhouChina,University of Chinese Academy of SciencesBeijingChina
| | - Wen Yi
- MOE Key Laboratory of Biosystems Homeostasis & ProtectionCollege of Life SciencesZhejiang UniversityHangzhouChina
| | - Yan Qin
- Key Laboratory of RNA BiologyInstitute of BiophysicsChinese Academy of SciencesBeijingChina
| | - Miguel A Esteban
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory)GuangzhouChina,University of Chinese Academy of SciencesBeijingChina,Laboratory of Integrative BiologyGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Institute of Stem Cells and RegenerationChinese Academy of SciencesBeijingChina,Joint School of Life SciencesGuangzhou Institutes of Biomedicine and Health and Guangzhou Medical UniversityGuangzhouChina
| | - Baoming Qin
- CAS Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cells and Regenerative Medicine, GIBH‐HKU Guangdong‐Hong Kong Stem Cell and Regenerative Medicine Research Center, Guangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Laboratory of Metabolism and Cell FateGuangzhou Institutes of Biomedicine and HealthChinese Academy of SciencesGuangzhouChina,Bioland Laboratory (Guangzhou Regenerative Medicine and Health Guangdong Laboratory)GuangzhouChina,University of Chinese Academy of SciencesBeijingChina,Joint School of Life SciencesGuangzhou Institutes of Biomedicine and Health and Guangzhou Medical UniversityGuangzhouChina
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13
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Wu S, Wagner G. Deep computational analysis details dysregulation of eukaryotic translation initiation complex eIF4F in human cancers. Cell Syst 2021; 12:907-923.e6. [PMID: 34358439 DOI: 10.1016/j.cels.2021.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 04/22/2021] [Accepted: 07/09/2021] [Indexed: 12/28/2022]
Abstract
eIF4F plays diverse roles in human cancers, which complicate the development of an overarching understanding of its functional and regulatory impacts across tumor types. Typically, eIF4F drives initiation from the mRNA 5' end (cap) and is composed of eIF4G1, eIF4A1, and cap-binding eIF4E. Cap-independent initiation is possible without eIF4E, from internal ribosomal entry sites (IRESs). By analyzing large public datasets, we found that cancers selectively overexpress EIF4G1 more than EIF4E. That expression imbalance supports EIF4G1 as a prognostic indicator in patients with cancer. It also attenuates "housekeeping" pathways that are usually regulated in a tissue-specific manner via cap-dependent initiation in healthy tissues and reinforce regulation of cancer-preferred pathways in cap-independent contexts. Cap-independent initiation is mechanistically attributable to eIF4G1 hyperphosphorylation that promotes binding to eIF4A1 and reduced eIF4E availability. Collectively, these findings reveal a novel model of dysregulated eIF4F function and highlight the clinical relevance of cap-(in)dependent initiation in cancer.
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Affiliation(s)
- Su Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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14
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Chu J, Zhang W, Cencic R, O'Connor PBF, Robert F, Devine WG, Selznick A, Henkel T, Merrick WC, Brown LE, Baranov PV, Porco JA, Pelletier J. Rocaglates Induce Gain-of-Function Alterations to eIF4A and eIF4F. Cell Rep 2021; 30:2481-2488.e5. [PMID: 32101697 PMCID: PMC7077502 DOI: 10.1016/j.celrep.2020.02.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 12/13/2019] [Accepted: 01/31/2020] [Indexed: 12/31/2022] Open
Abstract
Rocaglates are a diverse family of biologically active molecules that have gained tremendous interest in recent years due to their promising activities in pre-clinical cancer studies. As a result, this family of compounds has been significantly expanded through the development of efficient synthetic schemes. However, it is unknown whether all of the members of the rocaglate family act through similar mechanisms of action. Here, we present a comprehensive study comparing the biological activities of >200 rocaglates to better understand how the presence of different chemical entities influences their biological activities. Through this, we find that most rocaglates preferentially repress the translation of mRNAs containing purine-rich 5′ leaders, but certain rocaglates lack this bias in translation repression. We also uncover an aspect of rocaglate mechanism of action in which the pool of translationally active eIF4F is diminished due to the sequestration of the complex onto RNA. Rocaglates are a diverse family of small molecules that inhibit eIF4A. Chu et al. undertake a comparative analysis of the bioactivity of >200 rocaglates and uncover nuances in their mechanisms of action. Rocaglates interfere with eIF4F release from the cap and exert a bystander effect to inhibit translation.
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Affiliation(s)
- Jennifer Chu
- Department of Biochemistry, McGill University, Montreal, QC, Canada
| | - Wenhan Zhang
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA
| | - Regina Cencic
- Department of Biochemistry, McGill University, Montreal, QC, Canada
| | | | - Francis Robert
- Department of Biochemistry, McGill University, Montreal, QC, Canada
| | - William G Devine
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA
| | - Asher Selznick
- Department of Biochemistry, McGill University, Montreal, QC, Canada
| | | | - William C Merrick
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH 44106-4935, USA
| | - Lauren E Brown
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland; Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russia
| | - John A Porco
- Department of Chemistry and Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA.
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, QC, Canada; Department of Oncology, McGill University, Montreal, QC, Canada; Rosalind & Morris Goodman Cancer Research Centre, McGill University, Montreal, QC, Canada.
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15
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Naineni SK, Liang J, Hull K, Cencic R, Zhu M, Northcote P, Teesdale-Spittle P, Romo D, Nagar B, Pelletier J. Functional mimicry revealed by the crystal structure of an eIF4A:RNA complex bound to the interfacial inhibitor, desmethyl pateamine A. Cell Chem Biol 2021; 28:825-834.e6. [PMID: 33412110 DOI: 10.1016/j.chembiol.2020.12.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 11/15/2020] [Accepted: 12/16/2020] [Indexed: 12/17/2022]
Abstract
Interfacial inhibitors exert their biological effects through co-association with two macromolecules. The pateamine A (PatA) class of molecules function by stabilizing eukaryotic initiation factor (eIF) 4A RNA helicase onto RNA, resulting in translation initiation inhibition. Here, we present the crystal structure of an eIF4A1:RNA complex bound to an analog of the marine sponge-derived natural product PatA, C5-desmethyl PatA (DMPatA). One end of this small molecule wedges itself between two RNA bases while the other end is cradled by several protein residues. Strikingly, DMPatA interacts with the eIF4A1:RNA complex in an almost identical fashion as rocaglamide A (RocA), despite being completely unrelated from a structural standpoint. The structural data rationalize the ability of PatA analogs to target a wider range of RNA substrates compared to RocA. We define the molecular basis of how DMPatA is able to clamp eIF4A1 onto RNA, imparting potent inhibitory properties to this molecule.
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16
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Abstract
The stage at which ribosomes are recruited to messenger RNAs (mRNAs) is an elaborate and highly regulated phase of protein synthesis. Upon completion of this step, a ribosome is positioned at an appropriate initiation codon and primed to synthesize the encoded polypeptide product. In most circumstances, this step commits the ribosome to translate the mRNA. We summarize the knowledge regarding the initiation factors implicated in this activity as well as review different mechanisms by which this process is conducted.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada; , .,Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Quebec H3A 1A3, Canada.,Department of Oncology, McGill University, Montreal, Quebec H4A 3T2, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada; , .,Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Quebec H3A 1A3, Canada
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17
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Naineni SK, Itoua Maïga R, Cencic R, Putnam AA, Amador LA, Rodriguez AD, Jankowsky E, Pelletier J. A comparative study of small molecules targeting eIF4A. RNA 2020; 26:541-549. [PMID: 32014999 PMCID: PMC7161356 DOI: 10.1261/rna.072884.119] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 01/30/2020] [Indexed: 05/13/2023]
Abstract
The PI3K/Akt/mTOR kinase pathway is extensively deregulated in human cancers. One critical node under regulation of this signaling axis is eukaryotic initiation factor (eIF) 4F, a complex involved in the control of translation initiation rates. eIF4F-dependent addictions arise during tumor initiation and maintenance due to increased eIF4F activity-generally in response to elevated PI3K/Akt/mTOR signaling flux. There is thus much interest in exploring eIF4F as a small molecule target for the development of new anticancer drugs. The DEAD-box RNA helicase, eIF4A, is an essential subunit of eIF4F, and several potent small molecules (rocaglates, hippuristanol, pateamine A) affecting its activity have been identified and shown to demonstrate anticancer activity in vitro and in vivo in preclinical models. Recently, a number of new small molecules have been reported as having the capacity to target and inhibit eIF4A. Here, we undertook a comparative analysis of their biological activity and specificity relative to the eIF4A inhibitor, hippuristanol.
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Affiliation(s)
- Sai Kiran Naineni
- Department of Biochemistry, McGill University, Montreal, Québec H3G 1Y6, Canada
| | - Rayelle Itoua Maïga
- Department of Biochemistry, McGill University, Montreal, Québec H3G 1Y6, Canada
| | - Regina Cencic
- Department of Biochemistry, McGill University, Montreal, Québec H3G 1Y6, Canada
| | - Andrea A Putnam
- School of Medicine, Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Luis A Amador
- Department of Chemistry, Faculty of Natural Sciences, University of Puerto Rico, San Juan, 00931-3346, Puerto Rico
| | - Abimael D Rodriguez
- Department of Chemistry, Faculty of Natural Sciences, University of Puerto Rico, San Juan, 00931-3346, Puerto Rico
| | - Eckhard Jankowsky
- School of Medicine, Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, Ohio 44106, USA
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Québec H3G 1Y6, Canada
- Department of Oncology, McGill University, Montreal, Québec H4A 3T2, Canada
- Rosalind & Morris Goodman Cancer Research Centre, McGill University, Montreal, Québec H3A 1A3, Canada
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18
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Pringle ES, Robinson CA, McCormick C. Kaposi's Sarcoma-Associated Herpesvirus Lytic Replication Interferes with mTORC1 Regulation of Autophagy and Viral Protein Synthesis. J Virol 2019; 93:e00854-19. [PMID: 31375594 DOI: 10.1128/JVI.00854-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/30/2019] [Indexed: 12/20/2022] Open
Abstract
All viruses require host cell machinery to synthesize viral proteins. A host cell protein complex known as mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of protein synthesis. Under nutrient-rich conditions, mTORC1 is active and promotes protein synthesis to meet cellular anabolic demands. Under nutrient-poor conditions or under stress, mTORC1 is rapidly inhibited, global protein synthesis is arrested, and a cellular catabolic process known as autophagy is activated. Kaposi’s sarcoma-associated herpesvirus (KSHV) stimulates mTORC1 activity and utilizes host machinery to synthesize viral proteins. However, we discovered that mTORC1 activity was largely dispensable for viral protein synthesis, genome replication, and the release of infectious progeny. Likewise, during lytic replication, mTORC1 was no longer able to control autophagy. These findings suggest that KSHV undermines mTORC1-dependent cellular processes during the lytic cycle to ensure efficient viral replication. Mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of cellular metabolism. In nutrient-rich environments, mTORC1 kinase activity stimulates protein synthesis to meet cellular anabolic demands. Under nutrient-poor conditions or under stress, mTORC1 is rapidly inhibited, global protein synthesis is arrested, and a cellular catabolic process known as autophagy is activated. Kaposi’s sarcoma-associated herpesvirus (KSHV) encodes multiple proteins that stimulate mTORC1 activity or subvert autophagy, but precise roles for mTORC1 in different stages of KSHV infection remain incompletely understood. Here, we report that during latent and lytic stages of KSHV infection, chemical inhibition of mTORC1 caused eukaryotic initiation factor 4F (eIF4F) disassembly and diminished global protein synthesis, which indicated that mTORC1-mediated control of translation initiation was largely intact. We observed that mTORC1 was required for synthesis of the replication and transcription activator (RTA) lytic switch protein and reactivation from latency, but once early lytic gene expression had begun, mTORC1 was not required for genome replication, late gene expression, or the release of infectious progeny. Moreover, mTORC1 control of autophagy was dysregulated during lytic replication, whereby chemical inhibition of mTORC1 prevented ULK1 phosphorylation but did not affect autophagosome formation or rates of autophagic flux. Together, these findings suggest that mTORC1 is dispensable for viral protein synthesis and viral control of autophagy during lytic infection and that KSHV undermines mTORC1-dependent cellular processes during the lytic cycle to ensure efficient viral replication. IMPORTANCE All viruses require host cell machinery to synthesize viral proteins. A host cell protein complex known as mechanistic target of rapamycin complex 1 (mTORC1) is a master regulator of protein synthesis. Under nutrient-rich conditions, mTORC1 is active and promotes protein synthesis to meet cellular anabolic demands. Under nutrient-poor conditions or under stress, mTORC1 is rapidly inhibited, global protein synthesis is arrested, and a cellular catabolic process known as autophagy is activated. Kaposi’s sarcoma-associated herpesvirus (KSHV) stimulates mTORC1 activity and utilizes host machinery to synthesize viral proteins. However, we discovered that mTORC1 activity was largely dispensable for viral protein synthesis, genome replication, and the release of infectious progeny. Likewise, during lytic replication, mTORC1 was no longer able to control autophagy. These findings suggest that KSHV undermines mTORC1-dependent cellular processes during the lytic cycle to ensure efficient viral replication.
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19
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Shirokikh NE, Dutikova YS, Staroverova MA, Hannan RD, Preiss T. Migration of Small Ribosomal Subunits on the 5' Untranslated Regions of Capped Messenger RNA. Int J Mol Sci 2019; 20:E4464. [PMID: 31510048 DOI: 10.3390/ijms20184464] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 09/01/2019] [Accepted: 09/05/2019] [Indexed: 12/12/2022] Open
Abstract
Several control mechanisms of eukaryotic gene expression target the initiation step of mRNA translation. The canonical translation initiation pathway begins with cap-dependent attachment of the small ribosomal subunit (SSU) to the messenger ribonucleic acid (mRNA) followed by an energy-dependent, sequential ‘scanning’ of the 5′ untranslated regions (UTRs). Scanning through the 5′UTR requires the adenosine triphosphate (ATP)-dependent RNA helicase eukaryotic initiation factor (eIF) 4A and its efficiency contributes to the specific rate of protein synthesis. Thus, understanding the molecular details of the scanning mechanism remains a priority task for the field. Here, we studied the effects of inhibiting ATP-dependent translation and eIF4A in cell-free translation and reconstituted initiation reactions programmed with capped mRNAs featuring different 5′UTRs. An aptamer that blocks eIF4A in an inactive state away from mRNA inhibited translation of capped mRNA with the moderately structured β-globin sequences in the 5′UTR but not that of an mRNA with a poly(A) sequence as the 5′UTR. By contrast, the nonhydrolysable ATP analogue β,γ-imidoadenosine 5′-triphosphate (AMP-PNP) inhibited translation irrespective of the 5′UTR sequence, suggesting that complexes that contain ATP-binding proteins in their ATP-bound form can obstruct and/or actively block progression of ribosome recruitment and/or scanning on mRNA. Further, using primer extension inhibition to locate SSUs on mRNA (‘toeprinting’), we identify an SSU complex which inhibits primer extension approximately eight nucleotides upstream from the usual toeprinting stop generated by SSUs positioned over the start codon. This ‘−8 nt toeprint’ was seen with mRNA 5′UTRs of different length, sequence and structure potential. Importantly, the ‘−8 nt toeprint’ was strongly stimulated by the presence of the cap on the mRNA, as well as the presence of eIFs 4F, 4A/4B and ATP, implying active scanning. We assembled cell-free translation reactions with capped mRNA featuring an extended 5′UTR and used cycloheximide to arrest elongating ribosomes at the start codon. Impeding scanning through the 5′UTR in this system with elevated magnesium and AMP-PNP (similar to the toeprinting conditions), we visualised assemblies consisting of several SSUs together with one full ribosome by electron microscopy, suggesting direct detection of scanning intermediates. Collectively, our data provide additional biochemical, molecular and physical evidence to underpin the scanning model of translation initiation in eukaryotes.
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20
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Chu J, Zhang W, Cencic R, Devine WG, Beglov D, Henkel T, Brown LE, Vajda S, Porco JA, Pelletier J. Amidino-Rocaglates: A Potent Class of eIF4A Inhibitors. Cell Chem Biol 2019; 26:1586-1593.e3. [PMID: 31519508 DOI: 10.1016/j.chembiol.2019.08.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2019] [Revised: 07/28/2019] [Accepted: 08/21/2019] [Indexed: 12/16/2022]
Abstract
Rocaglates share a common cyclopenta[b]benzofuran core that inhibits eukaryotic translation initiation by modifying the behavior of the RNA helicase, eIF4A. Working as interfacial inhibitors, rocaglates stabilize the association between eIF4A and RNA, which can lead to the formation of steric barriers that block initiating ribosomes. There is significant interest in the development and expansion of rocaglate derivatives, as several members of this family have been shown to possess potent anti-neoplastic activity in vitro and in vivo. To further our understanding of rocaglate diversity and drug design, herein we explore the RNA clamping activity of >200 unique rocaglate derivatives. Through this, we report on the identification and characterization of a potent class of synthetic rocaglates called amidino-rocaglates. These compounds are among the most potent rocaglates documented to date and, taken together, this work offers important information that will guide the future design of rocaglates with improved biological properties.
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Affiliation(s)
- Jennifer Chu
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Wenhan Zhang
- Department of Chemistry, 590 Commonwealth Avenue, Boston University, Boston, MA 02215, USA; Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA
| | - Regina Cencic
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada
| | - William G Devine
- Department of Chemistry, 590 Commonwealth Avenue, Boston University, Boston, MA 02215, USA; Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA
| | - Dmitri Beglov
- Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | | | - Lauren E Brown
- Department of Chemistry, 590 Commonwealth Avenue, Boston University, Boston, MA 02215, USA; Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA
| | - Sandor Vajda
- Department of Chemistry, 590 Commonwealth Avenue, Boston University, Boston, MA 02215, USA; Department of Biomedical Engineering, Boston University, Boston, MA, USA
| | - John A Porco
- Department of Chemistry, 590 Commonwealth Avenue, Boston University, Boston, MA 02215, USA; Center for Molecular Discovery (BU-CMD), Boston University, Boston, MA, USA.
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada; Department of Oncology, McGill University, Montreal, Canada; Rosalind & Morris Goodman Cancer Research Centre, McGill University, Montreal, Canada.
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21
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Howard CM, Bearss N, Subramaniyan B, Tilley A, Sridharan S, Villa N, Fraser CS, Raman D. The CXCR4-LASP1- eIF4F Axis Promotes Translation of Oncogenic Proteins in Triple-Negative Breast Cancer Cells. Front Oncol 2019; 9:284. [PMID: 31106142 PMCID: PMC6499106 DOI: 10.3389/fonc.2019.00284] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 03/28/2019] [Indexed: 12/19/2022] Open
Abstract
Triple-negative breast cancer (TNBC) remains clinically challenging as effective targeted therapies are lacking. In addition, patient mortality mainly results from the metastasized lesions. CXCR4 has been identified to be one of the major chemokine receptors involved in breast cancer metastasis. Previously, our lab had identified LIM and SH3 Protein 1 (LASP1) to be a key mediator in CXCR4-driven invasion. To further investigate the role of LASP1 in this process, a proteomic screen was employed and identified a novel protein-protein interaction between LASP1 and components of eukaryotic initiation 4F complex (eIF4F). We hypothesized that activation of the CXCR4-LASP1-eIF4F axis may contribute to the preferential translation of oncogenic mRNAs leading to breast cancer progression and metastasis. To test this hypothesis, we first confirmed that the gene expression of CXCR4, LASP1, and eIF4A are upregulated in invasive breast cancer. Moreover, we demonstrate that LASP1 associated with eIF4A in a CXCL12-dependent manner via a proximity ligation assay. We then confirmed this finding, and the association of LASP1 with eIF4B via co-immunoprecipitation assays. Furthermore, we show that LASP1 can interact with eIF4A and eIF4B through a GST-pulldown approach. Activation of CXCR4 signaling increased the translation of oncoproteins downstream of eIF4A. Interestingly, genetic silencing of LASP1 interrupted the ability of eIF4A to translate oncogenic mRNAs into oncoproteins. This impaired ability of eIF4A was confirmed by a previously established 5′UTR luciferase reporter assay. Finally, lack of LASP1 sensitizes 231S cells to pharmacological inhibition of eIF4A by Rocaglamide A as evident through BIRC5 expression. Overall, our work identified the CXCR4-LASP1 axis to be a novel mediator in oncogenic protein translation. Thus, our axis of study represents a potential target for future TNBC therapies.
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Affiliation(s)
- Cory M Howard
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, OH, United States
| | - Nicole Bearss
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, OH, United States
| | - Boopathi Subramaniyan
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, OH, United States
| | - Augustus Tilley
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, OH, United States
| | - Sangita Sridharan
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, OH, United States
| | - Nancy Villa
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA, United States
| | - Dayanidhi Raman
- Department of Cancer Biology, University of Toledo Health Science Campus, Toledo, OH, United States
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22
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Liu X, Schuessler PJ, Sahoo A, Walker SE. Reconstitution and analyses of RNA interactions with eukaryotic translation initiation factors and ribosomal preinitiation complexes. Methods 2019; 162-163:42-53. [PMID: 30926531 DOI: 10.1016/j.ymeth.2019.03.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 03/22/2019] [Accepted: 03/23/2019] [Indexed: 11/25/2022] Open
Abstract
Control of translation initiation plays a critical role in the regulation of gene expression in all organisms, yet the mechanics of translation initiation in eukaryotic organisms are not well understood. Confounding studies of translation are the large number and overlapping functions of many initiation factors in cells, and a lack of cap-dependence in many in vitro systems. To shed light on intricate mechanisms that are often obscured in vivo, we use a fully reconstituted translation initiation system for analyzing RNA interactions with eukaryotic translation initiation factors and complexes from the model organism Saccharomyces cerevisiae. This system exhibits strong cap dependence, and dependence on translation factors varies with mRNA 5' UTR sequences as expected from genome-wide studies of translation. Here we provide optimized protocols for purification and analysis of the effects of labeled and unlabeled mRNA recruitment factors on both the rate and factor dependence of mRNA recruitment to the translation preinitiation complex in response to RNA sequence- and structure-changes. In addition to providing streamlined and detailed protocols, we describe a new construct for purification of higher yields of fluorescently labeled and unlabeled full-length eIF4G.
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Affiliation(s)
- Xiaozhuo Liu
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States
| | - Peter J Schuessler
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States
| | - Ansuman Sahoo
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States
| | - Sarah E Walker
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States.
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23
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Abstract
Over the past 15 years, sequencing of the human genome and The Cancer Genome Atlas (TCGA) project have led to comprehensive lists of single-nucleotide polymorphisms (SNPs) and gene mutations across a large number of human samples. However, our ability to predict the functional impact of SNPs and mutations on gene expression is still in its infancy. Here, we provide key examples to help understand how mutations present in genes can affect translational output.
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Affiliation(s)
- Francis Robert
- Department of Biochemistry, McGill University, Montreal, QC, Canada
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, QC, Canada.,Department of Oncology, McGill University, Montreal, QC, Canada.,Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, QC, Canada
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24
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Yourik P, Aitken CE, Zhou F, Gupta N, Hinnebusch AG, Lorsch JR. Yeast eIF4A enhances recruitment of mRNAs regardless of their structural complexity. eLife 2017; 6:31476. [PMID: 29192585 PMCID: PMC5726853 DOI: 10.7554/elife.31476] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2017] [Accepted: 11/23/2017] [Indexed: 12/11/2022] Open
Abstract
eIF4A is a DEAD-box RNA-dependent ATPase thought to unwind RNA secondary structure in the 5'-untranslated regions (UTRs) of mRNAs to promote their recruitment to the eukaryotic translation pre-initiation complex (PIC). We show that eIF4A's ATPase activity is markedly stimulated in the presence of the PIC, independently of eIF4E•eIF4G, but dependent on subunits i and g of the heteromeric eIF3 complex. Surprisingly, eIF4A accelerated the rate of recruitment of all mRNAs tested, regardless of their degree of structural complexity. Structures in the 5'-UTR and 3' of the start codon synergistically inhibit mRNA recruitment in a manner relieved by eIF4A, indicating that the factor does not act solely to melt hairpins in 5'-UTRs. Our findings that eIF4A functionally interacts with the PIC and plays important roles beyond unwinding 5'-UTR structure is consistent with a recent proposal that eIF4A modulates the conformation of the 40S ribosomal subunit to promote mRNA recruitment.
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Affiliation(s)
- Paul Yourik
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Colin Echeverría Aitken
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Fujun Zhou
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Neha Gupta
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Jon R Lorsch
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
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25
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Costello JL, Kershaw CJ, Castelli LM, Talavera D, Rowe W, Sims PFG, Ashe MP, Grant CM, Hubbard SJ, Pavitt GD. Dynamic changes in eIF4F-mRNA interactions revealed by global analyses of environmental stress responses. Genome Biol 2017; 18:201. [PMID: 29078784 PMCID: PMC5660459 DOI: 10.1186/s13059-017-1338-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 10/13/2017] [Indexed: 11/29/2022] Open
Abstract
Background Translation factors eIF4E and eIF4G form eIF4F, which interacts with the messenger RNA (mRNA) 5′ cap to promote ribosome recruitment and translation initiation. Variations in the association of eIF4F with individual mRNAs likely contribute to differences in translation initiation frequencies between mRNAs. As translation initiation is globally reprogrammed by environmental stresses, we were interested in determining whether eIF4F interactions with individual mRNAs are reprogrammed and how this may contribute to global environmental stress responses. Results Using a tagged-factor protein capture and RNA-sequencing (RNA-seq) approach, we have assessed how mRNA associations with eIF4E, eIF4G1 and eIF4G2 change globally in response to three defined stresses that each cause a rapid attenuation of protein synthesis: oxidative stress induced by hydrogen peroxide and nutrient stresses caused by amino acid or glucose withdrawal. We find that acute stress leads to dynamic and unexpected changes in eIF4F–mRNA interactions that are shared among each factor and across the stresses imposed. eIF4F–mRNA interactions stabilised by stress are predominantly associated with translational repression, while more actively initiating mRNAs become relatively depleted for eIF4F. Simultaneously, other mRNAs are insulated from these stress-induced changes in eIF4F association. Conclusion Dynamic eIF4F–mRNA interaction changes are part of a coordinated early translational control response shared across environmental stresses. Our data are compatible with a model where multiple mRNA closed-loop complexes form with differing stability. Hence, unexpectedly, in the absence of other stabilising factors, rapid translation initiation on mRNAs correlates with less stable eIF4F interactions. Electronic supplementary material The online version of this article (doi:10.1186/s13059-017-1338-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Joseph L Costello
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK.,Present address: Biosciences, College of Life and Environmental Sciences, Geoffrey Pope Building, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
| | - Christopher J Kershaw
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Lydia M Castelli
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK.,Present address: Sheffield Institute for Translational Neuroscience, The University of Sheffield, 385a Glossop Road, Sheffield, S10 2HQ, UK
| | - David Talavera
- Division of Cardiovascular Sciences, School of Medicine, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - William Rowe
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK.,Present address: Department of Chemistry, Loughborough University, Epinal Way, Loughborough, Leicestershire, LE11 3TU, UK
| | - Paul F G Sims
- Manchester Institute of Biotechnology (MIB), The University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| | - Mark P Ashe
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Christopher M Grant
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Simon J Hubbard
- Division of Evolution and Genomic Sciences, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK
| | - Graham D Pavitt
- Division of Molecular and Cellular Function, School of Biological Sciences, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester, M13 9PT, UK.
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26
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Coots RA, Liu XM, Mao Y, Dong L, Zhou J, Wan J, Zhang X, Qian SB. m 6A Facilitates eIF4F-Independent mRNA Translation. Mol Cell 2017; 68:504-514.e7. [PMID: 29107534 DOI: 10.1016/j.molcel.2017.10.002] [Citation(s) in RCA: 174] [Impact Index Per Article: 24.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 07/25/2017] [Accepted: 09/29/2017] [Indexed: 12/12/2022]
Abstract
In eukaryotic cells, protein synthesis typically begins with the binding of eIF4F to the 7-methylguanylate (m7G) cap found on the 5' end of the majority of mRNAs. Surprisingly, overall translational output remains robust under eIF4F inhibition. The broad spectrum of eIF4F-resistant translatomes is incompatible with cap-independent translation mediated by internal ribosome entry sites (IRESs). Here, we report that N6-methyladenosine (m6A) facilitates mRNA translation that is resistant to eIF4F inactivation. Depletion of the methyltransferase METTL3 selectively inhibits translation of mRNAs bearing 5' UTR methylation, but not mRNAs with 5' terminal oligopyrimidine (TOP) elements. We identify ABCF1 as a critical mediator of m6A-promoted translation under both stress and physiological conditions. Supporting the role of ABCF1 in m6A-facilitated mRNA translation, ABCF1-sensitive transcripts largely overlap with METTL3-dependent mRNA targets. By illustrating the scope and mechanism of eIF4F-independent mRNA translation, these findings reshape our current perceptions of cellular translational pathways.
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Affiliation(s)
- Ryan A Coots
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA; Graduate Field of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Xiao-Min Liu
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Yuanhui Mao
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Leiming Dong
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Jun Zhou
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Ji Wan
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Xingqian Zhang
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA
| | - Shu-Bing Qian
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA; Graduate Field of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
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27
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Oblinger JL, Burns SS, Huang J, Pan L, Ren Y, Shen R, Kinghorn AD, Welling DB, Chang LS. Overexpression of eIF4F components in meningiomas and suppression of meningioma cell growth by inhibiting translation initiation. Exp Neurol 2017; 299:299-307. [PMID: 28610844 DOI: 10.1016/j.expneurol.2017.06.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 06/03/2017] [Accepted: 06/09/2017] [Indexed: 10/19/2022]
Abstract
Meningiomas frequently display activation of the PI3K/AKT/mTOR pathway, leading to elevated levels of phospho-eukaryotic translation initiation factor 4E binding proteins, which enhances protein synthesis; however, it is not known whether inhibition of protein translation is an effective treatment option for meningiomas. We found that human meningiomas expressed high levels of the three components of the eukaryotic initiation factor 4F (eIF4F) translation initiation complex, eIF4A, eIF4E, and eIF4G. The expression of eIF4A and eIF4E was important in sustaining the growth of NF2-deficient benign meningioma Ben-Men-1 cells, as shRNA-mediated knockdown of these proteins strongly reduced cell proliferation. Among a series of 23 natural compounds evaluated, silvestrol, which inhibits eIF4A, was identified as being the most growth inhibitory in both primary meningioma and Ben-Men-1 cells. Silvestrol treatment of meningioma cells prominently induced G2/M arrest. Consistently, silvestrol significantly decreased the amounts of cyclins D1, E1, A, and B, PCNA, and Aurora A. In addition, total and phosphorylated AKT, ERK, and FAK, which have been shown to be important drivers for meningioma cell proliferation, were markedly lower in silvestrol-treated Ben-Men-1 cells. Our findings suggest that inhibiting protein translation could be a potential treatment for meningiomas.
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Affiliation(s)
- Janet L Oblinger
- Center for Childhood Cancer and Blood Diseases, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Sarah S Burns
- Center for Childhood Cancer and Blood Diseases, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Jie Huang
- Center for Childhood Cancer and Blood Diseases, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Li Pan
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University College of Pharmacy, Columbus, OH, USA
| | - Yulin Ren
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University College of Pharmacy, Columbus, OH, USA
| | - Rulong Shen
- Department of Pathology, The Ohio State University College of Medicine, Columbus, OH, USA
| | - A Douglas Kinghorn
- Division of Medicinal Chemistry and Pharmacognosy, The Ohio State University College of Pharmacy, Columbus, OH, USA
| | - D Bradley Welling
- Department of Otolaryngology-Head and Neck Surgery, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Long-Sheng Chang
- Center for Childhood Cancer and Blood Diseases, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA; Department of Otolaryngology-Head and Neck Surgery, The Ohio State University College of Medicine, Columbus, OH, USA; Department of Pathology, The Ohio State University College of Medicine, Columbus, OH, USA.
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28
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Kumar P, Hellen CUT, Pestova TV. Toward the mechanism of eIF4F-mediated ribosomal attachment to mammalian capped mRNAs. Genes Dev 2017; 30:1573-88. [PMID: 27401559 PMCID: PMC4949329 DOI: 10.1101/gad.282418.116] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/01/2016] [Indexed: 11/24/2022]
Abstract
Ribosomal attachment to mammalian capped mRNAs is achieved through the cap-eukaryotic initiation factor 4E (eIF4E)-eIF4G-eIF3-40S chain of interactions, but the mechanism by which mRNA enters the mRNA-binding channel of the 40S subunit remains unknown. To investigate this process, we recapitulated initiation on capped mRNAs in vitro using a reconstituted translation system. Formation of initiation complexes at 5'-terminal AUGs was stimulated by the eIF4E-cap interaction and followed "the first AUG" rule, indicating that it did not occur by backward scanning. Initiation complexes formed even at the very 5' end of mRNA, implying that Met-tRNAi (Met) inspects mRNA from the first nucleotide and that initiation does not have a "blind spot." In assembled initiation complexes, the cap was no longer associated with eIF4E. Omission of eIF4A or disruption of eIF4E-eIF4G-eIF3 interactions converted eIF4E into a specific inhibitor of initiation on capped mRNAs. Taken together, these results are consistent with the model in which eIF4E-eIF4G-eIF3-40S interactions place eIF4E at the leading edge of the 40S subunit, and mRNA is threaded into the mRNA-binding channel such that Met-tRNAi (Met) can inspect it from the first nucleotide. Before entering, eIF4E likely dissociates from the cap to overcome steric hindrance. We also found that the m(7)G cap specifically interacts with eIF3l.
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Affiliation(s)
- Parimal Kumar
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Christopher U T Hellen
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
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29
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Truniger V, Miras M, Aranda MA. Structural and Functional Diversity of Plant Virus 3'-Cap-Independent Translation Enhancers (3'-CITEs). Front Plant Sci 2017; 8:2047. [PMID: 29238357 PMCID: PMC5712577 DOI: 10.3389/fpls.2017.02047] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 11/15/2017] [Indexed: 05/12/2023]
Abstract
Most of the positive-strand RNA plant viruses lack the 5'-cap and/or the poly(A)-tail that act synergistically to stimulate canonical translation of cellular mRNAs. However, they have RNA elements in the 5'- or 3'-untranslated regions of their RNAs that are required for their cap-independent translation. Cap-independent translation enhancers (CITEs) have been identified in the genomic 3'-end of viruses belonging to the family Tombusviridae and the genus Luteovirus. Seven classes of 3'-CITEs have been described to date based on their different RNA structures. They generally control the efficient formation of the translation initiation complex by varying mechanisms. Some 3'-CITEs bind eukaryotic translation initiation factors, others ribosomal subunits, bridging these to the 5'-end by different mechanisms, often long-distance RNA-RNA interactions. As previously proposed and recently found in one case in nature, 3'-CITEs are functionally independent elements that are transferable through recombination between viral genomes, leading to potential advantages for virus multiplication. In this review, the knowledge on 3'-CITEs and their functioning is updated. We also suggest that there is local structural conservation in the regions interacting with eIF4E of 3'-CITEs belonging to different classes.
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30
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Steinberger J, Chu J, Maïga RI, Sleiman K, Pelletier J. Developing anti-neoplastic biotherapeutics against eIF4F. Cell Mol Life Sci 2016; 74:1681-1692. [PMID: 28004147 DOI: 10.1007/s00018-016-2430-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Revised: 11/16/2016] [Accepted: 12/01/2016] [Indexed: 02/08/2023]
Abstract
Biotherapeutics have revolutionized modern medicine by providing medicines that would not have been possible with small molecules. With respect to cancer therapies, this represents the current sector of the pharmaceutical industry having the largest therapeutic impact, as exemplified by the development of recombinant antibodies and cell-based therapies. In cancer, one of the most common regulatory alterations is the perturbation of translational control. Among these, changes in eukaryotic initiation factor 4F (eIF4F) are associated with tumor initiation, progression, and drug resistance in a number of settings. This, coupled with the fact that systemic suppression of eIF4F appears well tolerated, indicates that therapeutic agents targeting eIF4F hold much therapeutic potential. Here, we discuss opportunities offered by biologicals for this purpose.
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Affiliation(s)
- Jutta Steinberger
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Jennifer Chu
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Rayelle Itoua Maïga
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Katia Sleiman
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada
| | - Jerry Pelletier
- Department of Biochemistry, McGill University, McIntyre Medical Sciences Building, Rm 810, 3655 Drummond St., Montreal, QC, H3G 1Y6, Canada. .,The Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, QC, H3G 1Y6, Canada. .,Department of Oncology, McGill University, Montreal, QC, H3G 1Y6, Canada.
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31
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Malka-Mahieu H, Girault I, Rubington M, Leriche M, Welsch C, Kamsu-Kom N, Zhao Q, Desaubry L, Vagner S, Robert C. Synergistic effects of eIF4A and MEK inhibitors on proliferation of NRAS-mutant melanoma cell lines. Cell Cycle 2016; 15:2405-9. [PMID: 27533468 DOI: 10.1080/15384101.2016.1208862] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Activating mutations of the NRAS (neuroblastoma rat sarcoma viral oncogene) protein kinase, present in many cancers, induce a constitutive activation of both the RAS-RAF-MEK-ERK mitogen-activated protein kinase (MAPK) signal transduction pathway and the PI(3)K-AKT-mTOR, pathway. This in turn regulates the formation of the eIF4F eukaryotic translation initiation complex, comprising the eIF4E cap-binding protein, the eIF4G scaffolding protein and the eIF4A RNA helicase, which binds to the 7-methylguanylate cap (m(7)G) at the 5' end of messenger RNAs. Small molecules targeting MEK (MEKi: MEK inhibitors) have demonstrated activity in NRAS-mutant cell lines and tumors, but resistance sets in most cases within months of treatment. Using proximity ligation assays, that allows visualization of the binding of eIF4E to the scaffold protein eIF4G, generating the active eIF4F complex, we have found that resistance to MEKi is associated with the persistent formation of the eIF4F complex in MEKi-treated NRAS-mutant cell lines. Furthermore, inhibiting the eIF4A component of the eIF4F complex, with a small molecule of the flavagline/rocaglate family, synergizes with inhibiting MEK to kill NRAS-mutant cancer cell lines.
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Affiliation(s)
- Hélène Malka-Mahieu
- a INSERM U981 , Villejuif , France.,b Université Paris-Sud , Kremlin-Bicêtre , France
| | - Isabelle Girault
- a INSERM U981 , Villejuif , France.,g Gustave Roussy, Dermato-Oncology , Villejuif , France
| | - Margot Rubington
- a INSERM U981 , Villejuif , France.,b Université Paris-Sud , Kremlin-Bicêtre , France
| | - Melissa Leriche
- a INSERM U981 , Villejuif , France.,b Université Paris-Sud , Kremlin-Bicêtre , France
| | - Caroline Welsch
- a INSERM U981 , Villejuif , France.,b Université Paris-Sud , Kremlin-Bicêtre , France
| | - Nyam Kamsu-Kom
- a INSERM U981 , Villejuif , France.,b Université Paris-Sud , Kremlin-Bicêtre , France
| | - Qian Zhao
- c CNRS-Strasbourg University, UMR7200 , Illkirch , France
| | | | - Stéphan Vagner
- a INSERM U981 , Villejuif , France.,d Institut Curie, PSL Research University, CNRS UMR3348 , Orsay , France.,e Université Paris Sud, Université Paris-Saclay, CNRS UMR3348 , Orsay , France.,f Equipe Labellisée Ligue Contre le Cancer , Orsay , France
| | - Caroline Robert
- a INSERM U981 , Villejuif , France.,b Université Paris-Sud , Kremlin-Bicêtre , France.,g Gustave Roussy, Dermato-Oncology , Villejuif , France
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32
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Ho JJD, Lee S. A Cap for Every Occasion: Alternative eIF4F Complexes. Trends Biochem Sci 2016; 41:821-823. [PMID: 27283511 DOI: 10.1016/j.tibs.2016.05.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 05/10/2016] [Accepted: 05/13/2016] [Indexed: 11/28/2022]
Abstract
The eukaryotic translation initiation factor 4F (eIF4F) has become essentially synonymous with 5' cap-dependent mRNA translation. Recent studies demonstrate that cells assemble variants of eIF4F to produce adaptive, cap-dependent translatomes during physiological conditions that inhibit eIF4F. These findings challenge us to reassess classical perceptions of cellular translational pathways.
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Affiliation(s)
- J J David Ho
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Stephen Lee
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA.
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Ho JJD, Wang M, Audas TE, Kwon D, Carlsson SK, Timpano S, Evagelou SL, Brothers S, Gonzalgo ML, Krieger JR, Chen S, Uniacke J, Lee S. Systemic Reprogramming of Translation Efficiencies on Oxygen Stimulus. Cell Rep 2016; 14:1293-1300. [PMID: 26854219 DOI: 10.1016/j.celrep.2016.01.036] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 10/29/2015] [Accepted: 01/08/2016] [Indexed: 10/22/2022] Open
Abstract
Protein concentrations evolve under greater evolutionary constraint than mRNA levels. Translation efficiency of mRNA represents the chief determinant of basal protein concentrations. This raises a fundamental question of how mRNA and protein levels are coordinated in dynamic systems responding to physiological stimuli. This report examines the contributions of mRNA abundance and translation efficiency to protein output in cells responding to oxygen stimulus. We show that changes in translation efficiencies, and not mRNA levels, represent the major mechanism governing cellular responses to [O2] perturbations. Two distinct cap-dependent protein synthesis machineries select mRNAs for translation: the normoxic eIF4F and the hypoxic eIF4F(H). O2-dependent remodeling of translation efficiencies enables cells to produce adaptive translatomes from preexisting mRNA pools. Differences in mRNA expression observed under different [O2] are likely neutral, given that they occur during evolution. We propose that mRNAs contain translation efficiency determinants for their triage by the translation apparatus on [O2] stimulus.
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Affiliation(s)
- J J David Ho
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Miling Wang
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Timothy E Audas
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Deukwoo Kwon
- Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Biostatistics and Bioinformatics Core, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Steven K Carlsson
- Center for Therapeutic Innovation, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Sara Timpano
- Department of Molecular and Cellular Biology, College of Biological Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Sonia L Evagelou
- Department of Molecular and Cellular Biology, College of Biological Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Shaun Brothers
- Center for Therapeutic Innovation, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Department of Psychiatry, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Mark L Gonzalgo
- Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Department of Urology, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - Jonathan R Krieger
- SPARC BioCentre, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
| | - Steven Chen
- Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Biostatistics and Bioinformatics Core, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Division of Biostatistics, Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL 31336, USA
| | - James Uniacke
- Department of Molecular and Cellular Biology, College of Biological Science, University of Guelph, Guelph, ON N1G 2W1, Canada
| | - Stephen Lee
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL 31336, USA; Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON K1H 8M5, Canada.
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Abstract
The original purification of the heterotrimeric eIF4F was published over 30 years ago (Grifo, J. A., Tahara, S. M., Morgan, M. A., Shatkin, A. J., and Merrick, W. C. (1983) J. Biol. Chem. 258, 5804-5810). Since that time, numerous studies have been performed with the three proteins specifically required for the translation initiation of natural mRNAs, eIF4A, eIF4B, and eIF4F. These have involved enzymatic and structural studies of the proteins and a number of site-directed mutagenesis studies. The regulation of translation exhibited through the mammalian target of rapamycin (mTOR) pathway is predominately seen as the phosphorylation of 4E-BP, an inhibitor of protein synthesis that functions by binding to the cap binding subunit of eIF4F (eIF4E). A hypothesis that requires the disassembly of eIF4F during translation initiation to yield free subunits (eIF4A, eIF4E, and eIF4G) is presented.
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Affiliation(s)
- William C Merrick
- From the Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4935
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Peter D, Weber R, Köne C, Chung MY, Ebertsch L, Truffault V, Weichenrieder O, Igreja C, Izaurralde E. Mextli proteins use both canonical bipartite and novel tripartite binding modes to form eIF4E complexes that display differential sensitivity to 4E-BP regulation. Genes Dev 2015; 29:1835-49. [PMID: 26294658 PMCID: PMC4573856 DOI: 10.1101/gad.269068.115] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2015] [Accepted: 08/07/2015] [Indexed: 12/20/2022]
Abstract
Peter et al. present the crystal structures of the eIF4E-binding regions of the Drosophila melanogaster (Dm) and Caenorhabditis elegans (Ce) Mxt proteins in complex with eIF4E in the cap-bound and cap-free states. The structures reveal unexpected diversity in the binding modes of 4E-BPs, resulting in eIF4E complexes that display differential sensitivity to 4E-BP regulation. The eIF4E-binding proteins (4E-BPs) are a diverse class of translation regulators that share a canonical eIF4E-binding motif (4E-BM) with eIF4G. Consequently, they compete with eIF4G for binding to eIF4E, thereby inhibiting translation initiation. Mextli (Mxt) is an unusual 4E-BP that promotes translation by also interacting with eIF3. Here we present the crystal structures of the eIF4E-binding regions of the Drosophila melanogaster (Dm) and Caenorhabditis elegans (Ce) Mxt proteins in complex with eIF4E in the cap-bound and cap-free states. The structures reveal unexpected evolutionary plasticity in the eIF4E-binding mode, with a classical bipartite interface for Ce Mxt and a novel tripartite interface for Dm Mxt. Both interfaces comprise a canonical helix and a noncanonical helix that engage the dorsal and lateral surfaces of eIF4E, respectively. Remarkably, Dm Mxt contains a C-terminal auxiliary helix that lies anti-parallel to the canonical helix on the eIF4E dorsal surface. In contrast to the eIF4G and Ce Mxt complexes, the Dm eIF4E–Mxt complexes are resistant to competition by bipartite 4E-BPs, suggesting that Dm Mxt can bind eIF4E when eIF4G binding is inhibited. Our results uncovered unexpected diversity in the binding modes of 4E-BPs, resulting in eIF4E complexes that display differential sensitivity to 4E-BP regulation.
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Affiliation(s)
- Daniel Peter
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Ramona Weber
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Carolin Köne
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Min-Yi Chung
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Linda Ebertsch
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Vincent Truffault
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Oliver Weichenrieder
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Cátia Igreja
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Elisa Izaurralde
- Department of Biochemistry, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
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Abstract
Herpesviral mRNAs are produced and translated by cellular machinery, rendering them susceptible to the network of regulatory events that impact translation. In response, these viruses have evolved to infiltrate and hijack translational control pathways as well as to integrate specialized host translation strategies into their own repertoire. They are robust systems to dissect mechanisms of mammalian translational regulation and continue to offer insight into cis-acting mRNA features that impact assembly and activity of the translation apparatus. Here, I discuss recent advances revealing the extent to which the three herpesvirus subfamilies regulate both host and viral translation, thereby dramatically impacting the landscape of protein synthesis in infected cells.
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Affiliation(s)
- Britt A Glaunsinger
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720;
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Abstract
The process of peptide bond synthesis by ribosomes is conserved between species, but the initiation step differs greatly between the three kingdoms of life. This is illustrated by the evolution of roughly an order of magnitude more initiation factor mass found in humans compared with bacteria. Eukaryotic initiation of translation is comprised of a number of sub-steps: (i) recruitment of an mRNA and initiator methionyl-tRNA to the 40S ribosomal subunit; (ii) migration of the 40S subunit along the 5' UTR to locate the initiation codon; and (iii) recruitment of the 60S subunit to form the 80S initiation complex. Although the mechanism and regulation of initiation has been studied for decades, many aspects of the pathway remain unclear. In this review, I will focus discussion on what is known about the mechanism of mRNA selection and its recruitment to the 40S subunit. I will summarize how the 43S preinitiation complex (PIC) is formed and stabilized by interactions between its components. I will discuss what is known about the mechanism of mRNA selection by the eukaryotic initiation factor 4F (eIF4F) complex and how the selected mRNA is recruited to the 43S PIC. The regulation of this process by secondary structure located in the 5' UTR of an mRNA will also be discussed. Finally, I present a possible kinetic model with which to explain the process of mRNA selection and recruitment to the eukaryotic ribosome.
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Affiliation(s)
- Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA.
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Abstract
Pain is a crucial physiological response to injury and pathologies. The development and maintenance of pain requires the expression of novel genes. The expression of such genes occurs in highly regulated and orchestrated manner where protein translation provides an exquisite temporal and spatial fidelity within the axons and dendrites of neurons. Signaling pathways that regulate local translation are activated by cytokines, neurotrophic factors, or neurotransmitters, which are released either due to tissue damage or neuronal activity. In recent years, the ERK and mTOR pathways have been demonstrated to be central in regulating local translation in neurons of both the peripheral and central nervous systems in diverse models of chronic pain. The ERK and mTOR pathways converge onto the cap-dependent translational machinery that regulates genes essential for the development of nociceptive sensitization. Moreover, inhibition of these pathways has proved to be effective in normalizing the biochemical changes and the associated pain in various preclinical models.
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Affiliation(s)
- Ohannes K Melemedjian
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, Maryland, USA.
| | - Arkady Khoutorsky
- Department of Biochemistry, Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montréal, Quebec, Canada
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Takrouri K, Chen T, Papadopoulos E, Sahoo R, Kabha E, Chen H, Cantel S, Wagner G, Halperin JA, Aktas BH, Chorev M. Structure-activity relationship study of 4EGI-1, small molecule eIF4E/eIF4G protein-protein interaction inhibitors. Eur J Med Chem 2014; 77:361-77. [PMID: 24675136 DOI: 10.1016/j.ejmech.2014.03.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 03/04/2014] [Accepted: 03/12/2014] [Indexed: 01/15/2023]
Abstract
Protein-protein interactions are critical for regulating the activity of translation initiation factors and multitude of other cellular process, and form the largest block of untapped albeit most challenging targets for drug development. 4EGI-1, (E/Z)-2-(2-(4-(3,4-dichlorophenyl)thiazol-2-yl)hydrazono)-3-(2-nitrophenyl)propanoic acid, is a hit compound discovered in a screening campaign of small molecule libraries as an inhibitor of translation initiation factors eIF4E and eIF4G protein-protein interaction; it inhibits translation initiation in vitro and in vivo. A series of 4EGI-1-derived thiazol-2-yl hydrazones have been designed and synthesized in order to delineate the structural latitude and improve its binding affinity to eIF4E, and increase its potency in inhibiting the eIF4E/eIF4G interaction. Probing a wide range of substituents on both phenyl rings comprising the 3-phenylpropionic acid and 4-phenylthiazolidine moieties in the context of both E- and Z-isomers of 4EGI-1 led to analogs with enhanced binding affinity and translation initiation inhibitory activities.
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Affiliation(s)
- Khuloud Takrouri
- Laboratory for Translational Research, Hematology, Brigham and Women's Hospital, Harvard Medical School, 20 Shattuck Street, Thorn 7, Boston, MA 02115, USA
| | - Ting Chen
- Laboratory for Translational Research, Hematology, Brigham and Women's Hospital, Harvard Medical School, 20 Shattuck Street, Thorn 7, Boston, MA 02115, USA
| | - Evangelos Papadopoulos
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Rupam Sahoo
- Laboratory for Translational Research, Hematology, Brigham and Women's Hospital, Harvard Medical School, 20 Shattuck Street, Thorn 7, Boston, MA 02115, USA
| | - Eihab Kabha
- Laboratory for Translational Research, Harvard Medical School, USA
| | - Han Chen
- Laboratory for Translational Research, Harvard Medical School, USA
| | - Sonia Cantel
- Laboratory for Translational Research, Harvard Medical School, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA
| | - Jose A Halperin
- Laboratory for Translational Research, Hematology, Brigham and Women's Hospital, Harvard Medical School, 20 Shattuck Street, Thorn 7, Boston, MA 02115, USA
| | - Bertal H Aktas
- Laboratory for Translational Research, Hematology, Brigham and Women's Hospital, Harvard Medical School, 20 Shattuck Street, Thorn 7, Boston, MA 02115, USA
| | - Michael Chorev
- Laboratory for Translational Research, Hematology, Brigham and Women's Hospital, Harvard Medical School, 20 Shattuck Street, Thorn 7, Boston, MA 02115, USA.
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40
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Banerjee B, Goss DJ. Eukaryotic initiation factor (eIF) 4F binding to barley yellow dwarf virus (BYDV) 3'-untranslated region correlates with translation efficiency. J Biol Chem 2013; 289:4286-94. [PMID: 24379412 DOI: 10.1074/jbc.m113.530329] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic initiation factor (eIF) 4F binding to mRNA is the first committed step in cap-dependent protein synthesis. Barley yellow dwarf virus (BYDV) employs a cap-independent mechanism of translation initiation that is mediated by a structural BYDV translation element (BTE) located in the 3'-UTR of its mRNA. eIF4F bound the BTE and a translationally inactive mutant with high affinity, thus questioning the role of eIF4F in translation of BYDV. To examine the effects of eIF4F in BYDV translation initiation, BTE mutants with widely different in vitro translation efficiencies ranging from 5 to 164% compared with WT were studied. Using fluorescence anisotropy to obtain quantitative data, we show 1) the equilibrium binding affinity (complex stability) correlated well with translation efficiency, whereas the "on" rate of binding did not; 2) other unidentified proteins or small molecules in wheat germ extract prevented eIF4F binding to mutant BTE but not WT BTE; 3) BTE mutant-eIF4F interactions were found to be both enthalpically and entropically favorable with an enthalpic contribution of 52-90% to ΔG° at 25 °C, suggesting that hydrogen bonding contributes to stability; and 4) in contrast to cap-dependent and tobacco etch virus internal ribosome entry site interaction with eIF4F, poly(A)-binding protein did not increase eIF4F binding. Further, the eIF4F bound to the 3' BTE with higher affinity than for either m(7)G cap or tobacco etch virus internal ribosome entry site, suggesting that the 3' BTE may play a role in sequestering host cell initiation factors and possibly regulating the switch from replication to translation.
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Affiliation(s)
- Bidisha Banerjee
- From the Department of Chemistry, Hunter College and the Graduate Center of the City University of New York, New York, New York 10065
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Melemedjian OK, Mejia GL, Lepow TS, Zoph OK, Price TJ. Bidirectional regulation of P body formation mediated by eIF4F complex formation in sensory neurons. Neurosci Lett 2013; 563:169-74. [PMID: 24080374 DOI: 10.1016/j.neulet.2013.09.048] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 09/10/2013] [Accepted: 09/14/2013] [Indexed: 12/17/2022]
Abstract
Processing (P) bodies are RNA granules that comprise key cellular sites for the metabolism of mRNAs. In certain cells, including neurons, these RNA granules may also play an important role in storage of mRNAs in a translationally dormant state. Utilizing nerve growth factor (NGF) and interleukin 6 (IL6), which stimulate cap-dependent translation in sensory neurons, and adenosine monophosphate activated protein kinase (AMPK) activators, which inhibit cap-dependent translation, we have tested the hypothesis that cap-dependent translation is linked to P body formation in mammalian sensory neurons. Treatment with NGF and IL6 decreases, whereas metformin increases biochemical association of the P body marker and translational repressor/decapping activator Rck/p54/dhh1 with the 5'-mRNA-cap suggesting an ordered assembly of P bodies. Likewise, diverse AMPK activators enhance P body formation while NGF and IL6 decrease P bodies in sensory neurons. This bidirectional P body plasticity readily occurs in the axonal compartment of these neurons. These studies indicate that P body formation is intricately linked to cap-dependent translation in mammalian sensory neurons suggesting an important role for these organelles in the regulation of mRNA metabolism in the adult PNS.
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Affiliation(s)
| | - Galo L Mejia
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States.
| | - Talya S Lepow
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States.
| | - Olivia K Zoph
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States.
| | - Theodore J Price
- Department of Pharmacology, University of Arizona, Tucson, AZ, United States.
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