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Ide NA, Gentry RC, Rudbach MA, Yoo K, Velez PK, Comunale VM, Hartwick EW, Kinz-Thompson CD, Gonzalez RL, Aitken CE. A dynamic compositional equilibrium governs mRNA recognition by eIF3. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.25.581977. [PMID: 38712078 PMCID: PMC11071631 DOI: 10.1101/2024.04.25.581977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Eukaryotic translation initiation factor (eIF) 3 is a multi-subunit protein complex that binds both ribosomes and messenger RNAs (mRNAs) in order to drive a diverse set of mechanistic steps during translation. Despite its importance, a unifying framework explaining how eIF3 performs these numerous activities is lacking. Using single-molecule light scattering microscopy, we demonstrate that Saccharomyces cerevisiae eIF3 is an equilibrium mixture of the full complex, subcomplexes, and subunits. By extending our microscopy approach to an in vitro reconstituted eIF3 and complementing it with biochemical assays, we define the subspecies comprising this equilibrium and show that, rather than being driven by the full complex, mRNA binding by eIF3 is instead driven by the eIF3a subunit within eIF3a-containing subcomplexes. Our findings provide a mechanistic model for the role of eIF3 in the mRNA recruitment step of translation initiation and establish a mechanistic framework for explaining and investigating the other activities of eIF3.
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2
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Cao Y, Liu H, Lu SS, Jones KA, Govind AP, Jeyifous O, Simmons CQ, Tabatabaei N, Green WN, Holder JL, Tahmasebi S, George AL, Dickinson BC. RNA-based translation activators for targeted gene upregulation. Nat Commun 2023; 14:6827. [PMID: 37884512 PMCID: PMC10603104 DOI: 10.1038/s41467-023-42252-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 10/04/2023] [Indexed: 10/28/2023] Open
Abstract
Technologies capable of programmable translation activation offer strategies to develop therapeutics for diseases caused by insufficient gene expression. Here, we present "translation-activating RNAs" (taRNAs), a bifunctional RNA-based molecular technology that binds to a specific mRNA of interest and directly upregulates its translation. taRNAs are constructed from a variety of viral or mammalian RNA internal ribosome entry sites (IRESs) and upregulate translation for a suite of target mRNAs. We minimize the taRNA scaffold to 94 nucleotides, identify two translation initiation factor proteins responsible for taRNA activity, and validate the technology by amplifying SYNGAP1 expression, a haploinsufficiency disease target, in patient-derived cells. Finally, taRNAs are suitable for delivery as RNA molecules by lipid nanoparticles (LNPs) to cell lines, primary neurons, and mouse liver in vivo. taRNAs provide a general and compact nucleic acid-based technology to upregulate protein production from endogenous mRNAs, and may open up possibilities for therapeutic RNA research.
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Affiliation(s)
- Yang Cao
- Department of Chemistry, The University of Chicago, Chicago, IL, USA
| | - Huachun Liu
- Department of Chemistry, The University of Chicago, Chicago, IL, USA
| | - Shannon S Lu
- Department of Chemistry, The University of Chicago, Chicago, IL, USA
| | - Krysten A Jones
- Department of Chemistry, The University of Chicago, Chicago, IL, USA
| | - Anitha P Govind
- Department of Neurobiology, The University of Chicago, Chicago, IL, USA
| | - Okunola Jeyifous
- Department of Neurobiology, The University of Chicago, Chicago, IL, USA
| | - Christine Q Simmons
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Negar Tabatabaei
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - William N Green
- Department of Neurobiology, The University of Chicago, Chicago, IL, USA
| | - Jimmy L Holder
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA
| | - Soroush Tahmasebi
- Department of Pharmacology and Regenerative Medicine, University of Illinois College of Medicine, Chicago, IL, USA
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - Bryan C Dickinson
- Department of Chemistry, The University of Chicago, Chicago, IL, USA.
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3
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Mukhopadhyay S, Amodeo ME, Lee ASY. eIF3d controls the persistent integrated stress response. Mol Cell 2023; 83:3303-3313.e6. [PMID: 37683648 PMCID: PMC10528100 DOI: 10.1016/j.molcel.2023.08.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 05/26/2023] [Accepted: 08/09/2023] [Indexed: 09/10/2023]
Abstract
Cells respond to intrinsic and extrinsic stresses by reducing global protein synthesis and activating gene programs necessary for survival. Here, we show that the integrated stress response (ISR) is driven by the non-canonical cap-binding protein eIF3d that acts as a critical effector to control core stress response orchestrators, the translation factor eIF2α and the transcription factor ATF4. We find that during persistent stress, eIF3d activates the translation of the kinase GCN2, inducing eIF2α phosphorylation and inhibiting general protein synthesis. In parallel, eIF3d upregulates the m6A demethylase ALKBH5 to drive 5' UTR-specific demethylation of stress response genes, including ATF4. Ultimately, this cascade converges on ATF4 expression by increasing mRNA engagement of translation machinery and enhancing ribosome bypass of upstream open reading frames (uORFs). Our results reveal that eIF3d acts in a life-or-death decision point during chronic stress and uncover a synergistic signaling mechanism in which translational cascades complement transcriptional amplification to control essential cellular processes.
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Affiliation(s)
- Shaoni Mukhopadhyay
- Department of Cell Biology, Harvard Medical School, Boston, MA 02215, USA; Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Maria E Amodeo
- Department of Cell Biology, Harvard Medical School, Boston, MA 02215, USA; Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215, USA
| | - Amy S Y Lee
- Department of Cell Biology, Harvard Medical School, Boston, MA 02215, USA; Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, MA 02215, USA.
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4
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Bakti F, Stupperich H, Schmitt K, Valerius O, Köhler AM, Meister C, Strohdiek A, Harting R, Sasse C, Heimel K, Neumann P, Ficner R, Braus GH. Fungal COP9 signalosome assembly requires connection of two trimeric intermediates for integration of intrinsic deneddylase. Proc Natl Acad Sci U S A 2023; 120:e2305049120. [PMID: 37603767 PMCID: PMC10477865 DOI: 10.1073/pnas.2305049120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 08/01/2023] [Indexed: 08/23/2023] Open
Abstract
The conserved eight-subunit COP9 signalosome (CSN) is required for multicellular fungal development. The CSN deneddylase cooperates with the Cand1 exchange factor to control replacements of E3 ubiquitin cullin RING ligase receptors, providing specificity to eukaryotic protein degradation. Aspergillus nidulans CSN assembles through a heptameric pre-CSN, which is activated by integration of the catalytic CsnE deneddylase. Combined genetic and biochemical approaches provided the assembly choreography within a eukaryotic cell for native fungal CSN. Interactomes of functional GFP-Csn subunit fusions in pre-CSN deficient fungal strains were compared by affinity purifications and mass spectrometry. Two distinct heterotrimeric CSN subcomplexes were identified as pre-CSN assembly intermediates. CsnA-C-H and CsnD-F-G form independently of CsnB, which connects the heterotrimers to a heptamer and enables subsequent integration of CsnE to form the enzymatically active CSN complex. Surveillance mechanisms control accurate Csn subunit amounts and correct cellular localization for sequential assembly since deprivation of Csn subunits changes the abundance and location of remaining Csn subunits.
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Affiliation(s)
- Fruzsina Bakti
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Helena Stupperich
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Kerstin Schmitt
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Oliver Valerius
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Anna M. Köhler
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Cindy Meister
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Anja Strohdiek
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Rebekka Harting
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Christoph Sasse
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Kai Heimel
- Department of Microbial Cell Biology, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Piotr Neumann
- Department of Molecular Structural Biology, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
| | - Gerhard H. Braus
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Goettingen Center for Molecular Biosciences, University of Goettingen, 37077Goettingen, Germany
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5
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Bose P, Baron N, Pullaiahgari D, Ben-Zvi A, Shapira M. LeishIF3d is a non-canonical cap-binding protein in Leishmania. Front Mol Biosci 2023; 10:1191934. [PMID: 37325473 PMCID: PMC10266417 DOI: 10.3389/fmolb.2023.1191934] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 05/15/2023] [Indexed: 06/17/2023] Open
Abstract
Translation of most cellular mRNAs in eukaryotes proceeds through a cap-dependent pathway, whereby the cap-binding complex, eIF4F, anchors the pre-initiation complex at the 5' end of mRNAs driving translation initiation. The genome of Leishmania encodes a large repertoire of cap-binding complexes that fulfill a variety of functions possibly involved in survival along the life cycle. However, most of these complexes function in the promastigote life form that resides in the sand fly vector and decrease their activity in amastigotes, the mammalian life form. Here we examined the possibility that LeishIF3d drives translation in Leishmania using alternative pathways. We describe a non-canonical cap-binding activity of LeishIF3d and examine its potential role in driving translation. LeishIF3d is required for translation, as reducing its expression by a hemizygous deletion reduces the translation activity of the LeishIF3d(+/-) mutant cells. Proteomic analysis of the mutant cells highlights the reduced expression of flagellar and cytoskeletal proteins, as reflected in the morphological changes observed in the mutant cells. Targeted mutations in two predicted alpha helices diminish the cap-binding activity of LeishIF3d. Overall, LeishIF3d could serve as a driving force for alternative translation pathways, although it does not seem to offer an alternative pathway for translation in amastigotes.
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Affiliation(s)
- Priyanka Bose
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Nofar Baron
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | | | - Anat Ben-Zvi
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Michal Shapira
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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Liu Y, Wu Z, Wu D, Gao N, Lin J. Reconstitution of Multi-Protein Complexes through Ribozyme-Assisted Polycistronic Co-Expression. ACS Synth Biol 2022; 12:136-143. [PMID: 36512506 PMCID: PMC9872166 DOI: 10.1021/acssynbio.2c00416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In living cells, proteins often exert their functions by interacting with other proteins forming protein complexes. Obtaining homogeneous samples of protein complexes with correct fold and stoichiometry is critical for its biochemical and biophysical characterization as well as functional investigation. Here, we developed a Ribozyme-Assisted Polycistronic co-expression system (pRAP) for heterologous co-production and in vivo assembly of multi-subunit complexes. In the pRAP system, a polycistronic mRNA transcript is co-transcriptionally converted into individual mono-cistrons in vivo. Each cistron can initiate translation with comparable efficiency, resulting in balanced production for all subunits, thus permitting faithful protein complex assembly. With pRAP polycistronic co-expression, we have successfully reconstituted large functional multi-subunit complexes involved in mammalian translation initiation. Our invention provides a valuable tool for studying the molecular mechanisms of biological processes.
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Affiliation(s)
- Yan Liu
- State
Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan
Hospital, Fudan University, Shanghai 200438, China
| | - Zihan Wu
- State
Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan
Hospital, Fudan University, Shanghai 200438, China
| | - Damu Wu
- State
Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for
Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| | - Ning Gao
- State
Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for
Life Sciences, School of Life Sciences, Peking University, Beijing 100871, China
| | - Jinzhong Lin
- State
Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan
Hospital, Fudan University, Shanghai 200438, China,. Tel.: +86-21-31246764
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7
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A Label-Free Quantitative Analysis for the Search of Proteomic Differences between Goat Breeds. Animals (Basel) 2022; 12:ani12233336. [PMID: 36496858 PMCID: PMC9740416 DOI: 10.3390/ani12233336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 11/17/2022] [Accepted: 11/25/2022] [Indexed: 12/02/2022] Open
Abstract
The intensification and standardization of livestock farming are causing a decline in the number of animal breeds in many species, such as the goat. The availability of more studies on the potentiality of goat breeds could raise awareness of their importance, conservation and productive possibilities. Label-free quantitative analysis was applied in this study to investigate the proteomic differences between the autochthon Teramana and Saanen goats that could be useful for defining peculiar features of these breeds. A total of 2093 proteins were characterized in the muscle exudate proteome of the Teramana and Saanen breeds. A total of 41 proteins clearly separated the two breeds. Eukaryotic initiation factor proteins and aldehyde-dehydrogenase 7 family-member A1 were up-regulated in the autochthon breed and associated with its resilience, whereas catalase was down-regulated and associated with lower muscular mass. This study is the most detailed report of goat muscle proteome. Several differentially regulated proteins between the two breeds were identified, providing insights into functional pathways that define this organism and its biology.
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8
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Lin Z, Shen D, Yang B, Woo CM. Molecular and Structural Characterization of Lenalidomide-Mediated Sequestration of eIF3i. ACS Chem Biol 2022; 17:3229-3237. [PMID: 36325969 DOI: 10.1021/acschembio.2c00706] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Lenalidomide is a ligand of the E3 ligase substrate adapter cereblon (CRBN) that achieves its clinical effects in part by the promotion of substrate recruitment and degradation. In contrast to prior targets, eIF3i is recruited but not degraded upon complex formation with lenalidomide and CRBN, although the structural details and mechanistic outcomes of this interaction are unresolved. Here, we characterize the structural basis and mechanistic outcomes of lenalidomide-induced sequestration of eIF3i from the eIF3 complex. Identification of the binding interface on eIF3i by a covalent lenalidomide probe and mass spectrometry rationalizes the sequestration event. We further connect eIF3i and CRBN to lenalidomide-driven effects on angiogenic markers, Akt1 phosphorylation, and associated antiangiogenesis phenotypes. Finally, we find that eIF3i sequestration is observed in MM.1S and MOLM13 cells after the degradation of other substrates, such as IKZF1. The defined binding interface elucidated by chemical proteomics and the observation of eIF3i sequestration as a lenalidomide function open future directions in designing new chemical adapters for protein sequestration as a strategy to selectively control protein functions.
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Affiliation(s)
- Zhi Lin
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Dacheng Shen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Bo Yang
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Christina M Woo
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
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9
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EIF3C Promotes Lung Cancer Tumorigenesis by Regulating the APP/HSPA1A/LMNB1 Axis. DISEASE MARKERS 2022; 2022:9464094. [PMID: 36157221 PMCID: PMC9492341 DOI: 10.1155/2022/9464094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Accepted: 06/13/2022] [Indexed: 11/30/2022]
Abstract
Objective This study was designed to explore the role and mechanism of eukaryotic initiation factor 3C (EIF3C) in the proliferation and apoptosis of lung cancer cells. Methods EIF3C expression in clinic lung cancer tissues was detected by immunohistochemistry assay. Cell transfection with lentivirus EIF3C short hairpin RNA (shRNA) was performed with Lipofectamine 2000. Cell proliferation was evaluated by Celigo and MTT assays. Caspase-3/7 activity was assessed using caspase-3/7 assay kit for cell apoptosis detection. The apoptosis rate of lung cancer cells was assessed by flow cytometry. A transplanted tumor nude-mouse model was established to clarify the role of EIF3C in lung cancer. The potential mechanism of EIF3C was explored by mRNA microarray analysis. Among the top 30 up- and downregulated mRNAs selected for RT-qPCR, 5 were chosen for western blot analysis. Results EIF3C was abnormally overexpressed in lung cancer cell lines and tissues. Silencing EIF3C suppressed the proliferation and promoted the apoptosis of lung cancer cells. In vivo experiments using transplanted tumor nude-mouse model suggested that EIF3C promoted lung cancer tumorigenesis. Further, mRNA microarray analyses identified 189 upregulated and 83 downregulated differentially expressed mRNA between the KD and negative control groups. After validation by RT-qPCR and western blot, three downstream genes (APP, HSPA1A, and LMNB1) were confirmed. Conclusion EIF3C overexpression may facilitate the proliferation and hamper the apoptosis of lung cancer cells by regulating the APP/HSPA1A/LMNB1 axis.
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10
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An eIF3d-dependent switch regulates HCMV replication by remodeling the infected cell translation landscape to mimic chronic ER stress. Cell Rep 2022; 39:110767. [PMID: 35508137 PMCID: PMC9127984 DOI: 10.1016/j.celrep.2022.110767] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 02/07/2022] [Accepted: 04/11/2022] [Indexed: 11/20/2022] Open
Abstract
Regulated loading of eIF3-bound 40S ribosomes on capped mRNA is generally dependent upon the translation initiation factor eIF4E; however, mRNA translation often proceeds during physiological stress, such as virus infection, when eIF4E availability and activity are limiting. It remains poorly understood how translation of virus and host mRNAs are regulated during infection stress. While initially sensitive to mTOR inhibition, which limits eIF4E-dependent translation, we show that protein synthesis in human cytomegalovirus (HCMV)-infected cells unexpectedly becomes progressively reliant upon eIF3d. Targeting eIF3d selectively inhibits HCMV replication, reduces polyribosome abundance, and interferes with expression of essential virus genes and a host gene expression signature indicative of chronic ER stress that fosters HCMV reproduction. This reveals a strategy whereby cellular eIF3d-dependent protein production is hijacked to exploit virus-induced ER stress. Moreover, it establishes how switching between eIF4E and eIF3d-responsive cap-dependent translation can differentially tune virus and host gene expression in infected cells. Instead of eIF4E-regulated ribosome loading, Thompson et al. show capped mRNA translation in HCMV-infected cells becomes reliant upon eIF3d. Depleting eIF3d inhibits HCMV replication, reduces polyribosomes, and restricts virus late gene and host chronic ER stress-induced gene expression. Thus, switching to eIF3d-responsive translation tunes gene expression to support virus replication.
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11
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Warnsmann V, Meisterknecht J, Wittig I, Osiewacz HD. Aging of Podospora anserina Leads to Alterations of OXPHOS and the Induction of Non-Mitochondrial Salvage Pathways. Cells 2021; 10:cells10123319. [PMID: 34943827 PMCID: PMC8699231 DOI: 10.3390/cells10123319] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 11/22/2021] [Accepted: 11/24/2021] [Indexed: 01/19/2023] Open
Abstract
The accumulation of functionally impaired mitochondria is a key event in aging. Previous works with the fungal aging model Podospora anserina demonstrated pronounced age-dependent changes of mitochondrial morphology and ultrastructure, as well as alterations of transcript and protein levels, including individual proteins of the oxidative phosphorylation (OXPHOS). The identified protein changes do not reflect the level of the whole protein complexes as they function in-vivo. In the present study, we investigated in detail the age-dependent changes of assembled mitochondrial protein complexes, using complexome profiling. We observed pronounced age-depen-dent alterations of the OXPHOS complexes, including the loss of mitochondrial respiratory supercomplexes (mtRSCs) and a reduction in the abundance of complex I and complex IV. Additionally, we identified a switch from the standard complex IV-dependent respiration to an alternative respiration during the aging of the P. anserina wild type. Interestingly, we identified proteasome components, as well as endoplasmic reticulum (ER) proteins, for which the recruitment to mitochondria appeared to be increased in the mitochondria of older cultures. Overall, our data demonstrate pronounced age-dependent alterations of the protein complexes involved in energy transduction and suggest the induction of different non-mitochondrial salvage pathways, to counteract the age-dependent mitochondrial impairments which occur during aging.
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Affiliation(s)
- Verena Warnsmann
- Institute of Molecular Biosciences, Faculty of Biosciences, Goethe-University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
| | - Jana Meisterknecht
- Functional Proteomics, Institute of Cardiovascular Physiology, Faculty of Medicine, Goethe-University, Theodor-Stein-Kai 7, 60590 Frankfurt am Main, Germany
| | - Ilka Wittig
- Functional Proteomics, Institute of Cardiovascular Physiology, Faculty of Medicine, Goethe-University, Theodor-Stein-Kai 7, 60590 Frankfurt am Main, Germany
| | - Heinz D Osiewacz
- Institute of Molecular Biosciences, Faculty of Biosciences, Goethe-University, Max-von-Laue-Str. 9, 60438 Frankfurt, Germany
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12
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Gao R, Sun C. A marine bacterial community capable of degrading poly(ethylene terephthalate) and polyethylene. JOURNAL OF HAZARDOUS MATERIALS 2021; 416:125928. [PMID: 34489083 DOI: 10.1016/j.jhazmat.2021.125928] [Citation(s) in RCA: 81] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Revised: 04/15/2021] [Accepted: 04/16/2021] [Indexed: 05/18/2023]
Abstract
Plastic wastes are becoming the most common form of marine debris and present a growing global pollution problem. Here, we used a screening approach on hundreds of plastic waste-associated samples and discovered a marine bacterial community capable of efficiently colonizing and degrading both poly(ethylene terephthalate) (PET) and polyethylene (PE). Using absolute quantitative 16S rRNA sequencing and cultivation methods, we obtained corresponding abundance and purified cultures of three bacterial strains that mediated plastic degradation. We further performed numerous techniques to characterize the efficient degradation of PET and PE by the reconstituted bacterial community containing these three bacteria. Additionally, we used liquid chromatography-mass spectrometry to further demonstrate the degradation of PET and PE films by the reconstituted bacterial community. We conducted transcriptomic methods to investigate the plastic degradation process and potential degradation mechanisms mediated by our reconstituted bacterial community. Lastly, we overexpressed PE degradation enzymes based on transcriptomic results and verified their significant degradation effects on the PE films. Overall, our study establishes a stable marine bacterial community that efficiently degrades PET and PE and provides insights into plastic degradation pathways and their associated biological and mechanistic processes-paving the way for developing microbial products against plastic wastes.
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Affiliation(s)
- Rongrong Gao
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology & Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; College of Earth Science, University of Chinese Academy of Sciences, Beijing, China; Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China
| | - Chaomin Sun
- CAS and Shandong Province Key Laboratory of Experimental Marine Biology & Center of Deep Sea Research, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China; Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China; Center of Ocean Mega-Science, Chinese Academy of Sciences, Qingdao, China.
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13
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Lin L, Cao J, Du A, An Q, Chen X, Yuan S, Batool W, Shabbir A, Zhang D, Wang Z, Norvienyeku J. eIF3k Domain-Containing Protein Regulates Conidiogenesis, Appressorium Turgor, Virulence, Stress Tolerance, and Physiological and Pathogenic Development of Magnaporthe oryzae Oryzae. FRONTIERS IN PLANT SCIENCE 2021; 12:748120. [PMID: 34733303 PMCID: PMC8558559 DOI: 10.3389/fpls.2021.748120] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 09/22/2021] [Indexed: 05/05/2023]
Abstract
The eukaryotic translation initiation factor 3 (eIF3) complex consists of essential and non-essential sub-complexes. Non-essential eIF3 complex subunits, such as eIF3e, eIF3j, eIF3k, and eIF3l, modulate stress tolerance and enhance the lifespan of Neurospora crassa and Caenorhabditis elegans. However, there is limited knowledge of the role of the non-essential eIF3 sub-complex in the pathophysiological development of plant fungal pathogens. Here, we deployed genetic and biochemical techniques to explore the influence of a hypothetical protein containing eIF3k domain in Magnaporthe oryzae Oryzae (MoOeIF3k) on reproduction, hyphae morphogenesis, stress tolerance, and pathogenesis. Also, the targeted disruption of MoOeIF3k suppressed vegetative growth and asexual sporulation in ΔMoOeif3k strains significantly. We demonstrated that MoOeIF3k promotes the initiation and development of the rice blast disease by positively regulating the mobilization and degradation of glycogen, appressorium integrity, host penetration, and colonization during host-pathogen interaction. For the first time, we demonstrated that the eIF3k subunit supports the survival of the blast fungus by suppressing vegetative growth and possibly regulating the conversions and utilization of stored cellular energy reserves under starvation conditions. We also observed that the deletion of MoOeIF3k accelerated ribosomal RNA (rRNA) generation in the ΔMoOeif3k strains with a corresponding increase in total protein output. In summary, this study unravels the pathophysiological significance of eIF3k filamentous fungi. The findings also underscored the need to systematically evaluate the individual subunits of the non-essential eIF3 sub-complex during host-pathogen interaction. Further studies are required to unravel the influence of synergetic coordination between translation and transcriptional regulatory machinery on the pathogenesis of filamentous fungi pathogens.
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Affiliation(s)
- Lili Lin
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jiaying Cao
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Anqiang Du
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qiuli An
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiaomin Chen
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Shuangshuang Yuan
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Wajjiha Batool
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Ammarah Shabbir
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Dongmei Zhang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Zonghua Wang
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
- Institute of Oceanography, Minjiang University, Fuzhou, China
- Zonghua Wang,
| | - Justice Norvienyeku
- State Key Laboratory of Ecological Pest Control for Fujian and Taiwan Crops, Fujian Agriculture and Forestry University, Fuzhou, China
- Fujian University Key Laboratory for Plant-Microbe Interaction, Fujian Agriculture and Forestry University, Fuzhou, China
- Key Laboratory of Green Prevention and Control of Tropical Plant Diseases and Pests, Ministry of Education, College of Plant Protection, Hainan University, Haikou, China
- *Correspondence: Justice Norvienyeku,
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14
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Hayek H, Gross L, Janvier A, Schaeffer L, Martin F, Eriani G, Allmang C. eIF3 interacts with histone H4 messenger RNA to regulate its translation. J Biol Chem 2021; 296:100578. [PMID: 33766559 PMCID: PMC8102920 DOI: 10.1016/j.jbc.2021.100578] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 03/15/2021] [Accepted: 03/21/2021] [Indexed: 11/23/2022] Open
Abstract
In eukaryotes, various alternative translation initiation mechanisms have been unveiled for the translation of specific mRNAs. Some do not conform to the conventional scanning-initiation model. Translation initiation of histone H4 mRNA combines both canonical (cap-dependent) and viral initiation strategies (no-scanning, internal recruitment of initiation factors). Specific H4 mRNA structures tether the translation machinery directly onto the initiation codon and allow massive production of histone H4 during the S phase of the cell cycle. The human eukaryotic translation initiation factor 3 (eIF3), composed of 13 subunits (a-m), was shown to selectively recruit and control the expression of several cellular mRNAs. Whether eIF3 mediates H4 mRNA translation remains to be elucidated. Here, we report that eIF3 binds to a stem-loop structure (eIF3-BS) located in the coding region of H4 mRNA. Combining cross-linking and ribonucleoprotein immunoprecipitation experiments in vivo and in vitro, we also found that eIF3 binds to H1, H2A, H2B, and H3 histone mRNAs. We identified direct contacts between eIF3c, d, e, g subunits, and histone mRNAs but observed distinct interaction patterns to each histone mRNA. Our results show that eIF3 depletion in vivo reduces histone mRNA binding and modulates histone neosynthesis, suggesting that synthesis of histones is sensitive to the levels of eIF3. Thus, we provide evidence that eIF3 acts as a regulator of histone translation.
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Affiliation(s)
- Hassan Hayek
- Architecture et Réactivité de l'ARN, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France
| | - Lauriane Gross
- Architecture et Réactivité de l'ARN, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France
| | - Aurélie Janvier
- Architecture et Réactivité de l'ARN, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France
| | - Laure Schaeffer
- Architecture et Réactivité de l'ARN, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France
| | - Franck Martin
- Architecture et Réactivité de l'ARN, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France
| | - Gilbert Eriani
- Architecture et Réactivité de l'ARN, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France.
| | - Christine Allmang
- Architecture et Réactivité de l'ARN, Centre National de la Recherche Scientifique, Institut de Biologie Moléculaire et Cellulaire, Université de Strasbourg, Strasbourg, France.
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15
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Lamper AM, Fleming RH, Ladd KM, Lee ASY. A phosphorylation-regulated eIF3d translation switch mediates cellular adaptation to metabolic stress. Science 2020; 370:853-856. [PMID: 33184215 DOI: 10.1126/science.abb0993] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 08/20/2020] [Accepted: 09/24/2020] [Indexed: 12/20/2022]
Abstract
Shutoff of global protein synthesis is a conserved response to cellular stresses. This general phenomenon is accompanied by the induction of distinct gene programs tailored to each stress. Although the mechanisms driving repression of general protein synthesis are well characterized, how cells reprogram the translation machinery for selective gene expression remains poorly understood. Here, we found that the noncanonical 5' cap-binding protein eIF3d was activated in response to metabolic stress in human cells. Activation required reduced CK2-mediated phosphorylation near the eIF3d cap-binding pocket. eIF3d controls a gene program enriched in factors important for glucose homeostasis, including members of the mammalian target of rapamycin (mTOR) pathway. eIF3d-directed translation adaptation was essential for cell survival during chronic glucose deprivation. Thus, this mechanism of translation reprogramming regulates the cellular response to metabolic stress.
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Affiliation(s)
- Adam M Lamper
- Department of Biology, Brandeis University, Waltham, MA 02453, USA.
| | | | - Kayla M Ladd
- Department of Biology, Brandeis University, Waltham, MA 02453, USA
| | - Amy S Y Lee
- Department of Biology, Brandeis University, Waltham, MA 02453, USA.
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16
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Structural Differences in Translation Initiation between Pathogenic Trypanosomatids and Their Mammalian Hosts. Cell Rep 2020; 33:108534. [PMID: 33357443 PMCID: PMC7773551 DOI: 10.1016/j.celrep.2020.108534] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 10/08/2020] [Accepted: 11/25/2020] [Indexed: 11/25/2022] Open
Abstract
Canonical mRNA translation in eukaryotes begins with the formation of the 43S pre-initiation complex (PIC). Its assembly requires binding of initiator Met-tRNAiMet and several eukaryotic initiation factors (eIFs) to the small ribosomal subunit (40S). Compared to their mammalian hosts, trypanosomatids present significant structural differences in their 40S, suggesting substantial variability in translation initiation. Here, we determine the structure of the 43S PIC from Trypanosoma cruzi, the parasite causing Chagas disease. Our structure shows numerous specific features, such as the variant eIF3 structure and its unique interactions with the large rRNA expansion segments (ESs) 9S, 7S, and 6S, and the association of a kinetoplastid-specific DDX60-like helicase. It also reveals the 40S-binding site of the eIF5 C-terminal domain and structures of key terminal tails of several conserved eIFs underlying their activities within the PIC. Our results are corroborated by glutathione S-transferase (GST) pull-down assays in both human and T. cruzi and mass spectrometry data. Structure of the 43S pre-initiation complex from Trypanosoma cruzi is solved at 3.33 Å The kinetoplastids’ eIF3 core is a septamer that binds mainly the unique, extended ES7s A kinetoplastid-specific DDX60-like helicase binds to the 43S PIC entry pore The 40S positions of eIF5-CTD and key tails of several eIFs are determined
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17
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Bhardwaj U, Powell P, Goss DJ. Eukaryotic initiation factor (eIF) 3 mediates Barley Yellow Dwarf Viral mRNA 3'-5' UTR interactions and 40S ribosomal subunit binding to facilitate cap-independent translation. Nucleic Acids Res 2020; 47:6225-6235. [PMID: 31114905 PMCID: PMC6614841 DOI: 10.1093/nar/gkz448] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 05/06/2019] [Accepted: 05/09/2019] [Indexed: 12/30/2022] Open
Abstract
Barley Yellow Dwarf Virus (BYDV) is a positive strand RNA virus that lacks the canonical 5′ 7-methylguanosine cap and a 3′ poly-A tail. Instead, BYDV utilizes a cruciform cap independent translation element (CITE) in its 3′UTR RNA (BYDV-like CITE or BTE) that binds eukaryotic translation initiation factor (eIF) 4F and recruits 40S ribosomal subunits in the presence of active helicase factors (eIF4A, eIF4B, eIF4F and ATP). A long-range, 5-nucleotide, base-pairing kissing loop interaction between the 3′BTE and a 5′UTR stem-loop is necessary for translation to initiate. The 40S–eIF complex does not bind to the BYDV 5′UTR, suggesting the involvement of additional factors. We identified eIF3 as a component of the 3′BTE recruited complex using affinity-tagged 3′BTE RNA pull-down assays. Fluorescence anisotropy binding and gel shift assays showed that the 3′BTE and 5′UTR RNAs can simultaneously and non-competitively bind eIF3 in the presence of active helicase factors forming a single, macromolecular complex. Further, quantitative studies showed eIF3 increased recruitment of the 40S subunit by more than 25-fold. We propose a new role for eIF3, where eIF3 bridges BYDV’s UTRs, stabilizes the long-range 5′-3′ interaction, and facilitates recruitment of the 40S–eIF complex to the 5′UTR, leading to translation initiation.
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Affiliation(s)
- Usha Bhardwaj
- Department of Chemistry, Hunter College, CUNY, New York, NY 10065, USA
| | - Paul Powell
- Department of Chemistry, Hunter College, CUNY, New York, NY 10065, USA.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, USA
| | - Dixie J Goss
- Department of Chemistry, Hunter College, CUNY, New York, NY 10065, USA.,Ph.D. Program in Chemistry, The Graduate Center of the City University of New York, New York, NY 10016, USA.,Ph.D. Program in Biochemistry, The Graduate Center of the City University of New York, New York, NY 10016, USA
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18
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Raabe K, Honys D, Michailidis C. The role of eukaryotic initiation factor 3 in plant translation regulation. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 145:75-83. [PMID: 31665669 DOI: 10.1016/j.plaphy.2019.10.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/07/2019] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
Regulation of translation represents a critical step in the regulation of gene expression. In plants, the translation regulation plays an important role at all stages of development and, during stress responses, functions as a fast and flexible tool which not only modulates the global translation rate but also controls the production of specific proteins. Regulation of translation is mostly focused on the initiation phase. There, one of essential initiation factors is the large multisubunit protein complex of eukaryotic translation initiation factor 3 (eIF3). In all eukaryotes, the general eIF3 function is to scaffold the formation of the translation initiation complex and to enhance the accuracy of scanning mechanism for start codon selection. Over the past decades, additional eIF3 functions were described as necessary for development in various eukaryotic organisms, including plants. The importance of the eIF3 complex lies not only at the global level of initiation event, but also in the precise translation regulation of specific transcripts. This review gathers the available information on functions of the plant eIF3 complex.
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Affiliation(s)
- Karel Raabe
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic
| | - David Honys
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic
| | - Christos Michailidis
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic.
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19
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Johnson AG, Petrov AN, Fuchs G, Majzoub K, Grosely R, Choi J, Puglisi JD. Fluorescently-tagged human eIF3 for single-molecule spectroscopy. Nucleic Acids Res 2019; 46:e8. [PMID: 29136179 PMCID: PMC5778468 DOI: 10.1093/nar/gkx1050] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 10/24/2017] [Indexed: 01/09/2023] Open
Abstract
Human translation initiation relies on the combined activities of numerous ribosome-associated eukaryotic initiation factors (eIFs). The largest factor, eIF3, is an ∼800 kDa multiprotein complex that orchestrates a network of interactions with the small 40S ribosomal subunit, other eIFs, and mRNA, while participating in nearly every step of initiation. How these interactions take place during the time course of translation initiation remains unclear. Here, we describe a method for the expression and affinity purification of a fluorescently-tagged eIF3 from human cells. The tagged eIF3 dodecamer is structurally intact, functions in cell-based assays, and interacts with the HCV IRES mRNA and the 40S-IRES complex in vitro. By tracking the binding of single eIF3 molecules to the HCV IRES RNA with a zero-mode waveguides-based instrument, we show that eIF3 samples both wild-type IRES and an IRES that lacks the eIF3-binding region, and that the high-affinity eIF3-IRES interaction is largely determined by slow dissociation kinetics. The application of single-molecule methods to more complex systems involving eIF3 may unveil dynamics underlying mRNA selection and ribosome loading during human translation initiation.
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Affiliation(s)
- Alex G Johnson
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Alexey N Petrov
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
| | - Gabriele Fuchs
- The RNA Institute, Department of Biological Sciences, University of Albany, Albany, NY 12222, USA
| | - Karim Majzoub
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Junhong Choi
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
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20
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Genuth NR, Barna M. Heterogeneity and specialized functions of translation machinery: from genes to organisms. Nat Rev Genet 2019; 19:431-452. [PMID: 29725087 DOI: 10.1038/s41576-018-0008-z] [Citation(s) in RCA: 141] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Regulation of mRNA translation offers the opportunity to diversify the expression and abundance of proteins made from individual gene products in cells, tissues and organisms. Emerging evidence has highlighted variation in the composition and activity of several large, highly conserved translation complexes as a means to differentially control gene expression. Heterogeneity and specialized functions of individual components of the ribosome and of the translation initiation factor complexes eIF3 and eIF4F, which are required for recruitment of the ribosome to the mRNA 5' untranslated region, have been identified. In this Review, we summarize the evidence for selective mRNA translation by components of these macromolecular complexes as a means to dynamically control the translation of the proteome in time and space. We further discuss the implications of this form of gene expression regulation for a growing number of human genetic disorders associated with mutations in the translation machinery.
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Affiliation(s)
- Naomi R Genuth
- Departments of Genetics and Developmental Biology, Stanford University, Stanford, CA, USA.,Department of Biology, Stanford University, Stanford, CA, USA
| | - Maria Barna
- Departments of Genetics and Developmental Biology, Stanford University, Stanford, CA, USA.
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21
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Eliseev B, Yeramala L, Leitner A, Karuppasamy M, Raimondeau E, Huard K, Alkalaeva E, Aebersold R, Schaffitzel C. Structure of a human cap-dependent 48S translation pre-initiation complex. Nucleic Acids Res 2019; 46:2678-2689. [PMID: 29401259 PMCID: PMC5861459 DOI: 10.1093/nar/gky054] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 01/21/2018] [Indexed: 01/13/2023] Open
Abstract
Eukaryotic translation initiation is tightly regulated, requiring a set of conserved initiation factors (eIFs). Translation of a capped mRNA depends on the trimeric eIF4F complex and eIF4B to load the mRNA onto the 43S pre-initiation complex comprising 40S and initiation factors 1, 1A, 2, 3 and 5 as well as initiator-tRNA. Binding of the mRNA is followed by mRNA scanning in the 48S pre-initiation complex, until a start codon is recognised. Here, we use a reconstituted system to prepare human 48S complexes assembled on capped mRNA in the presence of eIF4B and eIF4F. The highly purified h-48S complexes are used for cross-linking/mass spectrometry, revealing the protein interaction network in this complex. We report the electron cryo-microscopy structure of the h-48S complex at 6.3 Å resolution. While the majority of eIF4B and eIF4F appear to be flexible with respect to the ribosome, additional density is detected at the entrance of the 40S mRNA channel which we attribute to the RNA-recognition motif of eIF4B. The eight core subunits of eIF3 are bound at the 40S solvent-exposed side, as well as the subunits eIF3d, eIF3b and eIF3i. elF2 and initiator-tRNA bound to the start codon are present at the 40S intersubunit side. This cryo-EM structure represents a molecular snap-shot revealing the h-48S complex following start codon recognition.
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Affiliation(s)
- Boris Eliseev
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Lahari Yeramala
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Alexander Leitner
- ETH Zürich, Institute of Molecular Systems Biology, Auguste-Piccard-Hof 1, 8093 Zürich, Switzerland
| | - Manikandan Karuppasamy
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Etienne Raimondeau
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Karine Huard
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Elena Alkalaeva
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Ruedi Aebersold
- ETH Zürich, Institute of Molecular Systems Biology, Auguste-Piccard-Hof 1, 8093 Zürich, Switzerland.,Faculty of Science, University of Zürich, 8057 Zürich, Switzerland
| | - Christiane Schaffitzel
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France.,School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
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22
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Shintani T, Higashisaka K, Maeda M, Hamada M, Tsuji R, Kurihara K, Kashiwagi Y, Sato A, Obana M, Yamamoto A, Kawasaki K, Lin Y, Kijima T, Kinehara Y, Miwa Y, Maeda S, Morii E, Kumanogoh A, Tsutsumi Y, Nagatomo I, Fujio Y. Eukaryotic translation initiation factor 3 subunit C is associated with acquired resistance to erlotinib in non-small cell lung cancer. Oncotarget 2018; 9:37520-37533. [PMID: 30680067 PMCID: PMC6331022 DOI: 10.18632/oncotarget.26494] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 12/10/2018] [Indexed: 12/20/2022] Open
Abstract
The acquisition of resistance to EGFR tyrosine kinase inhibitors (EGFR-TKIs) is one of the major problems in the pharmacotherapy against non-small cell lung cancers; however, molecular mechanisms remain to be fully elucidated. Here, using a newly-established erlotinib-resistant cell line, PC9/ER, from PC9 lung cancer cells, we demonstrated that the expression of translation-related molecules, including eukaryotic translation initiation factor 3 subunit C (eIF3c), was upregulated in PC9/ER cells by proteome analyses. Immunoblot analyses confirmed that eIF3c protein increased in PC9/ER cells, compared with PC9 cells. Importantly, the knockdown of eIF3c with its siRNAs enhanced the drug sensitivity in PC9/ER cells. Mechanistically, we found that LC3B-II was upregulated in PC9/ER cells, while downregulated by the knockdown of eIF3c. Consistently, the overexpression of eIF3c increased the number of autophagosomes, proposing the causality between eIF3c expression and autophagy. Moreover, chloroquine, an autophagy inhibitor, restored the sensitivity to erlotinib. Finally, immunohistochemical analyses of biopsy samples showed that the frequency of eIF3c-positive cases was higher in the patients with EGFR-TKI resistance than those prior to EGFR-TKI treatment. Moreover, the eIF3c-positive cases exhibited poor prognosis in EGFR-TKI treatment. Collectively, the upregulation of eIF3c could impair the sensitivity to EGFR-TKI as a novel mechanism of the drug resistance.
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Affiliation(s)
- Takuya Shintani
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.,Department of Pharmacy, Osaka University Hospital, Suita, Japan
| | - Kazuma Higashisaka
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.,Department of Legal Medicine, Osaka University Graduate School of Medicine, Suita, Japan
| | - Makiko Maeda
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Masaya Hamada
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Ryosuke Tsuji
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Koudai Kurihara
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Yuri Kashiwagi
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Atsuhiro Sato
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Masanori Obana
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Ayaha Yamamoto
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Keisuke Kawasaki
- Department of Pathology, Osaka University Graduate School of Medicine, Suita, Japan
| | - Ying Lin
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan
| | - Takashi Kijima
- Division of Respiratory Medicine, Department of Internal Medicine, Hyogo College of Medicine, Nishinomiya, Japan.,Department of Respiratory Medicine and Clinical Immunology, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yuhei Kinehara
- Department of Respiratory Medicine and Clinical Immunology, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yoshihiro Miwa
- Department of Pharmacy, Osaka University Hospital, Suita, Japan
| | - Shinichiro Maeda
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.,Department of Pharmacy, Osaka University Hospital, Suita, Japan
| | - Eiichi Morii
- Department of Pathology, Osaka University Graduate School of Medicine, Suita, Japan
| | - Atsushi Kumanogoh
- Department of Respiratory Medicine and Clinical Immunology, Graduate School of Medicine, Osaka University, Suita, Japan.,Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Suita, Japan
| | - Yasuo Tsutsumi
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.,The Center for Advanced Medical Engineering and Informatics, Osaka University, Suita, Japan
| | - Izumi Nagatomo
- Department of Respiratory Medicine and Clinical Immunology, Graduate School of Medicine, Osaka University, Suita, Japan
| | - Yasushi Fujio
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan.,Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Suita, Japan
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23
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Feng X, Li J, Liu P. The Biological Roles of Translation Initiation Factor 3b. Int J Biol Sci 2018; 14:1630-1635. [PMID: 30416377 PMCID: PMC6216031 DOI: 10.7150/ijbs.26932] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/05/2018] [Indexed: 11/12/2022] Open
Abstract
Translation has important roles in almost all physiological and pathological processes, and translation initiation factors are particularly relevant to the translation initiation step, which is the most important step in translation regulation. Translation initiation factor 3b (eIF3b), a key subunit of the largest translation initiation factor 3 (eIF3), is widely considered a scaffold protein that acts to ensure the accuracy of translation initiation. A series of recent finds has revealed that eIF3 is closely related to oncogenesis. However, the concrete mechanism by which eIF3b is involve in carcinogenesis remains elusive. Here, we summarize a series of research findings regarding the relationship between eIF3b, translation and cancer.
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Affiliation(s)
- Xuefei Feng
- Center for Translational Medicine, the First Affiliated Hospital of Xi'an Jiaotong University.,Key Laboratory for Tumor Precision Medicine of Shaanxi Province, the First Affiliated Hospital of Xi'an Jiaotong University
| | - Juan Li
- Center for Translational Medicine, the First Affiliated Hospital of Xi'an Jiaotong University.,Key Laboratory for Tumor Precision Medicine of Shaanxi Province, the First Affiliated Hospital of Xi'an Jiaotong University
| | - Peijun Liu
- Center for Translational Medicine, the First Affiliated Hospital of Xi'an Jiaotong University.,Key Laboratory for Tumor Precision Medicine of Shaanxi Province, the First Affiliated Hospital of Xi'an Jiaotong University
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24
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Sadato D, Ono T, Gotoh-Saito S, Kajiwara N, Nomura N, Ukaji M, Yang L, Sakimura K, Tajima Y, Oboki K, Shibasaki F. Eukaryotic translation initiation factor 3 (eIF3) subunit e is essential for embryonic development and cell proliferation. FEBS Open Bio 2018; 8:1188-1201. [PMID: 30087825 PMCID: PMC6070656 DOI: 10.1002/2211-5463.12482] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/13/2018] [Accepted: 06/12/2018] [Indexed: 11/06/2022] Open
Abstract
Mammalian eukaryotic translation initiation factor 3 (eIF3) is the largest complex of the translation initiation factors. The eIF3 complex is comprised of thirteen subunits, which are named eIF3a to eIF3 m in most multicellular organisms. The eIF3e gene locus is one of the most frequent integration sites of mouse mammary tumor virus (MMTV), which induces mammary tumors in mice. MMTV-integration events result in the expression of C-terminal-truncated eIF3e proteins, leading to mammary tumor formation. We have shown that tumor formation can be partly caused by activation of hypoxia-inducible factor 2α. To investigate the function of eIF3e in mammals, we generated eIF3e-deficient mice. These eIF3e-/- mice are embryonically lethal, while eIF3e+/- mice are much smaller than wild-type mice. In addition, eIF3e+/- mouse embryonic fibroblasts (MEFs) contained reduced levels of eIF3a and eIF3c subunits and exhibited reduced cellular proliferation. These results suggest that eIF3e is essential for embryonic development in mice and plays a role in maintaining eIF3 integrity.
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Affiliation(s)
- Daichi Sadato
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan.,Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
| | - Tomio Ono
- Center for Basic Technology Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Saki Gotoh-Saito
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Naoki Kajiwara
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Namiko Nomura
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Masako Ukaji
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Liying Yang
- Center for Basic Technology Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology Brain Research Institute Niigata University Japan
| | - Youichi Tajima
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Keisuke Oboki
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Futoshi Shibasaki
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
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25
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Szostak E, García-Beyaert M, Guitart T, Graindorge A, Coll O, Gebauer F. Hrp48 and eIF3d contribute to msl-2 mRNA translational repression. Nucleic Acids Res 2018; 46:4099-4113. [PMID: 29635389 PMCID: PMC5934621 DOI: 10.1093/nar/gky246] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 03/02/2018] [Accepted: 03/23/2018] [Indexed: 12/28/2022] Open
Abstract
Translational repression of msl-2 mRNA in females of Drosophila melanogaster is an essential step in the regulation of X-chromosome dosage compensation. Repression is orchestrated by Sex-lethal (SXL), which binds to both untranslated regions (UTRs) of msl-2 and inhibits translation initiation by poorly understood mechanisms. Here we identify Hrp48 as a SXL co-factor. Hrp48 binds to the 3' UTR of msl-2 and is required for optimal repression by SXL. Hrp48 interacts with eIF3d, a subunit of the eIF3 translation initiation complex. Reporter and RNA chromatography assays showed that eIF3d binds to msl-2 5' UTR, and is required for efficient translation and translational repression of msl-2 mRNA. In line with these results, eIF3d depletion -but not depletion of other eIF3 subunits- de-represses msl-2 expression in female flies. These data are consistent with a model where Hrp48 inhibits msl-2 translation by targeting eIF3d. Our results uncover an important step in the mechanism of msl-2 translation regulation, and illustrate how general translation initiation factors can be co-opted by RNA binding proteins to achieve mRNA-specific control.
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Affiliation(s)
- Emilia Szostak
- Gene Regulation, Stem Cells and Cancer Programme, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Marina García-Beyaert
- Gene Regulation, Stem Cells and Cancer Programme, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Tanit Guitart
- Gene Regulation, Stem Cells and Cancer Programme, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Antoine Graindorge
- Gene Regulation, Stem Cells and Cancer Programme, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Olga Coll
- Gene Regulation, Stem Cells and Cancer Programme, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
| | - Fátima Gebauer
- Gene Regulation, Stem Cells and Cancer Programme, Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, 08003 Barcelona, Spain
- Universitat Pompeu Fabra (UPF), 08003 Barcelona, Spain
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26
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Hashem Y, Frank J. The Jigsaw Puzzle of mRNA Translation Initiation in Eukaryotes: A Decade of Structures Unraveling the Mechanics of the Process. Annu Rev Biophys 2018; 47:125-151. [PMID: 29494255 DOI: 10.1146/annurev-biophys-070816-034034] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Translation initiation in eukaryotes is a highly regulated and rate-limiting process. It results in the assembly and disassembly of numerous transient and intermediate complexes involving over a dozen eukaryotic initiation factors (eIFs). This process culminates in the accommodation of a start codon marking the beginning of an open reading frame at the appropriate ribosomal site. Although this process has been extensively studied by hundreds of groups for nearly half a century, it has been only recently, especially during the last decade, that we have gained deeper insight into the mechanics of the eukaryotic translation initiation process. This advance in knowledge is due in part to the contributions of structural biology, which have shed light on the molecular mechanics underlying the different functions of various eukaryotic initiation factors. In this review, we focus exclusively on the contribution of structural biology to the understanding of the eukaryotic initiation process, a long-standing jigsaw puzzle that is just starting to yield the bigger picture.
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Affiliation(s)
- Yaser Hashem
- INSERM U1212, Institut Européen de Chimie et Biologie, Université de Bordeaux, Pessac 33607, France;
| | - Joachim Frank
- Department of Biological Sciences, Columbia University, New York, NY 10032, USA;
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27
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Mailliot J, Martin F. Viral internal ribosomal entry sites: four classes for one goal. WILEY INTERDISCIPLINARY REVIEWS. RNA 2018; 9. [PMID: 29193740 DOI: 10.1002/wrna.1458] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Revised: 09/19/2017] [Accepted: 10/02/2017] [Indexed: 12/22/2022]
Abstract
To ensure efficient propagation, viruses need to rapidly produce viral proteins after cell entrance. Since viral genomes do not encode any components of the protein biosynthesis machinery, viral proteins must be produced by the host cell. To hi-jack the host cellular translation, viruses use a great variety of distinct strategies. Many single-stranded positive-sensed RNA viruses contain so-called internal ribosome entry sites (IRESs). IRESs are structural RNA motifs that have evolved to specific folds that recruit the host ribosomes on the viral coding sequences in order to synthesize viral proteins. In host canonical translation, recruitment of the translation machinery components is essentially guided by the 5' cap (m7 G) of mRNA. In contrast, IRESs are able to promote efficient ribosome assembly internally and in cap-independent manner. IRESs have been categorized into four classes, based on their length, nucleotide sequence, secondary and tertiary structures, as well as their mode of action. Classes I and II require the assistance of cellular auxiliary factors, the eukaryotic intiation factors (eIF), for efficient ribosome assembly. Class III IRESs require only a subset of eIFs whereas Class IV, which are the more compact, can promote translation without any eIFs. Extensive functional and structural investigations of IRESs over the past decades have allowed a better understanding of their mode of action for viral translation. Because viral translation has a pivotal role in the infectious program, IRESs are therefore attractive targets for therapeutic purposes. WIREs RNA 2018, 9:e1458. doi: 10.1002/wrna.1458 This article is categorized under: Translation > Ribosome Structure/Function Translation > Translation Mechanisms RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes.
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Affiliation(s)
- Justine Mailliot
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS UMR7104, INSERM U964, Illkirch-Graffenstaden, France
| | - Franck Martin
- Institut de Biologie Moléculaire et Cellulaire, "Architecture et Réactivité de l'ARN" CNRS UPR9002, Université De Strasbourg, Strasbourg, France
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28
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El-Naggar AM, Sorensen PH. Translational control of aberrant stress responses as a hallmark of cancer. J Pathol 2018; 244:650-666. [PMID: 29293271 DOI: 10.1002/path.5030] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 12/21/2017] [Accepted: 12/22/2017] [Indexed: 12/12/2022]
Abstract
Altered mRNA translational control is emerging as a critical factor in cancer development and progression. Targeting specific elements of the translational machinery, such as mTORC1 or eIF4E, is emerging as a new strategy for innovative cancer therapy. While translation of most mRNAs takes place through cap-dependent mechanisms, a sub-population of cellular mRNA species, particularly stress-inducible mRNAs with highly structured 5'-UTR regions, are primarily translated through cap-independent mechanisms. Intriguingly, many of these mRNAs encode proteins that are involved in tumour cell adaptation to microenvironmental stress, and thus linked to aggressive behaviour including tumour invasion and metastasis. This necessitates a rigorous search for links between microenvironmental stress and aggressive tumour phenotypes. Under stress, cells block global protein synthesis to preserve energy while maintaining selective synthesis of proteins that support cell survival. One highly conserved mechanism to regulate protein synthesis under cell stress is to sequester mRNAs into cytosolic aggregates called stress granules (SGs), where their translation is silenced. SGs confer survival advantages and chemotherapeutic resistance to tumour cells under stress. Recently, it has been shown that genetically blocking SG formation dramatically reduces tumour invasive and metastatic capacity in vivo. Therefore, targeting SG formation might represent a potential treatment strategy to block cancer metastasis. Here, we present the critical link between selective mRNA translation, stress adaptation, SGs, and tumour progression. Further, we also explain how deciphering mechanisms of selective mRNA translation occurs under cell stress holds great promise for the identification of new targets in the treatment of cancer. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Amal M El-Naggar
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada.,Department of Molecular Oncology, British Columbia Cancer Research Centre, Vancouver, Canada.,Department of Pathology, Faculty of Medicine, Menoufia University, Egypt
| | - Poul H Sorensen
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada.,Department of Molecular Oncology, British Columbia Cancer Research Centre, Vancouver, Canada
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29
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Andreev DE, Dmitriev SE, Loughran G, Terenin IM, Baranov PV, Shatsky IN. Translation control of mRNAs encoding mammalian translation initiation factors. Gene 2018; 651:174-182. [PMID: 29414693 DOI: 10.1016/j.gene.2018.02.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/25/2018] [Accepted: 02/04/2018] [Indexed: 10/18/2022]
Abstract
Eukaryotic cells evolved highly complex and accurate protein synthesis machinery that is finely tuned by various signaling pathways. Dysregulation of translation is a hallmark of many diseases, including cancer, and thus pharmacological approaches to modulate translation become very promising. While there has been much progress in our understanding of mammalian mRNA-specific translation control, surprisingly, relatively little is known about whether and how the protein components of the translation machinery shape translation of their own mRNAs. Here we analyze mammalian mRNAs encoding components of the translation initiation machinery for potential regulatory features such as 5'TOP motifs, TISU motifs, poor start codon nucleotide context and upstream open reading frames.
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Affiliation(s)
- Dmitri E Andreev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
| | - Sergey E Dmitriev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia; Department of Biochemistry, Biological Faculty, Lomonosov Moscow State University, Moscow, Russia
| | - Gary Loughran
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Ilya M Terenin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Ivan N Shatsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
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30
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Ararso Z, Ma C, Qi Y, Feng M, Han B, Hu H, Meng L, Li J. Proteome Comparisons between Hemolymph of Two Honeybee Strains (Apis mellifera ligustica) Reveal Divergent Molecular Basis in Driving Hemolymph Function and High Royal Jelly Secretion. J Proteome Res 2017; 17:402-419. [DOI: 10.1021/acs.jproteome.7b00621] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Zewdu Ararso
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Chuan Ma
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Yuping Qi
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Mao Feng
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Bin Han
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Han Hu
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Lifeng Meng
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Jianke Li
- Institute of Apicultural
Research/Key Laboratory of Pollinating Insect Biology, Ministry of
Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China
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31
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Valášek LS, Zeman J, Wagner S, Beznosková P, Pavlíková Z, Mohammad MP, Hronová V, Herrmannová A, Hashem Y, Gunišová S. Embraced by eIF3: structural and functional insights into the roles of eIF3 across the translation cycle. Nucleic Acids Res 2017; 45:10948-10968. [PMID: 28981723 PMCID: PMC5737393 DOI: 10.1093/nar/gkx805] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 08/31/2017] [Indexed: 12/31/2022] Open
Abstract
Protein synthesis is mediated via numerous molecules including the ribosome, mRNA, tRNAs, as well as translation initiation, elongation and release factors. Some of these factors play several roles throughout the entire process to ensure proper assembly of the preinitiation complex on the right mRNA, accurate selection of the initiation codon, errorless production of the encoded polypeptide and its proper termination. Perhaps, the most intriguing of these multitasking factors is the eukaryotic initiation factor eIF3. Recent evidence strongly suggests that this factor, which coordinates the progress of most of the initiation steps, does not come off the initiation complex upon subunit joining, but instead it remains bound to 80S ribosomes and gradually falls off during the first few elongation cycles to: (1) promote resumption of scanning on the same mRNA molecule for reinitiation downstream—in case of translation of upstream ORFs short enough to preserve eIF3 bound; or (2) come back during termination on long ORFs to fine tune its fidelity or, if signaled, promote programmed stop codon readthrough. Here, we unite recent structural views of the eIF3–40S complex and discus all known eIF3 roles to provide a broad picture of the eIF3’s impact on translational control in eukaryotic cells.
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Affiliation(s)
- Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Jakub Zeman
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Petra Beznosková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Zuzana Pavlíková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Mahabub Pasha Mohammad
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Vladislava Hronová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Yaser Hashem
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France
| | - Stanislava Gunišová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
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32
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Johnson AG, Grosely R, Petrov AN, Puglisi JD. Dynamics of IRES-mediated translation. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0177. [PMID: 28138065 DOI: 10.1098/rstb.2016.0177] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 12/19/2022] Open
Abstract
Viral internal ribosome entry sites (IRESs) are unique RNA elements, which use stable and dynamic RNA structures to recruit ribosomes and drive protein synthesis. IRESs overcome the high complexity of the canonical eukaryotic translation initiation pathway, often functioning with a limited set of eukaryotic initiation factors. The simplest types of IRESs are typified by the cricket paralysis virus intergenic region (CrPV IGR) and hepatitis C virus (HCV) IRESs, both of which independently form high-affinity complexes with the small (40S) ribosomal subunit and bypass the molecular processes of cap-binding and scanning. Owing to their simplicity and ribosomal affinity, the CrPV and HCV IRES have been important models for structural and functional studies of the eukaryotic ribosome during initiation, serving as excellent targets for recent technological breakthroughs in cryogenic electron microscopy (cryo-EM) and single-molecule analysis. High-resolution structural models of ribosome : IRES complexes, coupled with dynamics studies, have clarified decades of biochemical research and provided an outline of the conformational and compositional trajectory of the ribosome during initiation. Here we review recent progress in the study of HCV- and CrPV-type IRESs, highlighting important structural and dynamics insights and the synergy between cryo-EM and single-molecule studies.This article is part of the themed issue 'Perspectives on the ribosome'.
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Affiliation(s)
- Alex G Johnson
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Alexey N Petrov
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
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33
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Cate JHD. Human eIF3: from 'blobology' to biological insight. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0176. [PMID: 28138064 PMCID: PMC5311922 DOI: 10.1098/rstb.2016.0176] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 02/06/2023] Open
Abstract
Translation in eukaryotes is highly regulated during initiation, a process impacted by numerous readouts of a cell's state. There are many cases in which cellular messenger RNAs likely do not follow the canonical ‘scanning’ mechanism of translation initiation, but the molecular mechanisms underlying these pathways are still being uncovered. Some RNA viruses such as the hepatitis C virus use highly structured RNA elements termed internal ribosome entry sites (IRESs) that commandeer eukaryotic translation initiation, by using specific interactions with the general eukaryotic translation initiation factor eIF3. Here, I present evidence that, in addition to its general role in translation, eIF3 in humans and likely in all multicellular eukaryotes also acts as a translational activator or repressor by binding RNA structures in the 5′-untranslated regions of specific mRNAs, analogous to the role of the mediator complex in transcription. Furthermore, eIF3 in multicellular eukaryotes also harbours a 5′ 7-methylguanosine cap-binding subunit—eIF3d—which replaces the general cap-binding initiation factor eIF4E in the translation of select mRNAs. Based on results from cell biological, biochemical and structural studies of eIF3, it is likely that human translation initiation proceeds through dozens of different molecular pathways, the vast majority of which remain to be explored. This article is part of the themed issue ‘Perspectives on the ribosome’.
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Affiliation(s)
- Jamie H D Cate
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, CA 94720-3220, USA .,Lawrence Berkeley National Laboratory, Division of Molecular Biophysics and Integrated Bioimaging, Berkeley, CA 94720, USA
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34
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Abstract
The eukaryotic initiation factor 3 (eIF3) is one of the most complex translation initiation factors in mammalian cells, consisting of several subunits (eIF3a to eIF3m). It is crucial in translation initiation and termination, and in ribosomal recycling. Accordingly, deregulated eIF3 expression is associated with different pathological conditions, including cancer. In this manuscript, we discuss the interactome and function of each subunit of the human eIF3 complex. Furthermore, we review how altered levels of eIF3 subunits correlate with neurodegenerative disorders and cancer onset and development; in addition, we evaluate how such misregulation may also trigger infection cascades. A deep understanding of the molecular mechanisms underlying eIF3 role in human disease is essential to develop new eIF3-targeted therapeutic approaches and thus, overcome such conditions.
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Affiliation(s)
- Andreia Gomes-Duarte
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
| | - Rafaela Lacerda
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
| | - Juliane Menezes
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
| | - Luísa Romão
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
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35
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Aguero T, Jin Z, Chorghade S, Kalsotra A, King ML, Yang J. Maternal Dead-end 1 promotes translation of nanos1 by binding the eIF3 complex. Development 2017; 144:3755-3765. [PMID: 28870987 DOI: 10.1242/dev.152611] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 08/22/2017] [Indexed: 12/30/2022]
Abstract
In the developing embryo, primordial germ cells (PGCs) represent the exclusive progenitors of the gametes, and their loss results in adult infertility. During early development, PGCs are exposed to numerous signals that specify somatic cell fates. To prevent somatic differentiation, PGCs must transiently silence their genome, an early developmental process that requires Nanos activity. However, it is unclear how Nanos translation is regulated in developing embryos. We report here that translation of nanos1 after fertilization requires Dead-end 1 (Dnd1), a vertebrate-specific germline RNA-binding protein. We provide evidence that Dnd1 protein, expression of which is low in oocytes, but increases dramatically after fertilization, directly interacts with, and relieves the inhibitory function of eukaryotic initiation factor 3f, a repressive component in the 43S preinitiation complex. This work uncovers a novel translational regulatory mechanism that is fundamentally important for germline development.
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Affiliation(s)
- Tristan Aguero
- Department of Cell Biology, University of Miami, Miami, FL 33136, USA
| | - Zhigang Jin
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, IL 61802, USA
| | - Sandip Chorghade
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Auinash Kalsotra
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Mary Lou King
- Department of Cell Biology, University of Miami, Miami, FL 33136, USA
| | - Jing Yang
- Department of Comparative Biosciences, University of Illinois at Urbana-Champaign, IL 61802, USA
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36
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Zhu Y, Huang P, Yang N, Liu R, Liu X, Dai H, Zhang L, Song F, Sun C. Establishment and Application of a High Throughput Screening System Targeting the Interaction between HCV Internal Ribosome Entry Site and Human Eukaryotic Translation Initiation Factor 3. Front Microbiol 2017; 8:977. [PMID: 28611766 PMCID: PMC5447080 DOI: 10.3389/fmicb.2017.00977] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 05/15/2017] [Indexed: 01/06/2023] Open
Abstract
Viruses are intracellular obligate parasites and the host cellular machinery is usually recruited for their replication. Human eukaryotic translation initiation factor 3 (eIF3) could be directly recruited by the hepatitis C virus (HCV) internal ribosome entry site (IRES) to promote the translation of viral proteins. In this study, we establish a fluorescence polarization (FP) based high throughput screening (HTS) system targeting the interaction between HCV IRES and eIF3. By screening a total of 894 compounds with this HTS system, two compounds (Mucl39526 and NP39) are found to disturb the interaction between HCV IRES and eIF3. And these two compounds are further demonstrated to inhibit the HCV IRES-dependent translation in vitro. Thus, this HTS system is functional to screen the potential HCV replication inhibitors targeting human eIF3, which is helpful to overcome the problem of viral resistance. Surprisingly, one compound HP-3, a kind of oxytocin antagonist, is discovered to significantly enhance the interaction between HCV IRES and eIF3 by this HTS system. HP-3 is demonstrated to directly interact with HCV IRES and promote the HCV IRES-dependent translation both in vitro and in vivo, which strongly suggests that HP-3 has potentials to promote HCV replication. Therefore, this HTS system is also useful to screen the potential HCV replication enhancers, which is meaningful for understanding the viral replication and screening novel antiviral drugs. To our knowledge, this is the first HTS system targeting the interaction between eIF3 and HCV IRES, which could be applied to screen both potential HCV replication inhibitors and enhancers.
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Affiliation(s)
- Yuying Zhu
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of SciencesQingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and TechnologyQingdao, China.,College of Earth Science, University of Chinese Academy of SciencesBeijing, China
| | - Pei Huang
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of SciencesBeijing, China
| | - Na Yang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of SciencesQingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and TechnologyQingdao, China
| | - Rui Liu
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of SciencesQingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and TechnologyQingdao, China
| | - Xueting Liu
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of SciencesBeijing, China
| | - Huanqin Dai
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of SciencesBeijing, China
| | - Lixin Zhang
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of SciencesBeijing, China.,State Key Laboratory of Bioreactor Engineering, East China University of Science and TechnologyShanghai, China
| | - Fuhang Song
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of SciencesBeijing, China
| | - Chaomin Sun
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of SciencesQingdao, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and TechnologyQingdao, China
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37
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Hinnebusch AG. Structural Insights into the Mechanism of Scanning and Start Codon Recognition in Eukaryotic Translation Initiation. Trends Biochem Sci 2017; 42:589-611. [PMID: 28442192 DOI: 10.1016/j.tibs.2017.03.004] [Citation(s) in RCA: 196] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 03/12/2017] [Accepted: 03/20/2017] [Indexed: 12/21/2022]
Abstract
Initiation of translation on eukaryotic mRNAs generally follows the scanning mechanism, wherein a preinitiation complex (PIC) assembled on the small (40S) ribosomal subunit and containing initiator methionyl tRNAi (Met-tRNAi) scans the mRNA leader for an AUG codon. In a current model, the scanning PIC adopts an open conformation and rearranges to a closed state, with fully accommodated Met-tRNAi, upon AUG recognition. Evidence from recent high-resolution structures of PICs assembled with different ligands supports this model and illuminates the molecular functions of eukaryotic initiation factors eIF1, eIF1A, and eIF2 in restricting to AUG codons the transition to the closed conformation. They also reveal that the eIF3 complex interacts with multiple functional sites in the PIC, rationalizing its participation in numerous steps of initiation.
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Affiliation(s)
- 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, MD 20892, USA.
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Li K, Zhou S, Guo Q, Chen X, Lai DH, Lun ZR, Guo X. The eIF3 complex of Trypanosoma brucei: composition conservation does not imply the conservation of structural assembly and subunits function. RNA (NEW YORK, N.Y.) 2017; 23:333-345. [PMID: 27932584 PMCID: PMC5311491 DOI: 10.1261/rna.058651.116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 11/24/2016] [Indexed: 05/03/2023]
Abstract
The multisubunit eukaryotic initiation factor 3 (eIF3) plays multiple roles in translation but is poorly understood in trypanosomes. The putative subunits eIF3a and eIF3f of Trypanosoma brucei (TbIF3a and TbIF3f) were overexpressed and purified, and 11 subunits were identified, TbIF3a through l minus j, which form a tight complex. Both TbIF3a and TbIF3f are essential for the viability of T. brucei RNAi knockdown of either of them severely reduced total translation and the ratio of the polysome/80S peak area. TbIF3f and TbIF3a RNAi cell lines were modified to express tagged-TbIF3a and -TbIF3f, respectively. RNAi in combination with affinity purification assays indicated that both subunits are variably required for TbIF3 stability and integrity. The relative abundance of other subunits in the TbIF3f-tag complex changed little upon TbIF3a depletion; while only subunits TbIF3b, i, and e copurified comparably with TbIF3a-tag upon TbIF3f depletion. A genome-wide UV-crosslinking assay showed that several TbIF3 subunits have direct RNA-binding activity, with TbIF3c showing the strongest signal. In addition, CrPV IRES, but neither EMCV IRES nor HCV IRES, was found to mediate translation in T. brucei These results together imply that the structure of TbIF3 and the subunits function have trypanosome-specific features, although the composition is evolutionarily conserved.
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Affiliation(s)
- Kunrao Li
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
| | - Shuru Zhou
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
| | - Qixuan Guo
- Chengde Nursing Vocational College, Chengde 067000, China
| | - Xin Chen
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
| | - De-Hua Lai
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| | - Zhao-Rong Lun
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xuemin Guo
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
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Miras M, Miller WA, Truniger V, Aranda MA. Non-canonical Translation in Plant RNA Viruses. FRONTIERS IN PLANT SCIENCE 2017; 8:494. [PMID: 28428795 PMCID: PMC5382211 DOI: 10.3389/fpls.2017.00494] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 03/21/2017] [Indexed: 05/03/2023]
Abstract
Viral protein synthesis is completely dependent upon the host cell's translational machinery. Canonical translation of host mRNAs depends on structural elements such as the 5' cap structure and/or the 3' poly(A) tail of the mRNAs. Although many viral mRNAs are devoid of one or both of these structures, they can still translate efficiently using non-canonical mechanisms. Here, we review the tools utilized by positive-sense single-stranded (+ss) RNA plant viruses to initiate non-canonical translation, focusing on cis-acting sequences present in viral mRNAs. We highlight how these elements may interact with host translation factors and speculate on their contribution for achieving translational control. We also describe other translation strategies used by plant viruses to optimize the usage of the coding capacity of their very compact genomes, including leaky scanning initiation, ribosomal frameshifting and stop-codon readthrough. Finally, future research perspectives on the unusual translational strategies of +ssRNA viruses are discussed, including parallelisms between viral and host mRNAs mechanisms of translation, particularly for host mRNAs which are translated under stress conditions.
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Affiliation(s)
- Manuel Miras
- Centro de Edafología y Biología Aplicada del Segura - CSICMurcia, Spain
| | - W. Allen Miller
- Department of Plant Pathology and Microbiology, Iowa State UniversityAmes, IA, USA
| | - Verónica Truniger
- Centro de Edafología y Biología Aplicada del Segura - CSICMurcia, Spain
| | - Miguel A. Aranda
- Centro de Edafología y Biología Aplicada del Segura - CSICMurcia, Spain
- *Correspondence: Miguel A. Aranda
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40
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Lin Y, Zhang R, Zhang P. Eukaryotic translation initiation factor 3 subunit D overexpression is associated with the occurrence and development of ovarian cancer. FEBS Open Bio 2016; 6:1201-1210. [PMID: 28203520 PMCID: PMC5302064 DOI: 10.1002/2211-5463.12137] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 08/29/2016] [Accepted: 09/21/2016] [Indexed: 12/24/2022] Open
Abstract
Ovarian cancer is the most common cause of gynaecological cancer-associated death; thus, promising biomarkers and new therapeutic targets for ovarian cancer must be explored. Here, we report that eukaryotic translation initiation factor 3 subunit D (EIF3D), a member of the EIF3 family, was overexpressed in ovarian cancer clinical tissues. Furthermore, the expression of EIF3D was correlated with the International Federation of Gynecology and Obstetrics stage and pathological differentiation stage. 3-(4,5-dimethylthylthiazol-2-yl)-2 (MTT) and colony formation assays revealed that the lentivirus-mediated knockdown of EIF3D suppresses cell proliferation in the ovarian tumour cell lines CAOV-3 and SKOV-3. Flow cytometry revealed that cells were arrested at the G2/M phase of the cell cycle and that cyclin-dependent kinase 1 was also altered after EIF3D silencing. The results presented here demonstrate that EIF3D may play an important role in the occurrence and development of ovarian cancer.
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Affiliation(s)
- Yaying Lin
- Department of Gynecology Xinhua Hospital Shanghai Jiao Tong University School of Medicine China
| | - Rongrong Zhang
- Department of Gynecology Xinhua Hospital Shanghai Jiao Tong University School of Medicine China
| | - Ping Zhang
- Department of Gynecology Xinhua Hospital Shanghai Jiao Tong University School of Medicine China
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41
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Wagner S, Herrmannová A, Šikrová D, Valášek LS. Human eIF3b and eIF3a serve as the nucleation core for the assembly of eIF3 into two interconnected modules: the yeast-like core and the octamer. Nucleic Acids Res 2016; 44:10772-10788. [PMID: 27924037 PMCID: PMC5159561 DOI: 10.1093/nar/gkw972] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 10/07/2016] [Accepted: 10/11/2016] [Indexed: 12/05/2022] Open
Abstract
The 12-subunit mammalian eIF3 is the largest and most complex translation initiation factor and has been implicated in numerous steps of translation initiation, termination and ribosomal recycling. Imbalanced eIF3 expression levels are observed in various types of cancer and developmental disorders, but the consequences of altered eIF3 subunit expression on its overall structure and composition, and on translation in general, remain unclear. We present the first complete in vivo study monitoring the effects of RNAi knockdown of each subunit of human eIF3 on its function, subunit balance and integrity. We show that the eIF3b and octameric eIF3a subunits serve as the nucleation core around which other subunits assemble in an ordered way into two interconnected modules: the yeast-like core and the octamer, respectively. In the absence of eIF3b neither module forms in vivo, whereas eIF3d knock-down results in severe proliferation defects with no impact on eIF3 integrity. Disrupting the octamer produces an array of subcomplexes with potential roles in translational regulation. This study, outlining the mechanism of eIF3 assembly and illustrating how imbalanced expression of eIF3 subunits impacts the factor's overall expression profile, thus provides a comprehensive guide to the human eIF3 complex and to the relationship between eIF3 misregulation and cancer.
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Affiliation(s)
- Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
| | - Darina Šikrová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
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42
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Schipany K, Rosner M, Ionce L, Hengstschläger M, Kovacic B. eIF3 controls cell size independently of S6K1-activity. Oncotarget 2016; 6:24361-75. [PMID: 26172298 PMCID: PMC4695191 DOI: 10.18632/oncotarget.4458] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/19/2015] [Indexed: 12/16/2022] Open
Abstract
All multicellular organisms require a life-long regulation of the number and the size of cells, which build up their organs. mTOR acts as a signaling nodule for the regulation of protein synthesis and growth. To activate the translational cascade, mTOR phosphorylates S6 kinase (S6K1), which is liberated from the eIF3-complex and mobilized for activation of its downstream targets. How S6K1 regulates cell size remains unclear. Here, we challenged cell size control through S6K1 by specifically depleting its binding partner eIF3 in normal and transformed cell lines. We show that loss of eIF3 leads to a massive reduction of cell size and cell number accompanied with an unexpected increase in S6K1-activity. The hyperactive S6K1-signaling was rapamycin-sensitive, suggesting an upstream mTOR-regulation. A selective S6K1 inhibitor (PF-4708671) was unable to interfere with the reduced size, despite efficiently inhibiting S6K1-activity. Restoration of eIF3 expression recovered size defects, without affecting the p-S6 levels. We further show that two, yet uncharacterized, cancer-associated mutations in the eIF3-complex, have the capacity to recover from reduced size phenotype, suggesting a possible role for eIF3 in regulating cancer cell size. Collectively, our results uncover a role for eIF3-complex in maintenance of normal and neoplastic cell size - independent of S6K1-signaling.
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Affiliation(s)
- Katharina Schipany
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Margit Rosner
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Loredana Ionce
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Markus Hengstschläger
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Boris Kovacic
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
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eIF3d is an mRNA cap-binding protein that is required for specialized translation initiation. Nature 2016; 536:96-9. [PMID: 27462815 PMCID: PMC5003174 DOI: 10.1038/nature18954] [Citation(s) in RCA: 231] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2015] [Accepted: 06/21/2016] [Indexed: 12/19/2022]
Abstract
Eukaryotic mRNAs contain a 5' cap structure critical for recruitment of the translation machinery and initiation of protein synthesis. mRNA recognition is thought to require direct interactions between eukaryotic initiation factor 4E (eIF4E) and the mRNA cap. However, translation of numerous capped mRNAs remains robust during cellular stress, early development, and cell cycle progression1 despite eIF4E inactivation. Here we describe a new cellular cap-dependent pathway of translation initiation that relies on a previously unknown cap-binding activity of eIF3d, a subunit of the 800-kilodalton eukaryotic initiation factor 3 (eIF3) complex. A 1.4 Å crystal structure of the eIF3d cap-binding domain reveals unexpected homology to endonucleases involved in RNA turnover, and allows modeling of cap recognition by eIF3d. eIF3d makes specific contacts to the cap, as exemplified by cap analog competition, and these interactions are essential for assembly of translation initiation complexes on eIF3-specialized mRNAs2 such as the cell proliferation regulator c-Jun. The c-Jun mRNA further encodes an inhibitory RNA element that blocks eIF4E recruitment, thus enforcing alternative cap recognition by eIF3d. Our results reveal a new mechanism of cap-dependent translation independent of eIF4E, and illustrate how modular RNA elements work in concert to direct specialized forms of translation initiation.
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Assembly of eIF3 Mediated by Mutually Dependent Subunit Insertion. Structure 2016; 24:886-96. [PMID: 27210288 DOI: 10.1016/j.str.2016.02.024] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 02/19/2016] [Accepted: 02/21/2016] [Indexed: 02/05/2023]
Abstract
Eukaryotic initiation factor 3 (eIF3), an essential multi-protein complex involved in translation initiation, is composed of 12 tightly associated subunits in humans. While the overall structure of eIF3 is known, the mechanism of its assembly and structural consequences of dysregulation of eIF3 subunit expression seen in many cancers is largely unknown. Here we show that subunits in eIF3 assemble into eIF3 in an interdependent manner. Assembly of eIF3 is governed primarily by formation of a helical bundle, composed of helices extending C-terminally from PCI-MPN domains in eight subunits. We propose that, while the minimal subcomplex of human-like eIF3 functional for translation initiation in cells consists of subunits a, b, c, f, g, i, and m, numerous other eIF3 subcomplexes exist under circumstances of subunit over- or underexpression. Thus, eIF3 subcomplexes formed or "released" due to dysregulated subunit expression may be determining factors contributing to eIF3-related cancers.
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Ribosomal Protein Rps26 Influences 80S Ribosome Assembly in Saccharomyces cerevisiae. mSphere 2016; 1:mSphere00109-15. [PMID: 27303706 PMCID: PMC4863615 DOI: 10.1128/msphere.00109-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Accepted: 02/04/2016] [Indexed: 11/20/2022] Open
Abstract
Rps26 is an essential protein of the eukaryotic small ribosomal subunit. Previous experiments demonstrated an interaction between the eukaryote-specific Y62–K70 segment of Rps26 and the 5′ untranslated region of mRNA. The data suggested a specific role of the Y62–K70 motif during translation initiation. Here, we report that single-site substitutions within the Y62–K70 peptide did not affect the growth of engineered yeast strains, arguing against its having a critical role during translation initiation via specific interactions with the 5′ untranslated region of mRNA molecules. Only the simultaneous replacement of five conserved residues within the Y62–K70 fragment or the replacement of the yeast protein with the human homolog resulted in growth defects and caused significant changes in polysome profiles. The results expand our knowledge of ribosomal protein function and suggest a role of Rps26 during ribosome assembly in yeast. The eukaryotic ribosome consists of a small (40S) and a large (60S) subunit. Rps26 is one of the essential ribosomal proteins of the 40S subunit and is encoded by two almost identical genes, RPS26a and RPS26b. Previous studies demonstrated that Rps26 interacts with the 5′ untranslated region of mRNA via the eukaryote-specific 62-YXXPKXYXK-70 (Y62–K70) motif. Those observations suggested that this peptide within Rps26 might play an important and specific role during translation initiation. By using alanine-scanning mutagenesis and engineered strains of the yeast Saccharomyces cerevisiae, we found that single amino acid substitutions within the Y62–K70 motif of Rps26 did not affect the in vivo function of the protein. In contrast, complete deletion of the Y62–K70 segment was lethal. The simultaneous replacement of five conserved residues within the Y62–K70 segment by alanines resulted in growth defects under stress conditions and produced distinct changes in polysome profiles that were indicative of the accumulation of free 60S subunits. Human Rps26 (Rps26-Hs), which displays significant homology with yeast Rps26, supported the growth of an S. cerevisiae Δrps26a Δrps26b strain. However, the Δrps26a Δrps26b double deletion strain expressing Rps26-Hs displayed substantial growth defects and an altered ratio of 40S/60S ribosomal subunits. The combined data strongly suggest that the eukaryote-specific motif within Rps26 does not play a specific role in translation initiation. Rather, the data indicate that Rps26 as a whole is necessary for proper assembly of the 40S subunit and the 80S ribosome in yeast. IMPORTANCE Rps26 is an essential protein of the eukaryotic small ribosomal subunit. Previous experiments demonstrated an interaction between the eukaryote-specific Y62–K70 segment of Rps26 and the 5′ untranslated region of mRNA. The data suggested a specific role of the Y62–K70 motif during translation initiation. Here, we report that single-site substitutions within the Y62–K70 peptide did not affect the growth of engineered yeast strains, arguing against its having a critical role during translation initiation via specific interactions with the 5′ untranslated region of mRNA molecules. Only the simultaneous replacement of five conserved residues within the Y62–K70 fragment or the replacement of the yeast protein with the human homolog resulted in growth defects and caused significant changes in polysome profiles. The results expand our knowledge of ribosomal protein function and suggest a role of Rps26 during ribosome assembly in yeast.
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Thakor N, Smith MD, Roberts L, Faye MD, Patel H, Wieden HJ, Cate JHD, Holcik M. Cellular mRNA recruits the ribosome via eIF3-PABP bridge to initiate internal translation. RNA Biol 2016; 14:553-567. [PMID: 26828225 PMCID: PMC5449081 DOI: 10.1080/15476286.2015.1137419] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
IRES-mediated translation of key cell fate regulating genes has been implicated in tumorigenesis. Concerted action of canonical eukaryotic initiation factors and IRES transacting factors (ITAFs) was shown to regulate cellular IRES mediated translation; however, the precise molecular mechanism of ribosome recruitment to cellular IRESes remains unclear. Here we show that the X-linked inhibitor of apoptosis (XIAP) IRES operates in an evolutionary conserved viral like mode and the structural integrity, particularly in the vicinity of AUG, is critical for ribosome recruitment. The binding of eIF3 together with PABP potentiates ribosome recruitment to the IRES. Our data support the model in which eIF3 binds directly to the XIAP IRES RNA in a structure-dependent manner and acts as a scaffold for IRES RNA, PABP and the 40S ribosome.
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Affiliation(s)
- Nehal Thakor
- a Apoptosis Research Center , Children's Hospital of Eastern Ontario Research Institute , Ottawa , Ontario , Canada.,c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - M Duane Smith
- d Department of Molecular and Cell Biology , University of California , Berkeley , CA , USA
| | - Luc Roberts
- c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - Mame Daro Faye
- a Apoptosis Research Center , Children's Hospital of Eastern Ontario Research Institute , Ottawa , Ontario , Canada
| | - Harshil Patel
- c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - Hans-Joachim Wieden
- c Department of Chemistry and Biochemistry , Alberta RNA Research and Training Institute, University of Lethbridge , Lethbridge , AB , Canada
| | - Jamie H D Cate
- d Department of Molecular and Cell Biology , University of California , Berkeley , CA , USA
| | - Martin Holcik
- a Apoptosis Research Center , Children's Hospital of Eastern Ontario Research Institute , Ottawa , Ontario , Canada.,b Department of Pediatrics , University of Ottawa , Ottawa , Ontario , Canada
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Takai K, Hisamatsu K. SfiNX: a method for assembly of protein coding sequences with high success rates. Biotechnol Lett 2016; 38:773-8. [DOI: 10.1007/s10529-016-2042-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Accepted: 01/06/2016] [Indexed: 01/18/2023]
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des Georges A, Dhote V, Kuhn L, Hellen CUT, Pestova TV, Frank J, Hashem Y. Structure of mammalian eIF3 in the context of the 43S preinitiation complex. Nature 2015; 525:491-5. [PMID: 26344199 DOI: 10.1038/nature14891] [Citation(s) in RCA: 172] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Accepted: 07/06/2015] [Indexed: 12/11/2022]
Abstract
During eukaryotic translation initiation, 43S complexes, comprising a 40S ribosomal subunit, initiator transfer RNA and initiation factors (eIF) 2, 3, 1 and 1A, attach to the 5'-terminal region of messenger RNA and scan along it to the initiation codon. Scanning on structured mRNAs also requires the DExH-box protein DHX29. Mammalian eIF3 contains 13 subunits and participates in nearly all steps of translation initiation. Eight subunits having PCI (proteasome, COP9 signalosome, eIF3) or MPN (Mpr1, Pad1, amino-terminal) domains constitute the structural core of eIF3, to which five peripheral subunits are flexibly linked. Here we present a cryo-electron microscopy structure of eIF3 in the context of the DHX29-bound 43S complex, showing the PCI/MPN core at ∼6 Å resolution. It reveals the organization of the individual subunits and their interactions with components of the 43S complex. We were able to build near-complete polyalanine-level models of the eIF3 PCI/MPN core and of two peripheral subunits. The implications for understanding mRNA ribosomal attachment and scanning are discussed.
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Affiliation(s)
- Amedee des Georges
- HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
| | - Vidya Dhote
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Lauriane Kuhn
- CNRS, Proteomic Platform Strasbourg - Esplanade, Strasbourg 67084, France
| | - Christopher U T Hellen
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Joachim Frank
- HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.,Department of Biological Sciences, Columbia University, New York, New York 10032, USA
| | - Yaser Hashem
- CNRS, Architecture et Réactivité de l'ARN, Université de Strasbourg, Strasbourg 67084, France
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49
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Meleppattu S, Kamus-Elimeleh D, Zinoviev A, Cohen-Mor S, Orr I, Shapira M. The eIF3 complex of Leishmania-subunit composition and mode of recruitment to different cap-binding complexes. Nucleic Acids Res 2015; 43:6222-35. [PMID: 26092695 PMCID: PMC4513851 DOI: 10.1093/nar/gkv564] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Revised: 05/13/2015] [Accepted: 05/16/2015] [Indexed: 11/14/2022] Open
Abstract
Eukaryotic initiation factor 3 (eIF3) is a multi-protein complex and a key participant in the assembly of the translation initiation machinery. In mammals, eIF3 comprises 13 subunits, most of which are characterized by conserved structural domains. The trypanosomatid eIF3 subunits are poorly conserved. Here, we identify 12 subunits that comprise the Leishmania eIF3 complex (LeishIF3a-l) by combining bioinformatics with affinity purification and mass spectrometry analyses. These results highlight the strong association of LeishIF3 with LeishIF1, LeishIF2 and LeishIF5, suggesting the existence of a multi-factor complex. In trypanosomatids, the translation machinery is tightly regulated in the different life stages of these organisms as part of their adaptation and survival in changing environments. We, therefore, addressed the mechanism by which LeishIF3 is recruited to different mRNA cap-binding complexes. A direct interaction was observed in vitro between the fully assembled LeishIF3 complex and recombinant LeishIF4G3, the canonical scaffolding protein of the cap-binding complex in Leishmania promastigotes. We further highlight a novel interaction between the C-terminus of LeishIF3a and LeishIF4E1, the only cap-binding protein that efficiently binds the cap structure under heat shock conditions, anchoring a complex that is deficient of any MIF4G-based scaffolding subunit.
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Affiliation(s)
- Shimi Meleppattu
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Dikla Kamus-Elimeleh
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Alexandra Zinoviev
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Shahar Cohen-Mor
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Irit Orr
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
| | - Michal Shapira
- Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva, Israel
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eIF3 targets cell-proliferation messenger RNAs for translational activation or repression. Nature 2015; 522:111-4. [PMID: 25849773 PMCID: PMC4603833 DOI: 10.1038/nature14267] [Citation(s) in RCA: 285] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 01/27/2015] [Indexed: 01/23/2023]
Abstract
Regulation of protein synthesis is fundamental for all aspects of eukaryotic biology by controlling development, homeostasis and stress responses. The 13-subunit, 800-kilodalton eukaryotic initiation factor 3 (eIF3) organizes initiation factor and ribosome interactions required for productive translation. However, current understanding of eIF3 function does not explain genetic evidence correlating eIF3 deregulation with tissue-specific cancers and developmental defects. Here we report the genome-wide discovery of human transcripts that interact with eIF3 using photoactivatable ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP). eIF3 binds to a highly specific program of messenger RNAs involved in cell growth control processes, including cell cycling, differentiation and apoptosis, via the mRNA 5' untranslated region. Surprisingly, functional analysis of the interaction between eIF3 and two mRNAs encoding the cell proliferation regulators c-JUN and BTG1 reveals that eIF3 uses different modes of RNA stem-loop binding to exert either translational activation or repression. Our findings illuminate a new role for eIF3 in governing a specialized repertoire of gene expression and suggest that binding of eIF3 to specific mRNAs could be targeted to control carcinogenesis.
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