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Abaeva IS, Arhab Y, Miścicka A, Hellen CUT, Pestova TV. In vitro reconstitution of SARS-CoV-2 Nsp1-induced mRNA cleavage reveals the key roles of the N-terminal domain of Nsp1 and the RRM domain of eIF3g. Genes Dev 2023; 37:844-860. [PMID: 37821106 PMCID: PMC10620056 DOI: 10.1101/gad.350829.123] [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: 05/25/2023] [Accepted: 09/19/2023] [Indexed: 10/13/2023]
Abstract
SARS CoV-2 nonstructural protein 1 (Nsp1) is the major pathogenesis factor that inhibits host translation using a dual strategy of impairing initiation and inducing endonucleolytic cleavage of cellular mRNAs. To investigate the mechanism of cleavage, we reconstituted it in vitro on β-globin, EMCV IRES, and CrPV IRES mRNAs that use unrelated initiation mechanisms. In all instances, cleavage required Nsp1 and only canonical translational components (40S subunits and initiation factors), arguing against involvement of a putative cellular RNA endonuclease. Requirements for initiation factors differed for these mRNAs, reflecting their requirements for ribosomal attachment. Cleavage of CrPV IRES mRNA was supported by a minimal set of components consisting of 40S subunits and eIF3g's RRM domain. The cleavage site was located in the coding region 18 nt downstream from the mRNA entrance, indicating that cleavage occurs on the solvent side of the 40S subunit. Mutational analysis identified a positively charged surface on Nsp1's N-terminal domain (NTD) and a surface above the mRNA-binding channel on eIF3g's RRM domain that contain residues essential for cleavage. These residues were required for cleavage on all three mRNAs, highlighting general roles of the Nsp1 NTD and eIF3g's RRM domain in cleavage per se, irrespective of the mode of ribosomal attachment.
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Affiliation(s)
- Irina S Abaeva
- Department of Cell Biology, State University of New York Downstate Health Sciences University, Brooklyn, New York 11203, USA
| | - Yani Arhab
- Department of Cell Biology, State University of New York Downstate Health Sciences University, Brooklyn, New York 11203, USA
| | - Anna Miścicka
- Department of Cell Biology, State University of New York Downstate Health Sciences University, Brooklyn, New York 11203, USA
| | - Christopher U T Hellen
- Department of Cell Biology, State University of New York Downstate Health Sciences University, Brooklyn, New York 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, State University of New York Downstate Health Sciences University, Brooklyn, New York 11203, USA
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2
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Abaeva IS, Arhab Y, Miścicka A, Hellen CUT, Pestova TV. In vitro reconstitution of SARS CoV-2 Nsp1-induced mRNA cleavage reveals the key roles of the N-terminal domain of Nsp1 and the RRM domain of eIF3g. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.25.542379. [PMID: 37292671 PMCID: PMC10245999 DOI: 10.1101/2023.05.25.542379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
SARS CoV-2 nonstructural protein 1 (Nsp1) is the major pathogenesis factor that inhibits host translation using a dual strategy of impairing initiation and inducing endonucleolytic cleavage of cellular mRNAs. To investigate the mechanism of cleavage, we reconstituted it in vitro on β-globin, EMCV IRES and CrPV IRES mRNAs that use unrelated initiation mechanisms. In all instances, cleavage required Nsp1 and only canonical translational components (40S subunits and initiation factors), arguing against involvement of a putative cellular RNA endonuclease. Requirements for initiation factors differed for these mRNAs, reflecting their requirements for ribosomal attachment. Cleavage of CrPV IRES mRNA was supported by a minimal set of components consisting of 40S subunits and eIF3g's RRM domain. The cleavage site was located in the coding region 18 nucleotides downstream from the mRNA entrance indicating that cleavage occurs on the solvent side of the 40S subunit. Mutational analysis identified a positively charged surface on Nsp1's N-terminal domain (NTD) and a surface above the mRNA-binding channel on eIF3g's RRM domain that contain residues essential for cleavage. These residues were required for cleavage on all three mRNAs, highlighting general roles of Nsp1-NTD and eIF3g's RRM domain in cleavage per se, irrespective of the mode of ribosomal attachment.
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Affiliation(s)
- Irina S. Abaeva
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Yani Arhab
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Anna Miścicka
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | | | - Tatyana V. Pestova
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
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3
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Paul EE, Marintchev A. The PCI domains are “winged” HEAT domains. PLoS One 2022; 17:e0268664. [PMID: 36094910 PMCID: PMC9467303 DOI: 10.1371/journal.pone.0268664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 08/17/2022] [Indexed: 11/18/2022] Open
Abstract
The HEAT domains are a family of helical hairpin repeat domains, composed of four or more hairpins. HEAT is derived from the names of four family members: huntingtin, eukaryotic translation elongation factor 3 (eEF3), protein phosphatase 2 regulatory A subunit (PP2A), and mechanistic target of rapamycin (mTOR). HEAT domain-containing proteins play roles in a wide range of cellular processes, such as protein synthesis, nuclear transport and metabolism, and cell signaling. The PCI domains are a related group of helical hairpin domains, with a “winged-helix” (WH) subdomain at their C-terminus, which is responsible for multi-subunit complex formation with other PCI domains. The name is derived from the complexes, where these domains are found: the 26S Proteasome “lid” regulatory subcomplex, the COP9 signalosome (CSN), and eukaryotic translation initiation factor 3 (eIF3). We noted that in structure similarity searches using HEAT domains, sometimes PCI domains appeared in the search results ahead of other HEAT domains, which indicated that the PCI domains could be members of the HEAT domain family, and not a related but separate group, as currently thought. Here, we report extensive structure similarity analysis of HEAT and PCI domains, both within and between the two groups of proteins. We present evidence that the PCI domains as a group have greater structural similarity with individual groups of HEAT domains than some of the HEAT domain groups have among each other. Therefore, our results indicate that the PCI domains have evolved from a HEAT domain that acquired a WH subdomain. The WH subdomain in turn mediated self-association into a multi-subunit complex, which eventually evolved into the common ancestor of the Proteasome lid/CSN/eIF3.
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Affiliation(s)
- Eleanor Elise Paul
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Assen Marintchev
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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4
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Ma S, Dong Z, Cui Q, Liu JY, Zhang JT. eIF3i regulation of protein synthesis, cell proliferation, cell cycle progression, and tumorigenesis. Cancer Lett 2020; 500:11-20. [PMID: 33301799 DOI: 10.1016/j.canlet.2020.12.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 11/22/2020] [Accepted: 12/06/2020] [Indexed: 02/07/2023]
Abstract
eIF3i, a 36-kDa protein, is a putative subunit of the eIF3 complex important for translation initiation of mRNAs. It is a WD40 domain-containing protein with seven WD40 repeats that forms a β-propeller structure with an important function in pre-initiation complex formation and mRNA translation initiation. In addition to participating in the eIF3 complex formation for global translational control, eIF3i may bind to specific mRNAs and regulate their translation individually. Furthermore, eIF3i has been shown to bind to TGF-β type II receptor and participate in TGF-β signaling. It may also participate in and regulate other signaling pathways including Wnt/β-catenin pathway via translational regulation of COX-2 synthesis. These multiple canonical and noncanonical functions of eIF3i in translational control and in regulating signal transduction pathways may be responsible for its role in cell differentiation, cell cycle regulation, proliferation, and tumorigenesis. In this review, we will critically evaluate recent progresses and assess future prospects in studying eIF3i.
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Affiliation(s)
- Shijie Ma
- Affiliated Cancer Hospital & Institute of Guangzhou Medical University, Guangzhou, Guangdong, 510095, China.
| | - Zizheng Dong
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA
| | - Qingbin Cui
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA
| | - Jing-Yuan Liu
- Department of Medicine, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA.
| | - Jian-Ting Zhang
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA.
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5
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Tumia R, Wang CJ, Dong T, Ma S, Beebe J, Chen J, Dong Z, Liu JY, Zhang JT. eIF3a Regulation of NHEJ Repair Protein Synthesis and Cellular Response to Ionizing Radiation. Front Cell Dev Biol 2020; 8:753. [PMID: 32974334 PMCID: PMC7466773 DOI: 10.3389/fcell.2020.00753] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 07/20/2020] [Indexed: 11/21/2022] Open
Abstract
Translation initiation in protein synthesis regulated by eukaryotic initiation factors (eIFs) is a crucial step in controlling gene expression. eIF3a has been shown to regulate protein synthesis and cellular response to treatments by anticancer agents including cisplatin by regulating nucleotide excision repair. In this study, we tested the hypothesis that eIF3a regulates the synthesis of proteins important for the repair of double-strand DNA breaks induced by ionizing radiation (IR). We found that eIF3a upregulation sensitized cellular response to IR while its downregulation caused resistance to IR. eIF3a increases IR-induced DNA damages and decreases non-homologous end joining (NHEJ) activity by suppressing the synthesis of NHEJ repair proteins. Furthermore, analysis of existing patient database shows that eIF3a expression associates with better overall survival of breast, gastric, lung, and ovarian cancer patients. These findings together suggest that eIF3a plays an important role in cellular response to DNA-damaging treatments by regulating the synthesis of DNA repair proteins and, thus, eIIF3a likely contributes to the outcome of cancer patients treated with DNA-damaging strategies including IR.
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Affiliation(s)
- Rima Tumia
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Chao J Wang
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Tianhan Dong
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Shijie Ma
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States
| | - Jenny Beebe
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Juan Chen
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Zizheng Dong
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States
| | - Jing-Yuan Liu
- Department of Medicine, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States
| | - Jian-Ting Zhang
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States.,Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, United States
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6
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Wagner S, Herrmannová A, Hronová V, Gunišová S, Sen ND, Hannan RD, Hinnebusch AG, Shirokikh NE, Preiss T, Valášek LS. Selective Translation Complex Profiling Reveals Staged Initiation and Co-translational Assembly of Initiation Factor Complexes. Mol Cell 2020; 79:546-560.e7. [PMID: 32589964 PMCID: PMC7447980 DOI: 10.1016/j.molcel.2020.06.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 04/10/2020] [Accepted: 05/18/2020] [Indexed: 11/25/2022]
Abstract
Translational control targeting the initiation phase is central to the regulation of gene expression. Understanding all of its aspects requires substantial technological advancements. Here we modified yeast translation complex profile sequencing (TCP-seq), related to ribosome profiling, and adapted it for mammalian cells. Human TCP-seq, capable of capturing footprints of 40S subunits (40Ss) in addition to 80S ribosomes (80Ss), revealed that mammalian and yeast 40Ss distribute similarly across 5'TRs, indicating considerable evolutionary conservation. We further developed yeast and human selective TCP-seq (Sel-TCP-seq), enabling selection of 40Ss and 80Ss associated with immuno-targeted factors. Sel-TCP-seq demonstrated that eIF2 and eIF3 travel along 5' UTRs with scanning 40Ss to successively dissociate upon AUG recognition; notably, a proportion of eIF3 lingers on during the initial elongation cycles. Highlighting Sel-TCP-seq versatility, we also identified four initiating 48S conformational intermediates, provided novel insights into ATF4 and GCN4 mRNA translational control, and demonstrated co-translational assembly of initiation factor complexes.
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Affiliation(s)
- Susan Wagner
- EMBL-Australia Collaborating Group, Department of Genome Sciences, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia; Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic.
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic
| | - Vladislava Hronová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic
| | - Stanislava Gunišová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic
| | - Neelam D Sen
- 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
| | - Ross D Hannan
- Australian Cancer Research Foundation Department of Cancer Biology and Therapeutics, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
| | - 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
| | - Nikolay E Shirokikh
- EMBL-Australia Collaborating Group, Department of Genome Sciences, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
| | - Thomas Preiss
- EMBL-Australia Collaborating Group, Department of Genome Sciences, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia; Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia.
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic.
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7
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Herrmannová A, Prilepskaja T, Wagner S, Šikrová D, Zeman J, Poncová K, Valášek LS. Adapted formaldehyde gradient cross-linking protocol implicates human eIF3d and eIF3c, k and l subunits in the 43S and 48S pre-initiation complex assembly, respectively. Nucleic Acids Res 2020; 48:1969-1984. [PMID: 31863585 PMCID: PMC7039009 DOI: 10.1093/nar/gkz1185] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Revised: 12/04/2019] [Accepted: 12/09/2019] [Indexed: 12/18/2022] Open
Abstract
One of the key roles of the 12-subunit eukaryotic translation initiation factor 3 (eIF3) is to promote the formation of the 43S and 48S pre-initiation complexes (PICs). However, particular contributions of its individual subunits to these two critical initiation reactions remained obscure. Here, we adapted formaldehyde gradient cross-linking protocol to translation studies and investigated the efficiency of the 43S and 48S PIC assembly in knockdowns of individual subunits of human eIF3 known to produce various partial subcomplexes. We revealed that eIF3d constitutes an important intermolecular bridge between eIF3 and the 40S subunit as its elimination from the eIF3 holocomplex severely compromised the 43S PIC assembly. Similarly, subunits eIF3a, c and e were found to represent an important binding force driving eIF3 binding to the 40S subunit. In addition, we demonstrated that eIF3c, and eIF3k and l subunits alter the efficiency of mRNA recruitment to 43S PICs in an opposite manner. Whereas the eIF3c knockdown reduces it, downregulation of eIF3k or eIF3l increases mRNA recruitment, suggesting that the latter subunits possess a regulatory potential. Altogether this study provides new insights into the role of human eIF3 in the initial assembly steps of the translational machinery.
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Affiliation(s)
- Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, the Czech Republic
| | - Terezie Prilepskaja
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, the Czech Republic
| | - Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, the Czech Republic
| | - Darina Šikrová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, the Czech Republic
| | - Jakub Zeman
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, the Czech Republic
| | - Kristýna Poncová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, the Czech Republic
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, the Czech Republic
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8
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Zeman J, Itoh Y, Kukačka Z, Rosůlek M, Kavan D, Kouba T, Jansen ME, Mohammad MP, Novák P, Valášek LS. Binding of eIF3 in complex with eIF5 and eIF1 to the 40S ribosomal subunit is accompanied by dramatic structural changes. Nucleic Acids Res 2019; 47:8282-8300. [PMID: 31291455 PMCID: PMC6735954 DOI: 10.1093/nar/gkz570] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 06/12/2019] [Accepted: 07/05/2019] [Indexed: 12/31/2022] Open
Abstract
eIF3 is a large multiprotein complex serving as an essential scaffold promoting binding of other eIFs to the 40S subunit, where it coordinates their actions during translation initiation. Perhaps due to a high degree of flexibility of multiple eIF3 subunits, a high-resolution structure of free eIF3 from any organism has never been solved. Employing genetics and biochemistry, we previously built a 2D interaction map of all five yeast eIF3 subunits. Here we further improved the previously reported in vitro reconstitution protocol of yeast eIF3, which we cross-linked and trypsin-digested to determine its overall shape in 3D by advanced mass-spectrometry. The obtained cross-links support our 2D subunit interaction map and reveal that eIF3 is tightly packed with its WD40 and RRM domains exposed. This contrasts with reported cryo-EM structures depicting eIF3 as a molecular embracer of the 40S subunit. Since the binding of eIF1 and eIF5 further fortified the compact architecture of eIF3, we suggest that its initial contact with the 40S solvent-exposed side makes eIF3 to open up and wrap around the 40S head with its extended arms. In addition, we mapped the position of eIF5 to the region below the P- and E-sites of the 40S subunit.
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Affiliation(s)
- Jakub Zeman
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Yuzuru Itoh
- Institute of Genetics and Molecular and Cellular Biology, CNRS UMR7104, INSERM UMR964, Illkirch, France
| | - Zdeněk Kukačka
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Michal Rosůlek
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Daniel Kavan
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Tomáš Kouba
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Myrte E Jansen
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Mahabub P Mohammad
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Petr Novák
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Leoš S Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
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9
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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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10
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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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11
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Dynamic Interaction of Eukaryotic Initiation Factor 4G1 (eIF4G1) with eIF4E and eIF1 Underlies Scanning-Dependent and -Independent Translation. Mol Cell Biol 2018; 38:MCB.00139-18. [PMID: 29987188 DOI: 10.1128/mcb.00139-18] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2018] [Accepted: 06/26/2018] [Indexed: 11/20/2022] Open
Abstract
Translation initiation of most mRNAs involves m7G-cap binding, ribosomal scanning, and AUG selection. Initiation from an m7G-cap-proximal AUG can be bypassed resulting in leaky scanning, except for mRNAs bearing the translation initiator of short 5' untranslated region (TISU) element. m7G-cap binding is mediated by the eukaryotic initiation factor 4E (eIF4E)-eIF4G1 complex. eIF4G1 also associates with eIF1, and both promote scanning and AUG selection. Understanding of the dynamics and significance of these interactions is lacking. We report that eIF4G1 exists in two complexes, either with eIF4E or with eIF1. Using an eIF1 mutant impaired in eIF4G1 binding, we demonstrate that eIF1-eIF4G1 interaction is important for leaky scanning and for avoiding m7G-cap-proximal initiation. Intriguingly, eIF4E-eIF4G1 antagonizes the scanning promoted by eIF1-eIF4G1 and is required for TISU. In mapping the eIF1-binding site on eIF4G1, we unexpectedly found that eIF4E also binds it indirectly. These findings uncover the RNA features underlying regulation by eIF4E-eIF4G1 and eIF1-eIF4G1 and suggest that 43S ribosome transition from the m7G-cap to scanning involves relocation of eIF4G1 from eIF4E to eIF1.
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12
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Shirokikh NE, Preiss T. Translation initiation by cap-dependent ribosome recruitment: Recent insights and open questions. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1473. [PMID: 29624880 DOI: 10.1002/wrna.1473] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/02/2018] [Accepted: 02/14/2018] [Indexed: 12/14/2022]
Abstract
Gene expression universally relies on protein synthesis, where ribosomes recognize and decode the messenger RNA template by cycling through translation initiation, elongation, and termination phases. All aspects of translation have been studied for decades using the tools of biochemistry and molecular biology available at the time. Here, we focus on the mechanism of translation initiation in eukaryotes, which is remarkably more complex than prokaryotic initiation and is the target of multiple types of regulatory intervention. The "consensus" model, featuring cap-dependent ribosome entry and scanning of mRNA leader sequences, represents the predominantly utilized initiation pathway across eukaryotes, although several variations of the model and alternative initiation mechanisms are also known. Recent advances in structural biology techniques have enabled remarkable molecular-level insights into the functional states of eukaryotic ribosomes, including a range of ribosomal complexes with different combinations of translation initiation factors that are thought to represent bona fide intermediates of the initiation process. Similarly, high-throughput sequencing-based ribosome profiling or "footprinting" approaches have allowed much progress in understanding the elongation phase of translation, and variants of them are beginning to reveal the remaining mysteries of initiation, as well as aspects of translation termination and ribosomal recycling. A current view on the eukaryotic initiation mechanism is presented here with an emphasis on how recent structural and footprinting results underpin axioms of the consensus model. Along the way, we further outline some contested mechanistic issues and major open questions still to be addressed. This article is categorized under: Translation > Translation Mechanisms Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Affiliation(s)
- Nikolay E Shirokikh
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Thomas Preiss
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
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13
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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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14
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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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15
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Yin JY, Zhang JT, Zhang W, Zhou HH, Liu ZQ. eIF3a: A new anticancer drug target in the eIF family. Cancer Lett 2017; 412:81-87. [PMID: 29031564 DOI: 10.1016/j.canlet.2017.09.055] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Revised: 09/12/2017] [Accepted: 09/25/2017] [Indexed: 02/04/2023]
Abstract
eIF3a is the largest subunit of eIF3, which is a key player in all steps of translation initiation. During the past years, eIF3a is recognized as a proto-oncogene, which is an important discovery in this field. It is widely reported to be correlated with cancer occurrence, metastasis, prognosis, and therapeutic response. Recently, the mechanisms of eIF3a action in the carcinogenesis are unveiled gradually. A number of cellular, physiological, and pathological processes involving eIF3a are identified. Most importantly, it is emerging as a new potential drug target in the eIF family, and some small molecule inhibitors are being developed. Thus, we perform a critical review of recent advances in understanding eIF3a physiological and pathological functions, with specific focus on its role in cancer and anticancer drug targets.
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Affiliation(s)
- Ji-Ye Yin
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, PR China.
| | - Jian-Ting Zhang
- Department of Pharmacology & Toxicology and IU Cancer Center, Indiana University School of Medicine, Indianapolis IN 46202, USA
| | - Wei Zhang
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, PR China
| | - Hong-Hao Zhou
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, PR China
| | - Zhao-Qian Liu
- Department of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, PR China; Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, PR China.
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16
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Mechanism and Regulation of Protein Synthesis in Saccharomyces cerevisiae. Genetics 2017; 203:65-107. [PMID: 27183566 DOI: 10.1534/genetics.115.186221] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/24/2016] [Indexed: 12/18/2022] Open
Abstract
In this review, we provide an overview of protein synthesis in the yeast Saccharomyces cerevisiae The mechanism of protein synthesis is well conserved between yeast and other eukaryotes, and molecular genetic studies in budding yeast have provided critical insights into the fundamental process of translation as well as its regulation. The review focuses on the initiation and elongation phases of protein synthesis with descriptions of the roles of translation initiation and elongation factors that assist the ribosome in binding the messenger RNA (mRNA), selecting the start codon, and synthesizing the polypeptide. We also examine mechanisms of translational control highlighting the mRNA cap-binding proteins and the regulation of GCN4 and CPA1 mRNAs.
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17
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Fang C, Chen YX, Wu NY, Yin JY, Li XP, Huang HS, Zhang W, Zhou HH, Liu ZQ. MiR-488 inhibits proliferation and cisplatin sensibility in non-small-cell lung cancer (NSCLC) cells by activating the eIF3a-mediated NER signaling pathway. Sci Rep 2017; 7:40384. [PMID: 28074905 PMCID: PMC5225486 DOI: 10.1038/srep40384] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 12/06/2016] [Indexed: 12/11/2022] Open
Abstract
Our previous studied indicated that eukaryotic translation initiation factor 3a (eIF3a) increases the sensitive of platinum-based chemotherapy in lung cancer. MiRNAs play an important role in lung carcinogenesis and drug response. In this study, we aimed to identify potential endogenous miRNAs that inhibit eIF3a expression and determine their influence of this inhibition on cisplatin resistance. Using bioinformatics analysis prediction and confirmation with dual-luciferase reporter assays, we found that miRNA-488 inhibited eIF3a expression by directly binding to the 3’UTR of eIF3a. In addition, the overexpression of miRNA-488 inhibited cell migration and invasion in A549 cells, and also inhibited cell proliferation, cell cycle progression by elevated P27 expression. Compared to the parental cell line, A549/cisplatin (DDP) resistant cells exhibited a higher level of miRNA-488. Moreover, we found that miRNA-488 was associated with cisplatin resistance in three NSCLC cells (A549, H1299 and SK-MES-1). The mechanism of miRNA-488 induced cisplatin resistance was that miRNA-488 activated nucleotide excision repair (NER) by increasing the expression of Replication Protein A (RPA) 14 and Xeroderma pigmentosum group C (XPC). In conclusion, our results demonstrated that miRNA-488 is a tumor suppressor miRNA that acts by targeting eIF3a. Moreover, miRNA-488 also participates in eIF3a mediated cisplatin resistance in NSCLC cells.
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Affiliation(s)
- Chao Fang
- Departments of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, P. R. China.,Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, P. R. China
| | - Yi-Xin Chen
- Departments of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, P. R. China.,Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, P. R. China
| | - Na-Yiyuan Wu
- Departments of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, P. R. China.,Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, P. R. China
| | - Ji-Ye Yin
- Departments of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, P. R. China.,Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, P. R. China
| | - Xiang-Ping Li
- Departments of Pharmacy, Xiangya Hospital, Central South University, Changsha 410008, P. R. China
| | - Hsuan-Shun Huang
- Department of Research, Cervical Cancer Prevention Center, Tzu Chi University, Hualien 970, Taiwan, Republic of China
| | - Wei Zhang
- Departments of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, P. R. China.,Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, P. R. China
| | - Hong-Hao Zhou
- Departments of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, P. R. China.,Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, P. R. China.,Hunan Province Cooperation Innovation Center for Molecular Target New Drug Study, Hengyang 421001, P. R. China
| | - Zhao-Qian Liu
- Departments of Clinical Pharmacology, Xiangya Hospital, Central South University, Changsha 410008, P. R. China.,Institute of Clinical Pharmacology, Central South University, Hunan Key Laboratory of Pharmacogenetics, Changsha 410078, P. R. China.,Hunan Province Cooperation Innovation Center for Molecular Target New Drug Study, Hengyang 421001, P. R. China
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18
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Pisareva VP, Pisarev AV. DHX29 and eIF3 cooperate in ribosomal scanning on structured mRNAs during translation initiation. RNA (NEW YORK, N.Y.) 2016; 22:1859-1870. [PMID: 27733651 PMCID: PMC5113206 DOI: 10.1261/rna.057851.116] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 09/12/2016] [Indexed: 06/06/2023]
Abstract
Eukaryotic translation initiation is a complex process involving many components. eIF3 is a scaffold for multiple initiation factors and plays multiple roles in initiation, and DHX29 helicase enhances the formation of the 48S initiation complex on structured mRNAs. Because DHX29 is not a processive helicase, the mechanism underlying its activity is unclear. Here, we show that DHX29 establishes many points of contact with eIF3. In particular, the unique N terminus of DHX29 associates with the RNA recognition motif of eIF3b and the C terminus of the eIF3a subunits of eIF3, and the disruption of either contact impairs DHX29 activity. In turn, DHX29 has weak points of contact with mRNA in the 48S initiation complex, and the pathway taken by mRNA remains unchanged. These results exclude the direct role for this protein in unwinding. Thus, DHX29 and eIF3 cooperate in scanning on structured mRNAs. Our findings support previous genetic data on the role of eIF3 during scanning.
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Affiliation(s)
- Vera P Pisareva
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Andrey V Pisarev
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
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19
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Aitken CE, Beznosková P, Vlčkova V, Chiu WL, Zhou F, Valášek LS, Hinnebusch AG, Lorsch JR. Eukaryotic translation initiation factor 3 plays distinct roles at the mRNA entry and exit channels of the ribosomal preinitiation complex. eLife 2016; 5. [PMID: 27782884 PMCID: PMC5153249 DOI: 10.7554/elife.20934] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/25/2016] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a central player in recruitment of the pre-initiation complex (PIC) to mRNA. We probed the effects on mRNA recruitment of a library of S. cerevisiae eIF3 functional variants spanning its 5 essential subunits using an in vitro-reconstituted system. Mutations throughout eIF3 disrupt its interaction with the PIC and diminish its ability to accelerate recruitment to a native yeast mRNA. Alterations to the eIF3a CTD and eIF3b/i/g significantly slow mRNA recruitment, and mutations within eIF3b/i/g destabilize eIF2•GTP•Met-tRNAi binding to the PIC. Using model mRNAs lacking contacts with the 40S entry or exit channels, we uncovered a critical role for eIF3 requiring the eIF3a NTD, in stabilizing mRNA interactions at the exit channel, and an ancillary role at the entry channel requiring residues of the eIF3a CTD. These functions are redundant: defects at each channel can be rescued by filling the other channel with mRNA. DOI:http://dx.doi.org/10.7554/eLife.20934.001 Cells use the genetic information stored within genes to build proteins, which are largely responsible for performing the molecular tasks essential for life. The ribosome is the molecular machine that translates the information within genes to assemble proteins in all cells, from bacteria to humans. To make a protein, the corresponding gene is first copied to make molecules of messenger ribonucleic acid (or mRNA for short). Then the ribosome binds to the mRNA in a process called translation initiation. Cells tightly regulate translation initiation so that they can decide which proteins to make, according to their needs and in response to changes in the environment. In fact, regulation of translation initiation is often disrupted during viral infections, cancer and other human diseases. A set of proteins called translation initiation factors drive translation initiation; the largest and least understood of these is called eIF3. Cells are unable to load the mRNA onto the ribosome without eIF3, which has two “arms” that sit near where the mRNA enters and exits the ribosome. Aitken et al. used mutant forms of eIF3 from genetically modified yeast to investigate how the arms of the protein work, and if they help the ribosome hold onto the mRNA. These experiments show that the two arms of eIF3 have unique roles. One arm sits near where mRNA exits the ribosome and is important for holding onto the mRNA. The other arm – which is near where mRNA enters the ribosome – helps hold the ribosome and other components of the translation machinery together. This arm may also help to open and close the channel through which messenger RNA enters the ribosome. The next challenges are to find out the precise role this arm plays in translation – in particular, how it helps to open and close the channel in the ribosome, and whether this helps the ribosome load the messenger RNA or even move along it. DOI:http://dx.doi.org/10.7554/eLife.20934.002
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Affiliation(s)
- Colin Echeverría Aitken
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Petra Beznosková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Prague, Czech Republic
| | - Vladislava Vlčkova
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Prague, Czech Republic
| | - Wen-Ling Chiu
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Fujun Zhou
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Prague, Czech Republic
| | - Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Jon R Lorsch
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
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20
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Wang W, Xu M, Liu X, Tu J. The Rice Eukaryotic Translation Initiation Factor 3 Subunit e (OseIF3e) Influences Organ Size and Pollen Maturation. FRONTIERS IN PLANT SCIENCE 2016; 7:1399. [PMID: 27703462 PMCID: PMC5028392 DOI: 10.3389/fpls.2016.01399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/02/2016] [Indexed: 05/24/2023]
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a large protein complex that participates in most translation initiation processes. While eIF3 has been well characterized, less is known about the roles of individual eIF3 subunits, particularly in plants. Here, we identified and characterized OseIF3e in rice (Oryza sativa L.). OseIF3e was constitutively expressed in various tissues, but most strongly in vigorously growing organs. Transgenic OseIF3e-silenced rice plants showed inhibited growth in seedling and vegetative stages. Repression of OseIF3e led to defects in pollen maturation but did not affect pollen mitosis. In rice, eIF3e interacted with eIF3 subunits b, d, e, f, h, and k, and with eIF6, forming homo- and heterodimers to initiate translation. Furthermore, OseIF3e was shown by yeast two-hybrid assay to specifically bind to inhibitors of cyclin-dependent kinases 1, 5, and 6. This interaction was mediated by the sequence of amino acid residues at positions 118-138, which included a conserved motif (IGPEQIETLYQFAKF). These results suggested although OseIF3e is not a "functional core" subunit of eIF3, it still plays crucial roles in rice growth and development, in combination with other factors. We proposed a pathway by which OseIF3e influence organ size and pollen maturation in rice, providing an opportunity to optimize plant architecture for crop breeding.
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21
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Simonetti A, Brito Querido J, Myasnikov AG, Mancera-Martinez E, Renaud A, Kuhn L, Hashem Y. eIF3 Peripheral Subunits Rearrangement after mRNA Binding and Start-Codon Recognition. Mol Cell 2016; 63:206-217. [PMID: 27373335 DOI: 10.1016/j.molcel.2016.05.033] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 04/07/2016] [Accepted: 05/23/2016] [Indexed: 11/30/2022]
Abstract
mRNA translation initiation in eukaryotes requires the cooperation of a dozen eukaryotic initiation factors (eIFs) forming several complexes, which leads to mRNA attachment to the small ribosomal 40S subunit, mRNA scanning for start codon, and accommodation of initiator tRNA at the 40S P site. eIF3, composed of 13 subunits, 8 core (a, c, e, f, h, l, k, and m) and 5 peripheral (b, d, g, i, and j), plays a central role during this process. Here we report a cryo-electron microscopy structure of a mammalian 48S initiation complex at 5.8 Å resolution. It shows the relocation of subunits eIF3i and eIF3g to the 40S intersubunit face on the GTPase binding site, at a late stage in initiation. On the basis of a previous study, we demonstrate the relocation of eIF3b to the 40S intersubunit face, binding below the eIF2-Met-tRNAi(Met) ternary complex upon mRNA attachment. Our analysis reveals the deep rearrangement of eIF3 and unravels the molecular mechanism underlying eIF3 function in mRNA scanning and timing of ribosomal subunit joining.
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Affiliation(s)
- Angelita Simonetti
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France.
| | - Jailson Brito Querido
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France
| | | | - Eder Mancera-Martinez
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France
| | - Adeline Renaud
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France
| | - Lauriane Kuhn
- CNRS, Proteomic Platform Strasbourg - Esplanade, 67084 Strasbourg, France
| | - Yaser Hashem
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France.
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22
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Schmidt C, Beilsten-Edmands V, Robinson CV. Insights into Eukaryotic Translation Initiation from Mass Spectrometry of Macromolecular Protein Assemblies. J Mol Biol 2015; 428:344-356. [PMID: 26497764 DOI: 10.1016/j.jmb.2015.10.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 09/28/2015] [Accepted: 10/14/2015] [Indexed: 02/05/2023]
Abstract
Translation initiation in eukaryotes requires the interplay of at least 10 initiation factors that interact at the different steps of this phase of gene expression. The interactions of initiation factors and related proteins are in general controlled by phosphorylation, which serves as a regulatory switch to turn protein translation on or off. The structures of initiation factors and a complete description of their post-translational modification (PTM) status are therefore required in order to fully understand these processes. In recent years, mass spectrometry has contributed considerably to provide this information and nowadays is proving to be indispensable when studying dynamic heterogeneous protein complexes such as the eukaryotic initiation factors. Herein, we highlight mass spectrometric approaches commonly applied to identify interacting subunits and their PTMs and the structural techniques that allow the architecture of protein complexes to be assessed. We present recent structural investigations of initiation factors and their interactions with other factors and with ribosomes and we assess the models generated. These models allow us to locate PTMs within initiation factor complexes and to highlight possible roles for phosphorylation sites in regulating interaction interfaces.
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Affiliation(s)
- Carla Schmidt
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
| | - Victoria Beilsten-Edmands
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
| | - Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
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23
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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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24
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Topological models of heteromeric protein assemblies from mass spectrometry: application to the yeast eIF3:eIF5 complex. ACTA ACUST UNITED AC 2014; 22:117-28. [PMID: 25544043 PMCID: PMC4306531 DOI: 10.1016/j.chembiol.2014.11.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 10/07/2014] [Accepted: 11/07/2014] [Indexed: 02/05/2023]
Abstract
Describing, understanding, and modulating the function of the cell require elucidation of the structures of macromolecular assemblies. Here, we describe an integrative method for modeling heteromeric complexes using as a starting point disassembly pathways determined by native mass spectrometry (MS). In this method, the pathway data and other available information are encoded as a scoring function on the positions of the subunits of the complex. The method was assessed on its ability to reproduce the native contacts in five benchmark cases with simulated MS data and two cases with real MS data. To illustrate the power of our method, we purified the yeast initiation factor 3 (eIF3) complex and characterized it by native MS and chemical crosslinking MS. We established substoichiometric binding of eIF5 and derived a model for the five-subunit eIF3 complex, at domain level, consistent with its role as a scaffold for other initiation factors. Integrative MS method allows topological characterization of heteromeric complexes Intersubunit crosslinks increase the precision of the predicted topologies A 3D model of eIF3:eIF5 complex was built using restraints from MS-based methods Integrative modeling reveals two submodules within eIF3: eIF3b:i:g and eIF3a:c
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25
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Rezende AM, Assis LA, Nunes EC, da Costa Lima TD, Marchini FK, Freire ER, Reis CRS, de Melo Neto OP. The translation initiation complex eIF3 in trypanosomatids and other pathogenic excavates--identification of conserved and divergent features based on orthologue analysis. BMC Genomics 2014; 15:1175. [PMID: 25539953 PMCID: PMC4320536 DOI: 10.1186/1471-2164-15-1175] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 12/16/2014] [Indexed: 12/24/2022] Open
Abstract
Background The initiation of translation in eukaryotes is supported by the action of several eukaryotic Initiation Factors (eIFs). The largest of these is eIF3, comprising of up to thirteen polypeptides (eIF3a through eIF3m), involved in multiple stages of the initiation process. eIF3 has been better characterized from model organisms, but is poorly known from more diverged groups, including unicellular lineages represented by known human pathogens. These include the trypanosomatids (Trypanosoma and Leishmania) and other protists belonging to the taxonomic supergroup Excavata (Trichomonas and Giardia sp.). Results An in depth bioinformatic search was carried out to recover the full content of eIF3 subunits from the available genomes of L. major, T. brucei, T. vaginalis and G. duodenalis. The protein sequences recovered were then submitted to homology analysis and alignments comparing them with orthologues from representative eukaryotes. Eleven putative eIF3 subunits were found from both trypanosomatids whilst only five and four subunits were identified from T. vaginalis and G. duodenalis, respectively. Only three subunits were found in all eukaryotes investigated, eIF3b, eIF3c and eIF3i. The single subunit found to have a related Archaean homologue was eIF3i, the most conserved of the eIF3 subunits. The sequence alignments revealed several strongly conserved residues/region within various eIF3 subunits of possible functional relevance. Subsequent biochemical characterization of the Leishmania eIF3 complex validated the bioinformatic search and yielded a twelfth eIF3 subunit in trypanosomatids, eIF3f (the single unidentified subunit in trypanosomatids was then eIF3m). The biochemical data indicates a lack of association of the eIF3j subunit to the complex whilst highlighting the strong interaction between eIF3 and eIF1. Conclusions The presence of most eIF3 subunits in trypanosomatids is consistent with an early evolution of a fully functional complex. Simplified versions in other excavates might indicate a primordial complex or secondary loss of selected subunits, as seen for some fungal lineages. The conservation in eIF3i sequence might indicate critical functions within eIF3 which have been overlooked. The identification of eIF3 subunits from distantly related eukaryotes provides then a basis for the study of conserved/divergent aspects of eIF3 function, leading to a better understanding of eukaryotic translation initiation. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1175) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | - Osvaldo P de Melo Neto
- Centro de Pesquisas Aggeu Magalhães, Fundação Oswaldo Cruz, Avenida Professor Moraes Rego s/n, Cidade Universitária, Recife, PE 50670-420, Brazil.
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26
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Gao L, Tuo D, Shen W, Yan P, Li X, Zhou P. NIa-Pro of Papaya ringspot virus interacts with Carica papaya eukaryotic translation initiation factor 3 subunit G (CpeIF3G). Virus Genes 2014; 50:97-103. [PMID: 25416301 DOI: 10.1007/s11262-014-1145-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Accepted: 11/12/2014] [Indexed: 11/29/2022]
Abstract
The interaction of papaya eukaryotic translation initiation factor 3 subunit G (CpeIF3G) with Papaya ringspot virus (PRSV) NIa-Pro was validated using a bimolecular fluorescence complementation assay in papaya protoplasts based on the previous yeast two-hybrid assay results. The C-terminal (residues 133-239) fragment of PRSV NIa-Pro and the central domain (residues 59-167) of CpeIF3G were required for effective interaction between NIa-Pro and CpeIF3G as shown by a Sos recruitment yeast two-hybrid system with several deletion mutants of NIa-Pro and CpeIF3G. The central domain of CpeIF3G, which contains a C2HC-type zinc finger motif, is required to bind to other eIFs of the translational machinery. In addition, quantitative real-time reverse transcription PCR assay confirmed that PRSV infection leads to a 2- to 4.5-fold up-regulation of CpeIF3G mRNA in papaya. Plant eIF3G is involved in various stress response by enhancing the translation of resistance-related proteins. It is proposed that the NIa-Pro-CpeIF3G interaction may impair translation preinitiation complex assembly of defense proteins and interfere with host defense.
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Affiliation(s)
- Le Gao
- Key Laboratory of Biology and Genetic Resources of Tropical Crops, Ministry of Agriculture, Institute of Tropical Bioscience and Biotechnology & Analysis and Testing Center, Chinese Academy of Tropical Agricultural Sciences, Haikou, 571101, People's Republic of China
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27
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Yue MM, Lv K, Meredith SC, Martindale JL, Gorospe M, Schuger L. Novel RNA-binding protein P311 binds eukaryotic translation initiation factor 3 subunit b (eIF3b) to promote translation of transforming growth factor β1-3 (TGF-β1-3). J Biol Chem 2014; 289:33971-83. [PMID: 25336651 DOI: 10.1074/jbc.m114.609495] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P311, a conserved 8-kDa intracellular protein expressed in brain, smooth muscle, regenerating tissues, and malignant glioblastomas, represents the first documented stimulator of TGF-β1-3 translation in vitro and in vivo. Here we initiated efforts to define the mechanism underlying P311 function. PONDR® (Predictor Of Naturally Disordered Regions) analysis suggested and CD confirmed that P311 is an intrinsically disordered protein, therefore requiring an interacting partner to acquire tertiary structure and function. Immunoprecipitation coupled with mass spectroscopy identified eIF3 subunit b (eIF3b) as a novel P311 binding partner. Immunohistochemical colocalization, GST pulldown, and surface plasmon resonance studies revealed that P311-eIF3b interaction is direct and has a Kd of 1.26 μm. Binding sites were mapped to the non-canonical RNA recognition motif of eIF3b and a central 11-amino acid-long region of P311, here referred to as eIF3b binding motif. Disruption of P311-eIF3b binding inhibited translation of TGF-β1, 2, and 3, as indicated by luciferase reporter assays, polysome fractionation studies, and Western blot analysis. RNA precipitation assays after UV cross-linking and RNA-protein EMSA demonstrated that P311 binds directly to TGF-β 5'UTRs mRNAs through a previously unidentified RNA recognition motif-like motif. Our results demonstrate that P311 is a novel RNA-binding protein that, by interacting with TGF-βs 5'UTRs and eIF3b, stimulates the translation of TGF-β1, 2, and 3.
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Affiliation(s)
| | | | - Stephen C Meredith
- From the Departments of Pathology and Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637 and
| | - Jennifer L Martindale
- the Laboratory of Genetics, NIA, National Institutes of Health, Baltimore, Maryland 21224
| | - Myriam Gorospe
- the Laboratory of Genetics, NIA, National Institutes of Health, Baltimore, Maryland 21224
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28
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Hiraishi H, Oatman J, Haller SL, Blunk L, McGivern B, Morris J, Papadopoulos E, Gutierrez W, Gordon M, Bokhari W, Ikeda Y, Miles D, Fellers J, Asano M, Wagner G, Tazi L, Rothenburg S, Brown SJ, Asano K. Essential role of eIF5-mimic protein in animal development is linked to control of ATF4 expression. Nucleic Acids Res 2014; 42:10321-30. [PMID: 25147208 PMCID: PMC4176352 DOI: 10.1093/nar/gku670] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Translational control of transcription factor ATF4 through paired upstream ORFs (uORFs) plays an important role in eukaryotic gene regulation. While it is typically induced by phosphorylation of eIF2α, ATF4 translation can be also induced by expression of a translational inhibitor protein, eIF5-mimic protein 1 (5MP1, also known as BZW2) in mammals. Here we show that the 5MP gene is maintained in eukaryotes under strong purifying selection, but is uniquely missing in two major phyla, nematoda and ascomycota. The common function of 5MP from protozoa, plants, fungi and insects is to control translation by inhibiting eIF2. The affinity of human 5MP1 to eIF2β was measured as being equivalent to the published value of human eIF5 to eIF2β, in agreement with effective competition of 5MP with eIF5 for the main substrate, eIF2. In the red flour beetle, Tribolium castaneum, RNA interference studies indicate that 5MP facilitates expression of GADD34, a downstream target of ATF4. Furthermore, both 5MP and ATF4 are essential for larval development. Finally, 5MP and the paired uORFs allowing ATF4 control are conserved in the entire metazoa except nematoda. Based on these findings, we discuss the phylogenetic and functional linkage between ATF4 regulation and 5MP expression in this group of eukaryotes.
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Affiliation(s)
- Hiroyuki Hiraishi
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Jamie Oatman
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Sherry L Haller
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Logan Blunk
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA Arthropod Genomics Center, Kansas State University, Manhattan, KS 66506, USA
| | - Benton McGivern
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA Arthropod Genomics Center, Kansas State University, Manhattan, KS 66506, USA
| | - Jacob Morris
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Evangelos Papadopoulos
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Wade Gutierrez
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA Arthropod Genomics Center, Kansas State University, Manhattan, KS 66506, USA
| | - Michelle Gordon
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA Arthropod Genomics Center, Kansas State University, Manhattan, KS 66506, USA
| | - Wahaj Bokhari
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Yuka Ikeda
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - David Miles
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - John Fellers
- USDA-ARS, Hard WinterWheat Genetics Research Unit, Kansas State University, Manhattan, KS 66506
| | - Masayo Asano
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Loubna Tazi
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Stefan Rothenburg
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Susan J Brown
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA Arthropod Genomics Center, Kansas State University, Manhattan, KS 66506, USA
| | - Katsura Asano
- Molecular Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
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29
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Qi J, Dong Z, Liu J, Zhang JT. EIF3i promotes colon oncogenesis by regulating COX-2 protein synthesis and β-catenin activation. Oncogene 2014; 33:4156-63. [PMID: 24056964 PMCID: PMC3962800 DOI: 10.1038/onc.2013.397] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 08/02/2013] [Accepted: 08/05/2013] [Indexed: 12/21/2022]
Abstract
Translational control of gene expression has recently been recognized as an important mechanism controlling cell proliferation and oncogenesis, and it mainly occurs in the initiation step of protein synthesis that involves multiple eukaryotic initiation factors (eIFs). Many eIFs have been found to have aberrant expression in human tumors and the aberrant expression may contribute to oncogenesis. However, how these previously considered house-keeping proteins are potentially oncogenic remains elusive. In this study, we investigated the expression of eIF3i in human colon cancers, tested its contribution to colon oncogenesis and determined the mechanism of eIF3i action in colon oncogenesis. We found that eIF3i expression was upregulated in both human colon adenocarcinoma and adenoma polyps as well as in model inducible colon tumorigenic cell lines. Overexpression of ectopic eIF3i in intestinal epithelial cells causes oncogenesis by directly upregulating the synthesis of cyclooxygenase-2 (COX-2) protein and activates the β-catenin/T-cell factor 4 signaling pathway that mediates the oncogenic function of eIF3i. Together, we conclude that eIF3i is a proto-oncogene that drives colon oncogenesis by translationally upregulating COX-2 and activating the β-catenin signaling pathway. These findings imply that proto-oncogenic eIFs likely exert their tumorigenic function by regulating/altering the synthesis level of downstream tumor suppressor or oncogenes.
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Affiliation(s)
- J Qi
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Z Dong
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - J Liu
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - J-T Zhang
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
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30
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Translation initiation factor eIF3b contains a nine-bladed β-propeller and interacts with the 40S ribosomal subunit. Structure 2014; 22:923-30. [PMID: 24768115 DOI: 10.1016/j.str.2014.03.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/13/2014] [Accepted: 03/21/2014] [Indexed: 11/20/2022]
Abstract
The multisubunit eukaryotic translation initiation factor 3, among which the subunit b (eIF3b) is a major scaffold protein, plays essential roles in protein synthesis. Here, we report the crystal structure of the WD40 domain of Chaetomium thermophilum eIF3b, revealing a nine-bladed β-propeller fold. Sequence analysis indicates that this propeller architecture is common to all eIF3b orthologs. Revisiting the cryoelectron microscopy (cryo-EM) map of the 43S preinitiation complex suggests an interaction of the eIF3b with the 40S ribosomal subunit involving the ribosomal protein S9e and the 18S rRNA. This model is strongly supported by the direct binding of eIF3b to 40S ribosomes and to the isolated ribosomal protein rpS9e in vitro.
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31
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Khoshnevis S, Gunišová S, Vlčková V, Kouba T, Neumann P, Beznosková P, Ficner R, Valášek LS. Structural integrity of the PCI domain of eIF3a/TIF32 is required for mRNA recruitment to the 43S pre-initiation complexes. Nucleic Acids Res 2014; 42:4123-39. [PMID: 24423867 PMCID: PMC3973348 DOI: 10.1093/nar/gkt1369] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Transfer of genetic information from genes into proteins is mediated by messenger RNA (mRNA) that must be first recruited to ribosomal pre-initiation complexes (PICs) by a mechanism that is still poorly understood. Recent studies showed that besides eIF4F and poly(A)-binding protein, eIF3 also plays a critical role in this process, yet the molecular mechanism of its action is unknown. We showed previously that the PCI domain of the eIF3c/NIP1 subunit of yeast eIF3 is involved in RNA binding. To assess the role of the second PCI domain of eIF3 present in eIF3a/TIF32, we performed its mutational analysis and identified a 10-Ala-substitution (Box37) that severely reduces amounts of model mRNA in the 43–48S PICs in vivo as the major, if not the only, detectable defect. Crystal structure analysis of the a/TIF32-PCI domain at 2.65-Å resolution showed that it is required for integrity of the eIF3 core and, similarly to the c/NIP1-PCI, is capable of RNA binding. The putative RNA-binding surface defined by positively charged areas contains two Box37 residues, R363 and K364. Their substitutions with alanines severely impair the mRNA recruitment step in vivo suggesting that a/TIF32-PCI represents one of the key domains ensuring stable and efficient mRNA delivery to the PICs.
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Affiliation(s)
- Sohail Khoshnevis
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, George-August University, Goettingen, Germany, 37077 and Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, 142 20 Prague, the Czech Republic
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32
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Luna RE, Arthanari H, Hiraishi H, Akabayov B, Tang L, Cox C, Markus MA, Luna LE, Ikeda Y, Watanabe R, Bedoya E, Yu C, Alikhan S, Wagner G, Asano K. The interaction between eukaryotic initiation factor 1A and eIF5 retains eIF1 within scanning preinitiation complexes. Biochemistry 2013; 52:9510-8. [PMID: 24319994 PMCID: PMC3917153 DOI: 10.1021/bi4009775] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Scanning of the mRNA transcript by the preinitiation complex (PIC) requires a panel of eukaryotic initiation factors, which includes eIF1 and eIF1A, the main transducers of stringent AUG selection. eIF1A plays an important role in start codon recognition; however, its molecular contacts with eIF5 are unknown. Using nuclear magnetic resonance, we unveil eIF1A's binding surface on the carboxyl-terminal domain of eIF5 (eIF5-CTD). We validated this interaction by observing that eIF1A does not bind to an eIF5-CTD mutant, altering the revealed eIF1A interaction site. We also found that the interaction between eIF1A and eIF5-CTD is conserved between humans and yeast. Using glutathione S-transferase pull-down assays of purified proteins, we showed that the N-terminal tail (NTT) of eIF1A mediates the interaction with eIF5-CTD and eIF1. Genetic evidence indicates that overexpressing eIF1 or eIF5 suppresses the slow growth phenotype of eIF1A-NTT mutants. These results suggest that the eIF1A-eIF5-CTD interaction during scanning PICs contributes to the maintenance of eIF1 within the open PIC.
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Affiliation(s)
- Rafael E. Luna
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Haribabu Arthanari
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Hiroyuki Hiraishi
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Barak Akabayov
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Leiming Tang
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Christian Cox
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Michelle A. Markus
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Lunet E. Luna
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Yuka Ikeda
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Ryosuke Watanabe
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Edward Bedoya
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Cathy Yu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Shums Alikhan
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Katsura Asano
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
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33
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Smith MD, Gu Y, Querol-Audí J, Vogan JM, Nitido A, Cate JHD. Human-like eukaryotic translation initiation factor 3 from Neurospora crassa. PLoS One 2013; 8:e78715. [PMID: 24250809 PMCID: PMC3826745 DOI: 10.1371/journal.pone.0078715] [Citation(s) in RCA: 30] [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: 08/15/2013] [Accepted: 09/22/2013] [Indexed: 02/05/2023] Open
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a key regulator of translation initiation, but its in vivo assembly and molecular functions remain unclear. Here we show that eIF3 from Neurospora crassa is structurally and compositionally similar to human eIF3. N. crassa eIF3 forms a stable 12-subunit complex linked genetically and biochemically to the 13th subunit, eIF3j, which in humans modulates mRNA start codon selection. Based on N. crassa genetic analysis, most subunits in eIF3 are essential. Subunits that can be deleted (e, h, k and l) map to the right side of the eIF3 complex, suggesting that they may coordinately regulate eIF3 function. Consistent with this model, subunits eIF3k and eIF3l are incorporated into the eIF3 complex as a pair, and their insertion depends on the presence of subunit eIF3h, a key regulator of vertebrate development. Comparisons to other eIF3 complexes suggest that eIF3 assembles around an eIF3a and eIF3c dimer, which may explain the coordinated regulation of human eIF3 levels. Taken together, these results show that Neurospora crassa eIF3 provides a tractable system for probing the structure and function of human-like eIF3 in the context of living cells.
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Affiliation(s)
- M. Duane Smith
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Yu Gu
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jordi Querol-Audí
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jacob M. Vogan
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Adam Nitido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jamie H. D. Cate
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- Department of Chemistry, University of California, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- * E-mail:
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34
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Valásek LS. 'Ribozoomin'--translation initiation from the perspective of the ribosome-bound eukaryotic initiation factors (eIFs). Curr Protein Pept Sci 2013; 13:305-30. [PMID: 22708493 PMCID: PMC3434475 DOI: 10.2174/138920312801619385] [Citation(s) in RCA: 103] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2011] [Revised: 01/16/2012] [Accepted: 02/16/2012] [Indexed: 02/05/2023]
Abstract
Protein synthesis is a fundamental biological mechanism bringing the DNA-encoded genetic information into
life by its translation into molecular effectors - proteins. The initiation phase of translation is one of the key points of gene
regulation in eukaryotes, playing a role in processes from neuronal function to development. Indeed, the importance of the
study of protein synthesis is increasing with the growing list of genetic diseases caused by mutations that affect mRNA
translation. To grasp how this regulation is achieved or altered in the latter case, we must first understand the molecular
details of all underlying processes of the translational cycle with the main focus put on its initiation. In this review I discuss
recent advances in our comprehension of the molecular basis of particular initiation reactions set into the context of
how and where individual eIFs bind to the small ribosomal subunit in the pre-initiation complex. I also summarize our
current knowledge on how eukaryotic initiation factor eIF3 controls gene expression in the gene-specific manner via reinitiation.
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Affiliation(s)
- Leos Shivaya Valásek
- Laboratory of Eukaryotic Gene Regulation, Institute of Microbiology AS CR, Prague, Czech Republic.
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35
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Yin JY, Dong ZZ, Liu RY, Chen J, Liu ZQ, Zhang JT. Translational regulation of RPA2 via internal ribosomal entry site and by eIF3a. Carcinogenesis 2013; 34:1224-31. [PMID: 23393223 DOI: 10.1093/carcin/bgt052] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
RPA2 is a subunit of a trimeric replication protein A (RPA) complex important for DNA repair and replication. Although it is known that RPA activity is regulated by post-translational modification, whether RPA expression is regulated and the mechanism therein is currently unknown. eIF3a, the largest subunit of eIF3, is an important player in translational control and has been suggested to regulate translation of a subset of messenger RNAs important for tumorigenesis, metastasis, cell cycle progression, drug response and DNA repair. In the present study, we show that RPA2 expression is regulated at translational level via internal ribosome entry site (IRES)-mediated initiation in response to DNA damage. We also found that eIF3a suppresses RPA2 synthesis and inhibits its cellular IRES activity by directly binding to the IRES element of RPA2 located at -50 to -150 bases upstream of the translation start site. Taken together, we conclude that RPA2 expression is translationally regulated via IRES and by eIF3a and that this regulation is partly accountable for cellular response to DNA damage and survival.
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Affiliation(s)
- Ji-Ye Yin
- Department of Pharmacology/Toxicology, IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN 46202, USA
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36
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The translational factor eIF3f: the ambivalent eIF3 subunit. Cell Mol Life Sci 2013; 70:3603-16. [PMID: 23354061 PMCID: PMC3771369 DOI: 10.1007/s00018-013-1263-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/18/2012] [Accepted: 01/07/2013] [Indexed: 11/15/2022]
Abstract
The regulation of the protein synthesis has a crucial role in governing the eukaryotic cell growth. Subtle changes of proteins involved in the translation process may alter the rate of the protein synthesis and modify the cell fate by shifting the balance from normal status into a tumoral or apoptotic one. The largest eukaryotic initiation factor involved in translation regulation is eIF3. Amongst the 13 factors constituting eIF3, the f subunit finely regulates this balance in a cell-type-specific manner. Loss of this factor causes malignancy in several cells, and atrophy in normal muscle cells. The intracellular interacting partners which influence its physiological significance in both cancer and muscle cells are detailed in this review. By delineating the global interaction network of this factor and by clarifying its intracellular role, it becomes apparent that the f subunit represents a promising candidate molecule to use for biotherapeutic applications.
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Khoshnevis S, Hauer F, Milón P, Stark H, Ficner R. Novel insights into the architecture and protein interaction network of yeast eIF3. RNA (NEW YORK, N.Y.) 2012; 18:2306-19. [PMID: 23105002 PMCID: PMC3504681 DOI: 10.1261/rna.032532.112] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 09/17/2012] [Indexed: 05/20/2023]
Abstract
Translation initiation in eukaryotes is a multistep process requiring the orchestrated interaction of several eukaryotic initiation factors (eIFs). The largest of these factors, eIF3, forms the scaffold for other initiation factors, promoting their binding to the 40S ribosomal subunit. Biochemical and structural studies on eIF3 need highly pure eIF3. However, natively purified eIF3 comprise complexes containing other proteins such as eIF5. Therefore we have established in vitro reconstitution protocols for Saccharomyces cerevisiae eIF3 using its five recombinantly expressed and purified subunits. This reconstituted eIF3 complex (eIF3(rec)) exhibits the same size and activity as the natively purified eIF3 (eIF3(nat)). The homogeneity and stoichiometry of eIF3(rec) and eIF3(nat) were confirmed by analytical size exclusion chromatography, mass spectrometry, and multi-angle light scattering, demonstrating the presence of one copy of each subunit in the eIF3 complex. The reconstituted and native eIF3 complexes were compared by single-particle electron microscopy showing a high degree of structural conservation. The interaction network between eIF3 proteins was studied by means of limited proteolysis, analytical size exclusion chromatography, in vitro binding assays, and isothermal titration calorimetry, unveiling distinct protein domains and subcomplexes that are critical for the integrity of the protein network in yeast eIF3. Taken together, the data presented here provide a novel procedure to obtain highly pure yeast eIF3, suitable for biochemical and structural analysis, in addition to a detailed picture of the network of protein interactions within this complex.
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Affiliation(s)
- Sohail Khoshnevis
- Department of Molecular Structural Biology, Institute of Microbiology and Genetics, Georg-August University Göttingen, 37077 Göttingen, Germany
| | | | - Pohl Milón
- Department of Physical Biochemistry, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Holger Stark
- Research Group 3D Electron Cryo-Microscopy
- Department of Molecular Cryo-Electron Microscopy, Institute of Microbiology and Genetics, Georg-August University Göttingen, 37077 Göttingen, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, Institute of Microbiology and Genetics, Georg-August University Göttingen, 37077 Göttingen, Germany
- Corresponding authorE-mail
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38
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Neusiedler J, Mocquet V, Limousin T, Ohlmann T, Morris C, Jalinot P. INT6 interacts with MIF4GD/SLIP1 and is necessary for efficient histone mRNA translation. RNA (NEW YORK, N.Y.) 2012; 18:1163-1177. [PMID: 22532700 PMCID: PMC3358639 DOI: 10.1261/rna.032631.112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 03/06/2012] [Indexed: 05/31/2023]
Abstract
The INT6/EIF3E protein has been implicated in mouse and human breast carcinogenesis. This subunit of the eIF3 translation initiation factor that includes a PCI domain exhibits specific features such as presence in the nucleus and ability to interact with other important cellular protein complexes like the 26S proteasome and the COP9 signalosome. It has been previously shown that INT6 was not essential for bulk translation, and this protein is considered to regulate expression of specific mRNAs. Based on the results of a two-hybrid screen performed with INT6 as bait, we characterize in this article the MIF4GD/SLIP1 protein as an interactor of this eIF3 subunit. MIF4GD was previously shown to associate with SLBP, which binds the stem-loop located at the 3' end of the histone mRNAs, and to be necessary for efficient translation of these cell cycle-regulated mRNAs that lack a poly(A) tail. In line with the interaction of both proteins, we show using the RNA interference approach that INT6 is also essential to S-phase histone mRNA translation. This was observed by analyzing expression of endogenous histones and by testing heterologous constructs placing the luciferase reporter gene under the control of the stem-loop element of various histone genes. With such a reporter plasmid, silencing and overexpression of INT6 exerted opposite effects. In agreement with these results, INT6 and MIF4GD were observed to colocalize in cytoplasmic foci. We conclude from these data that INT6, by establishing interactions with MIF4GD and SLBP, plays an important role in translation of poly(A) minus histone mRNAs.
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Affiliation(s)
- Julia Neusiedler
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Vincent Mocquet
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Taran Limousin
- Virologie Humaine, Unité 758, Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Theophile Ohlmann
- Virologie Humaine, Unité 758, Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Christelle Morris
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Pierre Jalinot
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
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39
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The human T-lymphotropic virus type 1 tax protein inhibits nonsense-mediated mRNA decay by interacting with INT6/EIF3E and UPF1. J Virol 2012; 86:7530-43. [PMID: 22553336 DOI: 10.1128/jvi.07021-11] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In this report, we analyzed whether the degradation of mRNAs by the nonsense-mediated mRNA decay (NMD) pathway was affected in human T-lymphotropic virus type 1 (HTLV-1)-infected cells. This pathway was indeed strongly inhibited in C91PL, HUT102, and MT2 cells, and such an effect was also observed by the sole expression of the Tax protein in Jurkat and HeLa cells. In line with this activity, Tax binds INT6/EIF3E (here called INT6), which is a subunit of the translation initiation factor eukaryotic initiation factor 3 (eIF3) required for efficient NMD, as well as the NMD core factor upstream frameshift protein 1 (UPF1). It was also observed that Tax expression alters the morphology of processing bodies (P-bodies), the cytoplasmic structures which concentrate RNA degradation factors. The presence of UPF1 in these subcellular compartments was increased by Tax, whereas that of INT6 was decreased. In line with these effects, the level of the phosphorylated form of UPF1 was increased in the presence of Tax. Analysis of several mutants of the viral protein showed that the interaction with INT6 is necessary for NMD inhibition. The alteration of mRNA stability was observed to affect viral transcripts, such as that coding for the HTLV-1 basic leucine zipper factor (HBZ), and also several cellular mRNAs sensitive to the NMD pathway. Our data indicate that the effect of Tax on viral and cellular gene expression is not restricted to transcriptional control but can also involve posttranscriptional regulation.
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40
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Molecular mechanism of scanning and start codon selection in eukaryotes. Microbiol Mol Biol Rev 2012; 75:434-67, first page of table of contents. [PMID: 21885680 DOI: 10.1128/mmbr.00008-11] [Citation(s) in RCA: 281] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The correct translation of mRNA depends critically on the ability to initiate at the right AUG codon. For most mRNAs in eukaryotic cells, this is accomplished by the scanning mechanism, wherein the small (40S) ribosomal subunit attaches to the 5' end of the mRNA and then inspects the leader base by base for an AUG in a suitable context, using complementarity with the anticodon of methionyl initiator tRNA (Met-tRNAiMet) as the key means of identifying AUG. Over the past decade, a combination of yeast genetics, biochemical analysis in reconstituted systems, and structural biology has enabled great progress in deciphering the mechanism of ribosomal scanning. A robust molecular model now exists, describing the roles of initiation factors, notably eukaryotic initiation factor 1 (eIF1) and eIF1A, in stabilizing an "open" conformation of the 40S subunit with Met-tRNAiMet bound in a low-affinity state conducive to scanning and in triggering rearrangement into a "closed" conformation incompatible with scanning, which features Met-tRNAiMet more tightly bound to the "P" site and base paired with AUG. It has also emerged that multiple DEAD-box RNA helicases participate in producing a single-stranded "landing pad" for the 40S subunit and in removing the secondary structure to enable the mRNA to traverse the 40S mRNA-binding channel in the single-stranded form for base-by-base inspection in the P site.
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41
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Functional reconstitution of human eukaryotic translation initiation factor 3 (eIF3). Proc Natl Acad Sci U S A 2011; 108:20473-8. [PMID: 22135459 DOI: 10.1073/pnas.1116821108] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Protein fate in higher eukaryotes is controlled by three complexes that share conserved architectural elements: the proteasome, COP9 signalosome, and eukaryotic translation initiation factor 3 (eIF3). Here we reconstitute the 13-subunit human eIF3 in Escherichia coli, revealing its structural core to be the eight subunits with conserved orthologues in the proteasome lid complex and COP9 signalosome. This structural core in eIF3 binds to the small (40S) ribosomal subunit, to translation initiation factors involved in mRNA cap-dependent initiation, and to the hepatitis C viral (HCV) internal ribosome entry site (IRES) RNA. Addition of the remaining eIF3 subunits enables reconstituted eIF3 to assemble intact initiation complexes with the HCV IRES. Negative-stain EM reconstructions of reconstituted eIF3 further reveal how the approximately 400 kDa molecular mass structural core organizes the highly flexible 800 kDa molecular mass eIF3 complex, and mediates translation initiation.
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42
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Herrmannová A, Daujotyte D, Yang JC, Cuchalová L, Gorrec F, Wagner S, Dányi I, Lukavsky PJ, Valásek LS. Structural analysis of an eIF3 subcomplex reveals conserved interactions required for a stable and proper translation pre-initiation complex assembly. Nucleic Acids Res 2011; 40:2294-311. [PMID: 22090426 PMCID: PMC3300007 DOI: 10.1093/nar/gkr765] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Translation initiation factor eIF3 acts as the key orchestrator of the canonical initiation pathway in eukaryotes, yet its structure is greatly unexplored. We report the 2.2 Å resolution crystal structure of the complex between the yeast seven-bladed β-propeller eIF3i/TIF34 and a C-terminal α-helix of eIF3b/PRT1, which reveals universally conserved interactions. Mutating these interactions displays severe growth defects and eliminates association of eIF3i/TIF34 and strikingly also eIF3g/TIF35 with eIF3 and 40S subunits in vivo. Unexpectedly, 40S-association of the remaining eIF3 subcomplex and eIF5 is likewise destabilized resulting in formation of aberrant pre-initiation complexes (PICs) containing eIF2 and eIF1, which critically compromises scanning arrest on mRNA at its AUG start codon suggesting that the contacts between mRNA and ribosomal decoding site are impaired. Remarkably, overexpression of eIF3g/TIF35 suppresses the leaky scanning and growth defects most probably by preventing these aberrant PICs to form. Leaky scanning is also partially suppressed by eIF1, one of the key regulators of AUG recognition, and its mutant sui1G107R but the mechanism differs. We conclude that the C-terminus of eIF3b/PRT1 orchestrates co-operative recruitment of eIF3i/TIF34 and eIF3g/TIF35 to the 40S subunit for a stable and proper assembly of 48S pre-initiation complexes necessary for stringent AUG recognition on mRNAs.
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Affiliation(s)
- Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, v.v.i., Videnska 1083, Prague, 142 20, Czech Republic
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43
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Peixeiro I, Inácio Â, Barbosa C, Silva AL, Liebhaber SA, Romão L. Interaction of PABPC1 with the translation initiation complex is critical to the NMD resistance of AUG-proximal nonsense mutations. Nucleic Acids Res 2011; 40:1160-73. [PMID: 21989405 PMCID: PMC3273812 DOI: 10.1093/nar/gkr820] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Nonsense-mediated mRNA decay (NMD) is a surveillance pathway that recognizes and rapidly degrades mRNAs containing premature termination codons (PTC). The strength of the NMD response appears to reflect multiple determinants on a target mRNA. We have previously reported that mRNAs containing PTCs in close proximity to the translation initiation codon (AUG-proximal PTCs) can substantially evade NMD. Here, we explore the mechanistic basis for this NMD resistance. We demonstrate that translation termination at an AUG-proximal PTC lacks the ribosome stalling that is evident in an NMD-sensitive PTC. This difference is associated with demonstrated interactions of the cytoplasmic poly(A)-binding protein 1, PABPC1, with the cap-binding complex subunit, eIF4G and the 40S recruitment factor eIF3 as well as the ribosome release factor, eRF3. These interactions, in combination, underlie critical 3′–5′ linkage of translation initiation with efficient termination at the AUG-proximal PTC and contribute to an NMD-resistant PTC definition at an early phase of translation elongation.
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Affiliation(s)
- Isabel Peixeiro
- Departamento de Genética, Instituto Nacional de Saúde Dr. Ricardo Jorge, 1649-016 Lisboa, Portugal
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44
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Harel-Sharvit L, Eldad N, Haimovich G, Barkai O, Duek L, Choder M. RNA polymerase II subunits link transcription and mRNA decay to translation. Cell 2010; 143:552-63. [PMID: 21074047 DOI: 10.1016/j.cell.2010.10.033] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 07/28/2010] [Accepted: 10/25/2010] [Indexed: 01/13/2023]
Abstract
Little is known about crosstalk between the eukaryotic transcription and translation machineries that operate in different cell compartments. The yeast proteins Rpb4p and Rpb7p represent one such link as they form a heterodimer that shuttles between the nucleus, where it functions in transcription, and the cytoplasm, where it functions in the major mRNA decay pathways. Here we show that the Rpb4/7 heterodimer interacts physically and functionally with components of the translation initiation factor 3 (eIF3), and is required for efficient translation initiation. Efficient translation in the cytoplasm depends on association of Rpb4/7 with RNA polymerase II (Pol II) in the nucleus, leading to a model in which Pol II remotely controls translation. Hence, like in prokaryotes, the eukaryotic translation is coupled to transcription. We propose that Rpb4/7, through its interactions at each step in the mRNA lifecycle, represents a class of factors, "mRNA coordinators," which integrate the various stages of gene expression into a system.
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Affiliation(s)
- Liat Harel-Sharvit
- Department of Molecular Microbiology, Rappaport Faculty of Medicine, Technion - Israel Institute of Technology, Haifa, 31096, Israel
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45
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Nemoto N, Singh CR, Udagawa T, Wang S, Thorson E, Winter Z, Ohira T, Ii M, Valášek L, Brown SJ, Asano K. Yeast 18 S rRNA is directly involved in the ribosomal response to stringent AUG selection during translation initiation. J Biol Chem 2010; 285:32200-12. [PMID: 20699223 PMCID: PMC2952221 DOI: 10.1074/jbc.m110.146662] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 08/09/2010] [Indexed: 11/06/2022] Open
Abstract
In eukaryotes, the 40 S ribosomal subunit serves as the platform of initiation factor assembly, to place itself precisely on the AUG start codon. Structural arrangement of the 18 S rRNA determines the overall shape of the 40 S subunit. Here, we present genetic evaluation of yeast 18 S rRNA function using 10 point mutations altering the polysome profile. All the mutants reduce the abundance of the mutant 40 S, making it limiting for translation initiation. Two of the isolated mutations, G875A, altering the core of the platform domain that binds eIF1 and eIF2, and A1193U, changing the h31 loop located below the P-site tRNA(i)(Met), show phenotypes indicating defective regulation of AUG selection. Evidence is provided that these mutations reduce the interaction with the components of the preinitiation complex, thereby inhibiting its function at different steps. These results indicate that the 18 S rRNA mutations impair the integrity of scanning-competent preinitiation complex, thereby altering the 40 S subunit response to stringent AUG selection. Interestingly, nine of the mutations alter the body/platform domains of 18 S rRNA, potentially affecting the bridges to the 60 S subunit, but they do not change the level of 18 S rRNA intermediates. Based on these results, we also discuss the mechanism of the selective degradation of the mutant 40 S subunits.
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MESH Headings
- Amino Acid Sequence
- Base Sequence
- Codon, Initiator/metabolism
- Molecular Sequence Data
- Nucleic Acid Conformation
- Point Mutation
- Protein Biosynthesis
- Protein Structure, Tertiary
- Protein Subunits/chemistry
- Protein Subunits/genetics
- Protein Subunits/metabolism
- RNA, Fungal
- RNA, Ribosomal, 18S/chemistry
- RNA, Ribosomal, 18S/genetics
- RNA, Ribosomal, 18S/metabolism
- Ribosome Subunits, Small, Eukaryotic/chemistry
- Ribosome Subunits, Small, Eukaryotic/genetics
- Ribosome Subunits, Small, Eukaryotic/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
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Affiliation(s)
- Naoki Nemoto
- From the Molecular Cellular and Developmental Biology Program and
| | | | - Tsuyoshi Udagawa
- From the Molecular Cellular and Developmental Biology Program and
| | - Suzhi Wang
- From the Molecular Cellular and Developmental Biology Program and
- Arthropod Genomics Center, Division of Biology, Kansas State University, Manhattan, Kansas 66506 and
| | | | - Zachery Winter
- From the Molecular Cellular and Developmental Biology Program and
| | - Takahiro Ohira
- From the Molecular Cellular and Developmental Biology Program and
| | - Miki Ii
- From the Molecular Cellular and Developmental Biology Program and
| | - Leoš Valášek
- the Laboratory of Regulation of Gene Expression, Institute of Microbiology, Academy of Sciences of the Czech Republic, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Susan J. Brown
- From the Molecular Cellular and Developmental Biology Program and
- Arthropod Genomics Center, Division of Biology, Kansas State University, Manhattan, Kansas 66506 and
| | - Katsura Asano
- From the Molecular Cellular and Developmental Biology Program and
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46
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Cuchalová L, Kouba T, Herrmannová A, Dányi I, Chiu WL, Valášek L. The RNA recognition motif of eukaryotic translation initiation factor 3g (eIF3g) is required for resumption of scanning of posttermination ribosomes for reinitiation on GCN4 and together with eIF3i stimulates linear scanning. Mol Cell Biol 2010; 30:4671-86. [PMID: 20679478 PMCID: PMC2950517 DOI: 10.1128/mcb.00430-10] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 05/25/2010] [Accepted: 07/26/2010] [Indexed: 12/15/2022] Open
Abstract
Recent reports have begun unraveling the details of various roles of individual eukaryotic translation initiation factor 3 (eIF3) subunits in translation initiation. Here we describe functional characterization of two essential Saccharomyces cerevisiae eIF3 subunits, g/Tif35 and i/Tif34, previously suggested to be dispensable for formation of the 48S preinitiation complexes (PICs) in vitro. A triple-Ala substitution of conserved residues in the RRM of g/Tif35 (g/tif35-KLF) or a single-point mutation in the WD40 repeat 6 of i/Tif34 (i/tif34-Q258R) produces severe growth defects and decreases the rate of translation initiation in vivo without affecting the integrity of eIF3 and formation of the 43S PICs in vivo. Both mutations also diminish induction of GCN4 expression, which occurs upon starvation via reinitiation. Whereas g/tif35-KLF impedes resumption of scanning for downstream reinitiation by 40S ribosomes terminating at upstream open reading frame 1 (uORF1) in the GCN4 mRNA leader, i/tif34-Q258R prevents full GCN4 derepression by impairing the rate of scanning of posttermination 40S ribosomes moving downstream from uORF1. In addition, g/tif35-KLF reduces processivity of scanning through stable secondary structures, and g/Tif35 specifically interacts with Rps3 and Rps20 located near the ribosomal mRNA entry channel. Together these results implicate g/Tif35 and i/Tif34 in stimulation of linear scanning and, specifically in the case of g/Tif35, also in proper regulation of the GCN4 reinitiation mechanism.
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Affiliation(s)
- Lucie Cuchalová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, Czech Republic, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892
| | - Tomáš Kouba
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, Czech Republic, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, Czech Republic, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892
| | - István Dányi
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, Czech Republic, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892
| | - Wen-ling Chiu
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, Czech Republic, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892
| | - Leoš Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, Czech Republic, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, Maryland 20892
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47
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Cai Q, Todorovic A, Andaya A, Gao J, Leary JA, Cate JHD. Distinct regions of human eIF3 are sufficient for binding to the HCV IRES and the 40S ribosomal subunit. J Mol Biol 2010; 403:185-96. [PMID: 20816988 DOI: 10.1016/j.jmb.2010.07.054] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2010] [Revised: 06/30/2010] [Accepted: 07/27/2010] [Indexed: 02/05/2023]
Abstract
Translation of the hepatitis C virus (HCV) genomic RNA initiates from an internal ribosome entry site (IRES) in its 5' untranslated region and requires a minimal subset of translation initiation factors to occur, namely eukaryotic initiation factor (eIF) 2 and eIF3. Low-resolution structural information has revealed how the HCV IRES RNA binds human eIF3 and the 40S ribosomal subunit and positions the start codon for initiation. However, the exact nature of the interactions between the HCV IRES RNA and the translational machinery remains unknown. Using limited proteolysis and mass spectrometry, we show that distinct regions of human eIF3 are sufficient for binding to the HCV IRES RNA and the 40S subunit. Notably, the eIF3 subunit eIF3b is protected by HCV IRES RNA binding, yet is exposed in the complex when compared to subunits eIF3e, eIF3f, eIF3h, and eIF3l. Limited proteolysis reveals that eIF3 binding to the 40S ribosomal subunit occurs through many redundant interactions that can compensate for each other. These data suggest how the HCV IRES binds to specific regions of eIF3 to target the translational machinery to the viral genomic RNA and provide a framework for modeling the architecture of intact human eIF3.
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Affiliation(s)
- Qi Cai
- California Institute for Quantitative Biosciences, University of California, Berkeley, CA 94720, USA
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48
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Rosenfeld AB, Racaniello VR. Components of the multifactor complex needed for internal initiation by the IRES of hepatitis C virus in Saccharomyces cerevisiae. RNA Biol 2010; 7:596-605. [PMID: 20935471 DOI: 10.4161/rna.7.5.13096] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Interaction between the 40S ribosomal subunit and the IRES of hepatitis C virus (HCV) is thought to be independent of initiation proteins, while joining of the 60S ribosomal subunit, and initiation of translation is dependent upon components of the translation machinery. An established in vivo functional assay for internal initiation mediated by the HCV IRES was used to identify proteins needed for IRES dependent translation in Saccharomyces cerevisiae strains possessing alterations of the translation machinery. Internal initiation dependent upon the HCV IRES was abrogated in strains lacking eIF5B, and reduced in strains with altered eIF3, either lacking the Hcr1p subunit, a component of eIF3 not previously known to interact with HCV RNA, or possessing an amino acid change in the Rpg1p subunit. The HCV RNA-induced conformational change in the 40S subunit might affect positioning of eIF3 and lead to different interactions between the ribosome, eIF3, and the multifactor complex. HCV IRES dependent initiation was unaffected in strains in which the concentration of the initiating tRNA was reduced. Alteration of the δ subunit of eIF2B, which leads to inefficient recycling, or substitution of aspartic acid for serine 51 of eIF2α had no effect on internal initiation. Production of human Pkr inhibited HCV IRES dependent initiation in yeast. The synthesis of Pkr in yeast is known to result in high levels of eIF2α phosphorylation, increased Gcn4p synthesis, and reduced ribosomal protein production. These alterations may explain the effect of Pkr synthesis on HCV IRES dependent initiation in yeast.
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Affiliation(s)
- Amy B Rosenfeld
- Department of Microbiology, Columbia University College of Physicians & Surgeons, New York, NY, USA.
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49
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Saletta F, Suryo Rahmanto Y, Richardson DR. The translational regulator eIF3a: the tricky eIF3 subunit! Biochim Biophys Acta Rev Cancer 2010; 1806:275-86. [PMID: 20647036 DOI: 10.1016/j.bbcan.2010.07.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 07/07/2010] [Accepted: 07/11/2010] [Indexed: 01/10/2023]
Abstract
Regulation of gene expression is a fundamental step in cellular physiology as abnormalities in this process may lead to de-regulated growth and cancer. Translation of mRNA is mainly regulated at the rate-limiting initiation step, where many eukaryotic initiation factors (eIFs) are involved. The largest and most complex initiation factor is eIF3 which plays a role in translational regulation, cell growth and cancer. The largest subunit of eIF3 is eIF3a, although it is not required for the general function of eIF3 in translation initiation. However, eIF3a may play a role as a regulator of a subset of mRNAs and has been demonstrated to regulate the expression of p27(kip1), tyrosinated α-tubulin and ribonucleotide reductase M2 subunit. These molecules have a pivotal role in the regulation of the cell cycle. Moreover, the eIF3a mRNA is ubiquitously expressed in all tissues at different levels and is found elevated in a number of cancer types. eIF3a can modulate the cell cycle and may be a translational regulator for proteins important for entrance into S phase. The expression of eIF3a is decreased in differentiated cells in culture and the suppression of eIF3a expression can reverse the malignant phenotype and change the sensitivity of cells to cell cycle modulators. However, the role of eIF3a in cancer is still unclear. In fact, some studies have identified eIF3a to be involved in cancer development, while other results indicate that it could provide protection against evolution into higher malignancy. Together, these findings highlight the "tricky" and interesting nature of eIF3a.
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Affiliation(s)
- Federica Saletta
- Iron Metabolism and Chelation Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales, 2006 Australia
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Xia C, Wang YJ, Li WQ, Chen YR, Deng Y, Zhang XQ, Chen LQ, Ye D. The Arabidopsis eukaryotic translation initiation factor 3, subunit F (AteIF3f), is required for pollen germination and embryogenesis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 63:189-202. [PMID: 20444226 PMCID: PMC7190160 DOI: 10.1111/j.1365-313x.2010.04237.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Previous studies have shown that subunits E (eIF3e), F (eIF3f) and H (elF3h) of eukaryotic translation initiation factor 3 play important roles in cell development in humans and yeast. eIF3e and eIF3h have also been reported to be important for normal cell growth in Arabidopsis. However, the functions of subunit eIF3f remain largely unknown in plant species. Here we report characterization of mutants for the Arabidopsis eIF3f (AteIF3f) gene. AteIF3f encodes a protein that is highly expressed in pollen grains, developing embryos and root tips, and interacts with Arabidopsis eIF3e and eIF3h proteins. A Ds insertional mutation in AteIF3f disrupted pollen germination and embryo development. Expression of some of the genes that are essential for pollen tube growth and embryogenesis is down-regulated in ateif3f-1 homozygous seedlings obtained by pollen rescue. These results suggested that AteIF3f might play important roles in Arabidopsis cell growth and differentiation in combination with eIF3e and eIF3h.
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Affiliation(s)
- Chuan Xia
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yu-Jiao Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Wen-Qing Li
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yi-Ran Chen
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yi Deng
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Xue-Qin Zhang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Li-Qun Chen
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - De Ye
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
- National Center for Plant Gene Research (Beijing), Beijing 100101, China
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