1
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Wang P, Li Z, Kim SH, Xu H, Huang H, Yang C, Snape A, Choi JH, Bermudez S, Boivin MN, Ferry N, Karamchandani J, Nagar B, Sonenberg N. PPM1G dephosphorylates eIF4E in control of mRNA translation and cell proliferation. Life Sci Alliance 2024; 7:e202402755. [PMID: 39111820 PMCID: PMC11306785 DOI: 10.26508/lsa.202402755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2024] [Revised: 07/29/2024] [Accepted: 07/30/2024] [Indexed: 08/10/2024] Open
Abstract
The mRNA 5'cap-binding eukaryotic translation initiation factor 4E (eIF4E) plays a critical role in the control of mRNA translation in health and disease. One mechanism of regulation of eIF4E activity is via phosphorylation of eIF4E by MNK kinases, which promotes the translation of a subset of mRNAs encoding pro-tumorigenic proteins. Work on eIF4E phosphatases has been paltry. Here, we show that PPM1G is the phosphatase that dephosphorylates eIF4E. We describe the eIF4E-binding motif in PPM1G that is similar to 4E-binding proteins (4E-BPs). We demonstrate that PPM1G inhibits cell proliferation by targeting phospho-eIF4E-dependent mRNA translation.
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Affiliation(s)
- Peng Wang
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
- Clinical Biological Imaging and Genetic (C-BIG) Repository, Montreal Neurological Institute-Hospital, Montreal, Canada
| | - Zixian Li
- https://ror.org/01pxwe438 Department of Biochemistry, Francesco Bellini Life Sciences Building, McGill University, Montreal, Canada
| | - Sung-Hoon Kim
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
| | - Haijin Xu
- https://ror.org/01pxwe438 Department of Physiology, McIntyre Medical Sciences Building, McGill University, Montreal, Canada
| | - Hao Huang
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
| | - Chutong Yang
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
| | - Abby Snape
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
| | - Jung-Hyun Choi
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
| | - Sara Bermudez
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
| | - Marie-Noelle Boivin
- Clinical Biological Imaging and Genetic (C-BIG) Repository, Montreal Neurological Institute-Hospital, Montreal, Canada
| | - Nicolas Ferry
- Clinical Biological Imaging and Genetic (C-BIG) Repository, Montreal Neurological Institute-Hospital, Montreal, Canada
| | - Jason Karamchandani
- Clinical Biological Imaging and Genetic (C-BIG) Repository, Montreal Neurological Institute-Hospital, Montreal, Canada
| | - Bhushan Nagar
- https://ror.org/01pxwe438 Department of Biochemistry, Francesco Bellini Life Sciences Building, McGill University, Montreal, Canada
| | - Nahum Sonenberg
- https://ror.org/01pxwe438 Department of Biochemistry and Goodman Cancer Institute, McGill University, Montreal, Canada
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2
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Villa N, Fraser CS. Human eukaryotic initiation factor 4G directly binds the 40S ribosomal subunit to promote efficient translation. J Biol Chem 2024; 300:107242. [PMID: 38569933 PMCID: PMC11063902 DOI: 10.1016/j.jbc.2024.107242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 03/15/2024] [Accepted: 03/19/2024] [Indexed: 04/05/2024] Open
Abstract
Messenger RNA (mRNA) recruitment to the 40S ribosomal subunit is mediated by eukaryotic initiation factor 4F (eIF4F). This complex includes three subunits: eIF4E (m7G cap-binding protein), eIF4A (DEAD-box helicase), and eIF4G. Mammalian eIF4G is a scaffold that coordinates the activities of eIF4E and eIF4A and provides a bridge to connect the mRNA and 40S ribosomal subunit through its interaction with eIF3. While the roles of many eIF4G binding domains are relatively clear, the precise function of RNA binding by eIF4G remains to be elucidated. In this work, we used an eIF4G-dependent translation assay to reveal that the RNA binding domain (eIF4G-RBD; amino acids 682-720) stimulates translation. This stimulating activity is observed when eIF4G is independently tethered to an internal region of the mRNA, suggesting that the eIF4G-RBD promotes translation by a mechanism that is independent of the m7G cap and mRNA tethering. Using a kinetic helicase assay, we show that the eIF4G-RBD has a minimal effect on eIF4A helicase activity, demonstrating that the eIF4G-RBD is not required to coordinate eIF4F-dependent duplex unwinding. Unexpectedly, native gel electrophoresis and fluorescence polarization assays reveal a previously unidentified direct interaction between eIF4G and the 40S subunit. Using binding assays, our data show that this 40S subunit interaction is separate from the previously characterized interaction between eIF4G and eIF3. Thus, our work reveals how eIF4F can bind to the 40S subunit using eIF3-dependent and eIF3-independent binding domains to promote translation initiation.
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Affiliation(s)
- Nancy Villa
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California, USA
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California, USA.
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3
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Lin CP, Levy PL, Alflen A, Apriamashvili G, Ligtenberg MA, Vredevoogd DW, Bleijerveld OB, Alkan F, Malka Y, Hoekman L, Markovits E, George A, Traets JJH, Krijgsman O, van Vliet A, Poźniak J, Pulido-Vicuña CA, de Bruijn B, van Hal-van Veen SE, Boshuizen J, van der Helm PW, Díaz-Gómez J, Warda H, Behrens LM, Mardesic P, Dehni B, Visser NL, Marine JC, Markel G, Faller WJ, Altelaar M, Agami R, Besser MJ, Peeper DS. Multimodal stimulation screens reveal unique and shared genes limiting T cell fitness. Cancer Cell 2024; 42:623-645.e10. [PMID: 38490212 PMCID: PMC11003465 DOI: 10.1016/j.ccell.2024.02.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 01/03/2024] [Accepted: 02/22/2024] [Indexed: 03/17/2024]
Abstract
Genes limiting T cell antitumor activity may serve as therapeutic targets. It has not been systematically studied whether there are regulators that uniquely or broadly contribute to T cell fitness. We perform genome-scale CRISPR-Cas9 knockout screens in primary CD8 T cells to uncover genes negatively impacting fitness upon three modes of stimulation: (1) intense, triggering activation-induced cell death (AICD); (2) acute, triggering expansion; (3) chronic, causing dysfunction. Besides established regulators, we uncover genes controlling T cell fitness either specifically or commonly upon differential stimulation. Dap5 ablation, ranking highly in all three screens, increases translation while enhancing tumor killing. Loss of Icam1-mediated homotypic T cell clustering amplifies cell expansion and effector functions after both acute and intense stimulation. Lastly, Ctbp1 inactivation induces functional T cell persistence exclusively upon chronic stimulation. Our results functionally annotate fitness regulators based on their unique or shared contribution to traits limiting T cell antitumor activity.
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Affiliation(s)
- Chun-Pu Lin
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Pierre L Levy
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Tumor Immunology and Immunotherapy Group, Vall d'Hebron Institute of Oncology (VHIO), Vall d'Hebron Barcelona Hospital Campus, 08035 Barcelona, Spain
| | - Astrid Alflen
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Department of Hematology and Medical Oncology, University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany; Research Center for Immunotherapy (FZI), University Medical Center, Johannes Gutenberg-University, 55131 Mainz, Germany
| | - Georgi Apriamashvili
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Maarten A Ligtenberg
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - David W Vredevoogd
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Onno B Bleijerveld
- Proteomics Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Ferhat Alkan
- Division of Oncogenomics, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Yuval Malka
- Division of Oncogenomics, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Liesbeth Hoekman
- Proteomics Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Ettai Markovits
- Ella Lemelbaum Institute for Immuno-oncology and Melanoma, Sheba Medical Center, Ramat Gan 52612, Israel; Department of Clinical Microbiology and Immunology, Faculty of Medicine, Tel Aviv University, Tel-Aviv 6997801, Israel
| | - Austin George
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Joleen J H Traets
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Division of Tumor Biology and Immunology, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Oscar Krijgsman
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Alex van Vliet
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Joanna Poźniak
- Laboratory for Molecular Cancer Biology, VIB Center for Cancer Biology, 3000 Leuven, Belgium; Laboratory for Molecular Cancer Biology, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Carlos Ariel Pulido-Vicuña
- Laboratory for Molecular Cancer Biology, VIB Center for Cancer Biology, 3000 Leuven, Belgium; Laboratory for Molecular Cancer Biology, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Beaunelle de Bruijn
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Susan E van Hal-van Veen
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Julia Boshuizen
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Pim W van der Helm
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Judit Díaz-Gómez
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Hamdy Warda
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Leonie M Behrens
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Paula Mardesic
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Bilal Dehni
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Nils L Visser
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Jean-Christophe Marine
- Laboratory for Molecular Cancer Biology, VIB Center for Cancer Biology, 3000 Leuven, Belgium; Laboratory for Molecular Cancer Biology, Department of Oncology, KU Leuven, 3000 Leuven, Belgium
| | - Gal Markel
- Department of Clinical Microbiology and Immunology, Faculty of Medicine, Tel Aviv University, Tel-Aviv 6997801, Israel; Davidoff Cancer Center and Samueli Integrative Cancer Pioneering Institute, Rabin Medical Center, Petach Tikva 4941492, Israel
| | - William J Faller
- Division of Oncogenomics, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Maarten Altelaar
- Proteomics Facility, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Biomolecular Mass Spectrometry and Proteomics, Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH Utrecht, the Netherlands
| | - Reuven Agami
- Division of Oncogenomics, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands
| | - Michal J Besser
- Ella Lemelbaum Institute for Immuno-oncology and Melanoma, Sheba Medical Center, Ramat Gan 52612, Israel; Department of Clinical Microbiology and Immunology, Faculty of Medicine, Tel Aviv University, Tel-Aviv 6997801, Israel; Davidoff Cancer Center and Samueli Integrative Cancer Pioneering Institute, Rabin Medical Center, Petach Tikva 4941492, Israel; Felsenstein Medical Research Center, Faculty of Medicine, Tel Aviv University, Tel Aviv 6997801, Israel
| | - Daniel S Peeper
- Division of Molecular Oncology and Immunology, Oncode Institute, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, the Netherlands; Department of Pathology, VU University Amsterdam, 1081 HV Amsterdam, the Netherlands.
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4
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Saha U, Gaine R, Paira S, Das S, Das B. RRM1 and PAB domains of translation initiation factor eIF4G (Tif4631p) play a crucial role in the nuclear degradation of export-defective mRNAs in Saccharomyces cerevisiae. FEBS J 2024; 291:897-926. [PMID: 37994298 DOI: 10.1111/febs.17016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 10/02/2023] [Accepted: 11/21/2023] [Indexed: 11/24/2023]
Abstract
In Saccharomyces cerevisiae, the CBC-Tif4631p-dependent exosomal targeting (CTEXT) complex consisting of Cbc1/2p, Tif4631p and Upf3p promotes the exosomal degradation of aberrantly long 3'-extended, export-defective transcripts and a small group of normal (termed 'special') mRNAs. We carried out a systematic analysis of all previously characterized functional domains of the major CTEXT component Tif4631p by deleting each of them and interrogating their involvement in the nuclear surveillance of abnormally long 3'-extended and export-defective messages. Our analyses show that the N-terminal RNA recognition motif 1 (RRM1) and poly(A)-binding protein (PAB) domains of Tif4631p, spanning amino acid residues, 1-82 and 188-299 in its primary structure, respectively, play a crucial role in degrading these aberrant messages. Furthermore, the physical association of the nuclear exosome with the altered/variant CTEXT complex harboring any of the mutant Tif4631p proteins lacking either the RRM1 or PAB domain becomes abolished. This finding indicates that the association between CTEXT and the exosome is accomplished via interaction between these Tif4631p domains with the major exosome component, Rrp6p. Abolition of interaction between altered CTEXT (harboring any of the RRM1/PAB-deleted versions of Tif4631p) and the exosome further leads to the impaired recruitment of the RNA targets to the Rrp6p subunit of the exosome carried out by the RRM1/PAB domains of Tif4631p. When analyzing the Tif4631p-interacting proteins, we identified a DEAD-box RNA helicase (Dbp2p), as an interacting partner that turned out to be a previously unknown component of CTEXT. The present study provides a more complete description of the CTEXT complex and offers insight into the functional relationship of this complex with the nuclear exosome.
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Grants
- BT/PR27917/BRB/10/1673/2018 Department of Biotechnology, Ministry of Science and Technology, India
- BT/PR6078/BRB/10/1114/2012 Department of Biotechnology, Ministry of Science and Technology, India
- 38/1427/16/EMR-II Council of Scientific and Industrial Research, India
- 38/1280/11/EMR-II Council of Scientific and Industrial Research, India
- SR/SO/BB/0066/2012 Department of Science and Technology, Ministry of Science and Technology, India
- Department of Science & Technology and Biotechnology, Government of West Bengal
- SR/WOS-A/LS-1067/2014 Department of Science and Technology, India, WOS-A
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Affiliation(s)
- Upasana Saha
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Rajlaxmi Gaine
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Sunirmal Paira
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Satarupa Das
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
| | - Biswadip Das
- Department of Life Science and Biotechnology, Jadavpur University, Kolkata, India
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5
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Brito Querido J, Sokabe M, Díaz-López I, Gordiyenko Y, Fraser CS, Ramakrishnan V. The structure of a human translation initiation complex reveals two independent roles for the helicase eIF4A. Nat Struct Mol Biol 2024; 31:455-464. [PMID: 38287194 PMCID: PMC10948362 DOI: 10.1038/s41594-023-01196-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 11/30/2023] [Indexed: 01/31/2024]
Abstract
Eukaryotic translation initiation involves recruitment of the 43S pre-initiation complex to the 5' end of mRNA by the cap-binding complex eIF4F, forming the 48S translation initiation complex (48S), which then scans along the mRNA until the start codon is recognized. We have previously shown that eIF4F binds near the mRNA exit channel of the 43S, leaving open the question of how mRNA secondary structure is removed as it enters the mRNA channel on the other side of the 40S subunit. Here we report the structure of a human 48S that shows that, in addition to the eIF4A that is part of eIF4F, there is a second eIF4A helicase bound at the mRNA entry site, which could unwind RNA secondary structures as they enter the 48S. The structure also reveals conserved interactions between eIF4F and the 43S, probaby explaining how eIF4F can promote mRNA recruitment in all eukaryotes.
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Affiliation(s)
- Jailson Brito Querido
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Department of Biological Chemistry and Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA
| | | | | | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA.
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6
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Wu S, Wagner G. Computational inference of eIF4F complex function and structure in human cancers. Proc Natl Acad Sci U S A 2024; 121:e2313589121. [PMID: 38266053 PMCID: PMC10835048 DOI: 10.1073/pnas.2313589121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 12/18/2023] [Indexed: 01/26/2024] Open
Abstract
The canonical eukaryotic initiation factor 4F (eIF4F) complex, composed of eIF4G1, eIF4A1, and the cap-binding protein eIF4E, plays a crucial role in cap-dependent translation initiation in eukaryotic cells. An alternative cap-independent initiation can occur, involving only eIF4G1 and eIF4A1 through internal ribosome entry sites (IRESs). This mechanism is considered complementary to cap-dependent initiation, particularly in tumors under stress conditions. However, the selection and molecular mechanism of specific translation initiation remains poorly understood in human cancers. Thus, we analyzed gene copy number variations (CNVs) in TCGA tumor samples and found frequent amplification of genes involved in translation initiation. Copy number gains in EIF4G1 and EIF3E frequently co-occur across human cancers. Additionally, EIF4G1 expression strongly correlates with genes from cancer cell survival pathways including cell cycle and lipogenesis, in tumors with EIF4G1 amplification or duplication. Furthermore, we revealed that eIF4G1 and eIF4A1 protein levels strongly co-regulate with ribosomal subunits, eIF2, and eIF3 complexes, while eIF4E co-regulates with 4E-BP1, ubiquitination, and ESCRT proteins. Utilizing Alphafold predictions, we modeled the eIF4F structure with and without eIF4E binding. For cap-dependent initiation, our modeling reveals extensive interactions between the N-terminal eIF4E-binding domain of eIF4G1 and eIF4E. Furthermore, the eIF4G1 HEAT-2 domain positions eIF4E near the eIF4A1 N-terminal domain (NTD), resulting in the collaborative enclosure of the RNA binding cavity within eIF4A1. In contrast, during cap-independent initiation, the HEAT-2 domain directly binds the eIF4A1-NTD, leading to a stronger interaction between eIF4G1 and eIF4A1, thus closing the mRNA binding cavity without the involvement of eIF4E.
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Affiliation(s)
- Su Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA02115
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA02115
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7
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Villa N, Fraser CS. Human eukaryotic initiation factor 4G directly binds the 40S ribosomal subunit to promote efficient translation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.29.560218. [PMID: 37808713 PMCID: PMC10557762 DOI: 10.1101/2023.09.29.560218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Messenger RNA (mRNA) recruitment to the 40S ribosomal subunit is mediated by eukaryotic initiation factor 4F (eIF4F). This complex includes 3 subunits: eIF4E (m 7 G cap binding protein), eIF4A (DEAD box helicase), and eIF4G. Mammalian eIF4G is a scaffold that coordinates the activities of eIF4E and eIF4A and provides a bridge to connect the mRNA and 40S ribosomal subunit through its interaction with eIF3. While the roles of many eIF4G binding domains are relatively clear, the precise function of RNA binding by eIF4G remains to be elucidated. In this work, we used an eIF4G-dependent translation assay to reveal that the RNA binding domain (eIF4G-RBD; amino acids 682-720) stimulates translation. This stimulating activity is observed when eIF4G is independently tethered to an internal region of the mRNA, suggesting that the eIF4G-RBD promotes translation by a mechanism that is independent of the m 7 G cap and mRNA tethering. Using a kinetic helicase assay, we show that the eIF4G-RBD has a minimal effect on eIF4A helicase activity, demonstrating that the eIF4G-RBD is not required to coordinate eIF4F-dependent duplex unwinding. Unexpectedly, native gel electrophoresis and fluorescence polarization assays reveal a previously unidentified direct interaction between eIF4G and the 40S subunit. Using binding assays, our data show that this 40S subunit interaction is separate from the previously characterized interaction between eIF4G and eIF3. Thus, our work reveals how eIF4F can bind to the 40S subunit using eIF3-dependent and eIF3-independent binding domains to promote translation initiation.
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8
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Wu S, Wagner G. Computational inference of eIF4F complex function and structure in human cancers. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.10.552450. [PMID: 37609226 PMCID: PMC10441403 DOI: 10.1101/2023.08.10.552450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
The canonical eukaryotic initiation factor 4F (eIF4F) complex, composed of eIF4G1, eIF4A1, and the cap-binding protein eIF4E, plays a crucial role in cap-dependent translation initiation in eukaryotic cells (1). However, cap-independent initiation can occur through internal ribosomal entry sites (IRESs), involving only eIF4G1 and eIF4A1 present, which is considered to be a complementary process to cap-dependent initiation in tumors under stress conditions (2). The selection and molecular mechanism of specific translation initiation in human cancers remains poorly understood. Thus, we analyzed gene copy number variations (CNVs) in TCGA tumor samples and found frequent amplification of genes involved in translation initiation. Copy number gains in EIF4G1 and EIF3E frequently co-occur across human cancers. Additionally, EIF4G1 expression strongly correlates with genes from cancer cell survival pathways including cell cycle and lipogenesis, in tumors with EIF4G1 amplification or duplication. Furthermore, we revealed that eIF4G1 and eIF4A1 protein levels strongly co-regulate with ribosomal subunits, eIF2, and eIF3 complexes, while eIF4E co-regulates with 4E-BP1, ubiquitination, and ESCRT proteins. Using Alphafold predictions, we modeled the eIF4F structure with and without eIF4G1-eIF4E binding. The modeling for cap-dependent initiation suggests that eIF4G1 interacts with eIF4E through its N-terminal eIF4E-binding domain, bringing eIF4E near the eIF4A1 mRNA binding cavity and closing the cavity with both eIF4G1 HEAT-2 domain and eIF4E. In the cap-independent mechanism, α-helix 5 of eIF4G1 HEAT-2 domain instead directly interacts with the eIF4A1 N-terminal domain to close the mRNA binding cavity without eIF4E involvement, resulting in a stronger interaction between eIF4G1 and eIF4A1. Significance Statement Translation initiation is primarily governed by eIF4F, employing a "cap-dependent" mechanism, but eIF4F dysregulation may lead to a "cap-independent" mechanism in stressed cancer cells. We found frequent amplification of translation initiation genes, and co-occurring copy number gains of EIF4G1 and EIF3E genes in human cancers. EIF4G1 amplification or duplication may be positively selected for its beneficial impact on the overexpression of cancer survival genes. The co-regulation of eIF4G1 and eIF4A1, distinctly from eIF4E, reveals eIF4F dysregulation favoring cap-independent initiation. Alphafold predicts changes in the eIF4F complex assembly to accommodate both initiation mechanisms. These findings have significant implications for evaluating cancer cell vulnerability to eIF4F inhibition and developing treatments that target cancer cells with dependency on the translation initiation mechanism.
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9
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Quddusi DM, Bajcinca N. Identification of genomic biomarkers and their pathway crosstalks for deciphering mechanistic links in glioblastoma. IET Syst Biol 2023; 17:143-161. [PMID: 37277696 PMCID: PMC10439498 DOI: 10.1049/syb2.12066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2022] [Revised: 04/22/2023] [Accepted: 05/03/2023] [Indexed: 06/07/2023] Open
Abstract
Glioblastoma is a grade IV pernicious neoplasm occurring in the supratentorial region of brain. As its causes are largely unknown, it is essential to understand its dynamics at the molecular level. This necessitates the identification of better diagnostic and prognostic molecular candidates. Blood-based liquid biopsies are emerging as a novel tool for cancer biomarker discovery, guiding the treatment and improving its early detection based on their tumour origin. There exist previous studies focusing on the identification of tumour-based biomarkers for glioblastoma. However, these biomarkers inadequately represent the underlying pathological state and incompletely illustrate the tumour because of non-recursive nature of this approach to monitor the disease. Also, contrary to the tumour biopsies, liquid biopsies are non-invasive and can be performed at any interval during the disease span to surveil the disease. Therefore, in this study, a unique dataset of blood-based liquid biopsies obtained primarily from tumour-educated blood platelets (TEP) is utilised. This RNA-seq data from ArrayExpress is acquired comprising human cohort with 39 glioblastoma subjects and 43 healthy subjects. Canonical and machine learning approaches are applied for identification of the genomic biomarkers for glioblastoma and their crosstalks. In our study, 97 genes appeared enriched in 7 oncogenic pathways (RAF-MAPK, P53, PRC2-EZH2, YAP conserved, MEK-MAPK, ErbB2 and STK33 signalling pathways) using GSEA, out of which 17 have been identified participating actively in crosstalks. Using PCA, 42 genes are found enriched in 7 pathways (cytoplasmic ribosomal proteins, translation factors, electron transport chain, ribosome, Huntington's disease, primary immunodeficiency pathways, and interferon type I signalling pathway) harbouring tumour when altered, out of which 25 actively participate in crosstalks. All the 14 pathways foster well-known cancer hallmarks and the identified DEGs can serve as genomic biomarkers, not only for the diagnosis and prognosis of Glioblastoma but also in providing a molecular foothold for oncogenic decision making in order to fathom the disease dynamics. Moreover, SNP analysis for the identified DEGs is performed to investigate their roles in disease dynamics in an elaborated manner. These results suggest that TEPs are capable of providing disease insights just like tumour cells with an advantage of being extracted anytime during the course of disease in order to monitor it.
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Affiliation(s)
- Darrak Moin Quddusi
- Chair of Mechatronics in the Faculty of Mechanical and Process EngineeringRheinland‐Pfälzische Technische Universität Kaiserslautern‐LandauKaiserslauternGermany
| | - Naim Bajcinca
- Chair of Mechatronics in the Faculty of Mechanical and Process EngineeringRheinland‐Pfälzische Technische Universität Kaiserslautern‐LandauKaiserslauternGermany
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10
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Shestakova ED, Smirnova VV, Shatsky IN, Terenin IM. Specific mechanisms of translation initiation in higher eukaryotes: the eIF4G2 story. RNA (NEW YORK, N.Y.) 2023; 29:282-299. [PMID: 36517212 PMCID: PMC9945437 DOI: 10.1261/rna.079462.122] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The eukaryotic initiation factor 4G2 (eIF4G2, DAP5, Nat1, p97) was discovered in 1997. Over the past two decades, dozens of papers have presented contradictory data on eIF4G2 function. Since its identification, eIF4G2 has been assumed to participate in noncanonical translation initiation mechanisms, but recent results indicate that it can be involved in scanning as well. In particular, eIF4G2 provides leaky scanning through some upstream open reading frames (uORFs), which are typical for long 5' UTRs of mRNAs from higher eukaryotes. It is likely the protein can also help the ribosome overcome other impediments during scanning of the 5' UTRs of animal mRNAs. This may explain the need for eIF4G2 in higher eukaryotes, as many mRNAs that encode regulatory proteins have rather long and highly structured 5' UTRs. Additionally, they often bind to various proteins, which also hamper the movement of scanning ribosomes. This review discusses the suggested mechanisms of eIF4G2 action, denotes obscure or inconsistent results, and proposes ways to uncover other fundamental mechanisms in which this important protein factor may be involved in higher eukaryotes.
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Affiliation(s)
- Ekaterina D Shestakova
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119234, Russia
| | - Victoria V Smirnova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - Ivan N Shatsky
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
| | - Ilya M Terenin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia
- Sirius University of Science and Technology, Sochi 354349, Russia
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11
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Abu-Hijleh HM, Al-Zoubi RM, Zarour A, Al- Ansari A, Bawadi H. The Therapeutic Role of Curcumin in Inflammation and Post-Surgical Outcomes. FOOD REVIEWS INTERNATIONAL 2023. [DOI: 10.1080/87559129.2023.2166525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Haya M. Abu-Hijleh
- Department of Human Nutrition, college of health Science, QU-health, Qatar University, Doha, Qatar
| | - Raed M. Al-Zoubi
- Department of biomedical Sciences, college of health Science, QU-Health, Qatar University, Doha, Qatar
- Surgical Research Section, Department of Surgery, Hamad Medical Corporation, Doha, Qatar
- Department of Chemistry, Jordan University of Science and Technology, Irbid, Jordan
| | - Ahmed Zarour
- Acute care Surgery Division, Department of Surgery, Hamad Medical Corporation, Doha, Qatar
| | - Abdulla Al- Ansari
- Surgical Research Section, Department of Surgery, Hamad Medical Corporation, Doha, Qatar
- Department of Surgery, Division of Urology/Andrology, Hamad Medical Corporation, Doha, Qatar
| | - Hiba Bawadi
- Department of Human Nutrition, college of health Science, QU-health, Qatar University, Doha, Qatar
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12
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Krause L, Willing F, Andreou AZ, Klostermeier D. The domains of yeast eIF4G, eIF4E and the cap fine-tune eIF4A activities through an intricate network of stimulatory and inhibitory effects. Nucleic Acids Res 2022; 50:6497-6510. [PMID: 35689631 PMCID: PMC9226541 DOI: 10.1093/nar/gkac437] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 04/19/2022] [Accepted: 05/23/2022] [Indexed: 12/13/2022] Open
Abstract
Translation initiation in eukaryotes starts with the recognition of the mRNA 5'-cap by eIF4F, a hetero-trimeric complex of eIF4E, the cap-binding protein, eIF4A, a DEAD-box helicase, and eIF4G, a scaffold protein. eIF4G comprises eIF4E- and eIF4A-binding domains (4E-BD, 4A-BD) and three RNA-binding regions (RNA1-RNA3), and interacts with eIF4A, eIF4E, and with the mRNA. Within the eIF4F complex, the helicase activity of eIF4A is increased. We showed previously that RNA3 of eIF4G is important for the stimulation of the eIF4A conformational cycle and its ATPase and helicase activities. Here, we dissect the interplay between the eIF4G domains and the role of the eIF4E/cap interaction in eIF4A activation. We show that RNA2 leads to an increase in the fraction of eIF4A in the closed state, an increased RNA affinity, and faster RNA unwinding. This stimulatory effect is partially reduced when the 4E-BD is present. eIF4E binding to the 4E-BD then further inhibits the helicase activity and closing of eIF4A, but does not affect the RNA-stimulated ATPase activity of eIF4A. The 5'-cap renders the functional interaction of mRNA with eIF4A less efficient. Overall, the activity of eIF4A at the 5'-cap is thus fine-tuned by a delicately balanced network of stimulatory and inhibitory interactions.
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Affiliation(s)
- Linda Krause
- Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, 48149 Muenster, Germany
| | - Florian Willing
- Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, 48149 Muenster, Germany
| | - Alexandra Zoi Andreou
- Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, 48149 Muenster, Germany
| | - Dagmar Klostermeier
- Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, 48149 Muenster, Germany
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13
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Friedrich D, Marintchev A, Arthanari H. The metaphorical swiss army knife: The multitude and diverse roles of HEAT domains in eukaryotic translation initiation. Nucleic Acids Res 2022; 50:5424-5442. [PMID: 35552740 PMCID: PMC9177959 DOI: 10.1093/nar/gkac342] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 04/20/2022] [Accepted: 04/22/2022] [Indexed: 11/24/2022] Open
Abstract
Biomolecular associations forged by specific interaction among structural scaffolds are fundamental to the control and regulation of cell processes. One such structural architecture, characterized by HEAT repeats, is involved in a multitude of cellular processes, including intracellular transport, signaling, and protein synthesis. Here, we review the multitude and versatility of HEAT domains in the regulation of mRNA translation initiation. Structural and cellular biology approaches, as well as several biophysical studies, have revealed that a number of HEAT domain-mediated interactions with a host of protein factors and RNAs coordinate translation initiation. We describe the basic structural architecture of HEAT domains and briefly introduce examples of the cellular processes they dictate, including nuclear transport by importin and RNA degradation. We then focus on proteins in the translation initiation system featuring HEAT domains, specifically the HEAT domains of eIF4G, DAP5, eIF5, and eIF2Bϵ. Comparative analysis of their remarkably versatile interactions, including protein-protein and protein-RNA recognition, reveal the functional importance of flexible regions within these HEAT domains. Here we outline how HEAT domains orchestrate fundamental aspects of translation initiation and highlight open mechanistic questions in the area.
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Affiliation(s)
- Daniel Friedrich
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Assen Marintchev
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, MA, USA
| | - Haribabu Arthanari
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
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14
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Das S. Analysis of domain organization and functional signatures of trypanosomatid keIF4Gs. Mol Cell Biochem 2022; 477:2415-2431. [PMID: 35585276 DOI: 10.1007/s11010-022-04464-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 05/02/2022] [Indexed: 11/25/2022]
Abstract
Translation initiation is the first step in three essential processes leading to protein synthesis. It is carried out by proteins called translation initiation factors and ribosomes on the mRNA. One of the critical translation initiation factors in eukaryotes is eIF4G which is a scaffold protein that helps assemble translation initiation complexes that carry out translation initiation which ultimately leads to polypeptide synthesis. Trypanosomatids are a large family of kinetoplastids, some of which are protozoan parasites that cause diseases in humans through transmission by vectors. While the protein translation mechanisms in eukaryotes and prokaryotes are well understood, the protein translation factors and mechanisms in trypanosomatids are poorly understood necessitating further studies. Unlike other eukaryotes, trypanosomatids contain five eIF4G orthologues with diversity in length and sequences. Here, I have used bioinformatics tools to look at trypanosomatid keIF4G orthologue sequences and report that there are similarities and considerable differences in their domains/motifs organization and signature amino acid sequences that are required for different functions as compared to human eIF4G. My analysis suggests that there is likely to be considerable diversity and complexity in trypanosomatid keIF4G functions as compared to other eukaryotes.
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Affiliation(s)
- Supratik Das
- Infection and Immunology, Translational Health Science and Technology Institute, Faridabad, Haryana, 121001, India.
- Translational Health Science and Technology Institute, NCR Biotech Science Cluster, 3rd Milestone, Faridabad-Gurgaon Expressway, PO Box #04, Faridabad, Haryana, 121001, India.
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15
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Mohammad MP, Smirnova A, Gunišová S, Valášek LS. eIF4G is retained on ribosomes elongating and terminating on short upstream ORFs to control reinitiation in yeast. Nucleic Acids Res 2021; 49:8743-8756. [PMID: 34352092 PMCID: PMC8421214 DOI: 10.1093/nar/gkab652] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 07/08/2021] [Accepted: 07/21/2021] [Indexed: 11/28/2022] Open
Abstract
Translation reinitiation is a gene-specific translational control mechanism. It is characterized by the ability of short upstream ORFs to prevent full ribosomal recycling and allow the post-termination 40S subunit to resume traversing downstream for the next initiation event. It is well known that variable transcript-specific features of various uORFs and their prospective interactions with initiation factors lend them an unequivocal regulatory potential. Here, we investigated the proposed role of the major initiation scaffold protein eIF4G in reinitiation and its prospective interactions with uORF’s cis-acting features in yeast. In analogy to the eIF3 complex, we found that eIF4G and eIF4A but not eIF4E (all constituting the eIF4F complex) are preferentially retained on ribosomes elongating and terminating on reinitiation-permissive uORFs. The loss of the eIF4G contact with eIF4A specifically increased this retention and, as a result, increased the efficiency of reinitiation on downstream initiation codons. Combining the eIF4A-binding mutation with that affecting the integrity of the eIF4G1–RNA2-binding domain eliminated this specificity and produced epistatic interaction with a mutation in one specific cis-acting feature. We conclude that similar to humans, eIF4G is retained on ribosomes elongating uORFs to control reinitiation also in yeast.
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Affiliation(s)
- Mahabub Pasha Mohammad
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AS CR, Prague, Videnska 1083, 142 20, Czech Republic
| | - Anna Smirnova
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AS CR, Prague, Videnska 1083, 142 20, Czech Republic
| | - Stanislava Gunišová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AS CR, Prague, Videnska 1083, 142 20, Czech Republic
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AS CR, Prague, Videnska 1083, 142 20, Czech Republic
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16
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Wu S, Wagner G. Deep computational analysis details dysregulation of eukaryotic translation initiation complex eIF4F in human cancers. Cell Syst 2021; 12:907-923.e6. [PMID: 34358439 DOI: 10.1016/j.cels.2021.07.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 04/22/2021] [Accepted: 07/09/2021] [Indexed: 12/28/2022]
Abstract
eIF4F plays diverse roles in human cancers, which complicate the development of an overarching understanding of its functional and regulatory impacts across tumor types. Typically, eIF4F drives initiation from the mRNA 5' end (cap) and is composed of eIF4G1, eIF4A1, and cap-binding eIF4E. Cap-independent initiation is possible without eIF4E, from internal ribosomal entry sites (IRESs). By analyzing large public datasets, we found that cancers selectively overexpress EIF4G1 more than EIF4E. That expression imbalance supports EIF4G1 as a prognostic indicator in patients with cancer. It also attenuates "housekeeping" pathways that are usually regulated in a tissue-specific manner via cap-dependent initiation in healthy tissues and reinforce regulation of cancer-preferred pathways in cap-independent contexts. Cap-independent initiation is mechanistically attributable to eIF4G1 hyperphosphorylation that promotes binding to eIF4A1 and reduced eIF4E availability. Collectively, these findings reveal a novel model of dysregulated eIF4F function and highlight the clinical relevance of cap-(in)dependent initiation in cancer.
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Affiliation(s)
- Su Wu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.
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17
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Zhang Z, Zheng B, Du S, Han G, Zhao H, Wu S, Jia S, Bachmann T, Bekker A, Tao YX. Eukaryotic initiation factor 4 gamma 2 contributes to neuropathic pain through down-regulation of Kv1.2 and the mu opioid receptor in mouse primary sensory neurones. Br J Anaesth 2021; 126:706-719. [PMID: 33303185 PMCID: PMC8014947 DOI: 10.1016/j.bja.2020.10.032] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 10/02/2020] [Accepted: 10/19/2020] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Nerve injury-induced changes in gene expression in the dorsal root ganglion (DRG) contribute to neuropathic pain genesis. Eukaryotic initiation factor 4 gamma 2 (eIF4G2) is a general repressor of cap-dependent mRNA translation. Whether DRG eIF4G2 participates in nerve injury-induced alternations in gene expression and nociceptive hypersensitivity is unknown. METHODS The expression and distribution of eIF4G2 mRNA and protein in mouse DRG after spinal nerve ligation (SNL) were assessed. Effects of eIF4G2 siRNA microinjected through a glass micropipette into the injured DRG on the SNL-induced DRG mu opioid receptor (MOR) and Kv1.2 downregulation and nociceptive hypersensitivity were examined. In addition, effects of DRG microinjection of adeno-associated virus 5-expressing eIF4G2 (AAV5-eIF4G2) on basal DRG MOR and Kv1.2 expression and nociceptive thresholds were analysed. RESULTS eIF4G2 protein co-expressed with Kv1.2 and MOR in DRG neurones. Levels of eIF4G2 mRNA (1.7 [0.24] to 2.3 [0.14]-fold of sham, P<0.01) and protein (1.6 [0.14] to 2.5 [0.22]-fold of sham, P<0.01) in injured DRG were time-dependently increased on days 3-14 after SNL. Blocking increased eIF4G2 through microinjection of eIF4G2 siRNA into the injured DRG attenuated SNL-induced downregulation of DRG MOR and Kv1.2 and development and maintenance of nociceptive hypersensitivities. DRG microinjection of AAV5-eIF4G2 reduced DRG MOR and Kv1.2 expression and elicited hypersensitivities to mechanical, heat and cold stimuli in naïve mice. CONCLUSIONS eIF4G2 contributes to neuropathic pain through participation in downregulation of Kv1.2 and MOR in injured DRG and is a potential target for treatment of this disorder.
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Affiliation(s)
- Zhen Zhang
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Bixin Zheng
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Shibin Du
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Guang Han
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Hui Zhao
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Shaogen Wu
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Shushan Jia
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Thomas Bachmann
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Alex Bekker
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA
| | - Yuan-Xiang Tao
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA; Departments of Cell Biology & Molecular Medicine and Physiology, Pharmacology & Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ, USA.
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18
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Donsbach P, Klostermeier D. Regulation of RNA helicase activity: principles and examples. Biol Chem 2021; 402:529-559. [PMID: 33583161 DOI: 10.1515/hsz-2020-0362] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 01/29/2021] [Indexed: 12/16/2022]
Abstract
RNA helicases are a ubiquitous class of enzymes involved in virtually all processes of RNA metabolism, from transcription, mRNA splicing and export, mRNA translation and RNA transport to RNA degradation. Although ATP-dependent unwinding of RNA duplexes is their hallmark reaction, not all helicases catalyze unwinding in vitro, and some in vivo functions do not depend on duplex unwinding. RNA helicases are divided into different families that share a common helicase core with a set of helicase signature motives. The core provides the active site for ATP hydrolysis, a binding site for non-sequence-specific interaction with RNA, and in many cases a basal unwinding activity. Its activity is often regulated by flanking domains, by interaction partners, or by self-association. In this review, we summarize the regulatory mechanisms that modulate the activities of the helicase core. Case studies on selected helicases with functions in translation, splicing, and RNA sensing illustrate the various modes and layers of regulation in time and space that harness the helicase core for a wide spectrum of cellular tasks.
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Affiliation(s)
- Pascal Donsbach
- Institute for Physical Chemistry, University of Münster, Corrensstrasse 30, D-48149Münster, Germany
| | - Dagmar Klostermeier
- Institute for Physical Chemistry, University of Münster, Corrensstrasse 30, D-48149Münster, Germany
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19
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Zheng BX, Malik A, Xiong M, Bekker A, Tao YX. Nerve trauma-caused downregulation of opioid receptors in primary afferent neurons: Molecular mechanisms and potential managements. Exp Neurol 2020; 337:113572. [PMID: 33340498 DOI: 10.1016/j.expneurol.2020.113572] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Revised: 12/06/2020] [Accepted: 12/13/2020] [Indexed: 12/18/2022]
Abstract
Neuropathic pain is the most common clinical disorder destroying the quality of patient life and leading to a marked economic and social burden. Opioids are still last option for pharmacological treatment of this disorder, but their antinociceptive effects are limited in part due to the downregulation of opioid receptors in the primary afferent neurons after peripheral nerve trauma. How this downregulation occurs is not completely understood, but recent studies have demonstrated that peripheral nerve trauma drives the alterations in epigenetic modifications (including DNA methylation, histone methylation and mciroRNAs), expression of transcription factors, post-transcriptional modifications (e.g., RNA methylation) and protein translation initiation in the neurons of nerve trauma-related dorsal root ganglion (DRG) and that these alternations may be associated with nerve trauma-caused downregulation of DRG opioid receptors. This review presents how opioid receptors are downregulated in the DRG after peripheral nerve trauma, specifically focusing on distinct molecular mechanisms underlying transcriptional and translational processes. This review also discusses how this downregulation contributes to the induction and maintenance of neuropathic pain. A deeper understanding of these molecular mechanisms likely provides a novel avenue for prevention and/or treatment of neuropathic pain.
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Affiliation(s)
- Bi-Xin Zheng
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA
| | - Ayma Malik
- Rutgers Graduate School of Biomedical Sciences, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA
| | - Ming Xiong
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA
| | - Alex Bekker
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA
| | - Yuan-Xiang Tao
- Department of Anesthesiology, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA; Department of Physiology, Pharmacology & Neuroscience, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA; Department of Cell Biology & Molecular Medicine, New Jersey Medical School, Rutgers, The State University of New Jersey, Newark, NJ 07103, USA.
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20
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Basak T, Dey AK, Banerjee R, Paul S, Maiti TK, Ain R. Sequestration of eIF4A by angiomotin: A novel mechanism to restrict global protein synthesis in trophoblast cells. STEM CELLS (DAYTON, OHIO) 2020; 39:210-226. [PMID: 33237582 DOI: 10.1002/stem.3305] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 11/13/2020] [Indexed: 11/10/2022]
Abstract
Enrichment of angiomotin (AMOT) in the ectoplacental cone of E7.5 murine placenta prompted our investigation on the role of AMOT in trophoblast differentiation. We show here that AMOT levels increased in mouse placenta during gestation and also upon induction of differentiation in trophoblast stem cell ex vivo. Proteomic data unravelling AMOT-interactome in trophoblast cells indicated a majority of AMOT interactors to be involved in protein translation. In-depth analysis of AMOT-interactome led to identification of eukaryotic translation initiation factor 4A (eIF4A) as the most plausible AMOT interactor. Loss of function of AMOT enhanced, whereas, gain in function resulted in decline of global protein synthesis in trophoblast cells. Bioinformatics analysis evaluating the potential energy of AMOT-eIF4A binding suggested a strong AMOT-eIF4A interaction using a distinct groove encompassing amino acid residue positions 238 to 255 of AMOT. Co-immunoprecipitation of AMOT with eIF4A reaffirmed AMOT-eIF4A association in trophoblast cells. Deletion of 238 to 255 amino acids of AMOT resulted in abrogation of AMOT-eIF4A interaction. In addition, 238 to 255 amino acid deletion of AMOT was ineffective in eliciting AMOT's function in reducing global protein synthesis. Interestingly, AMOT-dependent sequestration of eIF4A dampened its loading to the m7 -GTP cap and hindered its interaction with eIF4G. Furthermore, enhanced AMOT expression in placenta was associated with intrauterine growth restriction in both rats and humans. These results not only highlight a hitherto unknown novel function of AMOT in trophoblast cells but also have broad biological implications as AMOT might be an inbuilt switch to check protein synthesis in developmentally indispensable trophoblast cells.
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Affiliation(s)
- Trishita Basak
- Division of Cell Biology and Physiology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | | | - Rachana Banerjee
- Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Sandip Paul
- Division of Structural Biology and Bioinformatics, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | | | - Rupasri Ain
- Division of Cell Biology and Physiology, CSIR-Indian Institute of Chemical Biology, Kolkata, India
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21
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Robert F, Cencic R, Cai R, Schmeing TM, Pelletier J. RNA-tethering assay and eIF4G:eIF4A obligate dimer design uncovers multiple eIF4F functional complexes. Nucleic Acids Res 2020; 48:8562-8575. [PMID: 32749456 PMCID: PMC7470955 DOI: 10.1093/nar/gkaa646] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 07/05/2020] [Accepted: 07/30/2020] [Indexed: 12/11/2022] Open
Abstract
Eukaryotic cellular mRNAs possess a 5′ cap structure (m7GpppN) which plays a critical role in translation initiation mediated by eukaryotic initiation factor (eIF) 4F. The heterotrimeric eIF4F complex possesses several activities imparted by its subunits that include cap recognition (by eIF4E), RNA unwinding (eIF4A), and factor/ribosome recruitment (eIF4G). Mammalian cells have paralogs of all three eIF4F subunits and it remains an open question as to whether these all can participate in the process of ribosome recruitment. To query the activities of the eIF4F subunits in translation initiation, we adopted an RNA-tethering assay in which select subunits are recruited to a specific address on a reporter mRNA template. We find that all eIF4F subunits can participate in the initiation process. Based on eIF4G:eIF4A structural information, we also designed obligate dimer pairs to probe the activity of all combinations of eIF4G and eIF4A paralogs. We demonstrate that both eIF4GI and eIF4GII can associate with either eIF4A1 or eIF4A2 to recruit ribosomes to mRNA templates. In combination with eIF4E and eIF4E3, our results indicate the presence of up to eight eIF4F complexes that can operate in translation initiation.
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Affiliation(s)
- Francis Robert
- Department of Biochemistry, McGill University, Montreal, Canada
| | - Regina Cencic
- Department of Biochemistry, McGill University, Montreal, Canada
| | - Renying Cai
- Department of Biochemistry, McGill University, Montreal, Canada
| | | | - Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Canada.,Department of Oncology.,Rosalind & Morris Goodman Cancer Research Centre, McGill University, Montreal, Canada
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22
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Abstract
The stage at which ribosomes are recruited to messenger RNAs (mRNAs) is an elaborate and highly regulated phase of protein synthesis. Upon completion of this step, a ribosome is positioned at an appropriate initiation codon and primed to synthesize the encoded polypeptide product. In most circumstances, this step commits the ribosome to translate the mRNA. We summarize the knowledge regarding the initiation factors implicated in this activity as well as review different mechanisms by which this process is conducted.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada; , .,Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Quebec H3A 1A3, Canada.,Department of Oncology, McGill University, Montreal, Quebec H4A 3T2, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada; , .,Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Quebec H3A 1A3, Canada
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23
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Camillo dos Santos LP, de Matos BM, de Maman Ribeiro BC, Zanchin NIT, Guimarães BG. Crystal structure of the MIF4G domain of the Trypanosoma cruzi translation initiation factor EIF4G5. Acta Crystallogr F Struct Biol Commun 2019; 75:738-743. [PMID: 31797815 PMCID: PMC6891579 DOI: 10.1107/s2053230x19015061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 11/07/2019] [Indexed: 11/10/2022] Open
Abstract
Kinetoplastida, a class of early-diverging eukaryotes that includes pathogenic Trypanosoma and Leishmania species, display key differences in their translation machinery compared with multicellular eukaryotes. One of these differences involves a larger number of genes encoding eIF4E and eIF4G homologs and the interaction pattern between the translation initiation factors. eIF4G is a scaffold protein which interacts with the mRNA cap-binding factor eIF4E, the poly(A)-binding protein, the RNA helicase eIF4A and the eIF3 complex. It contains the so-called middle domain of eIF4G (MIF4G), a multipurpose adaptor involved in different protein-protein and protein-RNA complexes. Here, the crystal structure of the MIF4G domain of T. cruzi EIF4G5 is described at 2.4 Å resolution, which is the first three-dimensional structure of a trypanosomatid MIF4G domain to be reported. Structural comparison with IF4G homologs from other eukaryotes and other MIF4G-containing proteins reveals differences that may account for the specific interaction mechanisms of MIF4G despite its highly conserved overall fold.
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Affiliation(s)
- Lucca Pietro Camillo dos Santos
- Carlos Chagas Institute, Oswaldo Cruz Foundation, Curitiba, Paraná, Brazil
- Biosciences and Biotechnology Postgraduate Program, Carlos Chagas Institute, Curitiba, Paraná, Brazil
| | - Bruno Moisés de Matos
- Carlos Chagas Institute, Oswaldo Cruz Foundation, Curitiba, Paraná, Brazil
- Biochemistry Postgraduate Program, Federal University of Paraná, Curitiba, Paraná, Brazil
| | | | | | - Beatriz Gomes Guimarães
- Carlos Chagas Institute, Oswaldo Cruz Foundation, Curitiba, Paraná, Brazil
- Biosciences and Biotechnology Postgraduate Program, Carlos Chagas Institute, Curitiba, Paraná, Brazil
- Biochemistry Postgraduate Program, Federal University of Paraná, Curitiba, Paraná, Brazil
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24
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Mishra RK, Datey A, Hussain T. mRNA Recruiting eIF4 Factors Involved in Protein Synthesis and Its Regulation. Biochemistry 2019; 59:34-46. [DOI: 10.1021/acs.biochem.9b00788] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Rishi Kumar Mishra
- Department of Molecular Reproduction, Development and Genetics, Division of Biological Sciences, Indian Institute of Science, Bangalore 560012, India
| | - Ayushi Datey
- Department of Molecular Reproduction, Development and Genetics, Division of Biological Sciences, Indian Institute of Science, Bangalore 560012, India
| | - Tanweer Hussain
- Department of Molecular Reproduction, Development and Genetics, Division of Biological Sciences, Indian Institute of Science, Bangalore 560012, India
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25
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Meijer HA, Schmidt T, Gillen SL, Langlais C, Jukes-Jones R, de Moor CH, Cain K, Wilczynska A, Bushell M. DEAD-box helicase eIF4A2 inhibits CNOT7 deadenylation activity. Nucleic Acids Res 2019; 47:8224-8238. [PMID: 31180491 PMCID: PMC6736043 DOI: 10.1093/nar/gkz509] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 05/26/2019] [Accepted: 06/05/2019] [Indexed: 01/16/2023] Open
Abstract
The CCR4-NOT complex plays an important role in the translational repression and deadenylation of mRNAs. However, little is known about the specific roles of interacting factors. We demonstrate that the DEAD-box helicases eIF4A2 and DDX6 interact directly with the MA3 and MIF domains of CNOT1 and compete for binding. Furthermore, we now show that incorporation of eIF4A2 into the CCR4-NOT complex inhibits CNOT7 deadenylation activity in contrast to DDX6 which enhances CNOT7 activity. Polyadenylation tests (PAT) on endogenous mRNAs determined that eIF4A2 bound mRNAs have longer poly(A) tails than DDX6 bound mRNAs. Immunoprecipitation experiments show that eIF4A2 does not inhibit CNOT7 association with the CCR4-NOT complex but instead inhibits CNOT7 activity. We identified a CCR4-NOT interacting factor, TAB182, that modulates helicase recruitment into the CCR4-NOT complex, potentially affecting the outcome for the targeted mRNA. Together, these data show that the fate of an mRNA is dependent on the specific recruitment of either eIF4A2 or DDX6 to the CCR4-NOT complex which results in different pathways for translational repression and mRNA deadenylation.
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Affiliation(s)
- Hedda A Meijer
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
| | - Tobias Schmidt
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
| | - Sarah L Gillen
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
| | - Claudia Langlais
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
| | - Rebekah Jukes-Jones
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
| | - Cornelia H de Moor
- School of Pharmacy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Kelvin Cain
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
| | - Ania Wilczynska
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
| | - Martin Bushell
- Medical Research Council (MRC), Toxicology Unit, University of Cambridge, Hodgkin Building, Leicester LE1 9HN, UK
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26
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Kats IR, Klann E. Translating from cancer to the brain: regulation of protein synthesis by eIF4F. ACTA ACUST UNITED AC 2019; 26:332-342. [PMID: 31416906 PMCID: PMC6699409 DOI: 10.1101/lm.050047.119] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 07/03/2019] [Indexed: 12/27/2022]
Abstract
Formation of eukaryotic initiation factor 4F (eIF4F) is widely considered to be the rate-limiting step in cap-dependent translation initiation. Components of eIF4F are often up-regulated in various cancers, and much work has been done to elucidate the role of each of the translation initiation factors in cancer cell growth and survival. In fact, many of the basic mechanisms describing how eIF4F is assembled and how it functions to regulate translation initiation were first investigated in cancer cell lines. These same eIF4F translational control pathways also are relevant for neuronal signaling that underlies long-lasting synaptic plasticity and memory, and in neurological diseases where eIF4F and its upstream regulators are dysregulated. Although eIF4F is important in cancer and for brain function, there is not always a clear path to use the results of studies performed in cancer models to inform one of the roles that the same translation factors have in neuronal signaling. Issues arise when extrapolating from cell lines to tissue, and differences are likely to exist in how eIF4F and its upstream regulatory pathways are expressed in the diverse neuronal subtypes found in the brain. This review focuses on summarizing the role of eIF4F and its accessory proteins in cancer, and how this information has been utilized to investigate neuronal signaling, synaptic function, and animal behavior. Certain aspects of eIF4F regulation are consistent across cancer and neuroscience, whereas some results are more complicated to interpret, likely due to differences in the complexity of the brain, its billions of neurons and synapses, and its diverse cell types.
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Affiliation(s)
- Ilona R Kats
- Sackler Graduate Program, New York University School of Medicine, New York, New York 10016, USA.,Center for Neural Science, New York University, New York, New York 10003, USA
| | - Eric Klann
- Center for Neural Science, New York University, New York, New York 10003, USA.,NYU Neuroscience Institute, New York University School of Medicine, New York, New York 10016, USA
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27
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Sha Y, Liu W, Huang X, Li Y, Ji Z, Mei L, Lin S, Kong S, Lu J, Kong L, Zhu X, Lu Z, Ding L. EIF4G1 is a novel candidate gene associated with severe asthenozoospermia. Mol Genet Genomic Med 2019; 7:e807. [PMID: 31268247 PMCID: PMC6687618 DOI: 10.1002/mgg3.807] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 05/22/2019] [Accepted: 05/29/2019] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Asthenozoospermia (AZS), also known as asthenospermia, is characterized by reduced motility of ejaculated spermatozoa and is detected in more than 40% of infertile patients. Because the proportion of progressive spermatozoa in severe AZS is <1%, severe AZS is an urgent challenge in reproductive medicine. Several genes have been reported to be relevant to severe asthenospermia. However, these gene mutations are found only in sporadic cases and can explain only a small fraction of severe AZS, so additional genetic pathogenies need to be explored. METHODS AND RESULTS By screening the variant genes in a patient with severe AZS using whole exome sequencing, we identified biallelic mutations c.2521C>T: p.(Pro841Ser) (NC_000003.11: g.184043412C>T) in exon13 and c.2957C>G: p.(Ala986Gly) (NC_000003.11: g.184045117C>G) in exon17 in the eukaryotic translation initiation factor 4 gamma 1 gene (EIF4G1, RefSeq: NM_004953.4, OMIM: 600495) of the patient. Both of the mutation sites are rare and potentially deleterious. Transmission electron microscopy analysis showed a disrupted axonemal structure with mitochondrial sheath defects. The EIF4G1 protein level was extremely low, and the mitochondrial marker cytochrome c oxidase subunit 4I1 (COXIV, OMIM: 123864) and mitochondrially encoded ATP synthase 6 (ATP6, OMIM: 516060) protein levels were also decreased in the patient's spermatozoa as revealed by WB and IF analysis. This infertility associated with this condition was overcome by intracytoplasmic sperm injections, as his wife became pregnant successfully. CONCLUSION Our experimental findings indicate that the EIF4G1 gene is a novel candidate gene that may be relevant to severe AZS.
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Affiliation(s)
- Yanwei Sha
- Department of Andrology, United Diagnostic and Research Center for Clinical Genetics, School of Public Health & Women and Children's Hospital, Xiamen University, Xiamen, China
| | - Wensheng Liu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China
| | - Xianjing Huang
- Department of Andrology, United Diagnostic and Research Center for Clinical Genetics, School of Public Health & Women and Children's Hospital, Xiamen University, Xiamen, China
| | - Yang Li
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China
| | - Zhiyong Ji
- Department of Andrology, United Diagnostic and Research Center for Clinical Genetics, School of Public Health & Women and Children's Hospital, Xiamen University, Xiamen, China
| | - Libin Mei
- Department of Andrology, United Diagnostic and Research Center for Clinical Genetics, School of Public Health & Women and Children's Hospital, Xiamen University, Xiamen, China
| | - Shaobin Lin
- Department of Andrology, United Diagnostic and Research Center for Clinical Genetics, School of Public Health & Women and Children's Hospital, Xiamen University, Xiamen, China
| | - Shuangbo Kong
- Fujian Provincial Key Laboratory of Reproductive Health Research, Medical College of Xiamen University, Xiamen, China
| | - Jinhua Lu
- Fujian Provincial Key Laboratory of Reproductive Health Research, Medical College of Xiamen University, Xiamen, China
| | - Lingyuan Kong
- Department of Andrology, United Diagnostic and Research Center for Clinical Genetics, School of Public Health & Women and Children's Hospital, Xiamen University, Xiamen, China
| | - Xingshen Zhu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China
| | - Zhongxian Lu
- School of Pharmaceutical Sciences, State Key Laboratory of Cellular Stress Biology, Xiamen University, Xiamen, China.,Fujian Provincial Key Laboratory of Reproductive Health Research, Medical College of Xiamen University, Xiamen, China
| | - Lu Ding
- Department of Andrology, United Diagnostic and Research Center for Clinical Genetics, School of Public Health & Women and Children's Hospital, Xiamen University, Xiamen, China
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28
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Yun SJ, Kim H, Jung SH, Kim JH, Ryu JE, Singh NJ, Jeon J, Han JK, Kim CH, Kim S, Jang SK, Kim WJ. The mechanistic insight of a specific interaction between 15d-Prostaglandin-J2 and eIF4A suggests an evolutionary conserved role across species. Biol Open 2018; 7:bio035402. [PMID: 30257829 PMCID: PMC6262856 DOI: 10.1242/bio.035402] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 09/03/2018] [Indexed: 12/24/2022] Open
Abstract
15-deoxy-delta 12,14-prostaglandin J2 (15d-PGJ2) is an anti-inflammatory/anti-neoplastic prostaglandin that functions through covalent binding to cysteine residues of various target proteins. We previously showed that 15d-PGJ2 mediated anti-inflammatory responses are dependent on the translational inhibition through its interaction with eIF4A (Kim et al., 2007). Binding of 15d-PGJ2 to eIF4A specifically blocks the interaction between eIF4G and eIF4A, which leads to the formation of stress granules (SGs), which then cluster mRNAs with inhibited translation. Here, we show that the binding between 15d-PGJ2 and eIF4A specifically blocks the interaction between the MIF4G domain of eIF4G and eIF4A. To reveal the mechanism of this interaction, we used computational simulation-based docking studies and identified that the carboxyl tail of 15d-PGJ2 could stabilize the binding of 15d-PGJ2 to eIF4A through arginine 295 of eIF4A, which is the first suggestion that the 15d-PGJ2 tail plays a physiological role. Interestingly, the putative 15d-PGJ2 binding site on eiF4A is conserved across many species, suggesting a biological role. Our data propose that studying 15d-PGJ2 and its targets may uncover new therapeutic approaches in anti-inflammatory drug discovery.
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Affiliation(s)
- So Jeong Yun
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Hyunjoon Kim
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Seung-Hyun Jung
- Department of Biology, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Joon Hyun Kim
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Jeong Eun Ryu
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - N Jiten Singh
- Center for Superfunctional Materials, Department of Chemistry, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Jouhyun Jeon
- Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Jin-Kwan Han
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Cheol-Hee Kim
- Department of Biology, Chungnam National University, Daejeon 34134, Republic of Korea
| | - Sanguk Kim
- Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Sung Key Jang
- PBC, Department of Life Science, Pohang University of Science and Technology, Pohang 37673, Republic of Korea
| | - Woo Jae Kim
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, K1H 8M5, Canada
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29
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He Y, Lin Y, Zhu Y, Ping P, Wang G, Sun F. Murine PAIP1 stimulates translation of spermiogenic mRNAs stored by YBX2 via its interaction with YBX2†. Biol Reprod 2018; 100:561-572. [PMID: 30295753 DOI: 10.1093/biolre/ioy213] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 08/23/2018] [Accepted: 10/04/2018] [Indexed: 01/10/2023] Open
Affiliation(s)
- Yue He
- International Peace Maternity and Child Health Hospital, Shanghai Key Laboratory for Reproductive Medicine, School of Medicine, Shanghai Jiaotong University, 200030 Shanghai, China
| | - Yu Lin
- International Peace Maternity and Child Health Hospital, Shanghai Key Laboratory for Reproductive Medicine, School of Medicine, Shanghai Jiaotong University, 200030 Shanghai, China
| | - Yu Zhu
- International Peace Maternity and Child Health Hospital, Shanghai Key Laboratory for Reproductive Medicine, School of Medicine, Shanghai Jiaotong University, 200030 Shanghai, China
| | - Ping Ping
- International Peace Maternity and Child Health Hospital, Shanghai Key Laboratory for Reproductive Medicine, School of Medicine, Shanghai Jiaotong University, 200030 Shanghai, China
| | - Guishuan Wang
- Institute of Reproductive Medicine, School of Medicine, Nantong University, 226021 Nantong, Jiangsu, China
| | - Fei Sun
- International Peace Maternity and Child Health Hospital, Shanghai Key Laboratory for Reproductive Medicine, School of Medicine, Shanghai Jiaotong University, 200030 Shanghai, China
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30
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Ribosomal RACK1:Protein Kinase C βII Phosphorylates Eukaryotic Initiation Factor 4G1 at S1093 To Modulate Cap-Dependent and -Independent Translation Initiation. Mol Cell Biol 2018; 38:MCB.00304-18. [PMID: 30012863 DOI: 10.1128/mcb.00304-18] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 07/09/2018] [Indexed: 11/20/2022] Open
Abstract
Eukaryotic ribosomes contain the high-affinity protein kinase C βII (PKCβII) scaffold, receptor for activated C kinase (RACK1), but its role in protein synthesis control remains unclear. We found that RACK1:PKCβII phosphorylates eukaryotic initiation factor 4G1 (eIF4G1) at S1093 and eIF3a at S1364. We showed that reversible eIF4G(S1093) phosphorylation is involved in a global protein synthesis surge upon PKC-Raf-extracellular signal-regulated kinase 1/2 (ERK1/2) activation and in induction of phorbol ester-responsive transcripts, such as cyclooxygenase 2 (Cox-2) and cyclin-dependent kinase inhibitor (p21Cip1), or in 5' 7-methylguanosine (m7G) cap-independent enterovirus translation. Comparison of mRNA and protein levels revealed that eIF4G1 or RACK1 depletion blocked phorbol ester-induced Cox-2 or p21Cip1 expression mostly at the translational level, whereas PKCβ inhibition reduced them both at the translational and transcript levels. Our findings reveal a physiological role for ribosomal RACK1 in providing the molecular scaffold for PKCβII and its role in coordinating the translational response to PKC-Raf-ERK1/2 activation.
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31
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Fonseca BD, Lahr RM, Damgaard CK, Alain T, Berman AJ. LARP1 on TOP of ribosome production. WILEY INTERDISCIPLINARY REVIEWS. RNA 2018; 9:e1480. [PMID: 29722158 PMCID: PMC6214789 DOI: 10.1002/wrna.1480] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 03/06/2018] [Accepted: 03/07/2018] [Indexed: 12/27/2022]
Abstract
The ribosome is an essential unit of all living organisms that commands protein synthesis, ultimately fuelling cell growth (accumulation of cell mass) and cell proliferation (increase in cell number). The eukaryotic ribosome consists of 4 ribosomal RNAs (rRNAs) and 80 ribosomal proteins (RPs). Despite its fundamental role in every living organism, our present understanding of how higher eukaryotes produce the various ribosome components is incomplete. Uncovering the mechanisms utilized by human cells to generate functional ribosomes will likely have far-reaching implications in human disease. Recent biochemical and structural studies revealed La-related protein 1 (LARP1) as a key new player in RP production. LARP1 is an RNA-binding protein that belongs to the LARP superfamily; it controls the translation and stability of the mRNAs that encode RPs and translation factors, which are characterized by a 5' terminal oligopyrimidine (5'TOP) motif and are thus known as TOP mRNAs. The activity of LARP1 is regulated by the mammalian target of rapamycin complex 1 (mTORC1): a eukaryotic protein kinase complex that integrates nutrient sensing with mRNA translation, particularly that of TOP mRNAs. In this review, we provide an overview of the role of LARP1 in the control of ribosome production in multicellular eukaryotes. This article is categorized under: Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA Processing > Capping and 5' End Modifications.
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Affiliation(s)
| | | | | | - Tommy Alain
- Children’s Hospital of Eastern Ontario, Ottawa, ON, Canada
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32
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Shatsky IN, Terenin IM, Smirnova VV, Andreev DE. Cap-Independent Translation: What's in a Name? Trends Biochem Sci 2018; 43:882-895. [PMID: 29789219 DOI: 10.1016/j.tibs.2018.04.011] [Citation(s) in RCA: 68] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 04/15/2018] [Accepted: 04/22/2018] [Indexed: 02/05/2023]
Abstract
Eukaryotic translation initiation relies on the m7G cap present at the 5' end of all mRNAs. Some viral mRNAs employ alternative mechanisms of initiation based on internal ribosome entry. The 'IRES ideology' was adopted by researchers to explain the differential translation of cellular mRNAs when the cap recognition is suppressed. However, some cellular IRESs have already been challenged and others are awaiting their validation. As an alternative cap-independent mechanism, we propose adopting the concept of cap-independent translation enhancers (CITEs) for mammalian mRNAs. Unlike IRESs, CITEs can be located both within 5' and 3' UTRs and bind mRNA-recruiting translational components. The respective 5' UTRs are then inspected by the scanning machinery essentially in the same way as under cap-dependent translation.
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Affiliation(s)
- Ivan N Shatsky
- Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, Leninskie Gory 1, Bldg. 40, Moscow 119992, Russia.
| | - Ilya M Terenin
- Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, Leninskie Gory 1, Bldg. 40, Moscow 119992, Russia; Sechenov First Moscow State Medical University, Institute of Molecular Medicine, Trubetskaya Str. 8-2, 119991, Moscow, Russia
| | - Victoria V Smirnova
- Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, Leninskie Gory 1, Bldg. 40, Moscow 119992, Russia
| | - Dmitri E Andreev
- Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, Leninskie Gory 1, Bldg. 40, Moscow 119992, Russia
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33
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Kumar P, Hellen CUT, Pestova TV. Toward the mechanism of eIF4F-mediated ribosomal attachment to mammalian capped mRNAs. Genes Dev 2017; 30:1573-88. [PMID: 27401559 PMCID: PMC4949329 DOI: 10.1101/gad.282418.116] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 06/01/2016] [Indexed: 11/24/2022]
Abstract
Ribosomal attachment to mammalian capped mRNAs is achieved through the cap-eukaryotic initiation factor 4E (eIF4E)-eIF4G-eIF3-40S chain of interactions, but the mechanism by which mRNA enters the mRNA-binding channel of the 40S subunit remains unknown. To investigate this process, we recapitulated initiation on capped mRNAs in vitro using a reconstituted translation system. Formation of initiation complexes at 5'-terminal AUGs was stimulated by the eIF4E-cap interaction and followed "the first AUG" rule, indicating that it did not occur by backward scanning. Initiation complexes formed even at the very 5' end of mRNA, implying that Met-tRNAi (Met) inspects mRNA from the first nucleotide and that initiation does not have a "blind spot." In assembled initiation complexes, the cap was no longer associated with eIF4E. Omission of eIF4A or disruption of eIF4E-eIF4G-eIF3 interactions converted eIF4E into a specific inhibitor of initiation on capped mRNAs. Taken together, these results are consistent with the model in which eIF4E-eIF4G-eIF3-40S interactions place eIF4E at the leading edge of the 40S subunit, and mRNA is threaded into the mRNA-binding channel such that Met-tRNAi (Met) can inspect it from the first nucleotide. Before entering, eIF4E likely dissociates from the cap to overcome steric hindrance. We also found that the m(7)G cap specifically interacts with eIF3l.
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Affiliation(s)
- Parimal Kumar
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Christopher U T Hellen
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, USA
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Joyce CE, Yanez AG, Mori A, Yoda A, Carroll JS, Novina CD. Differential Regulation of the Melanoma Proteome by eIF4A1 and eIF4E. Cancer Res 2017; 77:613-622. [PMID: 27879264 PMCID: PMC5362820 DOI: 10.1158/0008-5472.can-16-1298] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 11/16/2016] [Accepted: 11/16/2016] [Indexed: 11/16/2022]
Abstract
Small molecules and antisense oligonucleotides that inhibit the translation initiation factors eIF4A1 and eIF4E have been explored as broad-based therapeutic agents for cancer treatment, based on the frequent upregulation of these two subunits of the eIF4F cap-binding complex in many cancer cells. Here, we provide support for these therapeutic approaches with mechanistic studies of eIF4F-driven tumor progression in a preclinical model of melanoma. Silencing eIF4A1 or eIF4E decreases melanoma proliferation and invasion. There were common effects on the level of cell-cycle proteins that could explain the antiproliferative effects in vitro Using clinical specimens, we correlate the common cell-cycle targets of eIF4A1 and eIF4E with patient survival. Finally, comparative proteomic and transcriptomic analyses reveal extensive mechanistic divergence in response to eIF4A1 or eIF4E silencing. Current models indicate that eIF4A1 and eIF4E function together through the 5'UTR to increase translation of oncogenes. In contrast, our data demonstrate that the common effects of eIF4A1 and eIF4E on translation are mediated by the coding region and 3'UTR. Moreover, their divergent effects occur through the 5'UTR. Overall, our work shows that it will be important to evaluate subunit-specific inhibitors of eIF4F in different disease contexts to fully understand their anticancer actions. Cancer Res; 77(3); 613-22. ©2016 AACR.
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Affiliation(s)
- Cailin E Joyce
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts
| | - Adrienne G Yanez
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts
| | - Akihiro Mori
- Program in Systems Biology and Program in Molecular Medicine, University of Massachusetts, Worcester, Massachusetts
- Onami team, The Systems Biology Institute, Tokyo, Japan
- Laboratory for Developmental Dynamics, RIKEN Quantitative Biology Center, Hyogo, Japan
| | - Akinori Yoda
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts
| | - Johanna S Carroll
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts
| | - Carl D Novina
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Boston, Massachusetts.
- Department of Medicine, Harvard Medical School, Boston, Massachusetts
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts
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Toribio R, Díaz-López I, Ventoso I. New insights into the topology of the scanning ribosome during translation initiation: Lessons from viruses. RNA Biol 2016; 13:1223-1227. [PMID: 27824302 DOI: 10.1080/15476286.2016.1247146] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
Location of the translation initiation codon generally requires scanning of the 43S ribosomal preinitiation complex (43S PIC) from the 5' of the mRNA. Associated RNA helicases can facilitate movement of the 43S PIC by removing secondary structure present in the 5' UTR of mRNA, which is required for codon inspection. The canonical RNA-dependent helicase eIF4A is directly involved in this process, as part of the eIF4F complex (eIF4G + eIF4A + eIF4E) that associates first with mRNA and then recruits the 43S PIC to initiate scanning. The topology and operational mechanism of the scanning PIC are probably the least understood aspects of the initiation step. Recent findings from translation of alphavirus mRNA, together with new biochemical and structural data of the 43S PIC, suggest a role for the ES6S region of 40S as the gateway for mRNA entry during scanning. The presence of eIF4G-eIF4A complex in this region, interacting with the incoming mRNA, supports a model where eIF4A could work ahead of the scanning complex during translation initiation. Here we present additional data supporting this model.
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Affiliation(s)
- René Toribio
- a Centro de Biología Molecular Severo Ochoa (CSIC-UAM) and Departamento de Biología Molecular , Universidad Autónoma de Madrid (UAM) , Madrid , Spain
| | - Irene Díaz-López
- a Centro de Biología Molecular Severo Ochoa (CSIC-UAM) and Departamento de Biología Molecular , Universidad Autónoma de Madrid (UAM) , Madrid , Spain
| | - Iván Ventoso
- a Centro de Biología Molecular Severo Ochoa (CSIC-UAM) and Departamento de Biología Molecular , Universidad Autónoma de Madrid (UAM) , Madrid , Spain
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36
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Das S, Das B. eIF4G—an integrator of mRNA metabolism? FEMS Yeast Res 2016; 16:fow087. [DOI: 10.1093/femsyr/fow087] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2016] [Indexed: 11/14/2022] Open
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Coordinated Regulation of Cap-Dependent Translation and MicroRNA Function by Convergent Signaling Pathways. Mol Cell Biol 2016; 36:2360-73. [PMID: 27354062 DOI: 10.1128/mcb.01011-15] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 06/14/2016] [Indexed: 01/08/2023] Open
Abstract
Cell growth and proliferation require the coordinated activation of many cellular processes, including cap-dependent mRNA translation. MicroRNAs oppose cap-dependent translation and set thresholds for expression of target proteins. Emerging data suggest that microRNA function is enhanced by cellular activation due in part to induction of the RNA-induced silencing complex (RISC) scaffold protein GW182. In the current study, we demonstrate that increased expression of GW182 in activated or transformed immune cells results from effects of phosphoinositol 3-kinase-Akt-mechanistic target of rapamycin (PI3K-Akt-mTOR) and Jak-Stat-Pim signaling on the translation of GW182 mRNA. Both signaling pathways enhanced polysome occupancy and eukaryotic initiation factor 4E (eIF4E) binding to the 5' 7mG cap of GW182 mRNA. The effect of Jak-Stat-Pim signaling on polysome occupancy and expression of GW182 protein was greater than that of PI3K-Akt-mTOR signaling, likely resulting from enhanced eIF4A-dependent unwinding of G-quadruplexes in the 5' untranslated region of GW182 mRNA. Consistent with this, GW182 expression and microRNA function were reduced by inhibition of mTOR or Pim kinases, translation initiation complex assembly, or eIF4A function. Taken together, these data provide a mechanistic link between microRNA function and cap-dependent translation that allows activated immune cells to maintain microRNA-mediated repression of targets despite enhanced rates of protein synthesis.
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The molecular choreography of protein synthesis: translational control, regulation, and pathways. Q Rev Biophys 2016; 49:e11. [PMID: 27658712 DOI: 10.1017/s0033583516000056] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Translation of proteins by the ribosome regulates gene expression, with recent results underscoring the importance of translational control. Misregulation of translation underlies many diseases, including cancer and many genetic diseases. Decades of biochemical and structural studies have delineated many of the mechanistic details in prokaryotic translation, and sketched the outlines of eukaryotic translation. However, translation may not proceed linearly through a single mechanistic pathway, but likely involves multiple pathways and branchpoints. The stochastic nature of biological processes would allow different pathways to occur during translation that are biased by the interaction of the ribosome with other translation factors, with many of the steps kinetically controlled. These multiple pathways and branchpoints are potential regulatory nexus, allowing gene expression to be tuned at the translational level. As research focus shifts toward eukaryotic translation, certain themes will be echoed from studies on prokaryotic translation. This review provides a general overview of the dynamic data related to prokaryotic and eukaryotic translation, in particular recent findings with single-molecule methods, complemented by biochemical, kinetic, and structural findings. We will underscore the importance of viewing the process through the viewpoints of regulation, translational control, and heterogeneous pathways.
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Vincent HA, Ziehr B, Moorman NJ. Human Cytomegalovirus Strategies to Maintain and Promote mRNA Translation. Viruses 2016; 8:97. [PMID: 27089357 PMCID: PMC4848592 DOI: 10.3390/v8040097] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 03/25/2016] [Accepted: 03/31/2016] [Indexed: 02/02/2023] Open
Abstract
mRNA translation requires the ordered assembly of translation initiation factors and ribosomal subunits on a transcript. Host signaling pathways regulate each step in this process to match levels of protein synthesis to environmental cues. In response to infection, cells activate multiple defenses that limit viral protein synthesis, which viruses must counteract to successfully replicate. Human cytomegalovirus (HCMV) inhibits host defenses that limit viral protein expression and manipulates host signaling pathways to promote the expression of both host and viral proteins necessary for virus replication. Here we review key regulatory steps in mRNA translation, and the strategies used by HCMV to maintain protein synthesis in infected cells.
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Affiliation(s)
- Heather A Vincent
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Benjamin Ziehr
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Nathaniel J Moorman
- Department of Microbiology & Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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Korneeva NL, Song A, Gram H, Edens MA, Rhoads RE. Inhibition of Mitogen-activated Protein Kinase (MAPK)-interacting Kinase (MNK) Preferentially Affects Translation of mRNAs Containing Both a 5'-Terminal Cap and Hairpin. J Biol Chem 2015; 291:3455-67. [PMID: 26668315 DOI: 10.1074/jbc.m115.694190] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Indexed: 12/22/2022] Open
Abstract
The MAPK-interacting kinases 1 and 2 (MNK1 and MNK2) are activated by extracellular signal-regulated kinases 1 and 2 (ERK1/2) or p38 in response to cellular stress and extracellular stimuli that include growth factors, cytokines, and hormones. Modulation of MNK activity affects translation of mRNAs involved in the cell cycle, cancer progression, and cell survival. However, the mechanism by which MNK selectively affects translation of these mRNAs is not understood. MNK binds eukaryotic translation initiation factor 4G (eIF4G) and phosphorylates the cap-binding protein eIF4E. Using a cell-free translation system from rabbit reticulocytes programmed with mRNAs containing different 5'-ends, we show that an MNK inhibitor, CGP57380, affects translation of only those mRNAs that contain both a cap and a hairpin in the 5'-UTR. Similarly, a C-terminal fragment of human eIF4G-1, eIF4G(1357-1600), which prevents binding of MNK to intact eIF4G, reduces eIF4E phosphorylation and inhibits translation of only capped and hairpin-containing mRNAs. Analysis of proteins bound to m(7)GTP-Sepharose reveals that both CGP and eIF4G(1357-1600) decrease binding of eIF4E to eIF4G. These data suggest that MNK stimulates translation only of mRNAs containing both a cap and 5'-terminal RNA duplex via eIF4E phosphorylation, thereby enhancing the coupled cap-binding and RNA-unwinding activities of eIF4F.
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Affiliation(s)
- Nadejda L Korneeva
- From the Departments of Emergency Medicine and Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932, and
| | - Anren Song
- Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932, and
| | - Hermann Gram
- the Novartis Institute for Biomedical Research, Forum 1, CH-4002 Basel, Switzerland
| | | | - Robert E Rhoads
- Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana 71130-3932, and
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Cleavage of DAP5 by coxsackievirus B3 2A protease facilitates viral replication and enhances apoptosis by altering translation of IRES-containing genes. Cell Death Differ 2015; 23:828-40. [PMID: 26586572 DOI: 10.1038/cdd.2015.145] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 09/17/2015] [Accepted: 09/25/2015] [Indexed: 12/22/2022] Open
Abstract
Cleavage of eukaryotic translation initiation factor 4G (eIF4G) by enterovirus proteases during infection leads to the shutoff of cellular cap-dependent translation, but does not affect the initiation of cap-independent translation of mRNAs containing an internal ribosome entry site (IRES). Death-associated protein 5 (DAP5), a structural homolog of eIF4G, is a translation initiation factor specific for IRES-containing mRNAs. Coxsackievirus B3 (CVB3) is a positive single-stranded RNA virus and a primary causal agent of human myocarditis. Its RNA genome harbors an IRES within the 5'-untranslated region and is translated by a cap-independent, IRES-driven mechanism. Previously, we have shown that DAP5 is cleaved during CVB3 infection. However, the protease responsible for cleavage, cleavage site and effects on the translation of target genes during CVB3 infection have not been investigated. In the present study, we demonstrated that viral protease 2A but not 3C is responsible for DAP5 cleavage, generating 45- and 52-kDa N- (DAP5-N) and C-terminal (DAP5-C) fragments, respectively. By site-directed mutagenesis, we found that DAP5 is cleaved at amino acid G434. Upon cleavage, DAP5-N largely translocated to the nucleus at the later time points of infection, whereas the DAP5-C largely remained in the cytoplasm. Overexpression of these DAP5 truncates demonstrated that DAP5-N retained the capability of initiating IRES-driven translation of apoptosis-associated p53, but not the prosurvival Bcl-2 (B-cell lymphoma 2) when compared with the full-length DAP5. Similarly, DAP5-N expression promoted CVB3 replication and progeny release; on the other hand, DAP5-C exerted a dominant-negative effect on cap-dependent translation. Taken together, viral protease 2A-mediated cleavage of DAP5 results in the production of two truncates that exert differential effects on protein translation of the IRES-containing genes, leading to enhanced host cell death.
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Rojas-Araya B, Ohlmann T, Soto-Rifo R. Translational Control of the HIV Unspliced Genomic RNA. Viruses 2015; 7:4326-51. [PMID: 26247956 PMCID: PMC4576183 DOI: 10.3390/v7082822] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 05/18/2015] [Accepted: 07/17/2015] [Indexed: 01/16/2023] Open
Abstract
Post-transcriptional control in both HIV-1 and HIV-2 is a highly regulated process that commences in the nucleus of the host infected cell and finishes by the expression of viral proteins in the cytoplasm. Expression of the unspliced genomic RNA is particularly controlled at the level of RNA splicing, export, and translation. It appears increasingly obvious that all these steps are interconnected and they result in the building of a viral ribonucleoprotein complex (RNP) that must be efficiently translated in the cytosolic compartment. This review summarizes our knowledge about the genesis, localization, and expression of this viral RNP.
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Affiliation(s)
- Bárbara Rojas-Araya
- Molecular and Cellular Virology Laboratory, Program of Virology, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Independencia 834100, Santiago, Chile.
| | - Théophile Ohlmann
- CIRI, International Center for Infectiology Research, Université de Lyon, Lyon 69007, France.
- Inserm, U1111, Lyon 69007, France.
- Ecole Normale Supérieure de Lyon, Lyon 69007, France.
- Université Lyon 1, Centre International de Recherche en Infectiologie, Lyon 69007, France.
- CNRS, UMR5308, Lyon 69007, France.
| | - Ricardo Soto-Rifo
- Molecular and Cellular Virology Laboratory, Program of Virology, Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Independencia 834100, Santiago, Chile.
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Pelletier J, Graff J, Ruggero D, Sonenberg N. Targeting the eIF4F translation initiation complex: a critical nexus for cancer development. Cancer Res 2015; 75:250-63. [PMID: 25593033 DOI: 10.1158/0008-5472.can-14-2789] [Citation(s) in RCA: 267] [Impact Index Per Article: 29.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Elevated protein synthesis is an important feature of many cancer cells and often arises as a consequence of increased signaling flux channeled to eukaryotic initiation factor 4F (eIF4F), the key regulator of the mRNA-ribosome recruitment phase of translation initiation. In many cellular and preclinical models of cancer, eIF4F deregulation results in changes in translational efficiency of specific mRNA classes. Importantly, many of these mRNAs code for proteins that potently regulate critical cellular processes, such as cell growth and proliferation, enhanced cell survival and cell migration that ultimately impinge on several hallmarks of cancer, including increased angiogenesis, deregulated growth control, enhanced cellular survival, epithelial-to-mesenchymal transition, invasion, and metastasis. By being positioned as the molecular nexus downstream of key oncogenic signaling pathways (e.g., Ras, PI3K/AKT/TOR, and MYC), eIF4F serves as a direct link between important steps in cancer development and translation initiation. Identification of mRNAs particularly responsive to elevated eIF4F activity that typifies tumorigenesis underscores the critical role of eIF4F in cancer and raises the exciting possibility of developing new-in-class small molecules targeting translation initiation as antineoplastic agents.
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Affiliation(s)
- Jerry Pelletier
- Department of Biochemistry, McGill University, Montreal, Québec, Canada. The Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Québec, Canada. Department of Oncology, McGill University, Montreal, Québec, Canada.
| | - Jeremy Graff
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana
| | - Davide Ruggero
- School of Medicine and Department of Urology, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Québec, Canada. The Rosalind and Morris Goodman Cancer Research Center, McGill University, Montreal, Québec, Canada
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Sinvani H, Haimov O, Svitkin Y, Sonenberg N, Tamarkin-Ben-Harush A, Viollet B, Dikstein R. Translational tolerance of mitochondrial genes to metabolic energy stress involves TISU and eIF1-eIF4GI cooperation in start codon selection. Cell Metab 2015; 21:479-92. [PMID: 25738462 DOI: 10.1016/j.cmet.2015.02.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/22/2014] [Accepted: 02/09/2015] [Indexed: 11/30/2022]
Abstract
Protein synthesis is a major energy-consuming process, which is rapidly repressed upon energy stress by AMPK. How energy deficiency affects translation of mRNAs that cope with the stress response is poorly understood. We found that mitochondrial genes remain translationally active upon energy deprivation. Surprisingly, inhibition of translation is partially retained in AMPKα1/AMPKα2 knockout cells. Mitochondrial mRNAs are enriched with TISU, a translation initiator of short 5' UTR, which confers resistance specifically to energy stress. Purified 48S preinitiation complex is sufficient for initiation via TISU AUG, when preceded by a short 5' UTR. eIF1 stimulates TISU but inhibits non-TISU-directed initiation. Remarkably, eIF4GI shares this activity and also interacts with eIF1. Furthermore, eIF4F is released upon 48S formation on TISU. These findings describe a specialized translation tolerance mechanism enabling continuous translation of TISU genes under energy stress and reveal that a key step in start codon selection of short 5' UTR is eIF4F release.
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Affiliation(s)
- Hadar Sinvani
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ora Haimov
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yuri Svitkin
- Department of Biochemistry and Goodman Cancer Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - Ana Tamarkin-Ben-Harush
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Benoit Viollet
- University Paris Descartes, Institut Cochin, 75014 Paris, France
| | - Rivka Dikstein
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel.
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Gallie DR. The role of the poly(A) binding protein in the assembly of the Cap-binding complex during translation initiation in plants. ACTA ACUST UNITED AC 2014; 2:e959378. [PMID: 26779409 DOI: 10.4161/2169074x.2014.959378] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/19/2014] [Accepted: 06/17/2014] [Indexed: 12/30/2022]
Abstract
Translation initiation in eukaryotes requires the involvement of multiple initiation factors (eIFs) that facilitate the binding of the 40 S ribosomal subunit to an mRNA and assemble the 80 S ribosome at the correct initiation codon. eIF4F, composed of eIF4E, eIF4A, and eIF4G, binds to the 5'-cap structure of an mRNA and prepares an mRNA for recruitment of a 40 S subunit. eIF4B promotes the ATP-dependent RNA helicase activity of eIF4A and eIF4F needed to unwind secondary structure present in a 5'-leader that would otherwise impede scanning of the 40 S subunit during initiation. The poly(A) binding protein (PABP), which binds the poly(A) tail, interacts with eIF4G and eIF4B to promote circularization of an mRNA and stimulates translation by promoting 40 S subunit recruitment. Thus, these factors serve essential functions in the early steps of protein synthesis. Their assembly and function requires multiple interactions that are competitive in nature and determine the nature of interactions between the termini of an mRNA. In this review, the domain organization and partner protein interactions are presented for the factors in plants which share similarities with those in animals and yeast but differ in several important respects. The functional consequences of their interactions on factor activity are also discussed.
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Affiliation(s)
- Daniel R Gallie
- Department of Biochemistry; University of California ; Riverside, CA USA
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Paulo JA, McAllister FE, Everley RA, Beausoleil SA, Banks AS, Gygi SP. Effects of MEK inhibitors GSK1120212 and PD0325901 in vivo using 10-plex quantitative proteomics and phosphoproteomics. Proteomics 2014; 15:462-73. [PMID: 25195567 DOI: 10.1002/pmic.201400154] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 08/05/2014] [Accepted: 09/01/2014] [Indexed: 12/11/2022]
Abstract
Multiplexed isobaric tag based quantitative proteomics and phosphoproteomics strategies can comprehensively analyze drug treatments effects on biological systems. Given the role of mitogen-activated protein/extracellular signal-regulated kinase (MEK) signaling in cancer and mitogen-activated protein kinase (MAPK)-dependent diseases, we sought to determine if this pathway could be inhibited safely by examining the downstream molecular consequences. We used a series of tandem mass tag 10-plex experiments to analyze the effect of two MEK inhibitors (GSK1120212 and PD0325901) on three tissues (kidney, liver, and pancreas) from nine mice. We quantified ∼ 6000 proteins in each tissue, but significant protein-level alterations were minimal with inhibitor treatment. Of particular interest was kidney tissue, as edema is an adverse effect of these inhibitors. From kidney tissue, we enriched phosphopeptides using titanium dioxide (TiO2 ) and quantified 10 562 phosphorylation events. Further analysis by phosphotyrosine peptide immunoprecipitation quantified an additional 592 phosphorylation events. Phosphorylation motif analysis revealed that the inhibitors decreased phosphorylation levels of proline-x-serine-proline (PxSP) and serine-proline (SP) sites, consistent with extracellular-signal-regulated kinase (ERK) inhibition. The MEK inhibitors had the greatest decrease on the phosphorylation of two proteins, Barttin and Slc12a3, which have roles in ion transport and fluid balance. Further studies will provide insight into the effect of these MEK inhibitors with respect to edema and other adverse events in mouse models and human patients.
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Affiliation(s)
- Joao A Paulo
- Department of Cell Biology, Harvard Medical School, Boston, MA, USA
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47
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Paip1, an effective stimulator of translation initiation, is targeted by WWP2 for ubiquitination and degradation. Mol Cell Biol 2014; 34:4513-22. [PMID: 25266661 DOI: 10.1128/mcb.00524-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Poly(A)-binding protein-interacting protein 1 (Paip1) stimulates translational initiation by inducing the circularization of mRNA. However, the mechanisms underlying Paip1 regulation, particularly its protein stability, are still unclear. Here, we show that the E6AP carboxyl terminus (HECT)-type ubiquitin ligase WW domain-containing protein 2 (WWP2), a homolog of the HECT-type ubiquitin ligase WWP1, interacts with and targets Paip1 for ubiquitination and proteasomal degradation. Mapping of the region including the WW domain of WWP2 revealed the interaction between WWP2 and the PABP-binding motif 2 (PAM2) of Paip1. The two consecutive PXXY motifs in PAM2 are required for WWP2-mediated ubiquitination and degradation. Furthermore, ectopic expression of WWP2 decreases translational stimulatory activity with the degradation of Paip1. We therefore provide evidence that the stability of Paip1 can be regulated by ubiquitin-mediated degradation, thus highlighting the importance of WWP2 as a suppressor of translation.
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48
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Pisareva VP, Pisarev AV. eIF5 and eIF5B together stimulate 48S initiation complex formation during ribosomal scanning. Nucleic Acids Res 2014; 42:12052-69. [PMID: 25260592 PMCID: PMC4231746 DOI: 10.1093/nar/gku877] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
48S initiation complex (48S IC) formation is the first stage in the eukaryotic translation process. According to the canonical mechanism, 40S ribosomal subunit binds to the 5′-end of messenger RNA (mRNA) and scans its 5′-untranslated region (5′-UTR) to the initiation codon where it forms the 48S IC. Entire process is mediated by initiation factors. Here we show that eIF5 and eIF5B together stimulate 48S IC formation influencing initiation codon selection during ribosomal scanning. Initiation on non-optimal start codons—following structured 5′-UTRs, in bad AUG context, within few nucleotides from 5′-end of mRNA and CUG start codon—is the most affected. eIF5-induced hydrolysis of eIF2-bound GTP is essential for stimulation. GTP hydrolysis increases the probability that scanning ribosomal complexes will recognize and arrest scanning at a non-optimal initiation codon. Such 48S ICs are less stable owing to dissociation of eIF2*GDP from initiator tRNA, and eIF5B is then required to stabilize the initiator tRNA in the P site of 40S subunit. Alternative model that eIF5 and eIF5B cause 43S pre-initiation complex rearrangement favoring more efficient initiation codon recognition during ribosomal scanning is equally possible. Mutational analysis of eIF1A and eIF5B revealed distinct functions of eIF5B in 48S IC formation and subunit joining.
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Affiliation(s)
- Vera P Pisareva
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY 11203, USA
| | - Andrey V Pisarev
- Department of Cell Biology, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY 11203, USA
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Rouya C, Siddiqui N, Morita M, Duchaine TF, Fabian MR, Sonenberg N. Human DDX6 effects miRNA-mediated gene silencing via direct binding to CNOT1. RNA (NEW YORK, N.Y.) 2014; 20:1398-409. [PMID: 25035296 PMCID: PMC4138323 DOI: 10.1261/rna.045302.114] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 05/20/2014] [Indexed: 05/25/2023]
Abstract
MicroRNAs (miRNAs) play critical roles in a variety of biological processes through widespread effects on protein synthesis. Upon association with the miRNA-induced silencing complex (miRISC), miRNAs repress target mRNA translation and accelerate mRNA decay. Degradation of the mRNA is initiated by shortening of the poly(A) tail by the CCR4-NOT deadenylase complex followed by the removal of the 5' cap structure and exonucleolytic decay of the mRNA. Here, we report a direct interaction between the large scaffolding subunit of CCR4-NOT, CNOT1, with the translational repressor and decapping activator protein, DDX6. DDX6 binds to a conserved CNOT1 subdomain in a manner resembling the interaction of the translation initiation factor eIF4A with eIF4G. Importantly, mutations that disrupt the DDX6-CNOT1 interaction impair miRISC-mediated gene silencing in human cells. Thus, CNOT1 facilitates recruitment of DDX6 to miRNA-targeted mRNAs, placing DDX6 as a downstream effector in the miRNA silencing pathway.
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Affiliation(s)
- Christopher Rouya
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1Y6, Canada Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Nadeem Siddiqui
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1Y6, Canada Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Masahiro Morita
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1Y6, Canada Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Thomas F Duchaine
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1Y6, Canada Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada
| | - Marc R Fabian
- Lady Davis Institute for Medical Research, SMBD-Jewish General Hospital, McGill University, Montreal, Quebec H3T 1E2, Canada
| | - Nahum Sonenberg
- Department of Biochemistry, McGill University, Montreal, Quebec, H3G 1Y6, Canada Goodman Cancer Research Centre, McGill University, Montreal, Quebec, H3A 1A3, Canada
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Joncourt R, Eberle AB, Rufener SC, Mühlemann O. Eukaryotic initiation factor 4G suppresses nonsense-mediated mRNA decay by two genetically separable mechanisms. PLoS One 2014; 9:e104391. [PMID: 25148142 PMCID: PMC4141738 DOI: 10.1371/journal.pone.0104391] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Accepted: 07/08/2014] [Indexed: 11/19/2022] Open
Abstract
Nonsense-mediated mRNA decay (NMD), which is best known for degrading mRNAs with premature termination codons (PTCs), is thought to be triggered by aberrant translation termination at stop codons located in an environment of the mRNP that is devoid of signals necessary for proper termination. In mammals, the cytoplasmic poly(A)-binding protein 1 (PABPC1) has been reported to promote correct termination and therewith antagonize NMD by interacting with the eukaryotic release factors 1 (eRF1) and 3 (eRF3). Using tethering assays in which proteins of interest are recruited as MS2 fusions to a NMD reporter transcript, we show that the three N-terminal RNA recognition motifs (RRMs) of PABPC1 are sufficient to antagonize NMD, while the eRF3-interacting C-terminal domain is dispensable. The RRM1-3 portion of PABPC1 interacts with eukaryotic initiation factor 4G (eIF4G) and tethering of eIF4G to the NMD reporter also suppresses NMD. We identified the interactions of the eIF4G N-terminus with PABPC1 and the eIF4G core domain with eIF3 as two genetically separable features that independently enable tethered eIF4G to inhibit NMD. Collectively, our results reveal a function of PABPC1, eIF4G and eIF3 in translation termination and NMD suppression, and they provide additional evidence for a tight coupling between translation termination and initiation.
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Affiliation(s)
- Raphael Joncourt
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Andrea B. Eberle
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
| | - Simone C. Rufener
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Oliver Mühlemann
- University of Bern, Department of Chemistry and Biochemistry, Bern, Switzerland
- * E-mail:
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