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Cate JHD. Human eIF3: from 'blobology' to biological insight. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0176. [PMID: 28138064 PMCID: PMC5311922 DOI: 10.1098/rstb.2016.0176] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 02/06/2023] Open
Abstract
Translation in eukaryotes is highly regulated during initiation, a process impacted by numerous readouts of a cell's state. There are many cases in which cellular messenger RNAs likely do not follow the canonical ‘scanning’ mechanism of translation initiation, but the molecular mechanisms underlying these pathways are still being uncovered. Some RNA viruses such as the hepatitis C virus use highly structured RNA elements termed internal ribosome entry sites (IRESs) that commandeer eukaryotic translation initiation, by using specific interactions with the general eukaryotic translation initiation factor eIF3. Here, I present evidence that, in addition to its general role in translation, eIF3 in humans and likely in all multicellular eukaryotes also acts as a translational activator or repressor by binding RNA structures in the 5′-untranslated regions of specific mRNAs, analogous to the role of the mediator complex in transcription. Furthermore, eIF3 in multicellular eukaryotes also harbours a 5′ 7-methylguanosine cap-binding subunit—eIF3d—which replaces the general cap-binding initiation factor eIF4E in the translation of select mRNAs. Based on results from cell biological, biochemical and structural studies of eIF3, it is likely that human translation initiation proceeds through dozens of different molecular pathways, the vast majority of which remain to be explored. This article is part of the themed issue ‘Perspectives on the ribosome’.
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Affiliation(s)
- Jamie H D Cate
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, CA 94720-3220, USA .,Lawrence Berkeley National Laboratory, Division of Molecular Biophysics and Integrated Bioimaging, Berkeley, CA 94720, USA
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Abstract
The eukaryotic initiation factor 3 (eIF3) is one of the most complex translation initiation factors in mammalian cells, consisting of several subunits (eIF3a to eIF3m). It is crucial in translation initiation and termination, and in ribosomal recycling. Accordingly, deregulated eIF3 expression is associated with different pathological conditions, including cancer. In this manuscript, we discuss the interactome and function of each subunit of the human eIF3 complex. Furthermore, we review how altered levels of eIF3 subunits correlate with neurodegenerative disorders and cancer onset and development; in addition, we evaluate how such misregulation may also trigger infection cascades. A deep understanding of the molecular mechanisms underlying eIF3 role in human disease is essential to develop new eIF3-targeted therapeutic approaches and thus, overcome such conditions.
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Affiliation(s)
- Andreia Gomes-Duarte
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
| | - Rafaela Lacerda
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
| | - Juliane Menezes
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
| | - Luísa Romão
- a Department of Human Genetics , Instituto Nacional de Saúde Doutor Ricardo Jorge , Lisbon , Portugal.,b Gene Expression and Regulation Group, Biosystems & Integrative Sciences Institute (BioISI), Faculdade de Ciências , Universidade de Lisboa , Lisbon , Portugal
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Zhao W, Li X, Wang J, Wang C, Jia Y, Yuan S, Huang Y, Shi Y, Tong Z. Decreasing Eukaryotic Initiation Factor 3C (EIF3C) Suppresses Proliferation and Stimulates Apoptosis in Breast Cancer Cell Lines Through Mammalian Target of Rapamycin (mTOR) Pathway. Med Sci Monit 2017; 23:4182-4191. [PMID: 28854163 PMCID: PMC5590544 DOI: 10.12659/msm.906389] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Background Translation initiation is the rate limiting step of protein synthesis and is highly regulated. Eukaryotic initiation factor 3C (EIF3C), an oncogene overexpressed in several human cancers, plays an important role in tumorigenesis and cell proliferation. Material/Methods Immunohistochemistry was used to determine the expression of EIF3C in breast cancer tissues from 42 patients. We investigated whether EIF3C silencing decreases breast cancer cell proliferation as assessed by colony formation assay, and whether EIF3C gene knockdown induces apoptosis as assessed by flow cytometry analysis. We utilized the stress and apoptosis signaling antibody array kit, while p-ERK1/2, p-Akt, p-Smad2, p-p38 MAPK, cleaved caspase-3, and cleaved caspase-7 were explored between EIF3C-siRNA and controls. Furthermore, the effects of EIF3C gene knockdown in mTOR pathway were analyzed by western blotting for different cell lines. Results In EIF3C-positive tumors, 32 out of 42 showed significantly higher frequencies of high grade group by immunoreactivity (p=0.0016). BrdU incorporation after four days of cell plating was significantly suppressed in MDA-MB-231 cells by EIF3C knockdown compared with controls, with average changes of 7.8-fold (p<0.01). Clone number was significantly suppressed in MDA-MB-231 cells by EIF3C knockdown compared with controls (p<0.05). Cell apoptosis was significantly increased in the EIF3C-siRNA group when compared with the cells that were transfected with scrambled siRNA (3.51±0.0842 versus 13.24±0.2307, p<0.01). The mTOR signaling pathway was involved in decreasing EIF3C translational efficiency. Conclusions Unveiling the mechanisms of EIF3 action in tumorigenesis may help identify attractive targets for cancer therapy.
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Affiliation(s)
- Weipeng Zhao
- Department of Breast Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China (mainland)
| | - Xichuan Li
- Department of Immunology, Biochemistry and Molecular Biology, 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Tianjin Medical University, Tianjin, China (mainland)
| | - Jun Wang
- Department of Oncology, General Hospital, Jinan Command of the People's Liberation Army, Jinan, Shandong, China (mainland)
| | - Chen Wang
- Department of Breast Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China (mainland)
| | - Yongsheng Jia
- Department of Breast Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China (mainland)
| | - Shunzong Yuan
- Department of Lymphoma, Head and Neck Cancer, The Affiliated Hospital of Academy of Military Medical Sciences, Beijing, China (mainland)
| | - Yong Huang
- Department of Pathology, People's Liberation Army General Hospital, Beijing, China (mainland)
| | - Yehui Shi
- Department of Breast Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China (mainland)
| | - Zhongsheng Tong
- Department of Breast Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China (mainland)
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Xin X, Wang T, Liu X, Sui G, Jin C, Yue Y, Yang S, Guo H. A yeast two-hybrid assay reveals CMYA1 interacting proteins. C R Biol 2017; 340:314-323. [DOI: 10.1016/j.crvi.2017.06.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 05/19/2017] [Accepted: 06/13/2017] [Indexed: 10/19/2022]
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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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Guo R, Lv Y, Ouyang Y, Liu S, Li D. The Role of miR‐497/EIF3A Axis in TGFβ1‐Induced Epithelial–Mesenchymal Transition and Extracellular Matrix in Rat Alveolar Epithelial Cells and Pulmonary Fibroblasts. J Cell Biochem 2017; 118:3401-3408. [DOI: 10.1002/jcb.25997] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 03/17/2017] [Indexed: 11/07/2022]
Affiliation(s)
- Ren Guo
- National Institution of Drug Clinical TrialXiangya HospitalCentral South UniversityChangsha410008China
- Department of PharmacyThe Third Xiangya HospitalCentral South UniversityChangsha410006China
| | - Yu Lv
- Department of PharmacyThe Third Xiangya HospitalCentral South UniversityChangsha410006China
| | - Yang Ouyang
- National Institution of Drug Clinical TrialXiangya HospitalCentral South UniversityChangsha410008China
| | - Siyu Liu
- National Institution of Drug Clinical TrialXiangya HospitalCentral South UniversityChangsha410008China
| | - Dai Li
- National Institution of Drug Clinical TrialXiangya HospitalCentral South UniversityChangsha410008China
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Hinnebusch AG. Structural Insights into the Mechanism of Scanning and Start Codon Recognition in Eukaryotic Translation Initiation. Trends Biochem Sci 2017; 42:589-611. [PMID: 28442192 DOI: 10.1016/j.tibs.2017.03.004] [Citation(s) in RCA: 199] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 03/12/2017] [Accepted: 03/20/2017] [Indexed: 12/21/2022]
Abstract
Initiation of translation on eukaryotic mRNAs generally follows the scanning mechanism, wherein a preinitiation complex (PIC) assembled on the small (40S) ribosomal subunit and containing initiator methionyl tRNAi (Met-tRNAi) scans the mRNA leader for an AUG codon. In a current model, the scanning PIC adopts an open conformation and rearranges to a closed state, with fully accommodated Met-tRNAi, upon AUG recognition. Evidence from recent high-resolution structures of PICs assembled with different ligands supports this model and illuminates the molecular functions of eukaryotic initiation factors eIF1, eIF1A, and eIF2 in restricting to AUG codons the transition to the closed conformation. They also reveal that the eIF3 complex interacts with multiple functional sites in the PIC, rationalizing its participation in numerous steps of initiation.
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Affiliation(s)
- Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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58
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Li K, Zhou S, Guo Q, Chen X, Lai DH, Lun ZR, Guo X. The eIF3 complex of Trypanosoma brucei: composition conservation does not imply the conservation of structural assembly and subunits function. RNA (NEW YORK, N.Y.) 2017; 23:333-345. [PMID: 27932584 PMCID: PMC5311491 DOI: 10.1261/rna.058651.116] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 11/24/2016] [Indexed: 05/03/2023]
Abstract
The multisubunit eukaryotic initiation factor 3 (eIF3) plays multiple roles in translation but is poorly understood in trypanosomes. The putative subunits eIF3a and eIF3f of Trypanosoma brucei (TbIF3a and TbIF3f) were overexpressed and purified, and 11 subunits were identified, TbIF3a through l minus j, which form a tight complex. Both TbIF3a and TbIF3f are essential for the viability of T. brucei RNAi knockdown of either of them severely reduced total translation and the ratio of the polysome/80S peak area. TbIF3f and TbIF3a RNAi cell lines were modified to express tagged-TbIF3a and -TbIF3f, respectively. RNAi in combination with affinity purification assays indicated that both subunits are variably required for TbIF3 stability and integrity. The relative abundance of other subunits in the TbIF3f-tag complex changed little upon TbIF3a depletion; while only subunits TbIF3b, i, and e copurified comparably with TbIF3a-tag upon TbIF3f depletion. A genome-wide UV-crosslinking assay showed that several TbIF3 subunits have direct RNA-binding activity, with TbIF3c showing the strongest signal. In addition, CrPV IRES, but neither EMCV IRES nor HCV IRES, was found to mediate translation in T. brucei These results together imply that the structure of TbIF3 and the subunits function have trypanosome-specific features, although the composition is evolutionarily conserved.
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Affiliation(s)
- Kunrao Li
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
| | - Shuru Zhou
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
| | - Qixuan Guo
- Chengde Nursing Vocational College, Chengde 067000, China
| | - Xin Chen
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
| | - De-Hua Lai
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| | - Zhao-Rong Lun
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
- Center for Parasitic Organisms, State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xuemin Guo
- Institute of Human Virology, Zhongshan School of Medicine, Sun Yat-Sen University, Guangzhou 510080, China
- Key Laboratory of Tropical Disease Control (Sun Yat-Sen University), Ministry of Education, Guangzhou 510080, China
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TGF beta receptor II interacting protein-1, an intracellular protein has an extracellular role as a modulator of matrix mineralization. Sci Rep 2016; 6:37885. [PMID: 27883077 PMCID: PMC5121659 DOI: 10.1038/srep37885] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 11/02/2016] [Indexed: 12/14/2022] Open
Abstract
Transforming growth factor beta receptor II interacting protein 1 (TRIP-1), a predominantly intracellular protein is localized in the ECM of bone. TRIP-1 lacks a signal peptide, therefore, in this study, we provide evidence that intracellular TRIP-1 can be packaged and exported to the ECM via exosomes. Overexpression of TRIP-1 in MC3T3-E1 cells resulted in increased matrix mineralization during differentiation and knockdown resulted in reduced effects. In vivo function of TRIP-1 was studied by an implantation assay performed using TRIP-1 overexpressing and knockdown cells cultured in a 3-dimmensional scaffold. After 4 weeks, the subcutaneous tissues from TRIP-1 overexpressing cells showed higher calcium and phosphate deposits, arranged collagen fibrils and increased expression of Runx2 and alkaline phosphatase. Nucleation studies on demineralized and deproteinized dentin wafer is a powerful tool to determine the functional role of noncollagenous proteins in matrix mineralization. Using this system, we provide evidence that TRIP-1 binds to Type-I collagen and can promote mineralization. Surface plasmon resonance analysis demonstrated that TRIP-1 binds to collagen with KD = 48 μM. SEM and TEM analysis showed that TRIP-1 promoted the nucleation and growth of calcium phosphate mineral aggregates. Taken together, we provide mechanistic insights of this intracellular protein in matrix mineralization.
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60
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Lin Y, Zhang R, Zhang P. Eukaryotic translation initiation factor 3 subunit D overexpression is associated with the occurrence and development of ovarian cancer. FEBS Open Bio 2016; 6:1201-1210. [PMID: 28203520 PMCID: PMC5302064 DOI: 10.1002/2211-5463.12137] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 08/29/2016] [Accepted: 09/21/2016] [Indexed: 12/24/2022] Open
Abstract
Ovarian cancer is the most common cause of gynaecological cancer-associated death; thus, promising biomarkers and new therapeutic targets for ovarian cancer must be explored. Here, we report that eukaryotic translation initiation factor 3 subunit D (EIF3D), a member of the EIF3 family, was overexpressed in ovarian cancer clinical tissues. Furthermore, the expression of EIF3D was correlated with the International Federation of Gynecology and Obstetrics stage and pathological differentiation stage. 3-(4,5-dimethylthylthiazol-2-yl)-2 (MTT) and colony formation assays revealed that the lentivirus-mediated knockdown of EIF3D suppresses cell proliferation in the ovarian tumour cell lines CAOV-3 and SKOV-3. Flow cytometry revealed that cells were arrested at the G2/M phase of the cell cycle and that cyclin-dependent kinase 1 was also altered after EIF3D silencing. The results presented here demonstrate that EIF3D may play an important role in the occurrence and development of ovarian cancer.
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Affiliation(s)
- Yaying Lin
- Department of Gynecology Xinhua Hospital Shanghai Jiao Tong University School of Medicine China
| | - Rongrong Zhang
- Department of Gynecology Xinhua Hospital Shanghai Jiao Tong University School of Medicine China
| | - Ping Zhang
- Department of Gynecology Xinhua Hospital Shanghai Jiao Tong University School of Medicine China
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61
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Cattie DJ, Richardson CE, Reddy KC, Ness-Cohn EM, Droste R, Thompson MK, Gilbert WV, Kim DH. Mutations in Nonessential eIF3k and eIF3l Genes Confer Lifespan Extension and Enhanced Resistance to ER Stress in Caenorhabditis elegans. PLoS Genet 2016; 12:e1006326. [PMID: 27690135 PMCID: PMC5045169 DOI: 10.1371/journal.pgen.1006326] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 08/26/2016] [Indexed: 11/18/2022] Open
Abstract
The translation initiation factor eIF3 is a multi-subunit protein complex that coordinates the assembly of the 43S pre-initiation complex in eukaryotes. Prior studies have demonstrated that not all subunits of eIF3 are essential for the initiation of translation, suggesting that some subunits may serve regulatory roles. Here, we show that loss-of-function mutations in the genes encoding the conserved eIF3k and eIF3l subunits of the translation initiation complex eIF3 result in a 40% extension in lifespan and enhanced resistance to endoplasmic reticulum (ER) stress in Caenorhabditis elegans. In contrast to previously described mutations in genes encoding translation initiation components that confer lifespan extension in C. elegans, loss-of-function mutations in eif-3.K or eif-3.L are viable, and mutants show normal rates of growth and development, and have wild-type levels of bulk protein synthesis. Lifespan extension resulting from EIF-3.K or EIF-3.L deficiency is suppressed by a mutation in the Forkhead family transcription factor DAF-16. Mutations in eif-3.K or eif-3.L also confer enhanced resistance to ER stress, independent of IRE-1-XBP-1, ATF-6, and PEK-1, and independent of DAF-16. Our data suggest a pivotal functional role for conserved eIF3k and eIF3l accessory subunits of eIF3 in the regulation of cellular and organismal responses to ER stress and aging.
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Affiliation(s)
- Douglas J. Cattie
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Claire E. Richardson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Kirthi C. Reddy
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Elan M. Ness-Cohn
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Rita Droste
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Howard Hughes Medical Institute, McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Mary K. Thompson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Wendy V. Gilbert
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Dennis H. Kim
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- * E-mail:
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Schipany K, Rosner M, Ionce L, Hengstschläger M, Kovacic B. eIF3 controls cell size independently of S6K1-activity. Oncotarget 2016; 6:24361-75. [PMID: 26172298 PMCID: PMC4695191 DOI: 10.18632/oncotarget.4458] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/19/2015] [Indexed: 12/16/2022] Open
Abstract
All multicellular organisms require a life-long regulation of the number and the size of cells, which build up their organs. mTOR acts as a signaling nodule for the regulation of protein synthesis and growth. To activate the translational cascade, mTOR phosphorylates S6 kinase (S6K1), which is liberated from the eIF3-complex and mobilized for activation of its downstream targets. How S6K1 regulates cell size remains unclear. Here, we challenged cell size control through S6K1 by specifically depleting its binding partner eIF3 in normal and transformed cell lines. We show that loss of eIF3 leads to a massive reduction of cell size and cell number accompanied with an unexpected increase in S6K1-activity. The hyperactive S6K1-signaling was rapamycin-sensitive, suggesting an upstream mTOR-regulation. A selective S6K1 inhibitor (PF-4708671) was unable to interfere with the reduced size, despite efficiently inhibiting S6K1-activity. Restoration of eIF3 expression recovered size defects, without affecting the p-S6 levels. We further show that two, yet uncharacterized, cancer-associated mutations in the eIF3-complex, have the capacity to recover from reduced size phenotype, suggesting a possible role for eIF3 in regulating cancer cell size. Collectively, our results uncover a role for eIF3-complex in maintenance of normal and neoplastic cell size - independent of S6K1-signaling.
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Affiliation(s)
- Katharina Schipany
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Margit Rosner
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Loredana Ionce
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Markus Hengstschläger
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
| | - Boris Kovacic
- Institute of Medical Genetics, Center of Pathobiochemistry and Genetics, Medical University of Vienna, A-1090 Vienna, Austria
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63
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Assembly of eIF3 Mediated by Mutually Dependent Subunit Insertion. Structure 2016; 24:886-96. [PMID: 27210288 DOI: 10.1016/j.str.2016.02.024] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2016] [Revised: 02/19/2016] [Accepted: 02/21/2016] [Indexed: 02/05/2023]
Abstract
Eukaryotic initiation factor 3 (eIF3), an essential multi-protein complex involved in translation initiation, is composed of 12 tightly associated subunits in humans. While the overall structure of eIF3 is known, the mechanism of its assembly and structural consequences of dysregulation of eIF3 subunit expression seen in many cancers is largely unknown. Here we show that subunits in eIF3 assemble into eIF3 in an interdependent manner. Assembly of eIF3 is governed primarily by formation of a helical bundle, composed of helices extending C-terminally from PCI-MPN domains in eight subunits. We propose that, while the minimal subcomplex of human-like eIF3 functional for translation initiation in cells consists of subunits a, b, c, f, g, i, and m, numerous other eIF3 subcomplexes exist under circumstances of subunit over- or underexpression. Thus, eIF3 subcomplexes formed or "released" due to dysregulated subunit expression may be determining factors contributing to eIF3-related cancers.
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McDaniel K, Hall C, Sato K, Lairmore T, Marzioni M, Glaser S, Meng F, Alpini G. Lin28 and let-7: roles and regulation in liver diseases. Am J Physiol Gastrointest Liver Physiol 2016; 310:G757-65. [PMID: 27012771 PMCID: PMC4888551 DOI: 10.1152/ajpgi.00080.2016] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Accepted: 03/16/2016] [Indexed: 01/31/2023]
Abstract
The diagnosis and treatment of liver disease remain a major health concern worldwide because of the diverse etiologies of this disease. For this reason, new therapeutic targets are greatly needed to halt the progression of this damaging disease. Upon initiation of liver injury by viral infection, autoimmune disease or toxin, and/or hepatitis, chronic disease may develop, which can progress to cirrhosis, hepatocellular carcinoma (HCC), cholangiocarcinoma, liver failure, or death. The Lin28/lethal-7 (let-7) molecular switch has emerged as a central regulator of multiorgan injuries and cancer development. Lin28 is a stem cell marker vital to initiation or maintenance of a stem cell phenotype. Lin28 has not been extensively studied in the liver, despite its ability to induce tissue regeneration via reprogramming of oxidative enzymes in other tissues and its involvement with numerous upstream regulators and downstream targets in liver disease. Theoretically, overexpression of Lin28 in certain forms of liver disease could be a potential treatment that aids in liver regeneration. Alternatively, Lin28 has been implicated numerous times in the progression of diverse cancer types and is associated with increased severity of disease. In this case, Lin28 could be a potential inhibitory target to prevent malignant transformation in the liver. This review seeks to characterize the role of Lin28 in liver disease.
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Affiliation(s)
- Kelly McDaniel
- 1Research, Central Texas Veterans Health Care System, Temple, Texas; ,2Baylor Scott & White Digestive Disease Research Center, Scott & White Memorial Hospital, Temple, Texas; ,3Operational Funds, Baylor Scott & White, Temple, Texas; ,4Department of Medicine, Baylor Scott & White and Texas A & M Health Science Center, Temple, Texas;
| | - Chad Hall
- 3Operational Funds, Baylor Scott & White, Temple, Texas; ,5Department of Surgery, Baylor Scott & White and Texas A & M Health Science Center, Temple, Texas; and
| | - Keisaku Sato
- 4Department of Medicine, Baylor Scott & White and Texas A & M Health Science Center, Temple, Texas;
| | - Terry Lairmore
- 3Operational Funds, Baylor Scott & White, Temple, Texas; ,5Department of Surgery, Baylor Scott & White and Texas A & M Health Science Center, Temple, Texas; and
| | - Marco Marzioni
- 6Department of Medicine, Universita' Politecnica delle Marche, Ancona, Italy
| | - Shannon Glaser
- 1Research, Central Texas Veterans Health Care System, Temple, Texas; ,2Baylor Scott & White Digestive Disease Research Center, Scott & White Memorial Hospital, Temple, Texas; ,3Operational Funds, Baylor Scott & White, Temple, Texas;
| | - Fanyin Meng
- 1Research, Central Texas Veterans Health Care System, Temple, Texas; ,2Baylor Scott & White Digestive Disease Research Center, Scott & White Memorial Hospital, Temple, Texas; ,3Operational Funds, Baylor Scott & White, Temple, Texas;
| | - Gianfranco Alpini
- Research, Central Texas Veterans Health Care System, Temple, Texas; Baylor Scott & White Digestive Disease Research Center, Scott & White Memorial Hospital, Temple, Texas; Department of Medicine, Baylor Scott & White and Texas A & M Health Science Center, Temple, Texas;
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Toompuu M, Kärblane K, Pata P, Truve E, Sarmiento C. ABCE1 is essential for S phase progression in human cells. Cell Cycle 2016; 15:1234-47. [PMID: 26985706 DOI: 10.1080/15384101.2016.1160972] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
ABCE1 is a highly conserved protein universally present in eukaryotes and archaea, which is crucial for the viability of different organisms. First identified as RNase L inhibitor, ABCE1 is currently recognized as an essential translation factor involved in several stages of eukaryotic translation and ribosome biogenesis. The nature of vital functions of ABCE1, however, remains unexplained. Here, we study the role of ABCE1 in human cell proliferation and its possible connection to translation. We show that ABCE1 depletion by siRNA results in a decreased rate of cell growth due to accumulation of cells in S phase, which is accompanied by inefficient DNA synthesis and reduced histone mRNA and protein levels. We infer that in addition to the role in general translation, ABCE1 is involved in histone biosynthesis and DNA replication and therefore is essential for normal S phase progression. In addition, we analyze whether ABCE1 is implicated in transcript-specific translation via its association with the eIF3 complex subunits known to control the synthesis of cell proliferation-related proteins. The expression levels of a few such targets regulated by eIF3A, however, were not consistently affected by ABCE1 depletion.
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Affiliation(s)
- Marina Toompuu
- a Department of Gene Technology , Tallinn University of Technology , Tallinn , Estonia
| | - Kairi Kärblane
- a Department of Gene Technology , Tallinn University of Technology , Tallinn , Estonia
| | - Pille Pata
- a Department of Gene Technology , Tallinn University of Technology , Tallinn , Estonia
| | - Erkki Truve
- a Department of Gene Technology , Tallinn University of Technology , Tallinn , Estonia
| | - Cecilia Sarmiento
- a Department of Gene Technology , Tallinn University of Technology , Tallinn , Estonia
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White TE, Surles-Zeigler MC, Ford GD, Gates AS, Davids B, Distel T, LaPlaca MC, Ford BD. Bilateral gene interaction hierarchy analysis of the cell death gene response emphasizes the significance of cell cycle genes following unilateral traumatic brain injury. BMC Genomics 2016; 17:130. [PMID: 26912237 PMCID: PMC4765060 DOI: 10.1186/s12864-016-2412-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 01/26/2016] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Delayed or secondary cell death that is caused by a cascade of cellular and molecular processes initiated by traumatic brain injury (TBI) may be reduced or prevented if an effective neuroprotective strategy is employed. Microarray and subsequent bioinformatic analyses were used to determine which genes, pathways and networks were significantly altered 24 h after unilateral TBI in the rat. Ipsilateral hemi-brain, the corresponding contralateral hemi-brain, and naïve (control) brain tissue were used for microarray analysis. RESULTS Ingenuity Pathway Analysis showed cell death and survival (CD) to be a top molecular and cellular function associated with TBI on both sides of the brain. One major finding was that the overall gene expression pattern suggested an increase in CD genes in ipsilateral brain tissue and suppression of CD genes contralateral to the injury which may indicate an endogenous protective mechanism. We created networks of genes of interest (GOI) and ranked the genes by the number of direct connections each had in the GOI networks, creating gene interaction hierarchies (GIHs). Cell cycle was determined from the resultant GIHs to be a significant molecular and cellular function in post-TBI CD gene response. CONCLUSIONS Cell cycle and apoptosis signalling genes that were highly ranked in the GIHs and exhibited either the inverse ipsilateral/contralateral expression pattern or contralateral suppression were identified and included STAT3, CCND1, CCND2, and BAX. Additional exploration into the remote suppression of CD genes may provide insight into neuroprotective mechanisms that could be used to develop therapies to prevent cell death following TBI.
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Affiliation(s)
- Todd E White
- Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA, 30310, USA.
| | - Monique C Surles-Zeigler
- Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA, 30310, USA.
| | - Gregory D Ford
- Division of Natural Sciences and Physical Education, Georgia Highlands College, 5441 Highway 20, NE, Cartersville, GA, 30121, USA.
| | - Alicia S Gates
- Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA, 30310, USA.
| | - Benem Davids
- Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA, 30310, USA.
| | - Timothy Distel
- Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA, 30310, USA.
- University of California-Riverside School of Medicine, 900 University Ave., Riverside, CA, 92521, USA.
| | - Michelle C LaPlaca
- Department of Biomedical Engineering, Georgia Institute of Technology, 313 Ferst Drive, Atlanta, GA, 30332, USA.
| | - Byron D Ford
- Department of Neurobiology, Neuroscience Institute, Morehouse School of Medicine, 720 Westview Drive SW, Atlanta, GA, 30310, USA.
- University of California-Riverside School of Medicine, 900 University Ave., Riverside, CA, 92521, USA.
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67
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Li Q, Deng Z, Gong C, Wang T. The Rice Eukaryotic Translation Initiation Factor 3 Subunit f (OseIF3f) Is Involved in Microgametogenesis. FRONTIERS IN PLANT SCIENCE 2016; 7:532. [PMID: 27200010 PMCID: PMC4844609 DOI: 10.3389/fpls.2016.00532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Accepted: 04/04/2016] [Indexed: 05/13/2023]
Abstract
Microgametogenesis is the post-meiotic pollen developmental phase when unicellular microspores develop into mature tricellular pollen. In rice, microgametogenesis can influence grain yields to a great degree because pollen abortion occurs more easily during microgametogenesis than during other stages of pollen development. However, our knowledge of the genes involved in microgametogenesis in rice remains limited. Due to the dependence of pollen development on the regulatory mechanisms of protein expression, we identified the encoding gene of the eukaryotic translation initiation factor 3, subunit f in Oryza sativa (OseIF3f). Immunoprecipitation combined with mass spectrometry confirmed that OseIF3f was a subunit of rice eIF3, which consisted of at least 12 subunits including eIF3a, eIF3b, eIF3c, eIF3d, eIF3e, eIF3f, eIF3g, eIF3h, eIF3i, eIF3k, eIF3l, and eIF3m. OseIF3f showed high mRNA levels in immature florets and is highly abundant in developing anthers. Subcellular localization analysis showed that OseIF3f was localized to the cytosol and the endoplasmic reticulum in rice root cells. We further analyzed the biological function of OseIF3f using the double-stranded RNA-mediated interference (RNAi) approach. The OseIF3f-RNAi lines grew normally at the vegetative stage but displayed a large reduction in seed production and pollen viability, which is associated with the down-regulation of OseIF3f. Further cytological observations of pollen development revealed that the OseIF3f-RNAi lines showed no obvious abnormalities at the male meiotic stage and the unicellular microspore stage. However, compared to the wild-type, OseIF3f-RNAi lines contained a higher percentage of arrested unicellular pollen at the bicellular stage and a higher percentage of arrested unicellular and bicellular pollen, and aborted pollen at the tricellular stage. These results indicate that OseIF3f plays a role in microgametogenesis.
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Affiliation(s)
- Qi Li
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of SciencesBeijing, China
- University of Chinese Academy of SciencesBeijing, China
| | - Zhuyun Deng
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of SciencesBeijing, China
| | - Chunyan Gong
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of SciencesBeijing, China
| | - Tai Wang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of SciencesBeijing, China
- *Correspondence: Tai Wang,
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68
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Biological insights into the expression of translation initiation factors from recombinant CHOK1SV cell lines and their relationship to enhanced productivity. Biochem J 2015; 472:261-73. [DOI: 10.1042/bj20150928] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 09/29/2015] [Indexed: 12/31/2022]
Abstract
We show for translation initiation factors involved in formation of the closed loop mRNA, their expression is associated with recombinant antibody productivity in Chinese hamster ovary cells and maintaining these is important in determining the cells capacity for antibody productivity.
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69
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des Georges A, Dhote V, Kuhn L, Hellen CUT, Pestova TV, Frank J, Hashem Y. Structure of mammalian eIF3 in the context of the 43S preinitiation complex. Nature 2015; 525:491-5. [PMID: 26344199 DOI: 10.1038/nature14891] [Citation(s) in RCA: 175] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Accepted: 07/06/2015] [Indexed: 12/11/2022]
Abstract
During eukaryotic translation initiation, 43S complexes, comprising a 40S ribosomal subunit, initiator transfer RNA and initiation factors (eIF) 2, 3, 1 and 1A, attach to the 5'-terminal region of messenger RNA and scan along it to the initiation codon. Scanning on structured mRNAs also requires the DExH-box protein DHX29. Mammalian eIF3 contains 13 subunits and participates in nearly all steps of translation initiation. Eight subunits having PCI (proteasome, COP9 signalosome, eIF3) or MPN (Mpr1, Pad1, amino-terminal) domains constitute the structural core of eIF3, to which five peripheral subunits are flexibly linked. Here we present a cryo-electron microscopy structure of eIF3 in the context of the DHX29-bound 43S complex, showing the PCI/MPN core at ∼6 Å resolution. It reveals the organization of the individual subunits and their interactions with components of the 43S complex. We were able to build near-complete polyalanine-level models of the eIF3 PCI/MPN core and of two peripheral subunits. The implications for understanding mRNA ribosomal attachment and scanning are discussed.
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Affiliation(s)
- Amedee des Georges
- HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA
| | - Vidya Dhote
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Lauriane Kuhn
- CNRS, Proteomic Platform Strasbourg - Esplanade, Strasbourg 67084, France
| | - Christopher U T Hellen
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Tatyana V Pestova
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Joachim Frank
- HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.,Department of Biological Sciences, Columbia University, New York, New York 10032, USA
| | - Yaser Hashem
- CNRS, Architecture et Réactivité de l'ARN, Université de Strasbourg, Strasbourg 67084, France
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Goichon A, Bertrand J, Chan P, Lecleire S, Coquard A, Cailleux AF, Vaudry D, Déchelotte P, Coëffier M. Enteral delivery of proteins enhances the expression of proteins involved in the cytoskeleton and protein biosynthesis in human duodenal mucosa. Am J Clin Nutr 2015; 102:359-67. [PMID: 26109581 PMCID: PMC7109707 DOI: 10.3945/ajcn.114.104216] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 05/20/2015] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Amino acids are well known to be key effectors of gut protein turnover. We recently reported that enteral delivery of proteins markedly stimulated global duodenal protein synthesis in carbohydrate-fed healthy humans, but specifically affected proteins remain unknown. OBJECTIVE We aimed to assess the influence of an enteral protein supply on the duodenal mucosal proteome in carbohydrate-fed humans. DESIGN Six healthy volunteers received for 5 h, on 2 occasions and in random order, either an enteral infusion of maltodextrins alone (0.25 g · kg⁻¹ · h⁻¹) mimicking the fed state or maltodextrins with a protein powder (0.14 g proteins · kg⁻¹ · h⁻¹). Endoscopic duodenal biopsy specimens were then collected and frozen until analysis. A 2-dimensional polyacrylamide gel electrophoresis-based comparative proteomics analysis was then performed, and differentially expressed proteins (at least ±1.5-fold change; Student's t test, P < 0.05) were identified by mass spectrometry. Protein expression changes were confirmed by Western blot analysis. RESULTS Thirty-two protein spots were differentially expressed after protein delivery compared with maltodextrins alone: 28 and 4 spots were up- or downregulated, respectively. Among the 22 identified proteins, 11 upregulated proteins were involved either in the cytoskeleton (ezrin, moesin, plastin 1, lamin B1, vimentin, and β-actin) or in protein biosynthesis (glutamyl-prolyl-transfer RNA synthetase, glutaminyl-transfer RNA synthetase, elongation factor 2, elongation factor 1δ, and eukaryotic translation and initiation factor 3 subunit f). CONCLUSIONS Enteral delivery of proteins altered the duodenal mucosal proteome and mainly stimulated the expression of proteins involved in cytoskeleton and protein biosynthesis. These results suggest that protein supply may affect intestinal morphology by stimulating actin cytoskeleton remodeling.
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Affiliation(s)
- Alexis Goichon
- INSERM Unit 1073, Rouen, France; Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France
| | - Julien Bertrand
- INSERM Unit 1073, Rouen, France; Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France
| | - Philippe Chan
- Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France; Platform of Proteomics PISSARO, Mont-Saint-Aignan, France
| | - Stéphane Lecleire
- INSERM Unit 1073, Rouen, France; Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France; Gastroenterology, Rouen University Hospital, Rouen, France
| | | | - Anne-Françoise Cailleux
- Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France; Clinical Investigation Centre CIC 1404-INSERM, Rouen, France
| | - David Vaudry
- Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France; INSERM Unit 982, Mont-Saint-Aignan, France; and Platform of Proteomics PISSARO, Mont-Saint-Aignan, France
| | - Pierre Déchelotte
- INSERM Unit 1073, Rouen, France; Institute for Research and Innovation in Biomedicine, Rouen University, Rouen, France; Departments of Nutrition,
| | - Moïse Coëffier
- INSERM Unit 1073, Rouen, France; Clinical Investigation Centre CIC 1404-INSERM, Rouen, France
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Borgo C, Franchin C, Salizzato V, Cesaro L, Arrigoni G, Matricardi L, Pinna LA, Donella-Deana A. Protein kinase CK2 potentiates translation efficiency by phosphorylating eIF3j at Ser127. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1693-701. [PMID: 25887626 DOI: 10.1016/j.bbamcr.2015.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 03/17/2015] [Accepted: 04/07/2015] [Indexed: 11/18/2022]
Abstract
In eukaryotic protein synthesis the translation initiation factor 3 (eIF3) is a key player in the recruitment and assembly of the translation initiation machinery. Mammalian eIF3 consists of 13 subunits, including the loosely associated eIF3j subunit that plays a stabilizing role in the eIF3 complex formation and interaction with the 40S ribosomal subunit. By means of both co-immunoprecipitation and mass spectrometry analyses we demonstrate that the protein kinase CK2 interacts with and phosphorylates eIF3j at Ser127. Inhibition of CK2 activity by CX-4945 or down-regulation of the expression of CK2 catalytic subunit by siRNA cause the dissociation of j-subunit from the eIF3 complex as judged from glycerol gradient sedimentation. This finding proves that CK2-phosphorylation of eIF3j is a prerequisite for its association with the eIF3 complex. Expression of Ser127Ala-eIF3j mutant impairs both the interaction of mutated j-subunit with the other eIF3 subunits and the overall protein synthesis. Taken together our data demonstrate that CK2-phosphorylation of eIF3j at Ser127 promotes the assembly of the eIF3 complex, a crucial step in the activation of the translation initiation machinery.
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Affiliation(s)
- Christian Borgo
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Cinzia Franchin
- Proteomic Center of Padova University, Via G. Orus B2, 35129 Padova, Italy
| | - Valentina Salizzato
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Luca Cesaro
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Giorgio Arrigoni
- Proteomic Center of Padova University, Via G. Orus B2, 35129 Padova, Italy
| | - Laura Matricardi
- Venitian Institute of Oncology (IOV-IRCCS), Via Gattamelata 64, 35128 Padova, Italy
| | - Lorenzo A Pinna
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Arianna Donella-Deana
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy.
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Suo J, Medina D, Herrera S, Zheng ZY, Jin L, Chamness GC, Contreras A, Gutierrez C, Hilsenbeck S, Umar A, Foekens JA, Hanash S, Schiff R, Zhang XHF, Chang EC. Int6 reduction activates stromal fibroblasts to enhance transforming activity in breast epithelial cells. Cell Biosci 2015; 5:10. [PMID: 25774287 PMCID: PMC4359526 DOI: 10.1186/s13578-015-0001-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 02/09/2015] [Indexed: 12/21/2022] Open
Abstract
Background The INT6 gene was first discovered as a site of integration in mouse mammary tumors by the mouse mammary tumor virus; however, INT6’s role in the development of human breast cancer remains largely unknown. By gene silencing, we have previously shown that repressing INT6 promotes transforming activity in untransformed human mammary epithelial cells. In the present study, guided by microarray data of human tumors, we have discovered a role of Int6 in stromal fibroblasts. Results We searched microarray databases of human tumors to assess Int6’s role in breast cancer. While INT6 expression levels, as expected, were lower in breast tumors than in adjacent normal breast tissue samples, INT6 expression levels were also substantially lower in tumor stroma. By immunohistochemistry, we determined that the low levels of INT6 mRNA observed in the microarray databases most likely occurs in stromal fibroblasts, because far fewer fibroblasts in the tumor tissue showed detectable levels of the Int6 protein. To directly investigate the effects of Int6 repression on fibroblasts, we silenced INT6 expression in immortalized human mammary fibroblasts (HMFs). When these INT6-repressed HMFs were co-cultured with breast cancer cells, the abilities of the latter to form colonies in soft agar and to invade were enhanced. We analyzed INT6-repressed HMFs and found an increase in the levels of a key carcinoma-associated fibroblast (CAF) marker, smooth muscle actin. Furthermore, like CAFs, these INT6-repressed HMFs secreted more stromal cell–derived factor 1 (SDF-1), and the addition of an SDF-1 antagonist attenuated the INT6-repressed HMFs’ ability to enhance soft agar colony formation when co-cultured with cancer cells. These INT6-repressed HMFs also expressed high levels of mesenchymal markers such as vimentin and N-cadherin. Intriguingly, when mesenchymal stem cells (MSCs) were induced to form CAFs, Int6 levels were reduced. Conclusion These data suggest that besides enhancing transforming activity in epithelial cells, INT6 repression can also induce fibroblasts, and possibly MSCs as well, via mesenchymal-mesenchymal transitions to promote the formation of CAFs, leading to a proinvasive microenvironment for tumorigenesis.
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Affiliation(s)
- Jinfeng Suo
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, 77030 TX USA ; Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Daniel Medina
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Sabrina Herrera
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Ze-Yi Zheng
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Lei Jin
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Gary C Chamness
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Alejandro Contreras
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Carolina Gutierrez
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Susan Hilsenbeck
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Arzu Umar
- Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | - John A Foekens
- Department of Medical Oncology, Erasmus MC Cancer Institute, Erasmus University Medical Center, Rotterdam, Netherlands
| | - Samir Hanash
- Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, 77030 TX USA
| | - Rachel Schiff
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Xiang H-F Zhang
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
| | - Eric C Chang
- Department of Molecular and Cellular Biology and Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, 77030 TX USA
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Cheng Y, Zhou J, Li H. Clinicopathologic Implications of Eukaryotic Initiation Factor 3f and Her-2/neu Expression in Gastric Cancer. Clin Transl Sci 2015; 8:320-5. [PMID: 25684180 DOI: 10.1111/cts.12263] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
BACKGROUND To detect the expression of eIF3f and human epidermal growth factor receptor 2 (Her-2)/neu in gastric cancer (GC), correlation with their clinicopathological parameters and the relationship of eIF3f and Her-2/neu in the occurrence and development of GC. METHODS A total of 195 gastrectomy specimens with stage I to III were examined for eIF3f expression by immunohistochemistry and for Her-2/neu expression by fluorescence in situ hybridization (FISH) with the median follow-up period of 38 months. RESULTS The positive expression rate of eIF3f in GC and adjacent noncancerous tissue were 33.8% and 59.5%, respectively. eIF3f levels were linked to more advanced tumor stages and likelihood of recurrence (all p < 0.05). The Kaplan-Meier survival curves indicated that decreased expression of eIF3f could serve as a prognosis marker for poor outcome of GC patients (p = 0.04). 15.9% of GC specimens were positive for Her-2/neu, but whose expression was of no correlation with patients' survival. Patients who were positive for Her-2/neu also had high eIF3f expression levels (p = 0.0295). CONCLUSION Results suggest that eIF3f may play an important role in recurrence, thus representing a promising predictive marker for the prognosis of GC. But Her-2/neu has no relationship with the prognosis of GC. The clinical significance of eIF3f and Her-2/neu remains to be further investigated.
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Affiliation(s)
- Yu Cheng
- Department of First Medical Oncology, Affiliated Yantai Yuhuangding Hospital of Qingdao University Medical, Yantai, Shandong, China
| | - Jin Zhou
- Department of Endocrinology, Affiliated Yantai Yuhuangding Hospital of Qingdao University Medical, Yantai, Shandong, China
| | - Honglun Li
- Department of Radiology, Affiliated Yantai Yuhuangding Hospital of Qingdao University Medical, Yantai, Shandong, China
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A new role for PGA1 in inhibiting hepatitis C virus-IRES-mediated translation by targeting viral translation factors. Antiviral Res 2015; 117:1-9. [PMID: 25666760 DOI: 10.1016/j.antiviral.2015.01.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2014] [Revised: 01/26/2015] [Accepted: 01/29/2015] [Indexed: 02/06/2023]
Abstract
Previous studies have demonstrated that cyclopentenone prostaglandins (cyPGs) inhibit the replication of a wide variety of DNA and RNA viruses in different mammalian cell types. We investigated a new role for prostaglandin A1 (PGA1) in the inhibition of hepatitis C virus (HCV)-IRES-mediated translation. PGA1 exhibited dose-dependent inhibitory effects on HCV translation in HCV replicon cells. Furthermore, repetitive PGA1 treatment demonstrated the potential to safely induce the suppression of HCV translation. We also validated a new role for PGA1 in the inhibition of HCV-IRES-mediated translation by targeting cellular translation factors, including the small ribosomal subunit (40S) and eukaryotic initiation factors (eIFs). In pull-down assays, biotinylated PGA1 co-precipitated with the entire HCV IRES RNA/eIF3-40S subunit complex. Moreover, the interactions between PGA1 and the elongation factors and ribosomal subunit were dependent upon HCV IRES RNA binding, and the PGA1/HCV IRES RNA/eIF3-40S subunit complex inhibited HCV-IRES-mediated translation. The novel mechanism revealed in this study may aid in the search for more effective anti-HCV drugs.
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75
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Sauert M, Temmel H, Moll I. Heterogeneity of the translational machinery: Variations on a common theme. Biochimie 2014; 114:39-47. [PMID: 25542647 DOI: 10.1016/j.biochi.2014.12.011] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/16/2014] [Indexed: 12/22/2022]
Abstract
In all organisms the universal process of protein synthesis is performed by the ribosome, a complex multi-component assembly composed of RNA and protein elements. Although ribosome heterogeneity was observed already more than 40 years ago, the ribosome is still traditionally viewed as an unchangeable entity that has to be equipped with all ribosomal components and translation factors in order to precisely accomplish all steps in protein synthesis. In the recent years this concept was challenged by several studies highlighting a broad variation in the composition of the translational machinery in response to environmental signals, which leads to its adaptation and functional specialization. Here, we summarize recent reports on the variability of the protein synthesis apparatus in diverse organisms and discuss the multiple mechanisms and possibilities that can lead to functional ribosome heterogeneity. Collectively, these results indicate that all cells are equipped with a remarkable toolbox to fine tune gene expression at the level of translation and emphasize the physiological importance of ribosome heterogeneity for the immediate implementation of environmental information.
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Affiliation(s)
- Martina Sauert
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Centre for Molecular Biology, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
| | - Hannes Temmel
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Centre for Molecular Biology, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
| | - Isabella Moll
- Department of Microbiology, Immunobiology and Genetics, Max F. Perutz Laboratories, Centre for Molecular Biology, University of Vienna, Dr. Bohrgasse 9/4, 1030 Vienna, Austria
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76
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Rezende AM, Assis LA, Nunes EC, da Costa Lima TD, Marchini FK, Freire ER, Reis CRS, de Melo Neto OP. The translation initiation complex eIF3 in trypanosomatids and other pathogenic excavates--identification of conserved and divergent features based on orthologue analysis. BMC Genomics 2014; 15:1175. [PMID: 25539953 PMCID: PMC4320536 DOI: 10.1186/1471-2164-15-1175] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2014] [Accepted: 12/16/2014] [Indexed: 12/24/2022] Open
Abstract
Background The initiation of translation in eukaryotes is supported by the action of several eukaryotic Initiation Factors (eIFs). The largest of these is eIF3, comprising of up to thirteen polypeptides (eIF3a through eIF3m), involved in multiple stages of the initiation process. eIF3 has been better characterized from model organisms, but is poorly known from more diverged groups, including unicellular lineages represented by known human pathogens. These include the trypanosomatids (Trypanosoma and Leishmania) and other protists belonging to the taxonomic supergroup Excavata (Trichomonas and Giardia sp.). Results An in depth bioinformatic search was carried out to recover the full content of eIF3 subunits from the available genomes of L. major, T. brucei, T. vaginalis and G. duodenalis. The protein sequences recovered were then submitted to homology analysis and alignments comparing them with orthologues from representative eukaryotes. Eleven putative eIF3 subunits were found from both trypanosomatids whilst only five and four subunits were identified from T. vaginalis and G. duodenalis, respectively. Only three subunits were found in all eukaryotes investigated, eIF3b, eIF3c and eIF3i. The single subunit found to have a related Archaean homologue was eIF3i, the most conserved of the eIF3 subunits. The sequence alignments revealed several strongly conserved residues/region within various eIF3 subunits of possible functional relevance. Subsequent biochemical characterization of the Leishmania eIF3 complex validated the bioinformatic search and yielded a twelfth eIF3 subunit in trypanosomatids, eIF3f (the single unidentified subunit in trypanosomatids was then eIF3m). The biochemical data indicates a lack of association of the eIF3j subunit to the complex whilst highlighting the strong interaction between eIF3 and eIF1. Conclusions The presence of most eIF3 subunits in trypanosomatids is consistent with an early evolution of a fully functional complex. Simplified versions in other excavates might indicate a primordial complex or secondary loss of selected subunits, as seen for some fungal lineages. The conservation in eIF3i sequence might indicate critical functions within eIF3 which have been overlooked. The identification of eIF3 subunits from distantly related eukaryotes provides then a basis for the study of conserved/divergent aspects of eIF3 function, leading to a better understanding of eukaryotic translation initiation. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-1175) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | - Osvaldo P de Melo Neto
- Centro de Pesquisas Aggeu Magalhães, Fundação Oswaldo Cruz, Avenida Professor Moraes Rego s/n, Cidade Universitária, Recife, PE 50670-420, Brazil.
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77
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Hershey JWB. The role of eIF3 and its individual subunits in cancer. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:792-800. [PMID: 25450521 DOI: 10.1016/j.bbagrm.2014.10.005] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 10/28/2014] [Accepted: 10/28/2014] [Indexed: 12/15/2022]
Abstract
Specific individual subunits of eIF3 are elevated or reduced in numerous human tumors, and their ectopic overexpression in immortal cells can result in malignant transformation. The structure and assembly of eIF3 and its role in promoting mRNA and methionyl-tRNAi binding to the ribosome during the initiation phase of protein synthesis are described. Methods employed to detect altered levels of eIF3 subunits in cancers are critically evaluated in order to conclude rigorously that such subunits may cause malignant transformation. Strong evidence is presented that the individual overexpression of eIF3 subunits 3a, 3b, 3c, 3h, 3i and 3m may cause malignant transformation, whereas underexpression of subunits 3e and 3f may cause a similar outcome. Possible mechanisms to explain the malignant phenotypes are examined. The involvement of eIF3 in cancer reinforces the view that translational control plays an important role in the regulation of cell proliferation, and provides new targets for the development of therapeutic agents. This article is part of a Special Issue entitled: Translation and Cancer.
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Affiliation(s)
- John W B Hershey
- Department of Biochemistry and Molecular Medicine, University of California, Davis, CA 95616, United States.
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78
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Yue MM, Lv K, Meredith SC, Martindale JL, Gorospe M, Schuger L. Novel RNA-binding protein P311 binds eukaryotic translation initiation factor 3 subunit b (eIF3b) to promote translation of transforming growth factor β1-3 (TGF-β1-3). J Biol Chem 2014; 289:33971-83. [PMID: 25336651 DOI: 10.1074/jbc.m114.609495] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
P311, a conserved 8-kDa intracellular protein expressed in brain, smooth muscle, regenerating tissues, and malignant glioblastomas, represents the first documented stimulator of TGF-β1-3 translation in vitro and in vivo. Here we initiated efforts to define the mechanism underlying P311 function. PONDR® (Predictor Of Naturally Disordered Regions) analysis suggested and CD confirmed that P311 is an intrinsically disordered protein, therefore requiring an interacting partner to acquire tertiary structure and function. Immunoprecipitation coupled with mass spectroscopy identified eIF3 subunit b (eIF3b) as a novel P311 binding partner. Immunohistochemical colocalization, GST pulldown, and surface plasmon resonance studies revealed that P311-eIF3b interaction is direct and has a Kd of 1.26 μm. Binding sites were mapped to the non-canonical RNA recognition motif of eIF3b and a central 11-amino acid-long region of P311, here referred to as eIF3b binding motif. Disruption of P311-eIF3b binding inhibited translation of TGF-β1, 2, and 3, as indicated by luciferase reporter assays, polysome fractionation studies, and Western blot analysis. RNA precipitation assays after UV cross-linking and RNA-protein EMSA demonstrated that P311 binds directly to TGF-β 5'UTRs mRNAs through a previously unidentified RNA recognition motif-like motif. Our results demonstrate that P311 is a novel RNA-binding protein that, by interacting with TGF-βs 5'UTRs and eIF3b, stimulates the translation of TGF-β1, 2, and 3.
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Affiliation(s)
| | | | - Stephen C Meredith
- From the Departments of Pathology and Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637 and
| | - Jennifer L Martindale
- the Laboratory of Genetics, NIA, National Institutes of Health, Baltimore, Maryland 21224
| | - Myriam Gorospe
- the Laboratory of Genetics, NIA, National Institutes of Health, Baltimore, Maryland 21224
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79
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Li Z, Lin S, Jiang T, Wang J, Lu H, Tang H, Teng M, Fan J. Overexpression of eIF3e is correlated with colon tumor development and poor prognosis. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2014; 7:6462-6474. [PMID: 25400724 PMCID: PMC4230162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 09/15/2014] [Indexed: 06/04/2023]
Abstract
EIF3e is a component of the eukaryotic translation initiation factor 3 (eIF-3) complexes, which is an essential factor for initiation of protein synthesis in mammalian cells. Translational control plays key roles in the complex mechanism of cancer development and progression. However, the clinical significance of eIF3e in colon cancer remains to be elucidated. We analyzed the eIF3e expression in a tissue microarray (TMA), which contained 173 colon cancer tissues paired with adjacent normal mucosa and lymph node metastasis. The expression of eIF3e was significantly elevated in colon cancer tissues in comparison with those in adjacent normal mucosa (P < 0.001) and lymph node metastasis (P < 0.001). The high expression of eIF3e in colon cancer was significantly correlated with tumor size (P < 0.001), lymph node involvement (P < 0.001), distant metastasis (P < 0.001), clinical stage (P < 0.001), histopathologic classification (P < 0.001), and vessel invasion (P = 0.036). Univariate and multivariate analysis revealed that eIF3e is an independent prognosis factor for overall survival and disease-free survival in colon cancer. Down-regulation of eIF3e in vitro inhibited colon cancer cell proliferation, clonality and promoted cell apoptosis. Taken together, high eIF3e expression may contribute to tumor progression and predict poor prognosis in colon cancer.
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Affiliation(s)
- Zhi Li
- Department of Anorectal Surgery, Qianfoshan Hospital Affiliated to Shandong University16766 Jingshi Road, Jinan 250014, Shandong, China
| | - Shengtao Lin
- Department of General Surgery, Shanghai Jiaotong University Affiliated First People’s Hospital85 Wujin Road, Shanghai 200080, China
| | - Tao Jiang
- Department of Anal-Colorectal Surgery, General Hospital of Ningxia Medical University804 South Shengli Road, Yinchuan 750004, China
| | - Jingtao Wang
- Department of General Surgery, Shanghai Jiaotong University Affiliated First People’s Hospital85 Wujin Road, Shanghai 200080, China
| | - Huijun Lu
- Department of Pathology, Shanghai Jiaotong University Affiliated First People’s Hospital85 Wujin Road, Shanghai 200080, China
| | - Huamei Tang
- Department of Pathology, Shanghai Jiaotong University Affiliated First People’s Hospital85 Wujin Road, Shanghai 200080, China
| | - Mujian Teng
- Department of General Surgery, Qianfoshan Hospital Affiliated to Shandong University16766 Jingshi Road, Jinan 250014, Shandong, China
| | - Junwei Fan
- Department of General Surgery, Shanghai Jiaotong University Affiliated First People’s Hospital85 Wujin Road, Shanghai 200080, China
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80
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Hutt DM, Roth DM, Vignaud H, Cullin C, Bouchecareilh M. The histone deacetylase inhibitor, Vorinostat, represses hypoxia inducible factor 1 alpha expression through translational inhibition. PLoS One 2014; 9:e106224. [PMID: 25166596 PMCID: PMC4148404 DOI: 10.1371/journal.pone.0106224] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Accepted: 07/30/2014] [Indexed: 01/11/2023] Open
Abstract
Hypoxia inducible factor 1α (HIF-1α) is a master regulator of tumor angiogenesis being one of the major targets for cancer therapy. Previous studies have shown that Histone Deacetylase Inhibitors (HDACi) block tumor angiogenesis through the inhibition of HIF-1α expression. As such, Vorinostat (Suberoylanilide Hydroxamic Acid/SAHA) and Romidepsin, two HDACis, were recently approved by the Food and Drug Administration (FDA) for the treatment of cutaneous T cell lymphoma. Although HDACis have been shown to affect HIF-1α expression by modulating its interactions with the Hsp70/Hsp90 chaperone axis or its acetylation status, the molecular mechanisms by which HDACis inhibit HIF-1α expression need to be further characterized. Here, we report that the FDA-approved HDACi Vorinostat/SAHA inhibits HIF-1α expression in liver cancer-derived cell lines, by a new mechanism independent of p53, prolyl-hydroxylases, autophagy and proteasome degradation. We found that SAHA or silencing of HDAC9 mechanism of action is due to inhibition of HIF-1α translation, which in turn, is mediated by the eukaryotic translation initiation factor - eIF3G. We also highlighted that HIF-1α translation is dramatically inhibited when SAHA is combined with eIF3H silencing. Taken together, we show that HDAC activity regulates HIF-1α translation, with HDACis such as SAHA representing a potential novel approach for the treatment of hepatocellular carcinoma.
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Affiliation(s)
- Darren M. Hutt
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Daniela Martino Roth
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Hélène Vignaud
- Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université de Bordeaux, Bordeaux, France
| | - Christophe Cullin
- Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université de Bordeaux, Bordeaux, France
| | - Marion Bouchecareilh
- Institut de Biochimie et Génétique Cellulaires, CNRS UMR 5095, Université de Bordeaux, Bordeaux, France
- * E-mail:
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81
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Qi J, Dong Z, Liu J, Zhang JT. EIF3i promotes colon oncogenesis by regulating COX-2 protein synthesis and β-catenin activation. Oncogene 2014; 33:4156-63. [PMID: 24056964 PMCID: PMC3962800 DOI: 10.1038/onc.2013.397] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2013] [Revised: 08/02/2013] [Accepted: 08/05/2013] [Indexed: 12/21/2022]
Abstract
Translational control of gene expression has recently been recognized as an important mechanism controlling cell proliferation and oncogenesis, and it mainly occurs in the initiation step of protein synthesis that involves multiple eukaryotic initiation factors (eIFs). Many eIFs have been found to have aberrant expression in human tumors and the aberrant expression may contribute to oncogenesis. However, how these previously considered house-keeping proteins are potentially oncogenic remains elusive. In this study, we investigated the expression of eIF3i in human colon cancers, tested its contribution to colon oncogenesis and determined the mechanism of eIF3i action in colon oncogenesis. We found that eIF3i expression was upregulated in both human colon adenocarcinoma and adenoma polyps as well as in model inducible colon tumorigenic cell lines. Overexpression of ectopic eIF3i in intestinal epithelial cells causes oncogenesis by directly upregulating the synthesis of cyclooxygenase-2 (COX-2) protein and activates the β-catenin/T-cell factor 4 signaling pathway that mediates the oncogenic function of eIF3i. Together, we conclude that eIF3i is a proto-oncogene that drives colon oncogenesis by translationally upregulating COX-2 and activating the β-catenin signaling pathway. These findings imply that proto-oncogenic eIFs likely exert their tumorigenic function by regulating/altering the synthesis level of downstream tumor suppressor or oncogenes.
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Affiliation(s)
- J Qi
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Z Dong
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - J Liu
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - J-T Zhang
- Department of Pharmacology and Toxicology and IU Simon Cancer Center, Indiana University School of Medicine, Indianapolis, IN, USA
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82
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Wagner S, Herrmannová A, Malík R, Peclinovská L, Valášek LS. Functional and biochemical characterization of human eukaryotic translation initiation factor 3 in living cells. Mol Cell Biol 2014; 34:3041-52. [PMID: 24912683 PMCID: PMC4135593 DOI: 10.1128/mcb.00663-14] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 06/04/2014] [Indexed: 11/20/2022] Open
Abstract
The main role of the translation initiation factor 3 (eIF3) is to orchestrate formation of 43S-48S preinitiation complexes (PICs). Until now, most of our knowledge on eIF3 functional contribution to regulation of gene expression comes from yeast studies. Hence, here we developed several novel in vivo assays to monitor the integrity of the 13-subunit human eIF3 complex, defects in assembly of 43S PICs, efficiency of mRNA recruitment, and postassembly events such as AUG recognition. We knocked down expression of the PCI domain-containing eIF3c and eIF3a subunits and of eIF3j in human HeLa and HEK293 cells and analyzed the functional consequences. Whereas eIF3j downregulation had barely any effect and eIF3a knockdown disintegrated the entire eIF3 complex, eIF3c knockdown produced a separate assembly of the a, b, g, and i subunits (closely resembling the yeast evolutionary conserved eIF3 core), which preserved relatively high 40S binding affinity and an ability to promote mRNA recruitment to 40S subunits and displayed defects in AUG recognition. Both eIF3c and eIF3a knockdowns also severely reduced protein but not mRNA levels of many other eIF3 subunits and indeed shut off translation. We propose that eIF3a and eIF3c control abundance and assembly of the entire eIF3 and thus represent its crucial scaffolding elements critically required for formation of PICs.
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Affiliation(s)
- Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, Czech Republic
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, Czech Republic
| | - Radek Malík
- Laboratory of Epigenetic Regulations, Institute of Molecular Genetics ASCR, Videnska, Prague, Czech Republic
| | - Lucie Peclinovská
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, Czech Republic
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, Czech Republic
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83
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Walsh D, Mohr I. Coupling 40S ribosome recruitment to modification of a cap-binding initiation factor by eIF3 subunit e. Genes Dev 2014; 28:835-40. [PMID: 24736843 PMCID: PMC4003276 DOI: 10.1101/gad.236752.113] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Recruitment of ribosomes to the mRNA 5′ terminus involves the activity of a large number of functionally discrete eukaryotic translation initiation factors (eIFs). However, how multiple eIFs coordinate during translation initiation remains poorly understood. Walsh and Mohr now identify an eIF3 subunit that regulates eIF4F modification and show that eIF3e is required for inducible eIF4E phosphorylation. This study establishes a mechanism by which 40S ribosome loading imparts a phosphorylation mark on the cap-binding eIF4F complex that regulates selective mRNA translation. 40S ribosomes are loaded onto capped mRNAs via the multisubunit translation initiation factors eIF3 and eIF4F. While eIF4E is the eIF4F cap recognition component, the eIF4G subunit associates with 40S-bound eIF3. How this intricate process is coordinated remains poorly understood. Here, we identify an eIF3 subunit that regulates eIF4F modification and show that eIF3e is required for inducible eIF4E phosphorylation. Significantly, recruitment of the eIF4E kinase Mnk1 (MAPK signal-integrating kinase 1) to eIF4F depended on eIF3e, and eIF3e was sufficient to promote Mnk1-binding to eIF4G. This establishes a mechanism by which 40S ribosome loading imparts a phosphorylation mark on the cap-binding eIF4F complex that regulates selective mRNA translation and is synchronized by a specific eIF3 subunit.
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Affiliation(s)
- Derek Walsh
- Department of Microbiology, New York University School of Medicine, New York, New York 10016, USA
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84
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Jongjitwimol J, Feng M, Zhou L, Wilkinson O, Small L, Baldock R, Taylor DL, Smith D, Bowler LD, Morley SJ, Watts FZ. The S. pombe translation initiation factor eIF4G is Sumoylated and associates with the SUMO protease Ulp2. PLoS One 2014; 9:e94182. [PMID: 24818994 PMCID: PMC4018355 DOI: 10.1371/journal.pone.0094182] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Accepted: 03/13/2014] [Indexed: 12/03/2022] Open
Abstract
SUMO is a small post-translational modifier, that is attached to lysine residues in target proteins. It acts by altering protein-protein interactions, protein localisation and protein activity. SUMO chains can also act as substrates for ubiquitination, resulting in proteasome-mediated degradation of the target protein. SUMO is removed from target proteins by one of a number of specific proteases. The processes of sumoylation and desumoylation have well documented roles in DNA metabolism and in the maintenance of chromatin structure. To further analyse the role of this modification, we have purified protein complexes containing the S. pombe SUMO protease, Ulp2. These complexes contain proteins required for ribosome biogenesis, RNA stability and protein synthesis. Here we have focussed on two translation initiation factors that we identified as co-purifying with Ulp2, eIF4G and eIF3h. We demonstrate that eIF4G, but not eIF3h, is sumoylated. This modification is increased under conditions that produce cytoplasmic stress granules. Consistent with this we observe partial co-localisation of eIF4G and SUMO in stressed cells. Using HeLa cells, we demonstrate that human eIF4GI is also sumoylated; in vitro studies indicate that human eIF4GI is modified on K1368 and K1588, that are located in the C-terminal eIF4A- and Mnk-binding sites respectively.
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Affiliation(s)
- Jirapas Jongjitwimol
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Min Feng
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Lihong Zhou
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Oliver Wilkinson
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Lauren Small
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Robert Baldock
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Deborah L. Taylor
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Duncan Smith
- Paterson Institute for Cancer Research, The University of Manchester, Manchester, United Kingdom
| | - Lucas D. Bowler
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Simon J. Morley
- Biochemistry and Biomedical Sciences, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
| | - Felicity Z. Watts
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, United Kingdom
- * E-mail:
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85
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Zhou F, Roy B, Dunlap JR, Enganti R, von Arnim AG. Translational control of Arabidopsis meristem stability and organogenesis by the eukaryotic translation factor eIF3h. PLoS One 2014; 9:e95396. [PMID: 24736281 PMCID: PMC3988188 DOI: 10.1371/journal.pone.0095396] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Accepted: 03/25/2014] [Indexed: 11/18/2022] Open
Abstract
Essentially all aboveground plant tissues develop from the stem cells in the primary shoot apical meristem. Proliferation of the stem cell population in the Arabidopsis shoot apical meristem is tightly controlled by a feedback loop formed primarily by the homeodomain transcription factor WUSCHEL (WUS) and the CLAVATA ligand-receptor system. In this study, it is shown that mutation of a translation initiation factor, eIF3h, causes a tendency to develop a strikingly enlarged shoot apical meristem with elevated and ectopic expression of WUS and CLAVATA3 (CLV3). Many of the mRNAs that function in apical meristem maintenance possess upstream open reading frames (uORFs), translational attenuators that render translation partially dependent on eIF3h. Specifically, the mRNA for the receptor kinase, CLV1, is undertranslated in the eif3h mutant as shown by transient and transgenic expression assays. Concordant phenotypic observations include defects in organ polarity and in translation of another uORF-containing mRNA, ASYMMETRIC LEAVES 1 (AS1), in eif3h. In summary, the expression of developmental regulatory mRNAs is attenuated by uORFs, and this attenuation is balanced in part by the translation initiation factor, eIF3h. Thus, translational control plays a key role in Arabidopsis stem cell regulation and organogenesis.
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Affiliation(s)
- Fujun Zhou
- Genome Science and Technology Program, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Bijoyita Roy
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - John R. Dunlap
- Division of Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Ramya Enganti
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
| | - Albrecht G. von Arnim
- Genome Science and Technology Program, The University of Tennessee, Knoxville, Tennessee, United States of America
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, Tennessee, United States of America
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86
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The chaperonin CCT interacts with and mediates the correct folding and activity of three subunits of translation initiation factor eIF3: b, i and h. Biochem J 2014; 458:213-24. [PMID: 24320561 DOI: 10.1042/bj20130979] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
eIF3 (eukaryotic initiation factor 3) is the largest and most complex eukaryotic mRNA translation factor in terms of the number of protein components or subunits. In mammals, eIF3 is composed of 13 different polypeptide subunits, of which five, i.e. a, b, c, g and i, are conserved and essential in vivo from yeasts to mammals. In the present study, we show that the eukaryotic cytosolic chaperonin CCT [chaperonin containing TCP-1 (tailless complex polypeptide 1)] binds to newly synthesized eIF3b and promotes the correct folding of eIF3h and eIF3i. Interestingly, overexpression of these last two subunits is associated with enhanced translation of specific mRNAs over and above the general enhancement of global translation. In agreement with this, our data show that, as CCT is required for the correct folding of eIF3h and eIF3i subunits, it indirectly influences gene expression with eIF3i overexpression enhancing both cap- and IRES (internal ribosome entry segment)-dependent translation initiation, whereas eIF3h overexpression selectively increases IRES-dependent translation initiation. Importantly, these studies demonstrate the requirement of the chaperonin machinery for the correct folding of essential components of the translational machinery and provide further evidence of the close interplay between the cell environment, cell signalling, cell proliferation, the chaperone machinery and translational apparatus.
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87
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Li G, Wang N, Sun C, Li B. Decreased expression of eukaryotic initiation factor 3f is an adverse prognostic factor for stage I-III gastric cancer. World J Surg Oncol 2014; 12:72. [PMID: 24678890 PMCID: PMC4046624 DOI: 10.1186/1477-7819-12-72] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 03/16/2014] [Indexed: 12/20/2022] Open
Abstract
Background It has been demonstrated that eIF3f expression is significantly decreased in many human cancers, a fact which plays an important role in human cancer. However, the expression of eIF3f in gastric cancer (GC) is not well understood to date. Therefore, the aim of this study is to detect the expression of eIF3f in GC. Methods The expression of eIF3f was examined by immunohistochemistry in tissues with stage I to III GC and adjacent non-cancerous tissues (ANCT) of 195 gastrectomy specimens; clinicopathological results, including survival, were analyzed. Results The positive expression rate of eIF3f was significantly higher in ANCT tissues than in GC. eIF3f levels were correlated with more advanced tumor stages and likelihood of recurrence (all P <0.05). The Kaplan-Meier survival curves indicated that decreased expression of eIF3f could serve as a prognosis marker for poor outcome of GC patients (P = 0.04). Conclusions eIF3f may play an important role in recurrence, thus representing a promising predictive marker for the prognosis of GC.
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Affiliation(s)
- Guanghua Li
- Department of General Surgery, The Second Hospital of Shandong University, 247th Beiyuan Avenue, Jinan 250200, China.
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88
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Cheng Y, Jia C, Li G, Li H. Expression of eukaryotic initiation factor 3f is associated with prognosis in gastric carcinomas. Oncol Res Treat 2014; 37:198-202. [PMID: 24732644 DOI: 10.1159/000360779] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Accepted: 02/10/2014] [Indexed: 12/12/2022]
Abstract
BACKGROUND Eukaryotic initiation factor 3f (eIF3f) expression, which plays an important role in human cancer, is significantly decreased in various types of cancers. The aim of this study was to detect the expression of eIF3f in gastric carcinoma (GC), which until now has not been reported. METHODS Expression of eIF3f was detected by immunohistochemistry in GC tissues and adjacent non-cancerous tissues (ANCT) from 195 patients with stage I-III GC who underwent curative gastrectomy. Clinicopathological results, including survival, were analyzed. RESULTS Expression rate of eIF3f in GC and ANCT were 44.8 and 81.7% respectively. Low expression of eIF3f was significantly associated with an increased serum level of carcinoma embryonic antigen (p = 0.02), but not with levels of carbohydrate antigen 19-9 (p = 0.29). eIF3f levels were linked to more advanced tumor stages and likelihood of recurrence (all p < 0.05).The Kaplan-Meier survival curves indicated that decreased expression of eIF3f was a significant factor for a poor prognosis for GC patients (p = 0.04). CONCLUSION eIF3f may play an important role in recurrence. Its function and potential as a prognostic marker should be further verified in GC.
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Affiliation(s)
- Yu Cheng
- Department of First Medical Oncology, Affiliated Yantai Yuhuangding Hospital of Qingdao University Medical College, Shandong, China
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89
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Nyp MF, Navarro A, Rezaiekhaligh MH, Perez RE, Mabry SM, Ekekezie II. TRIP-1 via AKT modulation drives lung fibroblast/myofibroblast trans-differentiation. Respir Res 2014; 15:19. [PMID: 24528651 PMCID: PMC3946032 DOI: 10.1186/1465-9921-15-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 02/11/2014] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Myofibroblasts are the critical effector cells in the pathogenesis of pulmonary fibrosis which carries a high degree of morbidity and mortality. We have previously identified Type II TGFβ receptor interacting protein 1 (TRIP-1), through proteomic analysis, as a key regulator of collagen contraction in primary human lung fibroblasts--a functional characteristic of myofibroblasts, and the last, but critical step in the process of fibrosis. However, whether or not TRIP-1 modulates fibroblast trans-differentiation to myofibroblasts is not known. METHODS TRIP-1 expression was altered in primary human lung fibroblasts by siRNA and plasmid transfection. Transfected fibroblasts were then analyzed for myofibroblast features and function such as α-SMA expression, collagen contraction ability, and resistance to apoptosis. RESULTS The down-regulation of TRIP-1 expression in primary human lung fibroblasts induces α-SMA expression and enhances resistance to apoptosis and collagen contraction ability. In contrast, TRIP-1 over-expression inhibits α-SMA expression. Remarkably, the effects of the loss of TRIP-1 are not abrogated by blockage of TGFβ ligand activation of the Smad3 pathway or by Smad3 knockdown. Rather, a TRIP-1 mediated enhancement of AKT phosphorylation is the implicated pathway. In TRIP-1 knockdown fibroblasts, AKT inhibition prevents α-SMA induction, and transfection with a constitutively active AKT construct drives collagen contraction and decreases apoptosis. CONCLUSIONS TRIP-1 regulates fibroblast acquisition of phenotype and function associated with myofibroblasts. The importance of this finding is it suggests TRIP-1 expression could be a potential target in therapeutic strategy aimed against pathological fibrosis.
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Affiliation(s)
- Michael F Nyp
- Department of Pediatrics, Section of Neonatal-Perinatal Medicine, Children’s Mercy Hospitals & Clinics, 2401 Gillham Road, 64108 Kansas City, MO, USA
- Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
| | - Angels Navarro
- Department of Pediatrics, Section of Neonatal-Perinatal Medicine, Children’s Mercy Hospitals & Clinics, 2401 Gillham Road, 64108 Kansas City, MO, USA
- Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
| | - Mohammad H Rezaiekhaligh
- Department of Pediatrics, Section of Neonatal-Perinatal Medicine, Children’s Mercy Hospitals & Clinics, 2401 Gillham Road, 64108 Kansas City, MO, USA
- Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
| | - Ricardo E Perez
- Department of Pediatrics, Section of Neonatal-Perinatal Medicine, Children’s Mercy Hospitals & Clinics, 2401 Gillham Road, 64108 Kansas City, MO, USA
- Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
| | - Sherry M Mabry
- Department of Pediatrics, Section of Neonatal-Perinatal Medicine, Children’s Mercy Hospitals & Clinics, 2401 Gillham Road, 64108 Kansas City, MO, USA
- Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
| | - Ikechukwu I Ekekezie
- Department of Pediatrics, Section of Neonatal-Perinatal Medicine, Children’s Mercy Hospitals & Clinics, 2401 Gillham Road, 64108 Kansas City, MO, USA
- Department of Pediatrics, University of Missouri-Kansas City School of Medicine, Kansas City, MO, USA
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90
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Abstract
In eukaryotes, the translation initiation codon is generally identified by the scanning mechanism, wherein every triplet in the messenger RNA leader is inspected for complementarity to the anticodon of methionyl initiator transfer RNA (Met-tRNAi). Binding of Met-tRNAi to the small (40S) ribosomal subunit, in a ternary complex (TC) with eIF2-GTP, is stimulated by eukaryotic initiation factor 1 (eIF1), eIF1A, eIF3, and eIF5, and the resulting preinitiation complex (PIC) joins the 5' end of mRNA preactivated by eIF4F and poly(A)-binding protein. RNA helicases remove secondary structures that impede ribosome attachment and subsequent scanning. Hydrolysis of eIF2-bound GTP is stimulated by eIF5 in the scanning PIC, but completion of the reaction is impeded at non-AUG triplets. Although eIF1 and eIF1A promote scanning, eIF1 and possibly the C-terminal tail of eIF1A must be displaced from the P decoding site to permit base-pairing between Met-tRNAi and the AUG codon, as well as to allow subsequent phosphate release from eIF2-GDP. A second GTPase, eIF5B, catalyzes the joining of the 60S subunit to produce an 80S initiation complex that is competent for elongation.
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Affiliation(s)
- Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892;
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91
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Beznosková P, Cuchalová L, Wagner S, Shoemaker CJ, Gunišová S, von der Haar T, Valášek LS. Translation initiation factors eIF3 and HCR1 control translation termination and stop codon read-through in yeast cells. PLoS Genet 2013; 9:e1003962. [PMID: 24278036 PMCID: PMC3836723 DOI: 10.1371/journal.pgen.1003962] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 10/01/2013] [Indexed: 11/19/2022] Open
Abstract
Translation is divided into initiation, elongation, termination and ribosome recycling. Earlier work implicated several eukaryotic initiation factors (eIFs) in ribosomal recycling in vitro. Here, we uncover roles for HCR1 and eIF3 in translation termination in vivo. A substantial proportion of eIF3, HCR1 and eukaryotic release factor 3 (eRF3) but not eIF5 (a well-defined "initiation-specific" binding partner of eIF3) specifically co-sediments with 80S couples isolated from RNase-treated heavy polysomes in an eRF1-dependent manner, indicating the presence of eIF3 and HCR1 on terminating ribosomes. eIF3 and HCR1 also occur in ribosome- and RNA-free complexes with both eRFs and the recycling factor ABCE1/RLI1. Several eIF3 mutations reduce rates of stop codon read-through and genetically interact with mutant eRFs. In contrast, a slow growing deletion of hcr1 increases read-through and accumulates eRF3 in heavy polysomes in a manner suppressible by overexpressed ABCE1/RLI1. Based on these and other findings we propose that upon stop codon recognition, HCR1 promotes eRF3·GDP ejection from the post-termination complexes to allow binding of its interacting partner ABCE1/RLI1. Furthermore, the fact that high dosage of ABCE1/RLI1 fully suppresses the slow growth phenotype of hcr1Δ as well as its termination but not initiation defects implies that the termination function of HCR1 is more critical for optimal proliferation than its function in translation initiation. Based on these and other observations we suggest that the assignment of HCR1 as a bona fide eIF3 subunit should be reconsidered. Together our work characterizes novel roles of eIF3 and HCR1 in stop codon recognition, defining a communication bridge between the initiation and termination/recycling phases of translation.
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Affiliation(s)
- Petra Beznosková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, the Czech Republic
| | - Lucie Cuchalová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, the Czech Republic
| | - Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, the Czech Republic
| | - Christopher J. Shoemaker
- Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Stanislava Gunišová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, the Czech Republic
| | | | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska, Prague, the Czech Republic
- * E-mail:
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92
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Smith MD, Gu Y, Querol-Audí J, Vogan JM, Nitido A, Cate JHD. Human-like eukaryotic translation initiation factor 3 from Neurospora crassa. PLoS One 2013; 8:e78715. [PMID: 24250809 PMCID: PMC3826745 DOI: 10.1371/journal.pone.0078715] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 09/22/2013] [Indexed: 02/05/2023] Open
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a key regulator of translation initiation, but its in vivo assembly and molecular functions remain unclear. Here we show that eIF3 from Neurospora crassa is structurally and compositionally similar to human eIF3. N. crassa eIF3 forms a stable 12-subunit complex linked genetically and biochemically to the 13th subunit, eIF3j, which in humans modulates mRNA start codon selection. Based on N. crassa genetic analysis, most subunits in eIF3 are essential. Subunits that can be deleted (e, h, k and l) map to the right side of the eIF3 complex, suggesting that they may coordinately regulate eIF3 function. Consistent with this model, subunits eIF3k and eIF3l are incorporated into the eIF3 complex as a pair, and their insertion depends on the presence of subunit eIF3h, a key regulator of vertebrate development. Comparisons to other eIF3 complexes suggest that eIF3 assembles around an eIF3a and eIF3c dimer, which may explain the coordinated regulation of human eIF3 levels. Taken together, these results show that Neurospora crassa eIF3 provides a tractable system for probing the structure and function of human-like eIF3 in the context of living cells.
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Affiliation(s)
- M. Duane Smith
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Yu Gu
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jordi Querol-Audí
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jacob M. Vogan
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Adam Nitido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jamie H. D. Cate
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- Department of Chemistry, University of California, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- * E-mail:
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93
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Olshen AB, Hsieh AC, Stumpf CR, Olshen RA, Ruggero D, Taylor BS. Assessing gene-level translational control from ribosome profiling. ACTA ACUST UNITED AC 2013; 29:2995-3002. [PMID: 24048356 DOI: 10.1093/bioinformatics/btt533] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
MOTIVATION The translational landscape of diverse cellular systems remains largely uncharacterized. A detailed understanding of the control of gene expression at the level of messenger RNA translation is vital to elucidating a systems-level view of complex molecular programs in the cell. Establishing the degree to which such post-transcriptional regulation can mediate specific phenotypes is similarly critical to elucidating the molecular pathogenesis of diseases such as cancer. Recently, methods for massively parallel sequencing of ribosome-bound fragments of messenger RNA have begun to uncover genome-wide translational control at codon resolution. Despite its promise for deeply characterizing mammalian proteomes, few analytical methods exist for the comprehensive analysis of this paired RNA and ribosome data. RESULTS We describe the Babel framework, an analytical methodology for assessing the significance of changes in translational regulation within cells and between conditions. This approach facilitates the analysis of translation genome-wide while allowing statistically principled gene-level inference. Babel is based on an errors-in-variables regression model that uses the negative binomial distribution and draws inference using a parametric bootstrap approach. We demonstrate the operating characteristics of Babel on simulated data and use its gene-level inference to extend prior analyses significantly, discovering new translationally regulated modules under mammalian target of rapamycin (mTOR) pathway signaling control.
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Affiliation(s)
- Adam B Olshen
- Department of Epidemiology and Biostatistics, Helen Diller Family Comprehensive Cancer Center, Department of Medicine and Department of Urology, University of California, San Francisco, CA 94158, USA and Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA 94305, USA
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94
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Salsman J, Pinder J, Tse B, Corkery D, Dellaire G. The translation initiation factor 3 subunit eIF3K interacts with PML and associates with PML nuclear bodies. Exp Cell Res 2013; 319:2554-65. [PMID: 24036361 DOI: 10.1016/j.yexcr.2013.09.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 08/08/2013] [Accepted: 09/02/2013] [Indexed: 12/17/2022]
Abstract
The promyelocytic leukemia protein (PML) is a tumor suppressor protein that regulates a variety of important cellular processes, including gene expression, DNA repair and cell fate decisions. Integral to its function is the ability of PML to form nuclear bodies (NBs) that serve as hubs for the interaction and modification of over 90 cellular proteins. There are seven canonical isoforms of PML, which encode diverse C-termini generated by alternative pre-mRNA splicing. Recruitment of specific cellular proteins to PML NBs is mediated by protein-protein interactions with individual PML isoforms. Using a yeast two-hybrid screen employing peptide sequences unique to PML isoform I (PML-I), we identified an interaction with the eukaryotic initiation factor 3 subunit K (eIF3K), and in the process identified a novel eIF3K isoform, which we term eIF3K-2. We further demonstrate that eIF3K and PML interact both in vitro via pull-down assays, as well as in vivo within human cells by co-immunoprecipitation and co-immunofluorescence. In addition, eIF3K isoform 2 (eIF3K-2) colocalizes to PML bodies, particularly those enriched in PML-I, while eIF3K isoform 1 associates poorly with PML NBs. Thus, we report eIF3K as the first known subunit of the eIF3 translation pre-initiation complex to interact directly with the PML protein, and provide data implicating alternative splicing of both PML and eIF3K as a possible regulatory mechanism for eIF3K localization at PML NBs.
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Affiliation(s)
- Jayme Salsman
- Department of Pathology, Dalhousie University, P.O. Box 15000, Halifax, Nova Scotia, Canada B3H 4R2
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95
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Zeng L, Wan Y, Li D, Wu J, Shao M, Chen J, Hui L, Ji H, Zhu X. The m subunit of murine translation initiation factor eIF3 maintains the integrity of the eIF3 complex and is required for embryonic development, homeostasis, and organ size control. J Biol Chem 2013; 288:30087-30093. [PMID: 24003236 DOI: 10.1074/jbc.m113.506147] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Mammalian eIF3 is composed of 13 subunits and is the largest eukaryotic initiation factor. eIF3 plays a key role in protein biosynthesis. However, it is not fully understood how different subunits contribute to the structural integrity and function of the eIF3 complex. Whether eIF3 is essential for embryonic development and homeostasis is also not known. Here, we show that eIF3m null embryos are lethal at the peri-implantation stage. Compound heterozygotes (eIF3m(flox)(/-)) or FABP4-Cre-mediated conditional knock-out mice are lethal at mid-gestation stages. Although the heterozygotes are viable, they show markedly reduced organ size and diminished body weight. Acute ablation of eIF3m in adult mouse liver leads to rapidly decreased body weight and death within 2 weeks; these effects are correlated with a severe decline of protein biogenesis in the liver. Protein analyses reveal that eIF3m deficiency significantly impairs the integrity of the eIF3 complex due to down-regulation of multiple other subunits. Two of the subunits, eIF3f and eIF3h, are stabilized by eIF3m through subcomplex formation. Therefore, eIF3m is required for the structural integrity and translation initiation function of eIF3. Furthermore, not only is eIF3m an essential gene, but its expression level is also important for mouse embryonic development and the control of organ size.
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Affiliation(s)
- Liyong Zeng
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Yihan Wan
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Dan Li
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Jing Wu
- the Model Animal Research Center, Nanjing University, Nanjing, Jiangsu 210061, China
| | - Mengle Shao
- the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
| | - Jiong Chen
- the Model Animal Research Center, Nanjing University, Nanjing, Jiangsu 210061, China
| | - Lijian Hui
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Hongbin Ji
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Xueliang Zhu
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and.
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96
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Dong Z, Qi J, Peng H, Liu J, Zhang JT. Spectrin domain of eukaryotic initiation factor 3a is the docking site for formation of the a:b:i:g subcomplex. J Biol Chem 2013; 288:27951-9. [PMID: 23921387 DOI: 10.1074/jbc.m113.483164] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
eIF3a (eukaryotic translation initiation factor 3a), one of the core subunits of the eIF3 complex, has been implicated in regulating translation of different mRNAs and in tumorigenesis. A subcomplex consisting of eIF3a, eIF3b, eIF3g, and eIF3i (eIF3(a:b:i:g)) has also been identified. However, how eIF3a participates in translational regulation and in formation of the eIF3(a:b:i:g) subcomplex remain to be solved. In this study, we used the tandem affinity purification approach in combination with tandem MS/MS and identified the spectrin domain of eIF3a as the docking site for the formation of eIF3(a:b:i:g) subcomplex. Although eIF3b and eIF3i bind concurrently to the spectrin domain of eIF3a within ∼10-15 amino acids apart, eIF3g binds to eIF3a indirectly via binding to the carboxyl-terminal domain of eIF3b. The binding of eIF3b to the spectrin domain of eIF3a occurs in its RNA recognition motif domain where eIF3j also binds in a mutually exclusive manner. Together, we conclude that the spectrin domain of eIF3a is responsible for the formation of eIF3(a:b:i:g) subcomplex and, because of mutually exclusive nature of bindings of eIF3a and eIF3j to eIF3b, different subcomplexes of eIF3 likely exist and may perform noncanonical functions in translational regulation.
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Affiliation(s)
- Zizheng Dong
- From the Department of Pharmacology and Toxicology and Indiana University Simon Cancer Center, Indiana University School of Medicine, Indianapolis, Indiana 46202
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97
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Hashem Y, des Georges A, Dhote V, Langlois R, Liao HY, Grassucci RA, Hellen CUT, Pestova TV, Frank J. Structure of the mammalian ribosomal 43S preinitiation complex bound to the scanning factor DHX29. Cell 2013; 153:1108-19. [PMID: 23706745 DOI: 10.1016/j.cell.2013.04.036] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 03/06/2013] [Accepted: 04/05/2013] [Indexed: 01/19/2023]
Abstract
Eukaryotic translation initiation begins with assembly of a 43S preinitiation complex. First, methionylated initiator methionine transfer RNA (Met-tRNAi(Met)), eukaryotic initiation factor (eIF) 2, and guanosine triphosphate form a ternary complex (TC). The TC, eIF3, eIF1, and eIF1A cooperatively bind to the 40S subunit, yielding the 43S preinitiation complex, which is ready to attach to messenger RNA (mRNA) and start scanning to the initiation codon. Scanning on structured mRNAs additionally requires DHX29, a DExH-box protein that also binds directly to the 40S subunit. Here, we present a cryo-electron microscopy structure of the mammalian DHX29-bound 43S complex at 11.6 Å resolution. It reveals that eIF2 interacts with the 40S subunit via its α subunit and supports Met-tRNAi(Met) in an unexpected P/I orientation (eP/I). The structural core of eIF3 resides on the back of the 40S subunit, establishing two principal points of contact, whereas DHX29 binds around helix 16. The structure provides insights into eukaryote-specific aspects of translation, including the mechanism of action of DHX29.
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Affiliation(s)
- Yaser Hashem
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
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98
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Eukaryotic translation initiation factors in cancer development and progression. Cancer Lett 2013; 340:9-21. [PMID: 23830805 DOI: 10.1016/j.canlet.2013.06.019] [Citation(s) in RCA: 113] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 06/11/2013] [Accepted: 06/14/2013] [Indexed: 01/03/2023]
Abstract
Eukaryotic gene expression is a complicated process primarily regulated at the levels of gene transcription and mRNA translation. The latter involves four main steps: initiation, elongation, termination and recycling. Translation regulation is primarily achieved during initiation which is orchestrated by 12 currently known eukaryotic initiation factors (eIFs). Here, we review the current state of eIF research and present a concise summary of the various eIF subunits. As eIFs turned out to be critically implicated in different oncogenic processes the various eIF members and their contribution to onset and progression of cancer are featured.
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99
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von Moeller H, Lerner R, Ricciardi A, Basquin C, Marzluff WF, Conti E. Structural and biochemical studies of SLIP1-SLBP identify DBP5 and eIF3g as SLIP1-binding proteins. Nucleic Acids Res 2013; 41:7960-71. [PMID: 23804756 PMCID: PMC3763545 DOI: 10.1093/nar/gkt558] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
In metazoans, replication-dependent histone mRNAs end in a stem-loop structure instead of the poly(A) tail characteristic of all other mature mRNAs. This specialized 3′ end is bound by stem-loop binding protein (SLBP), a protein that participates in the nuclear export and translation of histone mRNAs. The translational activity of SLBP is mediated by interaction with SLIP1, a middle domain of initiation factor 4G (MIF4G)-like protein that connects to translation initiation. We determined the 2.5 Å resolution crystal structure of zebrafish SLIP1 bound to the translation–activation domain of SLBP and identified the determinants of the recognition. We discovered a SLIP1-binding motif (SBM) in two additional proteins: the translation initiation factor eIF3g and the mRNA-export factor DBP5. We confirmed the binding of SLIP1 to DBP5 and eIF3g by pull-down assays and determined the 3.25 Å resolution structure of SLIP1 bound to the DBP5 SBM. The SBM-binding and homodimerization residues of SLIP1 are conserved in the MIF4G domain of CBP80/20-dependent translation initiation factor (CTIF). The results suggest how the SLIP1 homodimer or a SLIP1–CTIF heterodimer can function as platforms to bridge SLBP with SBM-containing proteins involved in different steps of mRNA metabolism.
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Affiliation(s)
- Holger von Moeller
- Structural Cell Biology Department, Max Planck Institute of Biochemistry, Munich, D-82152 Germany and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA
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100
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Morais AT, Terzian AC, Duarte DV, Bronzoni RV, Madrid MC, Gavioli AF, Gil LH, Oliveira AG, Zanelli CF, Valentini SR, Rahal P, Nogueira ML. The eukaryotic translation initiation factor 3 subunit L protein interacts with Flavivirus NS5 and may modulate yellow fever virus replication. Virol J 2013; 10:205. [PMID: 23800076 PMCID: PMC3698205 DOI: 10.1186/1743-422x-10-205] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 06/20/2013] [Indexed: 12/12/2022] Open
Abstract
Background Yellow fever virus (YFV) belongs to the Flavivirus genus and causes an important disease. An alarming resurgence of viral circulation and the expansion of YFV-endemic zones have been detected in Africa and South America in recent years. NS5 is a viral protein that contains methyltransferase and RNA-dependent RNA polymerase (RdRp) domains, which are essential for viral replication, and the interactions between NS5 and cellular proteins have been studied to better understand viral replication. The aim of this study was to characterize the interaction of the NS5 protein with eukaryotic translation initiation factor 3 subunit L (eIF3L) and to evaluate the role of eIF3L in yellow fever replication. Methods To identify interactions of YFV NS5 with cellular proteins, we performed a two-hybrid screen using the YFV NS5 RdRp domain as bait with a human cDNA library, and RNApol deletion mutants were generated and analyzed using the two-hybrid system for mapping the interactions. The RNApol region involved was segmented into three fragments and analyzed using an eIF3L-expressing yeast strain. To map the NS5 residues that are critical for the interactions, we performed site-direct mutagenesis in segment 3 of the interaction domain (ID) and confirmed the interaction using in vitro assays and in vivo coimmunoprecipitation. The significance of eIF3L for YFV replication was investigated using eIF3L overexpression and RNA interference. Results In this work, we describe and characterize the interaction of NS5 with the translation factor eIF3L. The interaction between NS5 and eIF3L was confirmed using in vitro binding and in vivo coimmunoprecipitation assays. This interaction occurs at a region (the interaction domain of the RNApol domain) that is conserved in several flaviviruses and that is, therefore, likely to be relevant to the genus. eIF3L overexpression and plaque reduction assays showed a slight effect on YFV replication, indicating that the interaction of eIF3L with YFV NS5 may play a role in YFV replication. Conclusions Although the precise function of eIF3L on interactions with viral proteins is not entirely understood, these results indicate an interaction of eIF3L with YF NS5 and that eIF3L overexpression facilitates translation, which has potential implications for virus replication.
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Affiliation(s)
- Ana Ts Morais
- Laboratório de Pesquisas em Virologia, Departamento de Doenças Dermatológicas, Infecciosas e Parasitárias, Faculdade de Medicina de São José do Rio Preto-FAMERP, Av. Brigadeiro Faria Lima 5416, São José do Rio Preto, SP 15090-000, Brazil
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