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Gajjar G, Huggins HP, Kim ES, Huang W, Bonnet FX, Updike DL, Keiper BD. Two germ granule eIF4E isoforms reside in different mRNPs to hand off C elegans mRNAs from translational repression to activation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.24.595216. [PMID: 38826235 PMCID: PMC11142241 DOI: 10.1101/2024.05.24.595216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
We studied the function of translation factor eIF4E isoforms in regulating mRNAs in germ cell granules/condensates. Translational control of mRNAs plays an essential role in germ cell gene regulation. Messenger ribonucleoprotein (mRNP) complexes assemble on mRNAs as they move from the nucleus into perinuclear germ granules to exert both positive and negative post-transcriptional regulation in the cytoplasm. In C. elegans , germ granules are surprisingly dynamic mRNP condensates that remodel during development. Two eIF4E isoforms (called IFE-1 and IFE-3), eIF4E-Interacting Proteins (4EIPs), RBPs, DEAD-box helicases, polyadenylated mRNAs, Argonautes and miRNAs all occupy positions in germ granules. Affinity purification of IFE-1 and IFE-3 allowed mass spectrometry and mRNA-Seq to identify the proteins and mRNAs that populate stable eIF4E mRNPs. We find translationally controlled mRNAs (e.g. pos-1, mex-3, spn-4, etc.) enriched in IFE-3 mRNPs, but excluded from IFE-1 mRNPs. These mRNAs also require IFE-1 for efficient translation. The findings support a model in which oocytes and embryos utilize the two eIF4Es for opposite purposes on critically regulated germline mRNAs. Careful colocalization of the eIF4Es with other germ granule components suggests an architecture in which GLH-1, PGL-1 and the IFEs are stratified to facilitate sequential interactions for mRNAs. Biochemical characterization demonstrates opposing yet cooperative roles for IFE-3 and IFE-1 to hand-off of translationally controlled mRNAs from the repressed to the activated state, respectively. The model involves eIF4E mRNPs shuttling mRNAs through nuclear pore-associated granules/condensates to cytoplasmic ribosomes.
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Brito Querido J, Díaz-López I, Ramakrishnan V. The molecular basis of translation initiation and its regulation in eukaryotes. Nat Rev Mol Cell Biol 2024; 25:168-186. [PMID: 38052923 DOI: 10.1038/s41580-023-00624-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2023] [Indexed: 12/07/2023]
Abstract
The regulation of gene expression is fundamental for life. Whereas the role of transcriptional regulation of gene expression has been studied for several decades, it has been clear over the past two decades that post-transcriptional regulation of gene expression, of which translation regulation is a major part, can be equally important. Translation can be divided into four main stages: initiation, elongation, termination and ribosome recycling. Translation is controlled mainly during its initiation, a process which culminates in a ribosome positioned with an initiator tRNA over the start codon and, thus, ready to begin elongation of the protein chain. mRNA translation has emerged as a powerful tool for the development of innovative therapies, yet the detailed mechanisms underlying the complex process of initiation remain unclear. Recent studies in yeast and mammals have started to shed light on some previously unclear aspects of this process. In this Review, we discuss the current state of knowledge on eukaryotic translation initiation and its regulation in health and disease. Specifically, we focus on recent advances in understanding the processes involved in assembling the 43S pre-initiation complex and its recruitment by the cap-binding complex eukaryotic translation initiation factor 4F (eIF4F) at the 5' end of mRNA. In addition, we discuss recent insights into ribosome scanning along the 5' untranslated region of mRNA and selection of the start codon, which culminates in joining of the 60S large subunit and formation of the 80S initiation complex.
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Affiliation(s)
- Jailson Brito Querido
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Irene Díaz-López
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
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3
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Ma L, Xue X, Zhang X, Yu K, Xu X, Tian X, Miao Y, Meng F, Liu X, Guo S, Qiu S, Wang Y, Cui J, Guo W, Li Y, Xia J, Yu Y, Wang J. The essential roles of m 6A RNA modification to stimulate ENO1-dependent glycolysis and tumorigenesis in lung adenocarcinoma. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2022; 41:36. [PMID: 35078505 PMCID: PMC8788079 DOI: 10.1186/s13046-021-02200-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/26/2021] [Indexed: 12/31/2022]
Abstract
Background Lung adenocarcinoma (LUAD) is the most common subtype of lung cancer. Patient prognosis is poor, and the existing therapeutic strategies for LUAD are far from satisfactory. Recently, targeting N6-methyladenosine (m6A) modification of RNA has been suggested as a potential strategy to impede tumor progression. However, the roles of m6A modification in LUAD tumorigenesis is unknown. Methods Global m6A levels and expressions of m6A writers, erasers and readers were evaluated by RNA methylation assay, dot blot, immunoblotting, immunohistochemistry and ELISA in human LUAD, mouse models and cell lines. Cell viability, 3D-spheroid generation, in vivo LUAD formation, experiments in cell- and patient-derived xenograft mice and survival analysis were conducted to explore the impact of m6A on LUAD. The RNA-protein interactions, translation, putative m6A sites and glycolysis were explored in the investigation of the mechanism underlying how m6A stimulates tumorigenesis. Results The elevation of global m6A level in most human LUAD specimens resulted from the combined upregulation of m6A writer methyltransferase 3 (METTL3) and downregulation of eraser alkB homolog 5 (ALKBH5). Elevated global m6A level was associated with a poor overall survival in LUAD patients. Reducing m6A levels by knocking out METTL3 and overexpressing ALKBH5 suppressed 3D-spheroid generation in LUAD cells and intra-pulmonary tumor formation in mice. Mechanistically, m6A-dependent stimulation of glycolysis and tumorigenesis occurred via enolase 1 (ENO1). ENO1 mRNA was m6A methylated at 359 A, which facilitated it’s binding with the m6A reader YTH N6-methyladenosine RNA binding protein 1 (YTHDF1) and resulted in enhanced translation of ENO1. ENO1 positively correlated with METTL3 and global m6A levels, and negatively correlated with ALKBH5 in human LUAD. In addition, m6A-dependent elevation of ENO1 was associated with LUAD progression. In preclinical models, tumors with a higher global m6A level showed a more sensitive response to the inhibition of pan-methylation, glycolysis and ENO activity in LUAD. Conclusions The m6A-dependent stimulation of glycolysis and tumorigenesis in LUAD is at least partially orchestrated by the upregulation of METTL3, downregulation of ALKBH5, and stimulation of YTHDF1-mediated ENO1 translation. Blocking this mechanism may represent a potential treatment strategy for m6A-dependent LUAD. Supplementary Information The online version contains supplementary material available at 10.1186/s13046-021-02200-5.
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Affiliation(s)
- Lifang Ma
- Department of Clinical Laboratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China.,Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Xiangfei Xue
- Department of Clinical Laboratory Medicine, Shanghai Tenth People's Hospital of Tongji University, 200072, Shanghai, China
| | - Xiao Zhang
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Keke Yu
- Department of Bio-bank, Shanghai Chest Hospital, Shanghai Jiao Tong University, 200030, Shanghai, China
| | - Xin Xu
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Xiaoting Tian
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Yayou Miao
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Fanyu Meng
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Xiaoxin Liu
- Nursing Department, Shanghai Chest Hospital, Shanghai Jiao Tong University, 200030, Shanghai, China
| | - Susu Guo
- Department of Clinical Laboratory Medicine, Shanghai Tenth People's Hospital of Tongji University, 200072, Shanghai, China
| | - Shiyu Qiu
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Yikun Wang
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Jiangtao Cui
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Wanxin Guo
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - You Li
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China
| | - Jinjing Xia
- Department of Respiratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China.
| | - Yongchun Yu
- Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China.
| | - Jiayi Wang
- Department of Clinical Laboratory Medicine, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China. .,Shanghai Institute of Thoracic Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, No. 241 West Huaihai Road, 200030, Shanghai, China. .,Department of Clinical Laboratory Medicine, Shanghai Tenth People's Hospital of Tongji University, 200072, Shanghai, China.
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Co-Targeting PIM Kinase and PI3K/mTOR in NSCLC. Cancers (Basel) 2021; 13:cancers13092139. [PMID: 33946744 PMCID: PMC8125027 DOI: 10.3390/cancers13092139] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 03/25/2021] [Accepted: 04/20/2021] [Indexed: 11/16/2022] Open
Abstract
Simple Summary PIM kinases interact with major oncogenic players, including the PI3K/Akt pathway, and provide an escape mechanism leading to drug resistance. This study examined PIM kinase expression in NSCLC and the potential of PIM1 as a prognostic marker. The effect on cell signaling of novel preclinical PI3K/mTOR/PIM kinase inhibitor IBL-301 was compared to PI3K/mTOR inhibition in vitro and ex vivo. PI3K-mTOR inhibitor sensitive (H1975P) and resistant (H1975GR) cells were compared for altered IL6/STAT3 pathway expression and sensitivity to IBL-301. All three PIM kinases are expressed in NSCLC and PIM1 is a marker of poor prognosis. IBL-301 inhibited c-Myc, the PI3K-Akt and JAK/STAT pathways in vitro and in NSCLC tumor tissue explants. IBL-301 also inhibited secreted pro-inflammatory cytokine MCP-1. PIM kinases were activated in H1975GR cells which were more sensitive to IBL-301 than H1975P cells. A miRNA signature of PI3K-mTOR resistance was validated. Co-targeting PIM kinase and PI3K-mTOR warrants further clinical investigation. Abstract PIM kinases are constitutively active proto-oncogenic serine/threonine kinases that play a role in cell cycle progression, metabolism, inflammation and drug resistance. PIM kinases interact with and stabilize p53, c-Myc and parallel signaling pathway PI3K/Akt. This study evaluated PIM kinase expression in NSCLC and in response to PI3K/mTOR inhibition. It investigated a novel preclinical PI3K/mTOR/PIM inhibitor (IBL-301) in vitro and in patient-derived NSCLC tumor tissues. Western blot analysis confirmed PIM1, PIM2 and PIM3 are expressed in NSCLC cell lines and PIM1 is a marker of poor prognosis in patients with NSCLC. IBL-301 decreased PIM1, c-Myc, pBAD and p4EBP1 (Thr37/46) and peIF4B (S406) protein levels in-vitro and MAP kinase, PI3K-Akt and JAK/STAT pathways in tumor tissue explants. IBL-301 significantly decreased secreted pro-inflammatory cytokine MCP-1. Altered mRNA expression, including activated PIM kinase and c-Myc, was identified in Apitolisib resistant cells (H1975GR) by an IL-6/STAT3 pathway array and validated by Western blot. H1975GR cells were more sensitive to IBL-301 than parent cells. A miRNA array identified a dysregulated miRNA signature of PI3K/mTOR drug resistance consisting of regulators of PIM kinase and c-Myc (miR17-5p, miR19b-3p, miR20a-5p, miR15b-5p, miR203a, miR-206). Our data provides a rationale for co-targeting PIM kinase and PI3K-mTOR to improve therapeutic response in NSCLC.
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Cysteine-Rich Angiogenic Inducer 61: Pro-Survival Function and Role as a Biomarker for Disseminating Breast Cancer Cells. Cancers (Basel) 2021; 13:cancers13030563. [PMID: 33540545 PMCID: PMC7867178 DOI: 10.3390/cancers13030563] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2020] [Revised: 01/20/2021] [Accepted: 01/28/2021] [Indexed: 12/28/2022] Open
Abstract
Simple Summary Metastasis is the leading cause of death in breast cancer, and it can be predicted by the detection of circulating tumor cells in the blood and disseminated tumor cells in the bone marrow, which are usually detected by epithelial marker proteins. However, tumor cells with mesenchymal attributes down-regulate the expression of epithelial marker proteins, and are therefore difficult to detect. Here, we found that the protein-cysteine–rich angiogenetic inducer 61 (Cyr61) is strongly expressed in tumor cells with mesenchymal attributes. Cyr61 expression was undetectable in normal blood cells, suggesting that Cyr61 might represent a tumor-associated protein. Functional experiments showed that the loss of Cyr61 reduces the viability of breast tumor cells. Thus, Cyr61 might represent an interesting anti-metastatic target that needs to be explored in future studies. Abstract (1) Background: the early detection of cancer cells in the blood or bone marrow of breast cancer patients improves the understanding of metastasis. Disseminating tumor cells in the bone marrow with a pronounced manifestation of mesenchymal markers (mDTC) are difficult to detect by epithelial markers, but they are relevant in the initiation of metastasis. (2) Methods: the breast cancer mDTC cell line BC-M1 was analyzed by mass spectrometry, which revealed high levels of the protein-cysteine–rich angiogenic inducer 61 (Cyr61). The function of Cyr61 was investigated using shRNA and hypoxia. Peripheral blood samples from 35 breast cancer patients were investigated for CTCs defined as cytokeratin-positive/CD45-negative cells. (3) Results: the Cyr61 levels are elevated in mDTC lines from breast, lung, and prostate cancer patients. The loss of Cyr61 resulted in the diminished expression of hypoxia-inducible factor 1-alpha, and increased apoptosis. Cyr61 was present in 47 (43%) of the 109 detected circulating tumor cells (CTCs), while the blood and bone marrow cells from healthy controls were Cyr61-negative. (4) Conclusions: Cyr61 is expressed in mDTC lines, supports the viability of cancer cells, and classifies a new subset of cytokeratin-positive CTCs, which deserves further investigation.
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6
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Bera A, Lewis SM. Regulation of Epithelial-to-Mesenchymal Transition by Alternative Translation Initiation Mechanisms and Its Implications for Cancer Metastasis. Int J Mol Sci 2020; 21:ijms21114075. [PMID: 32517298 PMCID: PMC7312463 DOI: 10.3390/ijms21114075] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 02/07/2023] Open
Abstract
Translation initiation plays a critical role in the regulation of gene expression for development and disease conditions. During the processes of development and disease, cells select specific mRNAs to be translated by controlling the use of diverse translation initiation mechanisms. Cells often switch translation initiation from a cap-dependent to a cap-independent mechanism during epithelial-to-mesenchymal transition (EMT), a process that plays an important role in both development and disease. EMT is involved in tumor metastasis because it leads to cancer cell migration and invasion, and is also associated with chemoresistance. In this review we will provide an overview of both the internal ribosome entry site (IRES)-dependent and N6-methyladenosine (m6A)-mediated translation initiation mechanisms and discuss how cap-independent translation enables cells from primary epithelial tumors to achieve a motile mesenchymal-like phenotype, which in turn drives tumor metastasis.
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Affiliation(s)
- Amit Bera
- Atlantic Cancer Research Institute, Moncton, NB E1C 8X3, Canada;
| | - Stephen M. Lewis
- Atlantic Cancer Research Institute, Moncton, NB E1C 8X3, Canada;
- Department of Chemistry & Biochemistry, Université de Moncton, Moncton, NB E1A 3E9, Canada
- Beatrice Hunter Cancer Research Institute, Halifax, NS B3H 4R2, Canada
- Correspondence: ; Tel.: +1-506-869-2892
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7
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Spiniello M, Steinbrink MI, Cesnik AJ, Miller RM, Scalf M, Shortreed MR, Smith LM. Comprehensive in vivo identification of the c-Myc mRNA protein interactome using HyPR-MS. RNA (NEW YORK, N.Y.) 2019; 25:1337-1352. [PMID: 31296583 PMCID: PMC6800478 DOI: 10.1261/rna.072157.119] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Accepted: 06/27/2019] [Indexed: 05/10/2023]
Abstract
Proteins bind mRNA through their entire life cycle from transcription to degradation. We analyzed c-Myc mRNA protein interactors in vivo using the HyPR-MS method to capture the crosslinked mRNA by hybridization and then analyzed the bound proteins using mass spectrometry proteomics. Using HyPR-MS, 229 c-Myc mRNA-binding proteins were identified, confirming previously proposed interactors, suggesting new interactors, and providing information related to the roles and pathways known to involve c-Myc. We performed structural and functional analysis of these proteins and validated our findings with a combination of RIP-qPCR experiments, in vitro results released in past studies, publicly available RIP- and eCLIP-seq data, and results from software tools for predicting RNA-protein interactions.
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Affiliation(s)
- Michele Spiniello
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
- Department of Medicine of Precision, University of Studi della Campania Luigi Vanvitelli, Naples 80138, Italy
- Division of Immuno-Hematology and Transfusion Medicine, Cardarelli Hospital, Naples 80131, Italy
| | - Maisie I Steinbrink
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Anthony J Cesnik
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Rachel M Miller
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Mark Scalf
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Michael R Shortreed
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Lloyd M Smith
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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8
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Sadato D, Ono T, Gotoh-Saito S, Kajiwara N, Nomura N, Ukaji M, Yang L, Sakimura K, Tajima Y, Oboki K, Shibasaki F. Eukaryotic translation initiation factor 3 (eIF3) subunit e is essential for embryonic development and cell proliferation. FEBS Open Bio 2018; 8:1188-1201. [PMID: 30087825 PMCID: PMC6070656 DOI: 10.1002/2211-5463.12482] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 04/13/2018] [Accepted: 06/12/2018] [Indexed: 11/06/2022] Open
Abstract
Mammalian eukaryotic translation initiation factor 3 (eIF3) is the largest complex of the translation initiation factors. The eIF3 complex is comprised of thirteen subunits, which are named eIF3a to eIF3 m in most multicellular organisms. The eIF3e gene locus is one of the most frequent integration sites of mouse mammary tumor virus (MMTV), which induces mammary tumors in mice. MMTV-integration events result in the expression of C-terminal-truncated eIF3e proteins, leading to mammary tumor formation. We have shown that tumor formation can be partly caused by activation of hypoxia-inducible factor 2α. To investigate the function of eIF3e in mammals, we generated eIF3e-deficient mice. These eIF3e-/- mice are embryonically lethal, while eIF3e+/- mice are much smaller than wild-type mice. In addition, eIF3e+/- mouse embryonic fibroblasts (MEFs) contained reduced levels of eIF3a and eIF3c subunits and exhibited reduced cellular proliferation. These results suggest that eIF3e is essential for embryonic development in mice and plays a role in maintaining eIF3 integrity.
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Affiliation(s)
- Daichi Sadato
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan.,Department of Applied Biological Science Faculty of Science and Technology Tokyo University of Science Noda Chiba Japan
| | - Tomio Ono
- Center for Basic Technology Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Saki Gotoh-Saito
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Naoki Kajiwara
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Namiko Nomura
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Masako Ukaji
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Liying Yang
- Center for Basic Technology Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Kenji Sakimura
- Department of Cellular Neurobiology Brain Research Institute Niigata University Japan
| | - Youichi Tajima
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Keisuke Oboki
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
| | - Futoshi Shibasaki
- Department of Molecular Medical Research Tokyo Metropolitan Institute of Medical Science Japan
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Xu F, Gu J, Wang L, Liu R, Yuan Y, Wang H, Jiang J, Mao W, Lu C, Ge D. Up-regulation Of EIF3e Is Associated with The Progression of Esophageal Squamous Cell Carcinoma and Poor Prognosis in Patients. J Cancer 2018; 9:1135-1144. [PMID: 29675094 PMCID: PMC5907661 DOI: 10.7150/jca.22546] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 12/16/2017] [Indexed: 01/13/2023] Open
Abstract
Introduction: Esophageal cancer is one of the most common malignant tumors in the world. Eukaryotic translation initiation factors 3e (eIF3e) makes a notable difference in the initiation of protein synthesis and tumor progression. However, the role of eIF3e in ESCC has not been revealed yet. This study aims to investigate the bio-functional and prognostic role of eIF3e in human ESCC tissues and cells. Methods: Immunohistochemical staining and Western blot were performed to detect the eIF3e expression in ESCC patients' tissues. The Kaplan-Meier product limit method and Cox regression were conducted to analyze the association between eIF3e expression, together with other related clinical/pathological features, and patients' prognosis. In the analysis of bio-functional role of eIF3e, CCK-8 and Transwell assay were performed to compare the proliferative and migrative ability after knockdown of eIF3e. Results: Up-regulation of eIF3e were demonstrated in ESCC tissues compared with the corresponding para-cancerous tissues. Overexpression of eIF3e was associated with deep tumor depth, lymph nodes metastasis, and advanced TNM stage. Importantly, the patients with high eIF3e expression suffered shorter overall and disease-free survival. Lymph node metastasis and histological grade served as independent prognostic predictors in patients' prognosis. Knockdown of eIF3e could inhibit cell proliferation and migration, in vitro. Conclusions: The eIF3e expression, or combined with other members of eIF3 complex, might predict poor prognosis of ESCC and serve as a potential breakthrough in the multimodality therapy of ESCC.
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Affiliation(s)
- Fengkai Xu
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Jie Gu
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Lin Wang
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Ronghua Liu
- Department of Immunology and Key Laboratory of Medical Molecular Virology of MOE/MOH, School of Basic Medical Sciences, Fudan University, Shanghai, P. R. China
| | - Yunfeng Yuan
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Hao Wang
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Jiahao Jiang
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Wei Mao
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Chunlai Lu
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
| | - Di Ge
- Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai, P. R. China
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10
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The eukaryotic translation initiation factor 3 subunit E binds to classical swine fever virus NS5A and facilitates viral replication. Virology 2018; 515:11-20. [DOI: 10.1016/j.virol.2017.11.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 11/19/2017] [Accepted: 11/23/2017] [Indexed: 01/12/2023]
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11
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Valášek LS, Zeman J, Wagner S, Beznosková P, Pavlíková Z, Mohammad MP, Hronová V, Herrmannová A, Hashem Y, Gunišová S. Embraced by eIF3: structural and functional insights into the roles of eIF3 across the translation cycle. Nucleic Acids Res 2017; 45:10948-10968. [PMID: 28981723 PMCID: PMC5737393 DOI: 10.1093/nar/gkx805] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 08/31/2017] [Indexed: 12/31/2022] Open
Abstract
Protein synthesis is mediated via numerous molecules including the ribosome, mRNA, tRNAs, as well as translation initiation, elongation and release factors. Some of these factors play several roles throughout the entire process to ensure proper assembly of the preinitiation complex on the right mRNA, accurate selection of the initiation codon, errorless production of the encoded polypeptide and its proper termination. Perhaps, the most intriguing of these multitasking factors is the eukaryotic initiation factor eIF3. Recent evidence strongly suggests that this factor, which coordinates the progress of most of the initiation steps, does not come off the initiation complex upon subunit joining, but instead it remains bound to 80S ribosomes and gradually falls off during the first few elongation cycles to: (1) promote resumption of scanning on the same mRNA molecule for reinitiation downstream—in case of translation of upstream ORFs short enough to preserve eIF3 bound; or (2) come back during termination on long ORFs to fine tune its fidelity or, if signaled, promote programmed stop codon readthrough. Here, we unite recent structural views of the eIF3–40S complex and discus all known eIF3 roles to provide a broad picture of the eIF3’s impact on translational control in eukaryotic cells.
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Affiliation(s)
- Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Jakub Zeman
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Petra Beznosková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Zuzana Pavlíková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Mahabub Pasha Mohammad
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Vladislava Hronová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Yaser Hashem
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France
| | - Stanislava Gunišová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
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12
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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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13
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Shaikho S, Dobson CC, Naing T, Samanfar B, Moteshareie H, Hajikarimloo M, Golshani A, Holcik M. Elevated levels of ribosomal proteins eL36 and eL42 control expression of Hsp90 in rhabdomyosarcoma. ACTA ACUST UNITED AC 2016; 4:e1244395. [PMID: 28090422 DOI: 10.1080/21690731.2016.1244395] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2016] [Revised: 09/13/2016] [Accepted: 09/28/2016] [Indexed: 01/08/2023]
Abstract
Mammalian 90 kDa heat shock protein (Hsp90) is a ubiquitous molecular chaperone whose expression is selectively upregulated during stress, although the precise control mechanism of this increase is yet to be fully elucidated. We used polysome profiling to show that Hsp90α mRNA is selectively translated, while global translation is inhibited during heat stress. Furthermore, we have identified 2 ribosomal proteins, eL36 and eL42 that modulate Hsp90α expression under both normal and heat shock conditions. Importantly, we noted that expression of eL36 and eL42 is elevated in a panel of human rhabdomyosarcomas where it drives high expression of Hsp90 and modulates sensitivity of these cells to an Hsp90 inhibitor 17-AAG.
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Affiliation(s)
- Sarah Shaikho
- Molecular Biomedicine Program, Children's Hospital of Eastern Ontario Research Institute , Ottawa, Ontario, Canada
| | - Christine C Dobson
- Molecular Biomedicine Program, Children's Hospital of Eastern Ontario Research Institute , Ottawa, Ontario, Canada
| | - Thet Naing
- Molecular Biomedicine Program, Children's Hospital of Eastern Ontario Research Institute , Ottawa, Ontario, Canada
| | - Bahram Samanfar
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University , Ottawa, Ontario, Canada
| | - Houman Moteshareie
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University , Ottawa, Ontario, Canada
| | - Maryam Hajikarimloo
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University , Ottawa, Ontario, Canada
| | - Ashkan Golshani
- Department of Biology and Ottawa Institute of Systems Biology, Carleton University , Ottawa, Ontario, Canada
| | - Martin Holcik
- Molecular Biomedicine Program, Children's Hospital of Eastern Ontario Research Institute , Ottawa, Ontario, Canada
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14
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An N, Xiong Y, LaRue AC, Kraft AS, Cen B. Activation of Pim Kinases Is Sufficient to Promote Resistance to MET Small-Molecule Inhibitors. Cancer Res 2016; 75:5318-28. [PMID: 26670562 DOI: 10.1158/0008-5472.can-15-0544] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Mesenchymal-epithelial transition (MET) blockade offers a new targeted therapy particularly in those cancers with MET amplification. However, the efficacy and the duration of the response to MET inhibitors are limited by the emergence of drug resistance. Here, we report that resistance to small-molecule inhibitors of MET can arise from increased expression of the prosurvival Pim protein kinases. This resistance mechanism was documented in non-small cell lung cancer and gastric cancer cells with MET amplification. Inhibition of Pim kinases enhanced cell death triggered by short-term treatment with MET inhibitors. Pim kinases control the translation of antiapoptotic protein Bcl-2 at an internal ribosome entry site and this mechanism was identified as the basis for Pim-mediated resistance to MET inhibitors. Protein synthesis was increased in drug-resistant cells, secondary to a Pim-mediated increase in cap-independent translation. In cells rendered drug resistant by chronic treatment with MET inhibitors, genetic or pharmacologic inhibition of Pim kinases was sufficient to restore sensitivity in vitro and in vivo. Taken together, our results rationalize Pim inhibition as a strategy to augment responses and blunt acquired resistance to MET inhibitors in cancer.
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Affiliation(s)
- Ningfei An
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina. The Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina
| | - Ying Xiong
- The Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina. Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina
| | - Amanda C LaRue
- The Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina. Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, South Carolina. Research Services, Ralph H. Johnson Veterans Affairs Medical Center, Charleston, South Carolina
| | | | - Bo Cen
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina. The Hollings Cancer Center, Medical University of South Carolina, Charleston, South Carolina.
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15
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Desnoyers G, Frost LD, Courteau L, Wall ML, Lewis SM. Decreased eIF3e Expression Can Mediate Epithelial-to-Mesenchymal Transition through Activation of the TGFβ Signaling Pathway. Mol Cancer Res 2015; 13:1421-30. [PMID: 26056130 DOI: 10.1158/1541-7786.mcr-14-0645] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 05/22/2015] [Indexed: 11/16/2022]
Abstract
UNLABELLED The eIF3e protein is a component of the multisubunit eIF3 complex, which is essential for cap-dependent translation initiation. Decreased eIF3e expression is often observed in breast and lung cancer and has been shown to induce epithelial-to-mesenchymal transition (EMT) in breast epithelial cells by an unknown mechanism. Here, we study the effect of decreased eIF3e expression in lung epithelial cells by creating stable clones of lung epithelial cells (A549) that express an eIF3e-targeting shRNA. Our data indicate that decreased eIF3e expression in lung epithelial cells leads to EMT, as it does in breast epithelial cells. Importantly, we show that decreased eIF3e expression in both lung and breast epithelial cells leads to the overproduction of the TGFβ cytokine and that inhibition of TGFβ signaling can reverse eIF3e-regulated EMT in lung epithelial cells. In addition, we discovered that several mRNAs that encode important EMT regulators are translated by a cap-independent mechanism when eIF3e levels are reduced. These findings indicate that EMT mediated by a decrease in eIF3e expression may be a general phenomenon in epithelial cells and that it requires activation and maintenance of the TGFβ signaling pathway. IMPLICATIONS These results indicate that inhibition of TGFβ signaling could be an efficient way to prevent metastasis in patients with NSCLC that display reduced eIF3e expression.
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Affiliation(s)
- Guillaume Desnoyers
- Atlantic Cancer Research Institute, Moncton, New Brunswick, Canada. Department of Biology, University of New Brunswick, Saint John, New Brunswick, Canada
| | - Laura D Frost
- Atlantic Cancer Research Institute, Moncton, New Brunswick, Canada
| | - Lynn Courteau
- Atlantic Cancer Research Institute, Moncton, New Brunswick, Canada
| | - Michael L Wall
- Atlantic Cancer Research Institute, Moncton, New Brunswick, Canada
| | - Stephen M Lewis
- Atlantic Cancer Research Institute, Moncton, New Brunswick, Canada. Department of Biology, University of New Brunswick, Saint John, New Brunswick, Canada. Department of Microbiology and Immunology, Dalhousie University, Halifax, Nova Scotia, Canada. Department of Chemistry and Biochemistry, Université de Moncton, Moncton, New Brunswick, Canada.
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16
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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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17
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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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18
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Decreased eIF3e/Int6 expression causes epithelial-to-mesenchymal transition in breast epithelial cells. Oncogene 2012; 32:3598-605. [PMID: 22907435 DOI: 10.1038/onc.2012.371] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 06/19/2012] [Accepted: 07/09/2012] [Indexed: 02/07/2023]
Abstract
eIF3e/Int6 is a component of the multi-subunit eIF3 complex, which binds directly to the 40S ribosome to facilitate ribosome recruitment to mRNA and hence protein synthesis. Reduced expression of eIF3e/Int6 has been found in up to 37% of human breast cancers, and expression of a truncated mutant version of the mouse eIF3e/Int6 protein leads to malignant transformation of normal mammary cells. These findings suggest that eIF3e/Int6 is a tumor suppressor; however, a recent study has reported that a reduction of eIF3e/Int6 expression in breast cancer cells leads to reduced translation of oncogenes, suggesting that eIF3e/Int6 may in fact have an oncogenic role in breast cancer. To gain a better understanding of the role of eIF3e/Int6 in breast cancer, we have examined the effects of decreased eIF3e/Int6 expression in an immortalized breast epithelial cell line, MCF-10A. Surprisingly, we find that decreased expression of eIF3e/Int6 causes breast epithelial cells to undergo epithelial-to-mesenchymal transition (EMT). We show that EMT induced by a decrease in eIF3e/Int6 expression imparts invasive and migratory properties to breast epithelial cells, suggesting that regulation of EMT by eIF3e/Int6 may have an important role in breast cancer metastasis. Furthermore, we show that reduced eIF3e/Int6 expression in breast epithelial cells causes a specific increase in the expression of the key EMT regulators Snail1 and Zeb2, which occurs at both the transcriptional and post-transcriptional levels. Together, our data indicate a novel role of eIF3e/Int6 in the regulation of EMT in breast epithelial cells and support a tumor suppressor role of eIF3e/Int6.
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Grzmil M, Hemmings BA. Translation Regulation as a Therapeutic Target in Cancer: Figure 1. Cancer Res 2012; 72:3891-900. [DOI: 10.1158/0008-5472.can-12-0026] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Tumor suppressor PDCD4 represses internal ribosome entry site-mediated translation of antiapoptotic proteins and is regulated by S6 kinase 2. Mol Cell Biol 2012; 32:1818-29. [PMID: 22431522 DOI: 10.1128/mcb.06317-11] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Apoptosis can be regulated by extracellular signals that are communicated by peptides such as fibroblast growth factor 2 (FGF-2) that have important roles in tumor cell proliferation. The prosurvival effects of FGF-2 are transduced by the activation of the ribosomal protein S6 kinase 2 (S6K2), which increases the expression of the antiapoptotic proteins X chromosome-linked Inhibitor of Apoptosis (XIAP) and Bcl-x(L). We now show that the FGF-2-S6K2 prosurvival signaling is mediated by the tumor suppressor programmed cell death 4 (PDCD4). We demonstrate that PDCD4 specifically binds to the internal ribosome entry site (IRES) elements of both the XIAP and Bcl-x(L) messenger RNAs and represses their translation by inhibiting the formation of the 48S translation initiation complex. Phosphorylation of PDCD4 by activated S6K2 leads to the degradation of PDCD4 and thus the subsequent derepression of XIAP and Bcl-x(L) translation. Our results identify PDCD4 as a specific repressor of the IRES-dependent translation of cellular mRNAs (such as XIAP and Bcl-x(L)) that mediate FGF-2-S6K2 prosurvival signaling and provide further insight into the role of PDCD4 in tumor suppression.
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21
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Denovan-Wright EM, Currie RW. The silence of the limbs. Cardiovasc Res 2011; 92:185-6. [DOI: 10.1093/cvr/cvr248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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