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Scudero OB, Santiago VF, Palmisano G, Simabuco FM, Ventura AM. The respiratory syncytial virus M2-2 protein is targeted for proteasome degradation and inhibits translation and stress granules assembly. PLoS One 2023; 18:e0289100. [PMID: 37490507 PMCID: PMC10368288 DOI: 10.1371/journal.pone.0289100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 07/12/2023] [Indexed: 07/27/2023] Open
Abstract
The M2-2 protein from the respiratory syncytial virus (RSV) is a 10 kDa protein expressed by the second ORF of the viral gene M2. During infection, M2-2 has been described as the polymerase cofactor responsible for promoting genome replication, which occurs by the induction of changes in interactions between the polymerase and other viral proteins at early stages of infection. Despite its well-explored role in the regulation of the polymerase activity, little has been made to investigate the relationship of M2-2 with cellular proteins. A previous report showed poor recruitment of M2-2 to viral structures, with the protein being mainly localized to the nucleus and cytoplasmic granules. To unravel which other functions M2-2 exerts during infection, we performed proteomic analysis of co-immunoprecipitated cellular partners, identifying enrichment of proteins involved with regulation of translation, protein folding and mRNA splicing. In approaches based on these data, we found that M2-2 expression downregulates eiF2α phosphorylation and inhibits both translation and stress granules assembly. Finally, we also verified that M2-2 is targeted for proteasome degradation, being localized to granules composed of defective ribosomal products at the cytoplasm. These results suggest that besides its functions in the replicative complex, M2-2 may exert additional functions to contribute to successful RSV infection.
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Affiliation(s)
- Orlando Bonito Scudero
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Verônica Feijoli Santiago
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Giuseppe Palmisano
- Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Fernando Moreira Simabuco
- Multidisciplinary Laboratory of Food and Health, School of Applied Sciences, University of Campinas, Limeira, São Paulo, Brazil
- Department of Biochemistry, Federal University of São Paulo, São Paulo, SP, Brazil
| | - Armando Morais Ventura
- Department of Microbiology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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Li Z, Ge Y, Dong J, Wang H, Zhao T, Wang X, Liu J, Gao S, Shi L, Yang S, Huang C, Hao J. BZW1 Facilitates Glycolysis and Promotes Tumor Growth in Pancreatic Ductal Adenocarcinoma Through Potentiating eIF2α Phosphorylation. Gastroenterology 2022; 162:1256-1271.e14. [PMID: 34951995 PMCID: PMC9436032 DOI: 10.1053/j.gastro.2021.12.249] [Citation(s) in RCA: 32] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 11/23/2021] [Accepted: 12/16/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND & AIMS Pancreatic ductal adenocarcinoma (PDAC) is characterized by severe metabolic stress due to fibrosis and poor vascularization. BZW1 is an eIF5-mimic protein involved in tumorigenesis and progression. The aim of this study was to investigate the role of BZW1 in metabolic stress resistance in PDAC. METHODS BZW1 expression was evaluated in human PDAC tissue microarray and PDAC cells. Glycolysis regulation of BZW1 and its correlation with glycolysis-related genes was analyzed. Tumor growth, cell proliferation, and apoptosis were evaluated in mice xenograft tumors and patient-derived organoids. RESULTS The results of bioinformatic screening identified that BZW1 was 1 of the top 3 genes favorable for tumor progression in PDAC. The analysis of our cohort confirmed that BZW1 was overexpressed in human PDAC tissues compared with nontumor tissues, and its abnormal expression was correlated with large tumor size and poor prognosis. BZW1 promoted cell proliferation and inhibited apoptosis in both mouse xenograft models and PDAC-derived organoids via facilitating glycolysis in the oxygen-glucose-deprivation condition. Mechanically, BZW1 served as an adaptor for PKR-like endoplasmic reticulum (ER) kinase (PERK), facilitated the phosphorylation of eIF2α, promoted internal ribosome entry site-dependent translation of HIF1α and c-Myc, and thereby boosted the Warburg effect. In organoid-based xenografts with high BZW1 levels, both the PERK/eIF2α phosphorylation inhibitor GSK2606414 and ISRIB significantly suppressed tumor growth and prolonged animal survival. CONCLUSIONS BZW1 is a key molecule in the internal ribosome entry site-dependent translation of HIF1α/c-Myc and plays crucial roles in the glycolysis of PDAC. BZW1 might serve as a therapeutic target for patients with pancreatic cancer.
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Affiliation(s)
- Zengxun Li
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Yi Ge
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Jie Dong
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Hongwei Wang
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Tiansuo Zhao
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Xiuchao Wang
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Jing Liu
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Song Gao
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China
| | - Lei Shi
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China
| | - Shengyu Yang
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Chongbiao Huang
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China.
| | - Jihui Hao
- Department of Pancreatic Cancer, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, China.
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Reprogramming translation for gene therapy. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2021; 182:439-476. [PMID: 34175050 DOI: 10.1016/bs.pmbts.2021.01.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Translational control plays a fundamental role in the regulation of gene expression in eukaryotes. Modulating translational efficiency allows the cell to fine-tune the expression of genes, spatially control protein localization, and trigger fast responses to environmental stresses. Translational regulation involves mechanisms acting on multiple steps of the protein synthesis pathway: initiation, elongation, and termination. Many cis-acting elements present in the 5' UTR of transcripts can influence translation at the initiation step. Among them, the Kozak sequence impacts translational efficiency by regulating the recognition of the start codon; upstream open reading frames (uORFs) are associated with inhibition of translation of the downstream protein; internal ribosomal entry sites (IRESs) can promote cap-independent translation. CRISPR-Cas technology is a revolutionary gene-editing tool that has also been applied to the regulation of gene expression. In this chapter, we focus on the genome editing approaches developed to modulate the translational efficiency with the aim to find novel therapeutic approaches, in particular acting on the cis-elements, that regulate the initiation of protein synthesis.
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Yadav KK, Boley PA, Fritts Z, Kenney SP. Ectopic Expression of Genotype 1 Hepatitis E Virus ORF4 Increases Genotype 3 HEV Viral Replication in Cell Culture. Viruses 2021; 13:v13010075. [PMID: 33430442 PMCID: PMC7827316 DOI: 10.3390/v13010075] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 01/05/2021] [Accepted: 01/05/2021] [Indexed: 02/07/2023] Open
Abstract
Hepatitis E virus (HEV) can account for up to a 30% mortality rate in pregnant women, with highest incidences reported for genotype 1 (gt1) HEV. Reasons contributing to adverse maternal-fetal outcome during pregnancy in HEV-infected pregnant women remain elusive in part due to the lack of a robust tissue culture model for some strains. Open reading frame (ORF4) was discovered overlapping ORF1 in gt1 HEV whose protein expression is regulated via an IRES-like RNA element. To experimentally determine whether gt3 HEV contains an ORF4-like gt1, gt1 and gt3 sequence comparisons were performed between the gt1 and the homologous gt3 sequence. To assess whether ORF4 protein could enhance gt3 replication, Huh7 cell lines constitutively expressing ORF4 were created and used to assess the replication of the Kernow-C1 gt3 and sar55 gt1 HEV. Virus stocks from transfected Huh7 cells with or without ORF4 were harvested and infectivity assessed via infection of HepG2/C3A cells. We also studied the replication of gt1 HEV in the ORF4-expressing tunicamycin-treated cell line. To directly show that HEV transcripts have productively replicated in the target cells, we assessed events at the single-cell level using indirect immunofluorescence and flow cytometry. Despite not naturally encoding ORF4, replication of gt3 HEV was enhanced by the presence of gt1 ORF4 protein. These results suggest that the function of ORF4 protein from gt1 HEV is transferrable, enhancing the replication of gt3 HEV. ORF4 may be utilized to enhance replication of difficult to propagate HEV genotypes in cell culture. IMPORTANCE: HEV is a leading cause of acute viral hepatitis (AVH) around the world. The virus is a threat to pregnant women, particularly during the second and third trimester of pregnancy. The factors enhancing virulence to pregnant populations are understudied. Additionally, field strains of HEV remain difficult to culture in vitro. ORF4 was recently discovered in gt1 HEV and is purported to play a role in pregnancy related pathology and enhanced replication. We present evidence that ORF4 protein provided in trans enhances the viral replication of gt3 HEV even though it does not encode ORF4 naturally in its genome. These data will aid in the development of cell lines capable of supporting replication of non-cell culture adapted HEV field strains, allowing viral titers sufficient for studying these strains in vitro. Furthermore, development of gt1/gt3 ORF4 chimeric virus may shed light on the role that ORF4 plays during pregnancy.
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Affiliation(s)
- Kush K. Yadav
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, OH 44691, USA; (K.K.Y.); (P.A.B.)
| | - Patricia A. Boley
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, OH 44691, USA; (K.K.Y.); (P.A.B.)
| | - Zachary Fritts
- Department of Electrical and Computer Engineering, University of Michigan, Ann Arbor, MI 48105, USA;
| | - Scott P. Kenney
- Food Animal Health Research Program, Ohio Agricultural Research and Development Center (OARDC), The Ohio State University, Wooster, OH 44691, USA; (K.K.Y.); (P.A.B.)
- Correspondence:
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Jeong SG, Ohn T, Jang CH, Vijayakumar K, Cho GW. The Role of Stress Granules in the Neuronal Differentiation of Stem Cells. Mol Cells 2020; 43:848-855. [PMID: 33028745 PMCID: PMC7604023 DOI: 10.14348/molcells.2020.0135] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 09/07/2020] [Accepted: 09/10/2020] [Indexed: 02/07/2023] Open
Abstract
creativecommons.org/licenses/by-nc-sa/3.0/. Cells assemble stress granules (SGs) to protect their RNAs from exposure to harmful chemical reactions induced by environmental stress. These SGs release RNAs, which resume translation once the stress is relieved. During stem cell differentiation, gene expression is altered to allow cells to adopt various functional and morphological features necessary to differentiate. This process induces stress within a cell, and cells that cannot overcome this stress die. Here, we investigated the role of SGs in the progression of stem cell differentiation. SGs aggregated during the neuronal differentiation of human bone marrow-mesenchymal stem cells, and not in cell lines that could not undergo differentiation. SGs were observed between one and three hours post-induction; RNA translation was restrained at the same time. Immediately after disassembly of SGs, the expression of the neuronal marker neurofilament-M (NFM) gradually increased. Assembled SGs that persisted in cells were exposed to salubrinal, which inhibited the dephosphorylation of eukaryotic translation initiation factor 2 subunit 1 (eIF2α), and in eIF2α/S51D mutant cells. When eIF2α/S51A mutant cells differentiated, SGs were not assembled. In all experiments, the disruption of SGs was accompanied by delayed NF-M expression and the number of neuronally differentiated cells was decreased. Decreased differentiation was accompanied by decreased cell viability, indicating the necessity of SGs for preventing cell death during neuronal differentiation. Collectively, these results demonstrate the essential role of SGs during the neuronal differentiation of stem cells.
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Affiliation(s)
- Sin-Gu Jeong
- Department of Biology, College of Natural Science, Chosun University, Gwangju 61452, Korea
- Department of Integrative Biological Science, BK21 FOUR Education Research Group for Age-Associated Disorder Control Technology, Chosun University, Gwangju 61452, Korea
- Department of Bio Research & Business Development, Biot Korea Inc., Gwangju 61001, Korea
| | - Takbum Ohn
- Department of Cellular & Molecular Medicine, College of Medicine, Chosun University, Gwangju 61452, Korea
| | - Chul Ho Jang
- Department of Otolaryngology, Chonnam National University Medical School, Gwangju 61469, Korea
| | - Karthikeyan Vijayakumar
- Department of Biology, College of Natural Science, Chosun University, Gwangju 61452, Korea
- Department of Integrative Biological Science, BK21 FOUR Education Research Group for Age-Associated Disorder Control Technology, Chosun University, Gwangju 61452, Korea
| | - Gwang-Won Cho
- Department of Biology, College of Natural Science, Chosun University, Gwangju 61452, Korea
- Department of Integrative Biological Science, BK21 FOUR Education Research Group for Age-Associated Disorder Control Technology, Chosun University, Gwangju 61452, Korea
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Akhbari P, Richardson SJ, Morgan NG. Type 1 Diabetes: Interferons and the Aftermath of Pancreatic Beta-Cell Enteroviral Infection. Microorganisms 2020; 8:microorganisms8091419. [PMID: 32942706 PMCID: PMC7565444 DOI: 10.3390/microorganisms8091419] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 09/09/2020] [Accepted: 09/11/2020] [Indexed: 02/07/2023] Open
Abstract
Enteroviruses (EVs) have long been implicated in the pathogenesis of type 1 diabetes (T1D), and accumulating evidence has associated virus-induced autoimmunity with the loss of pancreatic beta cells in T1D. Inflammatory cytokines including interferons (IFN) form a primary line of defence against viral infections, and their chronic elevation is a hallmark feature of many autoimmune diseases. IFNs play a key role in activating and regulating innate and adaptive immune responses, and to do so they modulate the expression of networks of genes and transcription factors known generically as IFN stimulated genes (ISGs). ISGs in turn modulate critical cellular processes ranging from cellular metabolism and growth regulation to endoplasmic reticulum (ER) stress and apoptosis. More recent studies have revealed that IFNs also modulate gene expression at an epigenetic as well as post-transcriptional and post-translational levels. As such, IFNs form a key link connecting the various genetic, environmental and immunological factors involved in the initiation and progression of T1D. Therefore, gaining an improved understanding of the mechanisms by which IFNs modulate beta cell function and survival is crucial in explaining the pathogenesis of virally-induced T1D. This should provide the means to prevent, decelerate or even reverse beta cell impairment.
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Piazzi M, Bavelloni A, Faenza I, Blalock W. Glycogen synthase kinase (GSK)-3 and the double-strand RNA-dependent kinase, PKR: When two kinases for the common good turn bad. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118769. [PMID: 32512016 PMCID: PMC7273171 DOI: 10.1016/j.bbamcr.2020.118769] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 05/29/2020] [Accepted: 05/31/2020] [Indexed: 01/08/2023]
Abstract
Glycogen synthase kinase (GSK)-3α/β and the double-stranded RNA-dependent kinase PKR are two sentinel kinases that carry-out multiple similar yet distinct functions in both the cytosol and the nucleus. While these kinases belong to separate signal transduction cascades, they demonstrate an uncanny propensity to regulate many of the same proteins either through direct phosphorylation or by altering transcription/translation, including: c-MYC, NF-κB, p53 and TAU, as well as each another. A significant number of studies centered on the GSK3 kinases have led to the identification of the GSK3 interactome and a number of substrates, which link GSK3 activity to metabolic control, translation, RNA splicing, ribosome biogenesis, cellular division, DNA repair and stress/inflammatory signaling. Interestingly, many of these same pathways and processes are controlled by PKR, but unlike the GSK3 kinases, a clear picture of proteins interacting with PKR and a complete listing of its substrates is still missing. In this review, we take a detailed look at what is known about the PKR and GSK3 kinases, how these kinases interact to influence common cellular processes (innate immunity, alternative splicing, translation, glucose metabolism) and how aberrant activation of these kinases leads to diseases such as Alzheimer's disease (AD), diabetes mellitus (DM) and cancer. GSK3α/β and PKR are major regulators of cellular homeostasis and the response to stress/inflammation and infection. GSK3α/β and PKR interact with and/or modify many of the same proteins and affect the expression of similar genes. A balance between AKT and PKR nuclear signaling may be responsible for regulating the activation of nuclear GSK3β. GSK3α/β- and PKR-dependent signaling influence major molecular mechanisms of the cell through similar intermediates. Aberrant activation of GSK3α/β and PKR is highly involved in cancer, metabolic disorders, and neurodegenerative diseases.
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Affiliation(s)
- Manuela Piazzi
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", Consiglio Nazionale delle Ricerche (IGM-CNR), Bologna, Italy; IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Alberto Bavelloni
- Laboratoria di Oncologia Sperimentale, IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy
| | - Irene Faenza
- Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, Bologna, Italy
| | - William Blalock
- Istituto di Genetica Molecolare "Luigi Luca Cavalli-Sforza", Consiglio Nazionale delle Ricerche (IGM-CNR), Bologna, Italy; IRCCS, Istituto Ortopedico Rizzoli, Bologna, Italy.
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Jaud M, Philippe C, Di Bella D, Tang W, Pyronnet S, Laurell H, Mazzolini L, Rouault-Pierre K, Touriol C. Translational Regulations in Response to Endoplasmic Reticulum Stress in Cancers. Cells 2020; 9:cells9030540. [PMID: 32111004 PMCID: PMC7140484 DOI: 10.3390/cells9030540] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/18/2020] [Accepted: 02/24/2020] [Indexed: 12/20/2022] Open
Abstract
During carcinogenesis, almost all the biological processes are modified in one way or another. Among these biological processes affected, anomalies in protein synthesis are common in cancers. Indeed, cancer cells are subjected to a wide range of stresses, which include physical injuries, hypoxia, nutrient starvation, as well as mitotic, oxidative or genotoxic stresses. All of these stresses will cause the accumulation of unfolded proteins in the Endoplasmic Reticulum (ER), which is a major organelle that is involved in protein synthesis, preservation of cellular homeostasis, and adaptation to unfavourable environment. The accumulation of unfolded proteins in the endoplasmic reticulum causes stress triggering an unfolded protein response in order to promote cell survival or to induce apoptosis in case of chronic stress. Transcription and also translational reprogramming are tightly controlled during the unfolded protein response to ensure selective gene expression. The majority of stresses, including ER stress, induce firstly a decrease in global protein synthesis accompanied by the induction of alternative mechanisms for initiating the translation of mRNA, later followed by a translational recovery. After a presentation of ER stress and the UPR response, we will briefly present the different modes of translation initiation, then address the specific translational regulatory mechanisms acting during reticulum stress in cancers and highlight the importance of translational control by ER stress in tumours.
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Affiliation(s)
- Manon Jaud
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
| | - Céline Philippe
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Doriana Di Bella
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Weiwei Tang
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Stéphane Pyronnet
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
| | - Henrik Laurell
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
- Inserm UMR1048, I2MC (Institut des Maladies Métaboliques et Cardiovasculaires), BP 84225, CEDEX 04, 31 432 Toulouse, France
| | - Laurent Mazzolini
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- CNRS ERL5294, CRCT, F-31037 Toulouse, France
| | - Kevin Rouault-Pierre
- Barts Cancer Institute, Queen Mary University of London, London E1 4NS, UK; (C.P.); (D.D.B.); (W.T.); (K.R.-P.)
| | - Christian Touriol
- Inserm UMR1037, CRCT (Cancer Research Center of Toulouse), F-31037 Toulouse, France; (M.J.); (S.P.); (L.M.)
- Université Toulouse III Paul-Sabatier, F-31000 Toulouse, France;
- Correspondence:
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Anda S, Grallert B. Cell-Cycle-Dependent Regulation of Translation: New Interpretations of Old Observations in Light of New Approaches. Bioessays 2019; 41:e1900022. [PMID: 31210378 DOI: 10.1002/bies.201900022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 04/29/2019] [Indexed: 12/22/2022]
Abstract
It is a long-standing view that global translation varies during the cell cycle and is much lower in mitosis than in other cell-cycle phases. However, the central papers in the literature are not in agreement about the extent of downregulation in mitosis, ranging from a dramatic decrease to only a marginal reduction. Herein, it is argued that the discrepancy derives from technical challenges. Cell-cycle-dependent variations are most conveniently studied in synchronized cells, but the synchronization methods by themselves often evoke stress responses that, in turn, affect translation rates. Further, it is argued that previously reported cell-cycle-dependent changes in the global translation rate to a large extent reflect responses to the synchronization methods. Recent findings strongly suggest that the global translation rate is not regulated in a cell-cycle-dependent manner. Novel techniques allowing a genome-wide analysis of translational profiles suggest that the extent and importance of selective translational regulation associated with cell-cycle transitions have been underestimated. Therefore, the main question is which messenger RNAs (mRNAs) are translated, rather than whether the global translation rate is decreased.
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Affiliation(s)
- Silje Anda
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, 0379, Oslo, Norway
| | - Beáta Grallert
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, 0379, Oslo, Norway
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Piazzi M, Bavelloni A, Gallo A, Faenza I, Blalock WL. Signal Transduction in Ribosome Biogenesis: A Recipe to Avoid Disaster. Int J Mol Sci 2019; 20:ijms20112718. [PMID: 31163577 PMCID: PMC6600399 DOI: 10.3390/ijms20112718] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 05/29/2019] [Accepted: 05/30/2019] [Indexed: 12/27/2022] Open
Abstract
Energetically speaking, ribosome biogenesis is by far the most costly process of the cell and, therefore, must be highly regulated in order to avoid unnecessary energy expenditure. Not only must ribosomal RNA (rRNA) synthesis, ribosomal protein (RP) transcription, translation, and nuclear import, as well as ribosome assembly, be tightly controlled, these events must be coordinated with other cellular events, such as cell division and differentiation. In addition, ribosome biogenesis must respond rapidly to environmental cues mediated by internal and cell surface receptors, or stress (oxidative stress, DNA damage, amino acid depletion, etc.). This review examines some of the well-studied pathways known to control ribosome biogenesis (PI3K-AKT-mTOR, RB-p53, MYC) and how they may interact with some of the less well studied pathways (eIF2α kinase and RNA editing/splicing) in higher eukaryotes to regulate ribosome biogenesis, assembly, and protein translation in a dynamic manner.
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Affiliation(s)
- Manuela Piazzi
- Istituto di Genetica Molecolare-Luigi Luca Cavalli Sforza, UOS Bologna, Consiglio Nazionale delle Ricerche (IGM-CNR), 40136 Bologna, Italy.
- IRCCS, Istituto Ortopedico Rizzoli, 40136 Bologna, Italy.
| | | | - Angela Gallo
- RNA Editing Laboratory, Dipartimento di Oncoematologia, IRCCS, Ospedale Pediatrica Bambino Gesù, 00146 Rome, Italy.
| | - Irene Faenza
- Dipartimento di Scienze Biomediche e Neuromotorie, Università di Bologna, 40126 Bologna, Italy.
| | - William L Blalock
- Istituto di Genetica Molecolare-Luigi Luca Cavalli Sforza, UOS Bologna, Consiglio Nazionale delle Ricerche (IGM-CNR), 40136 Bologna, Italy.
- IRCCS, Istituto Ortopedico Rizzoli, 40136 Bologna, Italy.
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Pereira IT, Spangenberg L, Robert AW, Amorín R, Stimamiglio MA, Naya H, Dallagiovanna B. Cardiomyogenic differentiation is fine-tuned by differential mRNA association with polysomes. BMC Genomics 2019; 20:219. [PMID: 30876407 PMCID: PMC6420765 DOI: 10.1186/s12864-019-5550-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 02/20/2019] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND Cardiac cell fate specification occurs through progressive steps, and its gene expression regulation features are still being defined. There has been an increasing interest in understanding the coordination between transcription and post-transcriptional regulation during the differentiation processes. Here, we took advantage of the polysome profiling technique to isolate and high-throughput sequence ribosome-free and polysome-bound RNAs during cardiomyogenesis. RESULTS We showed that polysome-bound RNAs exhibit the cardiomyogenic commitment gene expression and that mesoderm-to-cardiac progenitor stages are strongly regulated. Additionally, we compared ribosome-free and polysome-bound RNAs and found that the post-transcriptional regulation vastly contributes to cardiac phenotype determination, including RNA recruitment to and dissociation from ribosomes. Moreover, we found that protein synthesis is decreased in cardiomyocytes compared to human embryonic stem-cells (hESCs), possibly due to the down-regulation of translation-related genes. CONCLUSIONS Our data provided a powerful tool to investigate genes potentially controlled by post-transcriptional mechanisms during the cardiac differentiation of hESC. This work could prospect fundamental tools to develop new therapy and research approaches.
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Affiliation(s)
- Isabela Tiemy Pereira
- Basic Stem-cell Biology Laboratory, Instituto Carlos Chagas - FIOCRUZ-PR, Rua Professor Algacyr Munhoz Mader, 3775, Curitiba, PR, 81.350-010, Brazil
| | - Lucia Spangenberg
- Bioinformatics Unit, Institut Pasteur de Montevideo, Mataojo 2020, 11400, Montevideo, Uruguay
| | - Anny Waloski Robert
- Basic Stem-cell Biology Laboratory, Instituto Carlos Chagas - FIOCRUZ-PR, Rua Professor Algacyr Munhoz Mader, 3775, Curitiba, PR, 81.350-010, Brazil
| | - Rocío Amorín
- Bioinformatics Unit, Institut Pasteur de Montevideo, Mataojo 2020, 11400, Montevideo, Uruguay
| | - Marco Augusto Stimamiglio
- Basic Stem-cell Biology Laboratory, Instituto Carlos Chagas - FIOCRUZ-PR, Rua Professor Algacyr Munhoz Mader, 3775, Curitiba, PR, 81.350-010, Brazil
| | - Hugo Naya
- Bioinformatics Unit, Institut Pasteur de Montevideo, Mataojo 2020, 11400, Montevideo, Uruguay
| | - Bruno Dallagiovanna
- Basic Stem-cell Biology Laboratory, Instituto Carlos Chagas - FIOCRUZ-PR, Rua Professor Algacyr Munhoz Mader, 3775, Curitiba, PR, 81.350-010, Brazil.
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12
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Colli ML, Paula FM, Marselli L, Marchetti P, Roivainen M, Eizirik DL, Op de Beeck A. Coxsackievirus B Tailors the Unfolded Protein Response to Favour Viral Amplification in Pancreatic β Cells. J Innate Immun 2019; 11:375-390. [PMID: 30799417 DOI: 10.1159/000496034] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 12/03/2018] [Indexed: 12/15/2022] Open
Abstract
Type 1 diabetes (T1D) is an autoimmune disease characterized by islet inflammation and progressive pancreatic β cell destruction. The disease is triggered by a combination of genetic and environmental factors, but the mechanisms leading to the triggering of early innate and late adaptive immunity and consequent progressive pancreatic β cell death remain unclear. The insulin-producing β cells are active secretory cells and are thus particularly sensitive to endoplasmic reticulum (ER) stress. ER stress plays an important role in the pathologic pathway leading to autoimmunity, islet inflammation, and β cell death. We show here that group B coxsackievirus (CVB) infection, a putative causative factor for T1D, induces a partial ER stress in rat and human β cells. The activation of the PERK/ATF4/CHOP branch is blunted while the IRE1α branch leads to increased spliced XBP1 expression and c-Jun N-terminal kinase (JNK) activation. Interestingly, JNK1 activation is essential for CVB amplification in both human and rat β cells. Furthermore, a chemically induced ER stress preceding viral infection increases viral replication, in a process dependent on IRE1α activation. Our findings show that CVB tailors the unfolded protein response in β cells to support their replication, preferentially triggering the pro-viral IRE1α/XBP1s/JNK1 pathway while blocking the pro-apoptotic PERK/ATF4/CHOP pathway.
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Affiliation(s)
- Maikel L Colli
- ULB Center for Diabetes Research, Université Libre de Bruxelles, Brussels, Belgium
| | - Flavia M Paula
- ULB Center for Diabetes Research, Université Libre de Bruxelles, Brussels, Belgium
| | - Lorella Marselli
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Piero Marchetti
- Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Merja Roivainen
- Viral Infections Unit, Department of Infectious Disease, National Institute for Health and Welfare, Helsinki, Finland
| | - Decio L Eizirik
- ULB Center for Diabetes Research, Université Libre de Bruxelles, Brussels, Belgium
| | - Anne Op de Beeck
- ULB Center for Diabetes Research, Université Libre de Bruxelles, Brussels, Belgium,
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13
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Zhou ZD, Selvaratnam T, Lee JCT, Chao YX, Tan EK. Molecular targets for modulating the protein translation vital to proteostasis and neuron degeneration in Parkinson's disease. Transl Neurodegener 2019; 8:6. [PMID: 30740222 PMCID: PMC6360798 DOI: 10.1186/s40035-019-0145-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2018] [Accepted: 01/14/2019] [Indexed: 12/13/2022] Open
Abstract
Parkinson's disease (PD) is the most common neurodegenerative movement disorder, which is characterized by the progressive loss of dopaminergic neurons in the Substantia Nigra pars compacta concomitant with Lewy body formation in affected brain areas. The detailed pathogenic mechanisms underlying the selective loss of dopaminergic neurons in PD are unclear, and no drugs or treatments have been developed to alleviate progressive dopaminergic neuron degeneration in PD. However, the formation of α-synuclein-positive protein aggregates in Lewy body has been identified as a common pathological feature of PD, possibly stemming from the consequence of protein misfolding and dysfunctional proteostasis. Proteostasis is the mechanism for maintaining protein homeostasis via modulation of protein translation, enhancement of chaperone capacity and the prompt clearance of misfolded protein by the ubiquitin proteasome system and autophagy. Deregulated protein translation and impaired capacities of chaperone or protein degradation can disturb proteostasis processes, leading to pathological protein aggregation and neurodegeneration in PD. In recent years, multiple molecular targets in the modulation of protein translation vital to proteostasis and dopaminergic neuron degeneration have been identified. The potential pathophysiological and therapeutic significance of these molecular targets to neurodegeneration in PD is highlighted.
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Affiliation(s)
- Zhi Dong Zhou
- 1Department of Research, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433 Singapore.,3Signature Research Program in Neuroscience and Behavioural Disorders, Duke-NUS Medical School Singapore, 8 College Road, Singapore, Singapore
| | - Thevapriya Selvaratnam
- 1Department of Research, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433 Singapore
| | - Ji Chao Tristan Lee
- 1Department of Research, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433 Singapore
| | - Yin Xia Chao
- 1Department of Research, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433 Singapore
| | - Eng-King Tan
- 1Department of Research, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore, 308433 Singapore.,2Department of Neurology, Singapore General Hospital, Outram Road, Singapore, 169608 Singapore.,3Signature Research Program in Neuroscience and Behavioural Disorders, Duke-NUS Medical School Singapore, 8 College Road, Singapore, Singapore
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14
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Moore KS, von Lindern M. RNA Binding Proteins and Regulation of mRNA Translation in Erythropoiesis. Front Physiol 2018; 9:910. [PMID: 30087616 PMCID: PMC6066521 DOI: 10.3389/fphys.2018.00910] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Accepted: 06/21/2018] [Indexed: 12/12/2022] Open
Abstract
Control of gene expression in erythropoiesis has to respond to signals that may emerge from intracellular processes or environmental factors. Control of mRNA translation allows for relatively rapid modulation of protein synthesis from the existing transcriptome. For instance, the protein synthesis rate needs to be reduced when reactive oxygen species or unfolded proteins accumulate in the cells, but also when iron supply is low or when growth factors are lacking in the environment. In addition, regulation of mRNA translation can be important as an additional layer of control on top of gene transcription, in which RNA binding proteins (RBPs) can modify translation of a set of transcripts to the cell’s actual protein requirement. The 5′ and 3′ untranslated regions of mRNA (5′UTR, 3′UTR) contain binding sites for general and sequence specific translation factors. They also contain secondary structures that may hamper scanning of the 5′UTR by translation complexes or may help to recruit translation factors. In addition, the term 5′UTR is not fully correct because many transcripts contain small open reading frames in their 5′UTR that are translated and contribute to regulation of mRNA translation. It is becoming increasingly clear that the transcriptome only partly predicts the proteome. The aim of this review is (i) to summarize how the availability of general translation initiation factors can selectively regulate transcripts because the 5′UTR contains secondary structures or short translated sequences, (ii) to discuss mechanisms that control the length of the mRNA poly(A) tail in relation to mRNA translation, and (iii) to give examples of sequence specific RBPs and their targets. We focused on transcripts and RBPs required for erythropoiesis. Whereas differentiation of erythroblasts to erythrocytes is orchestrated by erythroid transcription factors, the production of erythrocytes needs to respond to the availability of growth factors and nutrients, particularly the availability of iron.
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Affiliation(s)
- Kat S Moore
- Department of Hematopoiesis, Sanquin Research, and Landsteiner Laboratory, Amsterdam UMC, Amsterdam, Netherlands
| | - Marieke von Lindern
- Department of Hematopoiesis, Sanquin Research, and Landsteiner Laboratory, Amsterdam UMC, Amsterdam, Netherlands
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15
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Marques-Ramos A, Candeias MM, Menezes J, Lacerda R, Willcocks M, Teixeira A, Locker N, Romão L. Cap-independent translation ensures mTOR expression and function upon protein synthesis inhibition. RNA (NEW YORK, N.Y.) 2017; 23:1712-1728. [PMID: 28821580 PMCID: PMC5648038 DOI: 10.1261/rna.063040.117] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 08/15/2017] [Indexed: 06/07/2023]
Abstract
The mechanistic/mammalian target of rapamycin (mTOR) is a conserved serine/threonine kinase that integrates cellular signals from the nutrient and energy status to act, namely, on the protein synthesis machinery. While major advances have emerged regarding the regulators and effects of the mTOR signaling pathway, little is known about the regulation of mTOR gene expression. Here, we show that the human mTOR transcript can be translated in a cap-independent manner, and that its 5' untranslated region (UTR) is a highly folded RNA scaffold capable of binding directly to the 40S ribosomal subunit. We further demonstrate that mTOR is able to bypass the cap requirement for translation both in normal and hypoxic conditions. Moreover, our data reveal that the cap-independent translation of mTOR is necessary for its ability to induce cell-cycle progression into S phase. These results suggest a novel regulatory mechanism for mTOR gene expression that integrates the global protein synthesis changes induced by translational inhibitory conditions.
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Affiliation(s)
- Ana Marques-Ramos
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Marco M Candeias
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Juliane Menezes
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Rafaela Lacerda
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Margaret Willcocks
- Microbial and Cellular Sciences Department, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7TE, United Kingdom
| | - Alexandre Teixeira
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
| | - Nicolas Locker
- Microbial and Cellular Sciences Department, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7TE, United Kingdom
| | - Luísa Romão
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
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16
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Anda S, Zach R, Grallert B. Activation of Gcn2 in response to different stresses. PLoS One 2017; 12:e0182143. [PMID: 28771613 PMCID: PMC5542535 DOI: 10.1371/journal.pone.0182143] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 07/12/2017] [Indexed: 12/12/2022] Open
Abstract
All organisms have evolved pathways to respond to different forms of cellular stress. The Gcn2 kinase is best known as a regulator of translation initiation in response to starvation for amino acids. Work in budding yeast has showed that the molecular mechanism of GCN2 activation involves the binding of uncharged tRNAs, which results in a conformational change and GCN2 activation. This pathway requires GCN1, which ensures delivery of the uncharged tRNA onto GCN2. However, Gcn2 is activated by a number of other stresses which do not obviously involve accumulation of uncharged tRNAs, raising the question how Gcn2 is activated under these conditions. Here we investigate the requirement for ongoing translation and tRNA binding for Gcn2 activation after different stresses in fission yeast. We find that mutating the tRNA-binding site on Gcn2 or deleting Gcn1 abolishes Gcn2 activation under all the investigated conditions. These results suggest that tRNA binding to Gcn2 is required for Gcn2 activation not only in response to starvation but also after UV irradiation and oxidative stress.
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Affiliation(s)
- Silje Anda
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Róbert Zach
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
| | - Beáta Grallert
- Department of Radiation Biology, Institute for Cancer Research, Oslo University Hospital, Oslo, Norway
- * E-mail:
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17
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Lacerda R, Menezes J, Romão L. More than just scanning: the importance of cap-independent mRNA translation initiation for cellular stress response and cancer. Cell Mol Life Sci 2017; 74:1659-1680. [PMID: 27913822 PMCID: PMC11107732 DOI: 10.1007/s00018-016-2428-2] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 11/24/2016] [Accepted: 11/29/2016] [Indexed: 12/11/2022]
Abstract
The scanning model for eukaryotic mRNA translation initiation states that the small ribosomal subunit, along with initiation factors, binds at the cap structure at the 5' end of the mRNA and scans the 5' untranslated region (5'UTR) until an initiation codon is found. However, under conditions that impair canonical cap-dependent translation, the synthesis of some proteins is kept by alternative mechanisms that are required for cell survival and stress recovery. Alternative modes of translation initiation include cap- and/or scanning-independent mechanisms of ribosomal recruitment. In most cap-independent translation initiation events there is a direct recruitment of the 40S ribosome into a position upstream, or directly at, the initiation codon via a specific internal ribosome entry site (IRES) element in the 5'UTR. Yet, in some cellular mRNAs, a different translation initiation mechanism that is neither cap- nor IRES-dependent seems to occur through a special RNA structure called cap-independent translational enhancer (CITE). Recent evidence uncovered a distinct mechanism through which mRNAs containing N 6-methyladenosine (m6A) residues in their 5'UTR directly bind eukaryotic initiation factor 3 (eIF3) and the 40S ribosomal subunit in order to initiate translation in the absence of the cap-binding proteins. This review focuses on the important role of cap-independent translation mechanisms in human cells and how these alternative mechanisms can either act individually or cooperate with other cis-acting RNA regulons to orchestrate specific translational responses triggered upon several cellular stress states, and diseases such as cancer. Elucidation of these non-canonical mechanisms reveals the complexity of translational control and points out their potential as prospective novel therapeutic targets.
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Affiliation(s)
- Rafaela Lacerda
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Av. Padre Cruz, 1649-016, Lisbon, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Juliane Menezes
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Av. Padre Cruz, 1649-016, Lisbon, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Luísa Romão
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Av. Padre Cruz, 1649-016, Lisbon, Portugal.
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.
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18
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Abstract
The past several years have seen dramatic leaps in our understanding of how gene expression is rewired at the translation level during tumorigenesis to support the transformed phenotype. This work has been driven by an explosion in technological advances and is revealing previously unimagined regulatory mechanisms that dictate functional expression of the cancer genome. In this Review we discuss emerging trends and exciting new discoveries that reveal how this translational circuitry contributes to specific aspects of tumorigenesis and cancer cell function, with a particular focus on recent insights into the role of translational control in the adaptive response to oncogenic stress conditions.
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Affiliation(s)
- Morgan L Truitt
- Department of Urology, University of California, San Francisco
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, California 94158, USA
| | - Davide Ruggero
- Department of Urology, University of California, San Francisco
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco
- Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, California 94158, USA
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19
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Enterovirus 71 induces dsRNA/PKR-dependent cytoplasmic redistribution of GRP78/BiP to promote viral replication. Emerg Microbes Infect 2016; 5:e23. [PMID: 27004760 PMCID: PMC4820672 DOI: 10.1038/emi.2016.20] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Revised: 11/19/2015] [Accepted: 11/23/2015] [Indexed: 12/16/2022]
Abstract
GRP78/BiP is an endoplasmic reticulum (ER) chaperone protein with the important function of maintaining ER homeostasis, and the overexpression of GRP78/BiP alleviates ER stress. Our previous studies showed that infection with enterovirus 71 (EV71), a (+)RNA picornavirus, induced GRP78/BiP upregulation; however, ectopic GRP78/BiP overexpression in ER downregulates virus replication and viral particle formation. The fact that a virus infection increases GRP78/BiP expression, which is unfavorable for virus replication, is counterintuitive. In this study, we found that the GRP78/BiP protein level was elevated in the cytoplasm instead of in the ER in EV71-infected cells. Cells transfected with polyinosinic-polycytidylic acid, a synthetic analog of replicative double-stranded RNA (dsRNA), but not with viral proteins, also exhibited upregulation and elevation of GRP78/BiP in the cytosol. Our results further demonstrate that EV71 infections induce the dsRNA/protein kinase R-dependent cytosolic accumulation of GRP78/BiP. The overexpression of a GRP78/BiP mutant lacking a KDEL retention signal failed to inhibit both dithiothreitol-induced eIF2α phosphorylation and viral replication in the context of viral protein synthesis and viral titers. These data revealed that EV71 infection might cause upregulation and aberrant redistribution of GRP78/BiP to the cytosol, thereby facilitating virus replication.
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20
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Vilas-Boas FDAS, da Silva AM, de Sousa LP, Lima KM, Vago JP, Bittencourt LFF, Dantas AE, Gomes DA, Vilela MC, Teixeira MM, Barcelos LS. Impairment of stress granule assembly via inhibition of the eIF2alpha phosphorylation sensitizes glioma cells to chemotherapeutic agents. J Neurooncol 2016; 127:253-60. [DOI: 10.1007/s11060-015-2043-3] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 12/25/2015] [Indexed: 12/16/2022]
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21
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Zhang C, Zhang M, Wu Q, Peng J, Ruan Y, Gu J. Hepsin inhibits CDK11p58 IRES activity by suppressing unr expression and eIF-2α phosphorylation in prostate cancer. Cell Signal 2015; 27:789-97. [PMID: 25576733 DOI: 10.1016/j.cellsig.2014.12.020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Accepted: 12/31/2014] [Indexed: 11/29/2022]
Abstract
Hepsin is a type II transmembrane serine protease frequently overexpressed in prostate cancer (PCa). However, the role of hepsin in PCa remains unclear. In this study, we found that hepsin inhibited the internal ribosome entry site (IRES) activity and expression of CDK11p58, which is associated with cell cycle progression and pro-apoptotic signaling in PCa. Hepsin suppressed CDK11p58 IRES activity in PCa by modulating unr expression and eIF-2α phosphorylation. Further studies revealed that hepsin inhibited the expression of unr by directly binding to unr IRES element and suppressing its activity, and also repressed eIF-2α phosphorylation through down-regulating the expression and phosphorylation of general control non-derepressible-2 (GCN2). Taken together, our data suggest a novel role of hepsin in regulating CDK11p58 IRES activity, and imply that hepsin may act on the machinery of translation to modulate cell cycle progression and survival in PCa cells.
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Affiliation(s)
- Chunyi Zhang
- Gene Research Center, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Mingming Zhang
- Gene Research Center, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Qingyu Wu
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
| | - Jianhao Peng
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA
| | - Yuanyuan Ruan
- Gene Research Center, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China.
| | - Jianxin Gu
- Gene Research Center, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
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22
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Jheng JR, Ho JY, Horng JT. ER stress, autophagy, and RNA viruses. Front Microbiol 2014; 5:388. [PMID: 25140166 PMCID: PMC4122171 DOI: 10.3389/fmicb.2014.00388] [Citation(s) in RCA: 162] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 07/11/2014] [Indexed: 12/19/2022] Open
Abstract
Endoplasmic reticulum (ER) stress is a general term for representing the pathway by which various stimuli affect ER functions. ER stress induces the evolutionarily conserved signaling pathways, called the unfolded protein response (UPR), which compromises the stimulus and then determines whether the cell survives or dies. In recent years, ongoing research has suggested that these pathways may be linked to the autophagic response, which plays a key role in the cell's response to various stressors. Autophagy performs a self-digestion function, and its activation protects cells against certain pathogens. However, the link between the UPR and autophagy may be more complicated. These two systems may act dependently, or the induction of one system may interfere with the other. Experimental studies have found that different viruses modulate these mechanisms to allow them to escape the host immune response or, worse, to exploit the host's defense to their advantage; thus, this topic is a critical area in antiviral research. In this review, we summarize the current knowledge about how RNA viruses, including influenza virus, poliovirus, coxsackievirus, enterovirus 71, Japanese encephalitis virus, hepatitis C virus, and dengue virus, regulate these processes. We also discuss recent discoveries and how these will produce novel strategies for antiviral treatment.
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Affiliation(s)
- Jia-Rong Jheng
- Department of Biochemistry and Molecular Biology, College of Medicine, Chang Gung University Kweishan, Taiwan
| | - Jin-Yuan Ho
- Department of Biochemistry and Molecular Biology, College of Medicine, Chang Gung University Kweishan, Taiwan
| | - Jim-Tong Horng
- Department of Biochemistry and Molecular Biology, College of Medicine, Chang Gung University Kweishan, Taiwan ; Research Center for Emerging Viral Infections, Chang Gung University Kweishan, Taiwan ; Department of Medical Research, Chang Gung Memorial Hospital Kweishan, Taiwan
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23
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Kim Y, Lee JH, Park JE, Cho J, Yi H, Kim VN. PKR is activated by cellular dsRNAs during mitosis and acts as a mitotic regulator. Genes Dev 2014; 28:1310-22. [PMID: 24939934 PMCID: PMC4066401 DOI: 10.1101/gad.242644.114] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
dsRNA-dependent protein kinase R (PKR) plays a key role in innate immunity. PKR binds viral dsRNA and undergoes autophosphorylation, which leads to translational repression and signaling pathway modulation in infected cells. Kim et al. now show that PKR is activated during mitosis in uninfected cells. PKR interacts with dsRNAs formed by inverted Alu repeats, which become accessible to PKR during mitosis. Phosphorylated PKR then suppresses translation and coordinates mitosis. This study unveils a novel function of PKR and endogenous dsRNA mitosis in uninfected cells. dsRNA-dependent protein kinase R (PKR) is a ubiquitously expressed enzyme well known for its roles in immune response. Upon binding to viral dsRNA, PKR undergoes autophosphorylation, and the phosphorylated PKR (pPKR) regulates translation and multiple signaling pathways in infected cells. Here, we found that PKR is activated in uninfected cells, specifically during mitosis, by binding to dsRNAs formed by inverted Alu repeats (IRAlus). While PKR and IRAlu-containing RNAs are segregated in the cytosol and nucleus of interphase cells, respectively, they interact during mitosis when nuclear structure is disrupted. Once phosphorylated, PKR suppresses global translation by phosphorylating the α subunit of eukaryotic initiation factor 2 (eIF2α). In addition, pPKR acts as an upstream kinase for c-Jun N-terminal kinase and regulates the levels of multiple mitotic factors such as CYCLINS A and B and POLO-LIKE KINASE 1 and phosphorylation of HISTONE H3. Disruption of PKR activation via RNAi or expression of a transdominant-negative mutant leads to misregulation of the mitotic factors, delay in mitotic progression, and defects in cytokinesis. Our study unveils a novel function of PKR and endogenous dsRNAs as signaling molecules during the mitosis of uninfected cells.
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Affiliation(s)
- Yoosik Kim
- Center for RNA Research, Institute for Basic Science, Seoul 151-742, Korea; School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Jung Hyun Lee
- Center for RNA Research, Institute for Basic Science, Seoul 151-742, Korea; School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Jong-Eun Park
- Center for RNA Research, Institute for Basic Science, Seoul 151-742, Korea; School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Jun Cho
- Center for RNA Research, Institute for Basic Science, Seoul 151-742, Korea; School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - Hyerim Yi
- Center for RNA Research, Institute for Basic Science, Seoul 151-742, Korea; School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
| | - V Narry Kim
- Center for RNA Research, Institute for Basic Science, Seoul 151-742, Korea; School of Biological Sciences, Seoul National University, Seoul 151-742, Korea
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24
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Matassa DS, Agliarulo I, Amoroso MR, Maddalena F, Sepe L, Ferrari MC, Sagar V, D'Amico S, Loreni F, Paolella G, Landriscina M, Esposito F. TRAP1-dependent regulation of p70S6K is involved in the attenuation of protein synthesis and cell migration: relevance in human colorectal tumors. Mol Oncol 2014; 8:1482-94. [PMID: 24962791 DOI: 10.1016/j.molonc.2014.06.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2014] [Revised: 05/20/2014] [Accepted: 06/04/2014] [Indexed: 12/24/2022] Open
Abstract
TNF receptor-associated protein 1 (TRAP1) is an HSP90 chaperone involved in stress protection and apoptosis in mitochondrial and extramitochondrial compartments. Remarkably, aberrant deregulation of TRAP1 function has been observed in several cancer types with potential new opportunities for therapeutic intervention in humans. Although previous studies by our group identified novel roles of TRAP1 in quality control of mitochondria-destined proteins through the attenuation of protein synthesis, molecular mechanisms are still largely unknown. To shed further light on the signaling pathways regulated by TRAP1 in the attenuation of protein synthesis, this study demonstrates that the entire pathway of cap-mediated translation is activated in cells following TRAP1 interference: consistently, expression and consequent phosphorylation of p70S6K and RSK1, two translation activating kinases, are increased upon TRAP1 silencing. Furthermore, we show that these regulatory functions affect the response to translational stress and cell migration in wound healing assays, processes involving both kinases. Notably, the regulatory mechanisms controlled by TRAP1 are conserved in colorectal cancer tissues, since an inverse correlation between TRAP1 and p70S6K expression is found in tumor tissues, thereby supporting the relevant role of TRAP1 translational regulation in vivo. Taken as a whole, these new findings candidate TRAP1 network for new anti-cancer strategies aimed at targeting the translational/quality control machinery of tumor cells.
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Affiliation(s)
- Danilo Swann Matassa
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Ilenia Agliarulo
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Maria Rosaria Amoroso
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy
| | - Francesca Maddalena
- Laboratory of Pre-Clinical and Translational Research, IRCCS, Referral Cancer Center of Basilicata, Rionero in Vulture, PZ, Italy
| | - Leandra Sepe
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy; Ceinge Biotecnologie Avanzate, Via G. Salvatore 486, 80145 Naples, Italy
| | - Maria Carla Ferrari
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy; Ceinge Biotecnologie Avanzate, Via G. Salvatore 486, 80145 Naples, Italy
| | - Vinay Sagar
- Department of Biology, University of Rome 'Tor Vergata', Via Ricerca Scientifica, Rome 00133, Italy
| | - Silvia D'Amico
- Department of Biology, University of Rome 'Tor Vergata', Via Ricerca Scientifica, Rome 00133, Italy
| | - Fabrizio Loreni
- Department of Biology, University of Rome 'Tor Vergata', Via Ricerca Scientifica, Rome 00133, Italy
| | - Giovanni Paolella
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy; Ceinge Biotecnologie Avanzate, Via G. Salvatore 486, 80145 Naples, Italy
| | - Matteo Landriscina
- Clinical Oncology Unit, Department of Medical and Surgical Sciences, University of Foggia, Foggia, Italy
| | - Franca Esposito
- Department of Molecular Medicine and Medical Biotechnology, University of Naples Federico II, Naples, Italy.
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25
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Chan SW. Establishment of chronic hepatitis C virus infection: Translational evasion of oxidative defence. World J Gastroenterol 2014; 20:2785-2800. [PMID: 24659872 PMCID: PMC3961964 DOI: 10.3748/wjg.v20.i11.2785] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2013] [Revised: 12/03/2013] [Accepted: 01/15/2014] [Indexed: 02/06/2023] Open
Abstract
Hepatitis C virus (HCV) causes a clinically important disease affecting 3% of the world population. HCV is a single-stranded, positive-sense RNA virus belonging to the genus Hepacivirus within the Flaviviridae family. The virus establishes a chronic infection in the face of an active host oxidative defence, thus adaptation to oxidative stress is key to virus survival. Being a small RNA virus with a limited genomic capacity, we speculate that HCV deploys a different strategy to evade host oxidative defence. Instead of counteracting oxidative stress, it utilizes oxidative stress to facilitate its own survival. Translation is the first step in the replication of a plus strand RNA virus so it would make sense if the virus can exploit the host oxidative defence in facilitating this very first step. This is particularly true when HCV utilizes an internal ribosome entry site element in translation, which is distinctive from that of cap-dependent translation of the vast majority of cellular genes, thus allowing selective translation of genes under conditions when global protein synthesis is compromised. Indeed, we were the first to show that HCV translation was stimulated by an important pro-oxidant-hydrogen peroxide in hepatocytes, suggesting that HCV is able to adapt to and utilize the host anti-viral response to facilitate its own translation thus allowing the virus to thrive under oxidative stress condition to establish chronicity. Understanding how HCV translation is regulated under oxidative stress condition will advance our knowledge on how HCV establishes chronicity. As chronicity is the initiator step in disease progression this will eventually lead to a better understanding of pathogenicity, which is particularly relevant to the development of anti-virals and improved treatments of HCV patients using anti-oxidants.
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26
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Chen TM, Shih YH, Tseng JT, Lai MC, Wu CH, Li YH, Tsai SJ, Sun HS. Overexpression of FGF9 in colon cancer cells is mediated by hypoxia-induced translational activation. Nucleic Acids Res 2013; 42:2932-44. [PMID: 24334956 PMCID: PMC3950685 DOI: 10.1093/nar/gkt1286] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Human fibroblast growth factor 9 (FGF9) is a potent mitogen involved in many physiological processes. Although FGF9 messenger RNA (mRNA) is ubiquitously expressed in embryos, FGF9 protein expression is generally low and restricted to a few adult organs. Aberrant expression of FGF9 usually results in human malignancies including cancers, but the mechanism remains largely unknown. Here, we report that FGF9 protein, but not mRNA, was increased in hypoxia. Two sequence elements, the upstream open reading frame (uORF) and the internal ribosome entry site (IRES), were identified in the 5' UTR of FGF9 mRNA. Functional assays indicated that FGF9 protein synthesis was normally controlled by uORF-mediated translational repression, which kept the protein at a low level, but was upregulated in response to hypoxia through a switch to IRES-dependent translational control. Our data demonstrate that FGF9 IRES functions as a cellular switch to turn FGF9 protein synthesis ‘on’ during hypoxia, a likely mechanism underlying FGF9 overexpression in cancer cells. Finally, we provide evidence to show that hypoxia-induced translational activation promotes FGF9 protein expression in colon cancer cells. Altogether, this dynamic working model may provide a new direction in anti-tumor therapies and cancer intervention.
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Affiliation(s)
- Tsung-Ming Chen
- Department of Physiology, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan, Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan, Institute of Bioinformatics and Biosignaling, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 70101, Taiwan and Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan
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27
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Rødland GE, Tvegård T, Boye E, Grallert B. Crosstalk between the Tor and Gcn2 pathways in response to different stresses. Cell Cycle 2013; 13:453-61. [PMID: 24280780 DOI: 10.4161/cc.27270] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Regulating growth and the cell cycle in response to environmental fluctuations is important for all organisms in order to maintain viability. Two major pathways for translational regulation are found in higher eukaryotes: the Tor signaling pathway and those operating through the eIF2α kinases. Studies from several organisms indicate that the two pathways are interlinked, in that Tor complex 1 (TORC1) negatively regulates the Gcn2 kinase. Furthermore, inactivation of TORC1 may be required for activation of Gcn2 in response to stress. Here, we use the model organism Schizosaccharomyces pombe to investigate this crosstalk further. We find that the relationship is more complex than previously thought. First, in response to UV irradiation and oxidative stress, Gcn2 is fully activated in the presence of TORC1 signaling. Second, during amino-acid starvation, activation of Gcn2 is dependent on Tor2 activity, and Gcn2 is required for timely inactivation of the Tor pathway. Our data show that the crosstalk between the two pathways varies with the actual stress applied.
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Affiliation(s)
- Gro Elise Rødland
- Department of Cell Biology; Institute for Cancer Research; Oslo University Hospital; Oslo, Norway
| | - Tonje Tvegård
- Department of Cell Biology; Institute for Cancer Research; Oslo University Hospital; Oslo, Norway
| | - Erik Boye
- Department of Cell Biology; Institute for Cancer Research; Oslo University Hospital; Oslo, Norway; Institute for Molecular Biosciences; University of Oslo; Oslo, Norway
| | - Beáta Grallert
- Department of Cell Biology; Institute for Cancer Research; Oslo University Hospital; Oslo, Norway
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28
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Barhoom S, Farrell I, Shai B, Dahary D, Cooperman BS, Smilansky Z, Elroy-Stein O, Ehrlich M. Dicodon monitoring of protein synthesis (DiCoMPS) reveals levels of synthesis of a viral protein in single cells. Nucleic Acids Res 2013; 41:e177. [PMID: 23965304 PMCID: PMC3794613 DOI: 10.1093/nar/gkt686] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The current report represents a further advancement of our previously reported technology termed Fluorescent transfer RNA (tRNA) for Translation Monitoring (FtTM), for monitoring of active global protein synthesis sites in single live cells. FtTM measures Förster resonance energy transfer (FRET) signals, generated when fluorescent tRNAs (fl-tRNAs), separately labeled as a FRET pair, occupy adjacent sites on the ribosome. The current technology, termed DiCodon Monitoring of Protein Synthesis (DiCoMPS), was developed for monitoring active synthesis of a specific protein. In DiCoMPS, specific fl-tRNA pair combinations are selected for transfection, based on the degree of enrichment of a dicodon sequence to which they bind in the mRNA of interest, relative to the background transcriptome of the cell in which the assay is performed. In this study, we used cells infected with the Epizootic Hemorrhagic Disease Virus 2-Ibaraki and measured, through DiCoMPS, the synthesis of the viral non-structural protein 3 (NS3), which is enriched in the AUA:AUA dicodon. fl-tRNAIleUAU-generated FRET signals were specifically enhanced in infected cells, increased in the course of infection and were diminished on siRNA-mediated knockdown of NS3. Our results establish an experimental approach for the single-cell measurement of the levels of synthesis of a specific viral protein.
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Affiliation(s)
- Sima Barhoom
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel, Anima Cell Metrology, Inc., Bernardsville, NJ 07924-2270, USA and Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA
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29
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Elbarbary RA, Li W, Tian B, Maquat LE. STAU1 binding 3' UTR IRAlus complements nuclear retention to protect cells from PKR-mediated translational shutdown. Genes Dev 2013; 27:1495-510. [PMID: 23824540 PMCID: PMC3713430 DOI: 10.1101/gad.220962.113] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 05/29/2013] [Indexed: 11/24/2022]
Abstract
For a number of human genes that encode transcripts containing inverted repeat Alu elements (IRAlus) within their 3' untranslated region (UTR), product mRNA is efficiently exported to the cytoplasm when the IRAlus, which mediate nuclear retention, are removed by alternative polyadenylation. Here we report a new mechanism that promotes gene expression by targeting mRNAs that maintain their 3' UTR IRAlus: Binding of the dsRNA-binding protein Staufen1 (STAU1) to 3' UTR IRAlus inhibits nuclear retention so as to augment the nuclear export of 3' UTR IRAlus-containing mRNAs (IRAlus mRNAs). Moreover, we found that 3' UTR IRAlus-bound STAU1 enhances 3' UTR IRAlus mRNA translation by precluding protein kinase R (PKR) binding, which obviates PKR activation, eukaryotic translation initiation factor 2α (eIF2α) phosphorylation, and repression of global cell translation. Thus, STAU1 binding to 3' UTR IRAlus functions along with 3' UTR IRAlus-mediated nuclear retention to suppress the shutdown of cellular translation triggered by PKR binding to endogenous cytoplasmic dsRNAs. We also show that a changing STAU1/PKR ratio contributes to myogenesis via effects on the 3' UTR IRAlus of mRNA encoding the microRNA-binding protein LIN28.
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Affiliation(s)
- Reyad A. Elbarbary
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry
- Center for RNA Biology, University of Rochester, Rochester, New York 14642, USA
| | - Wencheng Li
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey–New Jersey Medical School, Newark, New Jersey 07101, USA
| | - Bin Tian
- Department of Biochemistry and Molecular Biology, University of Medicine and Dentistry of New Jersey–New Jersey Medical School, Newark, New Jersey 07101, USA
| | - Lynne E. Maquat
- Department of Biochemistry and Biophysics, School of Medicine and Dentistry
- Center for RNA Biology, University of Rochester, Rochester, New York 14642, USA
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30
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White-Gilbertson S, Hua Y, Liu B. The role of endoplasmic reticulum stress in maintaining and targeting multiple myeloma: a double-edged sword of adaptation and apoptosis. Front Genet 2013; 4:109. [PMID: 23781234 PMCID: PMC3678081 DOI: 10.3389/fgene.2013.00109] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 05/27/2013] [Indexed: 11/13/2022] Open
Abstract
Increased cellular protein production places stress on the endoplasmic reticulum (ER), because many of the nascent proteins pass through the ER for folding and trafficking. Accumulation of misfolded proteins in the ER triggers the activation of three well-known pathways including IRE1 (inositol requiring kinase 1), ATF6 (activating transcription factor 6), and PERK (double stranded RNA-activated protein kinase-like ER kinase). The activity of each sensor modulates the overall ER strategy for managing protein quality control as cellular needs change due to growth, differentiation, infection, transformation, and host of other possible physiological states. Here we review the role of ER stress in multiple myeloma (MM), an incurable plasma cell neoplasm. MM is closely linked to dysregulated unfolded protein response in the ER due to the heightened production of immunoglobulin and the metabolic demands of malignant uncontrolled proliferation. Together, these forces may mean that myeloma cells have an “Achilles heel” which can be exploited as a treatment target: their ER stress response must be constitutively active at a remarkably high level to survive their unique metabolic needs. Therefore, inhibition of the ER stress response is likely to injure the cells, as is any further demand on an already over-worked system. Evidence for this vulnerability is summarized here, along with an overview of how each of the three ER stress sensors has been implicated in myeloma pathogenesis and treatment.
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Affiliation(s)
- Shai White-Gilbertson
- Department of Microbiology and Immunology, Hollings Cancer Center, Medical University of South Carolina Charleston, SC, USA
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31
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Liu LY, Wang J, Huang Y, Pan HB, Zhang X, Huang ZX, Zhao SM, Gao SZ. The effect of dietary protein levels on the expression of genes coding for four selected protein translation initiation factors in muscle tissue of Wujin pig. J Anim Physiol Anim Nutr (Berl) 2013; 98:310-7. [PMID: 23718228 DOI: 10.1111/jpn.12081] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Accepted: 04/11/2013] [Indexed: 01/11/2023]
Abstract
The objective of this study was to investigate the regulatory mechanism underlying the increased muscle protein accumulation in pigs while were fed a high protein diet. The eukaryotic initiation factors (eIFs) have been reported to involve in muscle protein synthesis. We investigated the mRNA and protein expression levels of eIF2B1, 4A1, 4B and 4E in Wujin pigs fed either a high protein (HP: 18%) or a low protein (LP: 14%) diet at 30, 60 or 100 kg body weight, based on real-time PCR and western blotting analyses. Our results indicated that the expression levels of eIF2B1 mRNA and protein were increased by HP diet at all body weight. The HP diet showed higher mRNA and protein levels of eIF4B gene at 60 and 100 kg. The protein expression of eIF4E phosphorylation was increased by HP diet only at 30 kg. These data suggested that the HP diet promoted porcine muscle protein accumulation mainly by up-regulating eIF2B1, 4B and 4E rather than 4A1 expression along the growth stages.
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Affiliation(s)
- L Y Liu
- College of Life Sciences, Yunnan Normal University, Kunming, Yunnan, China
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32
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Chan CP, Kok KH, Tang HMV, Wong CM, Jin DY. Internal ribosome entry site-mediated translational regulation of ATF4 splice variant in mammalian unfolded protein response. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2165-75. [PMID: 23665047 DOI: 10.1016/j.bbamcr.2013.05.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 04/30/2013] [Accepted: 05/02/2013] [Indexed: 02/04/2023]
Abstract
Activating transcription factor 4 (ATF4) is a master regulator of genes involved in unfolded protein response (UPR) and its translation is regulated through reinitiation at upstream open reading frames. Here, we demonstrate internal ribosome entry site (IRES)-mediated translation of an alternatively spliced variant of human ATF4. This variant that contains four upstream open reading frames in the 5' leader region was expressed in leukocytes and other tissues. mRNA and protein expression of this variant was activated in the UPR. Its translation was neither inhibited by steric hindrance nor affected by eIF4G1 inactivation, indicating a cap-independent and IRES-dependent mechanism not mediated by ribosome scanning-reinitiation. The IRES activity mapped to a highly structured region that partially overlaps with the third and fourth open reading frames was unlikely attributed to cryptic promoter or splicing, but was activated by PERK-induced eIF2α phosphorylation. Taken together, our findings reveal a new mechanism for translational regulation of ATF4 in mammalian UPR.
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Affiliation(s)
- Ching-Ping Chan
- Department of Biochemistry, The University of Hong Kong, Pokfulam, Hong Kong
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33
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Ben-Hur V, Denichenko P, Siegfried Z, Maimon A, Krainer A, Davidson B, Karni R. S6K1 alternative splicing modulates its oncogenic activity and regulates mTORC1. Cell Rep 2012; 3:103-15. [PMID: 23273915 DOI: 10.1016/j.celrep.2012.11.020] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 10/09/2012] [Accepted: 11/27/2012] [Indexed: 10/27/2022] Open
Abstract
Ribosomal S6 kinase 1 (S6K1) is a major mTOR downstream signaling molecule that regulates cell size and translation efficiency. Here, we report that short isoforms of S6K1 are overproduced in breast cancer cell lines and tumors. Overexpression of S6K1 short isoforms induces transformation of human breast epithelial cells. The long S6K1 variant (Iso-1) induced opposite effects. It inhibits Ras-induced transformation and tumor formation, while its knockdown or knockout induces transformation, suggesting that Iso-1 has a tumor-suppressor activity. Furthermore, we found that S6K1 short isoforms bind and activate mTORC1, elevating 4E-BP1 phosphorylation, cap-dependent translation, and Mcl-1 protein levels. Both a phosphorylation-defective 4E-BP1 mutant and the mTORC1 inhibitor rapamycin partially blocked the oncogenic effects of S6K1 short isoforms, suggesting that these are mediated by mTORC1 and 4E-BP1. Thus, alternative splicing of S6K1 acts as a molecular switch in breast cancer cells, elevating oncogenic isoforms that activate mTORC1.
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Affiliation(s)
- Vered Ben-Hur
- Department of Biochemistry and Molecular Biology, the Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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34
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Modem S, Dicarlo SE, Reddy TR. Fresh Garlic Extract Induces Growth Arrest and Morphological Differentiation of MCF7 Breast Cancer Cells. Genes Cancer 2012; 3:177-86. [PMID: 23050048 DOI: 10.1177/1947601912458581] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 07/29/2012] [Indexed: 01/19/2023] Open
Abstract
Consumption of diets rich in fruits and vegetables is often associated with a reduced risk of developing cancer, particularly breast cancer. Considering that 1 in 8 women in the United States will develop breast cancer in the course of her lifetime, dietary manipulation could have a major impact on the incidence of breast cancer. We report here that fresh extracts of garlic (not boiled) arrested the growth and altered the morphology of MCF7 breast cancer cells. Deregulated levels of E-cadherin, cytokeratin8/18, and β-catenin correlated with the altered phenotype. We propose that early down-regulation of cyclin D1, reduced phosphorylation of ERK1, and increased phosphorylation of eIF2-α triggered the phenotypical changes. Reduced expression of hsp27 and sam68 and elevated levels of Rb and p21 further contributed to the sustained growth reduction. These findings provide a better understanding of the cellular responses to dietary supplements and provide potential options to treat breast cancer.
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Affiliation(s)
- Suhasini Modem
- Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI, USA
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35
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Muranen T, Selfors LM, Worster DT, Iwanicki MP, Song L, Morales FC, Gao S, Mills GB, Brugge JS. Inhibition of PI3K/mTOR leads to adaptive resistance in matrix-attached cancer cells. Cancer Cell 2012; 21:227-39. [PMID: 22340595 PMCID: PMC3297962 DOI: 10.1016/j.ccr.2011.12.024] [Citation(s) in RCA: 347] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Revised: 10/07/2011] [Accepted: 12/20/2011] [Indexed: 02/05/2023]
Abstract
The PI3K/mTOR-pathway is the most commonly dysregulated pathway in epithelial cancers and represents an important target for cancer therapeutics. Here, we show that dual inhibition of PI3K/mTOR in ovarian cancer-spheroids leads to death of inner matrix-deprived cells, whereas matrix-attached cells are resistant. This matrix-associated resistance is mediated by drug-induced upregulation of cellular survival programs that involve both FOXO-regulated transcription and cap-independent translation. Inhibition of any one of several upregulated proteins, including Bcl-2, EGFR, or IGF1R, abrogates resistance to PI3K/mTOR inhibition. These results demonstrate that acute adaptive responses to PI3K/mTOR inhibition in matrix-attached cells resemble well-conserved stress responses to nutrient and growth factor deprivation. Bypass of this resistance mechanism through rational design of drug combinations could significantly enhance PI3K-targeted drug efficacy.
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Affiliation(s)
- Taru Muranen
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, 02115, USA
| | - Laura M. Selfors
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, 02115, USA
| | - Devin T. Worster
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, 02115, USA
| | - Marcin P. Iwanicki
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, 02115, USA
| | - Loling Song
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, 02115, USA
| | - Fabiana C. Morales
- Department of Systems Biology, MD Anderson Cancer Center, Houston, Texas, 77030, USA
| | - Sizhen Gao
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, 02115, USA
| | - Gordon B. Mills
- Department of Systems Biology, MD Anderson Cancer Center, Houston, Texas, 77030, USA
| | - Joan S. Brugge
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, 02115, USA
- Corresponding author , Department of Cell Biology, 240 Longwood Ave, Boston MA 02115, Phone: 617 432 3974, Fax: 617 432 3969
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36
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Silvera D, Koloteva-Levine N, Burma S, Elroy-Stein O. Effect of Ku proteins on IRES-mediated translation. Biol Cell 2012; 98:353-61. [PMID: 16448389 DOI: 10.1042/bc20050060] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION Ku is an abundant nuclear heterodimeric protein composed of 70 and 86 kDa subunits. As an activator of the catalytic subunit of DNA-PK (DNA-dependent protein kinase), Ku plays an important role in DNA repair and recombination. Ku is also involved in actions independent of DNA-PK, such as transcription regulation and telomere maintenance. Although Ku is localized in the cytoplasm under specific cellular conditions, no functions for Ku outside of the nucleus have as yet been reported. In addition to DNA binding, Ku binds specific RNA sequences with high affinity. However, no specific cellular mRNA targets for Ku have been identified. RESULTS In a yeast three-hybrid system, Ku70 bound to an RNA bait that contained an IRES (internal ribosomal entry site) element. A single band with migration properties similar to those of Ku70 was immunoprecipitated with anti-Ku antibody, using UV cross-linked complexes formed by HeLa cell nuclear extracts and an IRES-containing RNA probe. IRES activity was reduced in Ku80(-/-) cells. Overexpression of Ku proteins stimulated IRES-dependent translation. CONCLUSIONS The present study suggests that Ku binds IRES elements within RNA molecules, and that Ku plays a role in the modulation of IRES-mediated mRNA translation.
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Affiliation(s)
- Deborah Silvera
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Science, Tel Aviv University, Tel Aviv 69978, Israel
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37
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Sivan G, Aviner R, Elroy-Stein O. Mitotic modulation of translation elongation factor 1 leads to hindered tRNA delivery to ribosomes. J Biol Chem 2011; 286:27927-35. [PMID: 21665947 PMCID: PMC3151038 DOI: 10.1074/jbc.m111.255810] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 06/06/2011] [Indexed: 01/31/2023] Open
Abstract
Translation elongation in eukaryotes is mediated by the concerted actions of elongation factor 1A (eEF1A), which delivers aminoacylated tRNA to the ribosome; elongation factor 1B (eEF1B) complex, which catalyzes the exchange of GDP to GTP on eEF1A; and eEF2, which facilitates ribosomal translocation. Here we present evidence in support of a novel mode of translation regulation by hindered tRNA delivery during mitosis. A conserved consensus phosphorylation site for the mitotic cyclin-dependent kinase 1 on the catalytic delta subunit of eEF1B (termed eEF1D) is required for its posttranslational modification during mitosis, resulting in lower affinity to its substrate eEF1A. This modification is correlated with reduced availability of eEF1A·tRNA complexes, as well as reduced delivery of tRNA to and association of eEF1A with elongating ribosomes. This mode of regulation by hindered tRNA delivery, although first discovered in mitosis, may represent a more globally applicable mechanism employed under other physiological conditions that involve down-regulation of protein synthesis at the elongation level.
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Affiliation(s)
- Gilad Sivan
- From the Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Ranen Aviner
- From the Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Orna Elroy-Stein
- From the Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Barhoom S, Kaur J, Cooperman BS, Smorodinsky NI, Smilansky Z, Ehrlich M, Elroy-Stein O. Quantitative single cell monitoring of protein synthesis at subcellular resolution using fluorescently labeled tRNA. Nucleic Acids Res 2011; 39:e129. [PMID: 21795382 PMCID: PMC3201886 DOI: 10.1093/nar/gkr601] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We have developed a novel technique of using fluorescent tRNA for translation monitoring (FtTM). FtTM enables the identification and monitoring of active protein synthesis sites within live cells at submicron resolution through quantitative microscopy of transfected bulk uncharged tRNA, fluorescently labeled in the D-loop (fl-tRNA). The localization of fl-tRNA to active translation sites was confirmed through its co-localization with cellular factors and its dynamic alterations upon inhibition of protein synthesis. Moreover, fluorescence resonance energy transfer (FRET) signals, generated when fl-tRNAs, separately labeled as a FRET pair occupy adjacent sites on the ribosome, quantitatively reflect levels of protein synthesis in defined cellular regions. In addition, FRET signals enable detection of intra-populational variability in protein synthesis activity. We demonstrate that FtTM allows quantitative comparison of protein synthesis between different cell types, monitoring effects of antibiotics and stress agents, and characterization of changes in spatial compartmentalization of protein synthesis upon viral infection.
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Affiliation(s)
- Sima Barhoom
- Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
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Welnowska E, Sanz MA, Redondo N, Carrasco L. Translation of viral mRNA without active eIF2: the case of picornaviruses. PLoS One 2011; 6:e22230. [PMID: 21779397 PMCID: PMC3136507 DOI: 10.1371/journal.pone.0022230] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Accepted: 06/17/2011] [Indexed: 12/19/2022] Open
Abstract
Previous work by several laboratories has established that translation of picornavirus RNA requires active eIF2α for translation in cell free systems or after transfection in culture cells. Strikingly, we have found that encephalomyocarditis virus protein synthesis at late infection times is resistant to inhibitors that induce the phosphorylation of eIF2α whereas translation of encephalomyocarditis virus early during infection is blocked upon inactivation of eIF2α by phosphorylation induced by arsenite. The presence of this compound during the first hour of infection leads to a delay in the appearance of late protein synthesis in encephalomyocarditis virus-infected cells. Depletion of eIF2α also provokes a delay in the kinetics of encephalomyocarditis virus protein synthesis, whereas at late times the levels of viral translation are similar in control or eIF2α-depleted HeLa cells. Immunofluorescence analysis reveals that eIF2α, contrary to eIF4GI, does not colocalize with ribosomes or with encephalomyocarditis virus 3D polymerase. Taken together, these findings support the novel idea that eIF2 is not involved in the translation of encephalomyocarditis virus RNA during late infection. Moreover, other picornaviruses such as foot-and-mouth disease virus, mengovirus and poliovirus do not require active eIF2α when maximal viral translation is taking place. Therefore, translation of picornavirus RNA may exhibit a dual mechanism as regards the participation of eIF2. This factor would be necessary to translate the input genomic RNA, but after viral RNA replication, the mechanism of viral RNA translation switches to one independent of eIF2.
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Affiliation(s)
- Ewelina Welnowska
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Universidad Autónoma de Madrid, Madrid, Spain
| | - Miguel Angel Sanz
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Universidad Autónoma de Madrid, Madrid, Spain
- * E-mail:
| | - Natalia Redondo
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Universidad Autónoma de Madrid, Madrid, Spain
| | - Luis Carrasco
- Centro de Biología Molecular “Severo Ochoa” (CSIC-UAM), Universidad Autónoma de Madrid, Madrid, Spain
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Mielke N, Schwarzer R, Calkhoven CF, Kaufman RJ, Dörken B, Leutz A, Jundt F. Eukaryotic initiation factor 2alpha phosphorylation is required for B-cell maturation and function in mice. Haematologica 2011; 96:1261-8. [PMID: 21565905 DOI: 10.3324/haematol.2011.042853] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND The control of translation initiation is a crucial component in the regulation of gene expression. The eukaryotic initiation factor 2α (eIF2α) mediates binding of the initiator transfer-messenger-RNA to the AUG initiation codon, and thus controls a rate-limiting step in translation initiation. Phosphorylation of eIF2α at serine 51 is linked to cellular stress response and attenuates translation initiation. The biochemistry of translation inhibition mediated by eIF2α phosphorylation is well characterized, yet the physiological importance in hematopoiesis remains only partially known. DESIGN AND METHODS Using hematopoietic stem cells carrying a non-phosphorylatable mutant form of eIF2α (eIF2αAA), we examined the efficiency of reconstitution in wild-type and B-cell-deficient microMT C57BL/6 recipients in two independent models. RESULTS We provide evidence that phosphorylation-deficient eIF2α mutant hematopoietic stem cells may repopulate lethally irradiated mice but have a defect in the development and maintenance of newly formed B cells in the bone marrow and of naïve follicular B cells in the periphery. The mature B-cell compartment is markedly reduced in bone marrow, spleen and peripheral blood, and B-cell receptor-mediated proliferation in vitro and serum immunoglobulin secretion in vivo are impaired. CONCLUSIONS The data suggest that regulation of translation through eIF2α phosphorylation is dispensable in hematopoietic reconstitution but essential during late B-cell development.
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Affiliation(s)
- Nina Mielke
- Department of Hematology and Oncology, Charité, Campus Virchow-Klinikum, University Medicine Berlin, Berlin, Germany
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Ashwal R, Hemi R, Tirosh A, Gordin R, Yissachar E, Cohen-Dayag A, Rosenberg A, Karasik A, Blüher M, Kanety H. Differential expression of novel adiponectin receptor-1 transcripts in skeletal muscle of subjects with normal glucose tolerance and type 2 diabetes. Diabetes 2011; 60:936-46. [PMID: 21289205 PMCID: PMC3046855 DOI: 10.2337/db09-0532] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVE Adiponectin receptor-1 (AdipoR1) expression in skeletal muscle has been suggested to play an important role in insulin resistance and diabetes. We aimed at evaluating the presence of novel AdiopR1 splice variants in human muscle and their regulation under physiological and pathophysiological states. RESEARCH DESIGN AND METHODS AdipoR1 5'UTR mRNA transcripts, predicted from bioinformatics data, were evaluated in fetal and adult human tissues. Expression and function of the identified transcripts were assessed in cultured human skeletal muscle cells and in muscle biopsies obtained from individuals with normal glucose tolerance (NGT) and type 2 diabetes (n = 49). RESULTS Screening of potential AdipoR1 5'UTR splice variants revealed a novel highly abundant muscle transcript (R1T3) in addition to the previously described transcript (R1T1). Unlike R1T1, R1T3 expression was significantly increased during fetal development and myogenesis, paralleled with increased AdipoR1 protein expression. The 5'UTR of R1T3 was found to contain upstream open reading frames that repress translation of downstream coding sequences. Conversely, AdipoR1 3'UTR was associated with enhanced translation efficiency during myoblast-myotube differentiation. A marked reduction in muscle expression of R1T3, R1T1, and R1T3-to-R1T1 ratio was observed in individuals with type 2 diabetes compared with expression levels of NGT subjects, paralleled with decreased expression of the differentiation marker myogenin. Among NGT subjects, R1T3 expression was positively correlated with insulin sensitivity. CONCLUSIONS These results indicate that AdipoR1 receptor expression in human skeletal muscle is subjected to posttranscriptional regulation, including alternative splicing and translational control. These mechanisms play an important role during myogenesis and may be important for whole-body insulin sensitivity.
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Affiliation(s)
- Reut Ashwal
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Rina Hemi
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
| | - Amir Tirosh
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
| | - Reut Gordin
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | - Eleanor Yissachar
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
| | | | | | - Avraham Karasik
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Matthias Blüher
- Department of Medicine, University of Leipzig, Leipzig, Germany
| | - Hannah Kanety
- Institute of Endocrinology, Chaim Sheba Medical Center, Tel-Hashomer, Israel
- Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Corresponding author: Hannah Kanety,
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42
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Komar AA, Hatzoglou M. Cellular IRES-mediated translation: the war of ITAFs in pathophysiological states. Cell Cycle 2011; 10:229-40. [PMID: 21220943 DOI: 10.4161/cc.10.2.14472] [Citation(s) in RCA: 297] [Impact Index Per Article: 22.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Translation of cellular mRNAs via initiation at Internal Ribosome Entry Sites (IRESs) has received increased attention during recent years due to its emerging significance for many physiological and pathological stress conditions in eukaryotic cells. Expression of genes bearing IRES elements in their mRNAs is controlled by multiple molecular mechanisms, with IRES-mediated translation favored under conditions when cap-dependent translation is compromised. In this review, we discuss recent advances in the field and future directions that may bring us closer to understanding the complex mechanisms that guide cellular IRES-mediated expression. We present examples in which the competitive action of IRES-transacting factors (ITAFs) plays a pivotal role in IRES-mediated translation and thereby controls cell-fate decisions leading to either pro-survival stress adaptation or cell death.
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Affiliation(s)
- Anton A Komar
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological and Environmental Sciences, Cleveland State University, Cleveland, OH, USA.
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43
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An implication for post-transcriptional control: reciprocal changes of melanocortin receptor type 2 mRNA and protein expression in alopecia areata. Med Hypotheses 2010; 76:122-4. [PMID: 20884125 DOI: 10.1016/j.mehy.2010.08.048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Revised: 08/26/2010] [Accepted: 08/27/2010] [Indexed: 11/23/2022]
Abstract
Alopecia areata (AA) is a hair follicle-specific autoimmune disease that is inherited genetically but triggered environmentally. Stress response is believed to play a role in the pathogenesis of AA. The hypothalamic-pituitary-adrenal axis (HPA axis), known as the stress axis, plays a cardinal role in the stress response. Growing evidence demonstrates that stress responses are under the control of both the central and peripheral nervous systems. Skin and hair follicles display peripheral HPA axis-like signaling systems. Some studies have revealed that a modified HPA axis, which is characterized by enhanced CRH/CRHR and insufficient glucocorticoid, is involved in the pathology of AA, suggesting that the paradoxical expression differs from that of normal control and should be further examined. Because adrenocorticotropic hormone (ACTH) is an intermediary in the HPA axis, MC2R, which specifically binds ACTH, may be important in the stress response of skin. Therefore, we investigated the gene and protein expression of MC2R in AA lesions and tried to elucidate the connection between HPA axis regulation, MC2R and AA. Reciprocal changes in MC2R mRNA and proteins in human AA were observed in our study; while mRNA levels were higher in lesions from AA patients compared with scalp tissues from normal controls, protein levels of MC2R were lower. The paradoxical expression of MC2R gene and protein levels coincided with evidence that over-responsive HPA activity coexists with a deficient HPA response in AA. We hypothesized that the HPA axis response in human AA may be the following: stressors first activate excess CRH/CRHR to produce increased ACTH, which up-regulates the expression of MC2R mRNA, but the stress response cannot create sufficient cortisol when the binding of ACTH/MC2R is deficient due to decreased MC2R protein. This hypothesis rationally clarifies the changed HPA axis in human AA and highlights the importance of MC2R in the pathogenesis of AA. The inconsistent expression of protein and mRNA implicates post-transcriptional control of human MC2R gene expression as found in murine MC2R gene.
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Kawagishi H, Nakamura H, Maruyama M, Mizutani S, Sugimoto K, Takagi M, Sugimoto M. ARF suppresses tumor angiogenesis through translational control of VEGFA mRNA. Cancer Res 2010; 70:4749-58. [PMID: 20501856 DOI: 10.1158/0008-5472.can-10-0368] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Vascular endothelial growth factor A (VEGFA) is a specific mitogen for vascular endothelial cells that plays a critical role in cancer neoangiogenesis. Here, we report that the nucleolar tumor suppressor p19(ARF) suppresses VEGFA expression, acting at the level of mRNA translation without affecting the transcription of the VEGFA gene. Translational repression of VEGFA mRNA by p19(ARF) does not require p53, a major target of the ARF tumor suppressor pathway, but instead correlates with binding to nucleophosmin/B23. Maintaining VEGFA expression relies on nucleophosmin/B23, and downregulating this protein by RNAi or p19(ARF) leads to translational repression of VEGFA. p19(ARF) inhibits VEGFA-dependent tumor angiogenesis in nude mice. Additionally, p14(ARF) expression and microvessel density are inversely correlated in human colon carcinomas. Taken together, our results define a mechanism by which the ARF tumor suppressor targets the translational repression of specific oncogenes during neoplastic transformation.
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Affiliation(s)
- Hiroyuki Kawagishi
- Department of Mechanism of Aging, National Center for Geriatrics and Gerontology, Aichi, Japan.
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45
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Blalock WL, Bavelloni A, Piazzi M, Faenza I, Cocco L. A role for PKR in hematologic malignancies. J Cell Physiol 2010; 223:572-91. [PMID: 20232306 DOI: 10.1002/jcp.22092] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The double-stranded RNA-dependent kinase PKR has been described for many years as strictly a pro-apoptotic kinase. Recent data suggest that the main purpose of this kinase is damage control and repair following stress and, if all else fails, apoptosis. Aberrant activation of PKR has been reported in numerous neurodegenerative diseases and cancer. Although a subset of myelodysplastic syndromes (MDS) and chronic lymphocytic leukemia contain low levels of PKR expression and activity, elevated PKR activity and/or expression have been detected in a wide range of hematologic malignancies, from bone marrow failure disorders to acute leukemia. With the recent findings that cancers containing elevated PKR activity are highly sensitive to PKR inhibition, we explore the role of PKR in hematologic malignancies, signal transduction pathways affected by PKR, and how PKR may contribute to leukemic transformation.
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Affiliation(s)
- William L Blalock
- Department of Human Anatomical Sciences, University of Bologna, Bologna, Italy
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Graber TE, Baird SD, Kao PN, Mathews MB, Holcik M. NF45 functions as an IRES trans-acting factor that is required for translation of cIAP1 during the unfolded protein response. Cell Death Differ 2009; 17:719-29. [PMID: 19893574 DOI: 10.1038/cdd.2009.164] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Expression of the cellular inhibitor of apoptosis protein 1 (cIAP1) is unexpectedly repressed at the level of translation under normal physiological conditions in many cell lines. We have previously shown that the 5' untranslated region of cIAP1 mRNA contains a stress-inducible internal ribosome entry site (IRES) that governs expression of cIAP1 protein. Although inactive in unstressed cells, the IRES supports cap-independent translation of cIAP1 in response to endoplasmic reticulum stress. To gain an insight into the mechanism of cIAP1 IRES function, we empirically derived the minimal free energy secondary structure of the cIAP1 IRES using enzymatic cleavage mapping. We subsequently used RNA affinity chromatography to identify several cellular proteins, including nuclear factor 45 (NF45) as cIAP1 IRES binding proteins. In this report we show that NF45 is a novel RNA binding protein that enhances IRES-dependent translation of endogenous cIAP1. Further, we show that NF45 is required for IRES-mediated induction of cIAP1 protein during the unfolded protein response. The data presented are consistent with a model in which translation of cIAP1 is governed, at least in part, by NF45, a novel cellular IRES trans-acting factor.
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Affiliation(s)
- T E Graber
- Apoptosis Research Centre, Children's Hospital of Eastern Ontario, Ottawa, Ontario, Canada
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47
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Blalock WL, Grimaldi C, Fala F, Follo M, Horn S, Basecke J, Martinelli G, Cocco L, Martelli AM. PKR activity is required for acute leukemic cell maintenance and growth: a role for PKR-mediated phosphatase activity to regulate GSK-3 phosphorylation. J Cell Physiol 2009; 221:232-41. [PMID: 19507191 DOI: 10.1002/jcp.21848] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Recent reports demonstrate that PKR is constitutively active in a variety of tumors and is required for tumor maintenance and growth. Here we report acute leukemia cell lines contain elevated levels of p-T451 PKR and PKR activity as compared to normal controls. Inhibition of PKR with a specific inhibitor, as well as overexpression of a dominant-negative PKR, inhibited cell proliferation and induced cell death. Interestingly, PKR inhibition using the specific inhibitor resulted in a time-dependent augmentation of AKT S473 and GSK-3alpha S21 phosphorylation, which was confirmed in patient samples. Increased phosphorylation of AKT and GSK-3alpha was not dependent on PI3K activity. PKR inhibition augmented levels of p-S473 AKT and p-S21/9 GSK-3alpha/beta in the presence of the PI3K inhibitor, LY294002, but was unable to augment GSK-3alpha or beta phosphorylation in the presence of the AKT inhibitor, A443654. Pre-treatment with the PKR inhibitor blocked the ability of A443654 and LY294002 to promote phosphorylation of eIF2alpha, indicating the mechanism leading to AKT phosphorylation and activation did not require eIF2alpha phosphorylation. The effects of PKR inhibition on AKT and GSK-3 phosphorylation were found to be, in part, PP2A-dependent. These data indicate that, in acute leukemia cell lines, constitutive basal activity of PKR is required for leukemic cell homeostasis and growth and functions as a negative regulator of AKT, thereby increasing the pool of potentially active GSK-3.
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Affiliation(s)
- William L Blalock
- Cell Signalling Laboratory, Department of Human Anatomical Sciences, University of Bologna, Bologna, Italy
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Spriggs KA, Cobbold LC, Ridley SH, Coldwell M, Bottley A, Bushell M, Willis AE, Siddle K. The human insulin receptor mRNA contains a functional internal ribosome entry segment. Nucleic Acids Res 2009; 37:5881-93. [PMID: 19654240 PMCID: PMC2761284 DOI: 10.1093/nar/gkp623] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Regulation of mRNA translation is an important mechanism determining the level of expression of proteins in eukaryotic cells. Translation is most commonly initiated by cap-dependent scanning, but many eukaryotic mRNAs contain internal ribosome entry segments (IRESs), providing an alternative means of initiation capable of independent regulation. Here, we show by using dicistronic luciferase reporter vectors that the 5′-UTR of the mRNA encoding human insulin receptor (hIR) contains a functional IRES. RNAi-mediated knockdown showed that the protein PTB was required for maximum IRES activity. Electrophoretic mobility shift assays confirmed that PTB1, PTB2 and nPTB, but not unr or PTB4, bound to hIR mRNA, and deletion mapping implicated a CCU motif 448 nt upstream of the initiator AUG in PTB binding. The IR-IRES was functional in a number of cell lines, and most active in cells of neuronal origin, as assessed by luciferase reporter assays. The IRES was more active in confluent than sub-confluent cells, but activity did not change during differentiation of 3T3-L1 fibroblasts to adipocytes. IRES activity was stimulated by insulin in sub-confluent cells. The IRES may function to maintain expression of IR protein in tissues such as the brain where mRNA translation by cap-dependent scanning is less effective.
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Affiliation(s)
- Keith A Spriggs
- University of Nottingham, School of Pharmacy, University Park, Nottingham NG7 2RD, UK
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49
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Dang Do AN, Kimball SR, Cavener DR, Jefferson LS. eIF2alpha kinases GCN2 and PERK modulate transcription and translation of distinct sets of mRNAs in mouse liver. Physiol Genomics 2009; 38:328-41. [PMID: 19509078 DOI: 10.1152/physiolgenomics.90396.2008] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
In eukaryotes, selective derepression of mRNA translation through altered utilization of upstream open reading frames (uORF) or internal ribosomal entry sites (IRES) regulatory motifs following exposure to stress is regulated at the initiation stage through the increased phosphorylation of eukaryotic initiation factor 2 on its alpha-subunit (eIF2alpha). While there is only one known eIF2alpha kinase in yeast, general control nonderepressible 2 (GCN2), mammals have evolved to express at least four: GCN2, heme-regulated inhibitor kinase (HRI), double-stranded RNA-activated protein kinase (PKR), and PKR-like endoplasmic reticulum-resident kinase (PERK). So far, the main known distinction among these four kinases is their activation in response to different acute stressors. In the present study, we used the in situ perfused mouse liver model and hybridization array analyses to assess the general translational response to stress regulated by two of these kinases, GCN2 and PERK, and to differentiate between the downstream effects of activating GCN2 versus PERK. The resulting data showed that at least 2.5% of mouse liver mRNAs are subject to derepressed translation following stress. In addition, the data demonstrated that eIF2alpha kinases GCN2 and PERK differentially regulate mRNA transcription and translation, which in the latter case suggests that increased eIF2alpha phosphorylation is not sufficient for derepression of translation. These findings open an avenue for more focused future research toward groups of mRNAs that code for the early cellular stress response proteins.
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Affiliation(s)
- An N Dang Do
- Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, USA
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50
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The hnRNA-binding proteins hnRNP L and PTB are required for efficient translation of the Cat-1 arginine/lysine transporter mRNA during amino acid starvation. Mol Cell Biol 2009; 29:2899-912. [PMID: 19273590 DOI: 10.1128/mcb.01774-08] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The response to amino acid starvation involves the global decrease of protein synthesis and an increase in the translation of some mRNAs that contain an internal ribosome entry site (IRES). It was previously shown that translation of the mRNA for the arginine/lysine amino acid transporter Cat-1 increases during amino acid starvation via a mechanism that utilizes an IRES in the 5' untranslated region of the Cat-1 mRNA. It is shown here that polypyrimidine tract binding protein (PTB) and an hnRNA binding protein, heterogeneous nuclear ribonucleoprotein L (hnRNP L), promote the efficient translation of Cat-1 mRNA during amino acid starvation. Association of both proteins with Cat-1 mRNA increased during starvation with kinetics that paralleled that of IRES activation, although the levels and subcellular distribution of the proteins were unchanged. The sequence CUUUCU within the Cat-1 IRES was important for PTB binding and for the induction of translation during amino acid starvation. Binding of hnRNP L to the IRES or the Cat-1 mRNA in vivo was independent of PTB binding but was not sufficient to increase IRES activity or Cat-1 mRNA translation during amino acid starvation. In contrast, binding of PTB to the Cat-1 mRNA in vivo required hnRNP L. A wider role of hnRNP L in mRNA translation was suggested by the decrease of global protein synthesis in cells with reduced hnRNP L levels. It is proposed that PTB and hnRNP L are positive regulators of Cat-1 mRNA translation via the IRES under stress conditions that cause a global decrease of protein synthesis.
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