101
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Wigington CP, Jung J, Rye EA, Belauret SL, Philpot AM, Feng Y, Santangelo PJ, Corbett AH. Post-transcriptional regulation of programmed cell death 4 (PDCD4) mRNA by the RNA-binding proteins human antigen R (HuR) and T-cell intracellular antigen 1 (TIA1). J Biol Chem 2014; 290:3468-87. [PMID: 25519906 DOI: 10.1074/jbc.m114.631937] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Post-transcriptional processing of mRNA transcripts plays a critical role in establishing the gene expression profile of a cell. Such processing events are mediated by a host of factors, including RNA-binding proteins and microRNAs. A number of critical cellular pathways are subject to regulation at multiple levels that allow fine-tuning of key biological responses. Programmed cell death 4 (PDCD4) is a tumor suppressor and an important modulator of mRNA translation that is regulated by a number of mechanisms, most notably as a target of the oncomiR, miR-21. Here, we provide evidence for post-transcriptional regulation of PDCD4 by the RNA-binding proteins, HuR and TIA1. Complementary approaches reveal binding of both HuR and TIA1 to the PDCD4 transcript. Consistent with a model where RNA-binding proteins modulate the PDCD4 transcript, knockdown of HuR and/or TIA1 results in a significant decrease in steady-state PDCD4 mRNA and protein levels. However, fractionation experiments suggest that the mode of regulation of the PDCD4 transcript likely differs in the cytoplasm and the nucleus as the pool of PDCD4 mRNA present in the cytoplasm is more stable than the nuclear pool of PDCD4 transcript. We observe a competitive mode of binding between HuR and TIA1 on the PDCD4 transcript in the cytoplasm, suggesting that these two factors dynamically interact with one another as well as the PDCD4 transcript to maintain tight control of PDCD4 levels. Overall, this study reveals an additional set of regulatory interactions that modulate the expression of PDCD4, a key pro-apoptotic factor, and also reveals new insights into how HuR and TIA1 functions are integrated to achieve such regulation.
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Affiliation(s)
- Callie P Wigington
- From the Department of Biochemistry and Graduate Program in Biochemistry, Cell and Developmental Biology, Emory University, Atlanta, Georgia 30322
| | - Jeenah Jung
- the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, and Emory University, Atlanta, Georgia 30332
| | - Emily A Rye
- From the Department of Biochemistry and Graduate Program in Biochemistry, Cell and Developmental Biology, Emory University, Atlanta, Georgia 30322
| | - Sara L Belauret
- the School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30322
| | - Akahne M Philpot
- From the Department of Biochemistry and the Summer Scholars Research Program, Winship Cancer Institute, Atlanta, Georgia 30332, and
| | - Yue Feng
- the Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Philip J Santangelo
- the Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, and Emory University, Atlanta, Georgia 30332
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102
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RNA recognition and stress granule formation by TIA proteins. Int J Mol Sci 2014; 15:23377-88. [PMID: 25522169 PMCID: PMC4284772 DOI: 10.3390/ijms151223377] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2014] [Revised: 12/05/2014] [Accepted: 12/11/2014] [Indexed: 02/04/2023] Open
Abstract
Stress granule (SG) formation is a primary mechanism through which gene expression is rapidly modulated when the eukaryotic cell undergoes cellular stresses (including heat, oxidative, viral infection, starvation). In particular, the sequestration of specifically targeted translationally stalled mRNAs into SGs limits the expression of a subset of genes, but allows the expression of heatshock proteins that have a protective effect in the cell. The importance of SGs is seen in several disease states in which SG function is disrupted. Fundamental to SG formation are the T cell restricted intracellular antigen (TIA) proteins (TIA-1 and TIA-1 related protein (TIAR)), that both directly bind to target RNA and self-associate to seed the formation of SGs. Here a summary is provided of the current understanding of the way in which TIA proteins target specific mRNA, and how TIA self-association is triggered under conditions of cellular stress.
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103
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Tessier SN, Audas TE, Wu CW, Lee S, Storey KB. The involvement of mRNA processing factors TIA-1, TIAR, and PABP-1 during mammalian hibernation. Cell Stress Chaperones 2014; 19:813-25. [PMID: 24590458 PMCID: PMC4389841 DOI: 10.1007/s12192-014-0505-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Revised: 02/11/2014] [Accepted: 02/12/2014] [Indexed: 01/10/2023] Open
Abstract
Mammalian hibernators survive low body temperatures, ischemia-reperfusion, and restricted nutritional resources via global reductions in energy-expensive cellular processes and selective increases in stress pathways. Consequently, studies that analyze hibernation uncover mechanisms which balance metabolism and support survival by enhancing stress tolerance. We hypothesized processing factors that influence messenger ribonucleic acid (mRNA) maturation and translation may play significant roles in hibernation. We characterized the amino acid sequences of three RNA processing proteins (T cell intracellular antigen 1 (TIA-1), TIA1-related (TIAR), and poly(A)-binding proteins (PABP-1)) from thirteen-lined ground squirrels (Ictidomys tridecemlineatus), which all displayed a high degree of sequence identity with other mammals. Alternate Tia-1 and TiaR gene variants were found in the liver with higher expression of isoform b versus a in both cases. The localization of RNA-binding proteins to subnuclear structures was assessed by immunohistochemistry and confirmed by subcellular fractionation; TIA-1 was identified as a major component of subnuclear structures with up to a sevenfold increase in relative protein levels in the nucleus during hibernation. By contrast, there was no significant difference in the relative protein levels of TIARa/TIARb in the nucleus, and a decrease was observed for TIAR isoforms in cytoplasmic fractions of torpid animals. Finally, we used solubility tests to analyze the formation of reversible aggregates that are associated with TIA-1/R function during stress; a shift towards the soluble fraction (TIA-1a, TIA-1b) was observed during hibernation suggesting enhanced protein aggregation was not present during torpor. The present study identifies novel posttranscriptional regulatory mechanisms that may play a role in reducing translational rates and/or mRNA processing under unfavorable environmental conditions.
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Affiliation(s)
- Shannon N. Tessier
- />Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
| | - Timothy E. Audas
- />Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5 Canada
| | - Cheng-Wei Wu
- />Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
| | - Stephen Lee
- />Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON K1H 8M5 Canada
| | - Kenneth B. Storey
- />Institute of Biochemistry, Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6 Canada
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104
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Huang S, Liu N, Li H, Zhao J, Su L, Zhang Y, Zhang S, Zhao B, Miao J. TIA1 interacts with annexin A7 in regulating vascular endothelial cell autophagy. Int J Biochem Cell Biol 2014; 57:115-22. [PMID: 25461769 DOI: 10.1016/j.biocel.2014.10.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 09/27/2014] [Accepted: 10/09/2014] [Indexed: 01/11/2023]
Abstract
T-cell intracellular antigen-1 (TIA1) is a DNA/RNA binding protein broadly expressed in eukaryotic cells, participating in multiple aspects of cellular metabolism. TIA1 phosphorylation was related with cell apoptosis and its RNA binding activity, however, the regulator and other functions of TIA1 phosphorylation were very little known. To find the modulator of TIA1 phosphorylation, we performed yeast two-hybrid screening and identified annexin A7 (ANXA7) as an interaction protein of TIA1. Recent study showed that a small molecule ABO could directly target ANXA7 and inhibit ANXA7 activity and its targets' phosphorylation. As a GTPase, ANXA7 was speculated to modulate TIA1 phosphorylation. Our results showed that ABO treatment promoted the interaction between TIA1 and ANXA7, and then greatly inhibited phosphorylation of TIA1 in HUVECs. Further results showed that ABO-increased interaction between ANXA7 and TIA1 significantly promoted the processing of a pro-autophagic factor FLJ11812 and the expression of ATG13. Moreover, we found that ABO increased TIA1 protein level, co-localization of ANXA7 and TIA1, and ATG13 expression in the aortic endothelium of apoE(-/-) mice. These data highlighted the new role of TIA1 phosphorylation in autophagy.
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Affiliation(s)
- Shuya Huang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Science, Shandong University, Jinan 250100, China
| | - Ning Liu
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Science, Shandong University, Jinan 250100, China
| | - Haiying Li
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Science, Shandong University, Jinan 250100, China
| | - Jing Zhao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Science, Shandong University, Jinan 250100, China
| | - Le Su
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Science, Shandong University, Jinan 250100, China
| | - Yun Zhang
- The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Shandong University Qilu Hospital, Jinan 250012, China
| | - Shangli Zhang
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Science, Shandong University, Jinan 250100, China
| | - Baoxiang Zhao
- Institute of Organic Chemistry, School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China.
| | - Junying Miao
- Shandong Provincial Key Laboratory of Animal Cells and Developmental Biology, School of Life Science, Shandong University, Jinan 250100, China; The Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education and Chinese Ministry of Health, Shandong University Qilu Hospital, Jinan 250012, China.
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105
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Systems vaccinology: probing humanity's diverse immune systems with vaccines. Proc Natl Acad Sci U S A 2014; 111:12300-6. [PMID: 25136102 DOI: 10.1073/pnas.1400476111] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Homo sapiens are genetically diverse, but dramatic demographic and socioeconomic changes during the past century have created further diversification with respect to age, nutritional status, and the incidence of associated chronic inflammatory disorders and chronic infections. These shifting demographics pose new challenges for vaccination, as emerging evidence suggests that age, the metabolic state, and chronic infections can exert major influences on the immune system. Thus, a key public health challenge is learning how to reprogram suboptimal immune systems to induce effective vaccine immunity. Recent advances have applied systems biological analysis to define molecular signatures induced early after vaccination that correlate with and predict the later adaptive immune responses in humans. Such "systems vaccinology" approaches offer an integrated picture of the molecular networks driving vaccine immunity, and are beginning to yield novel insights about the immune system. Here we discuss the promise of systems vaccinology in probing humanity's diverse immune systems, and in delineating the impact of genes, the environment, and the microbiome on protective immunity induced by vaccination. Such insights will be critical in reengineering suboptimal immune systems in immunocompromised populations.
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106
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Carpenter S, Ricci EP, Mercier BC, Moore MJ, Fitzgerald KA. Post-transcriptional regulation of gene expression in innate immunity. Nat Rev Immunol 2014; 14:361-76. [PMID: 24854588 DOI: 10.1038/nri3682] [Citation(s) in RCA: 275] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Innate immune responses combat infectious microorganisms by inducing inflammatory responses, antimicrobial pathways and adaptive immunity. Multiple genes within each of these functional categories are coordinately and temporally regulated in response to distinct external stimuli. The substantial potential of these responses to drive pathological inflammation and tissue damage highlights the need for rigorous control of these responses. Although transcriptional control of inflammatory gene expression has been studied extensively, the importance of post-transcriptional regulation of these processes is less well defined. In this Review, we discuss the regulatory mechanisms that occur at the level of mRNA splicing, mRNA polyadenylation, mRNA stability and protein translation, and that have instrumental roles in controlling both the magnitude and duration of the inflammatory response.
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Affiliation(s)
- Susan Carpenter
- 1] Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2]
| | - Emiliano P Ricci
- 1] Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2]
| | - Blandine C Mercier
- 1] Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2]
| | - Melissa J Moore
- Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA
| | - Katherine A Fitzgerald
- 1] Program in Innate Immunity, Division of Infectious Diseases and Immunology, Department of Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. [2] Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, 7491 Trondheim, Norway
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107
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Alves LR, Oliveira C, Mörking PA, Kessler RL, Martins ST, Romagnoli BAA, Marchini FK, Goldenberg S. The mRNAs associated to a zinc finger protein from Trypanosoma cruzi shift during stress conditions. RNA Biol 2014; 11:921-33. [PMID: 25180711 PMCID: PMC4179965 DOI: 10.4161/rna.29622] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Trypanosome gene expression is regulated almost exclusively at the posttranscriptional level, through mRNA stability, storage and degradation. Here, we characterize the ribonucleoprotein complex (mRNPs) corresponding to the zinc finger protein TcZC3H39 from T. cruzi comparing cells growing in normal conditions and under nutritional stress. The nutritional stress is a key step during T. cruzi differentiation from epimastigote form to human infective metacyclic trypomastigote form. The mechanisms by which the stress, altogether with other stimuli, triggers differentiation is not well understood. This work aims to characterize the TcZC3H39 protein during stress response. Using cells cultured in normal and stress conditions, we observed a dynamic change in TcZC3H39 granule distribution, which appeared broader in stressed epimastigotes. The protein core of the TcZC3H39-mRNP is composed of ribosomes, translation factors and RBPs. The TcZC3H39-mRNP could act sequestering highly expressed mRNAs and their associated ribosomes, potentially slowing translation in stress conditions. A shift were observed in the mRNAs associated with TcZC3H39: the number of targets in unstressed epimastigotes was smaller than that in stressed parasites, with no clear functional clustering in normal conditions. By contrast, in stressed parasites, the targets of TcZC3H39 were mRNAs encoding ribosomal proteins and a remarkable enrichment in mRNAs for the cytochrome c complex (COX), highly expressed mRNAs in the replicative form. This identification of a new component of RNA granules in T. cruzi, the TcZC3H39 protein, provides new insight into the mechanisms involved in parasite stress responses and the regulation of gene expression during T. cruzi differentiation.
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108
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The stress granule component TIA-1 binds tick-borne encephalitis virus RNA and is recruited to perinuclear sites of viral replication to inhibit viral translation. J Virol 2014; 88:6611-22. [PMID: 24696465 DOI: 10.1128/jvi.03736-13] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
UNLABELLED Flaviviruses are a major cause of disease in humans and animals worldwide. Tick-borne encephalitis virus (TBEV) is the most important arthropod-borne flavivirus endemic in Europe and is the etiological agent of tick-borne encephalitis, a potentially fatal infection of the central nervous system. However, the contributions of host proteins during TBEV infection are poorly understood. In this work, we investigate the cellular protein TIA-1 and its cognate factor TIAR, which are stress-induced RNA-binding proteins involved in the repression of initiation of translation of cellular mRNAs and in the formation of stress granules. We show that TIA-1 and TIAR interact with viral RNA in TBEV-infected cells. During TBEV infection, cytoplasmic TIA-1 and TIAR are recruited at sites of viral replication with concomitant depletion from stress granules. This effect is specific, since G3BP1, another component of these cytoplasmic structures, remains localized to stress granules. Moreover, heat shock induction of stress granules containing TIA-1, but not G3BP1, is inhibited in TBEV-infected cells. Infection of cells depleted of TIA-1 or TIAR by small interfering RNA (siRNA) or TIA-1(-/-) mouse fibroblasts, leads to a significant increase in TBEV extracellular infectivity. Interestingly, TIAR(-/-) fibroblasts show the opposite effect on TBEV infection, and this phenotype appears to be related to an excess of TIA-1 in these cells. Taking advantage of a TBE-luciferase replicon system, we also observed increased luciferase activity in TIA-1(-/-) mouse fibroblasts at early time points, consistent with TIA-1-mediated inhibition at the level of the first round of viral translation. These results indicate that, in response to TBEV infection, TIA-1 is recruited to sites of virus replication to bind TBEV RNA and modulate viral translation independently of stress granule (SG) formation. IMPORTANCE This study (i) extends previous work that showed TIA-1/TIAR recruitment at sites of flavivirus replication, (ii) demonstrates that TIAR behaves like TIA-1 as an inhibitor of viral replication using an RNA interference (RNAi) approach in human cells that contradicts the previous hypothesis based on mouse embryonic fibroblast (MEF) knockouts only, (iii) demonstrates that tick-borne encephalitis virus (TBEV) is capable of inducing bona fide G3BP1/eIF3/eIF4B-positive stress granules, (iv) demonstrates a differential phenotype of stress response proteins following viral infection, and (v) implicates TIA-1 in viral translation and as a modulator of TBEV replication.
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109
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Kim HJ, Raphael AR, LaDow ES, McGurk L, Weber RA, Trojanowski JQ, Lee VMY, Finkbeiner S, Gitler AD, Bonini NM. Therapeutic modulation of eIF2α phosphorylation rescues TDP-43 toxicity in amyotrophic lateral sclerosis disease models. Nat Genet 2014; 46:152-60. [PMID: 24336168 PMCID: PMC3934366 DOI: 10.1038/ng.2853] [Citation(s) in RCA: 288] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 11/22/2013] [Indexed: 12/12/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a fatal, late-onset neurodegenerative disease primarily affecting motor neurons. A unifying feature of many proteins associated with ALS, including TDP-43 and ataxin-2, is that they localize to stress granules. Unexpectedly, we found that genes that modulate stress granules are strong modifiers of TDP-43 toxicity in Saccharomyces cerevisiae and Drosophila melanogaster. eIF2α phosphorylation is upregulated by TDP-43 toxicity in flies, and TDP-43 interacts with a central stress granule component, polyA-binding protein (PABP). In human ALS spinal cord neurons, PABP accumulates abnormally, suggesting that prolonged stress granule dysfunction may contribute to pathogenesis. We investigated the efficacy of a small molecule inhibitor of eIF2α phosphorylation in ALS models. Treatment with this inhibitor mitigated TDP-43 toxicity in flies and mammalian neurons. These findings indicate that the dysfunction induced by prolonged stress granule formation might contribute directly to ALS and that compounds that mitigate this process may represent a novel therapeutic approach.
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Affiliation(s)
- Hyung-Jun Kim
- 1] Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA. [2]
| | - Alya R Raphael
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Eva S LaDow
- Gladstone Institute of Neurological Disease, San Francisco, California, USA
| | - Leeanne McGurk
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Ross A Weber
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - John Q Trojanowski
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Virginia M-Y Lee
- Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Steven Finkbeiner
- Gladstone Institute of Neurological Disease, San Francisco, California, USA
| | - Aaron D Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
| | - Nancy M Bonini
- Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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110
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Ravindran R, Khan N, Nakaya HI, Li S, Loebbermann J, Maddur MS, Park Y, Jones DP, Chappert P, Davoust J, Weiss DS, Virgin HW, Ron D, Pulendran B. Vaccine activation of the nutrient sensor GCN2 in dendritic cells enhances antigen presentation. Science 2014; 343:313-317. [PMID: 24310610 PMCID: PMC4048998 DOI: 10.1126/science.1246829] [Citation(s) in RCA: 158] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The yellow fever vaccine YF-17D is one of the most successful vaccines ever developed in humans. Despite its efficacy and widespread use in more than 600 million people, the mechanisms by which it stimulates protective immunity remain poorly understood. Recent studies using systems biology approaches in humans have revealed that YF-17D-induced early expression of general control nonderepressible 2 kinase (GCN2) in the blood strongly correlates with the magnitude of the later CD8(+) T cell response. We demonstrate a key role for virus-induced GCN2 activation in programming dendritic cells to initiate autophagy and enhanced antigen presentation to both CD4(+) and CD8(+) T cells. These results reveal an unappreciated link between virus-induced integrated stress response in dendritic cells and the adaptive immune response.
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Affiliation(s)
- Rajesh Ravindran
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
| | - Nooruddin Khan
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
- Department of Biotechnology, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India
| | - Helder I. Nakaya
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322, USA
| | - Shuzhao Li
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
| | - Jens Loebbermann
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
| | - Mohan S. Maddur
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
| | - Youngja Park
- College of Pharmacy, Korea University, 339-700 Korea
| | - Dean P. Jones
- Department of Medicine, Division of Pulmonary, Allergy and Critical Care, Emory University, Atlanta, GA 30322, USA
| | - Pascal Chappert
- Institut National de la Santéet de la Recherche Médicale U1013, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris 75743 Paris Cedex 15, France
| | - Jean Davoust
- Institut National de la Santéet de la Recherche Médicale U1013, Paris, France
- Université Paris Descartes, Sorbonne Paris Cité, Paris 75743 Paris Cedex 15, France
| | - David S. Weiss
- Department of Medicine, Division of Infectious Diseases, Emory University, Atlanta, GA 30329, USA
| | - Herbert W. Virgin
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - David Ron
- University of Cambridge Metabolic Research Laboratories and NIHR Cambridge Biomedical Research Centre, Cambridge CB2 0QQ, UK
| | - Bali Pulendran
- Emory Vaccine Center, Yerkes National Primate Research Center, Emory University, 954 Gatewood Road, Atlanta, GA 30329, USA
- Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322, USA
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111
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Aktaş C, Kurtman C, Ozbilgin MK, Tek I, Toprak SK. An Experimental Study of Radiation Effect on Normal Tissue: Analysis of HIF-1α, VEGF, eIF2, TIA-1, and TSP-1 Expression. Turk J Haematol 2013; 30:371-8. [PMID: 24385827 PMCID: PMC3874960 DOI: 10.4274/tjh.2012.0142] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Accepted: 02/18/2013] [Indexed: 01/20/2023] Open
Abstract
Objective: This study investigated whether or not the stress and hypoxia, which are the effects of radiation on normal vascular endothelium, leading to the release of HIF-1α, VEGF, eIF2, TIA-1, and TSP-1 were related and the possibility of them stimulating angiogenesis.
Materials and Methods: Twenty-four male Swiss Albino mice were separated into 4 groups. The first group was the control group (Group 1), and the second, third, and fourth groups were euthanized after 24 h (Group 2), 48 h (Group 3), and 7 days (Group 4), respectively. A single-fractioned 10 Gy of ionizing radiation was applied to all mice’s pelvic zone with Co-60. Bladders were removed completely from the pelvic region. Immunohistochemistry and light microscopy were used to investigate whether there would be an increase or not in the angiogenesis pathway by using the HIF-1α, VEGF, eIF2, TIA-1, and TSP-1 antibodies. Results: The HIF-1α antibody showed strong staining in Group 3, while the staining intensity was less in other groups. VEGF showed weak staining in Groups 1 and 4, while moderate staining in Group 2 and strong staining in Group 3 was observed. eIF2 showed strong staining in Groups 1 and 4. Groups 2 and 3 were stained weakly. In the present study, staining with TSP-1 was very strong in the samples belonging to Group 1, while other groups showed very weak staining. Conclusion: When normal tissue was exposed to radiation, the positively effective factors (HIF-1, VEGF, eIF2, and TIA-1) on the angiogenesis pathway were increased while the negative factor (TSP-1) was decreased. Radiation may initiate physiological angiogenesis in the normal tissue and accelerate healing in the damaged normal tissue.
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Affiliation(s)
- Caner Aktaş
- Bülent Ecevit University School of Medicine, Department of Radiation Oncology, Zonguldak, Turkey
| | - Cengiz Kurtman
- Ankara University School of Medicine, Department of Radiation Oncology, Ankara, Turkey
| | - M Kemal Ozbilgin
- Celal Bayar University School of Medicine, Department of Histology and Embryology, Manisa, Turkey
| | - Ibrahim Tek
- Medicana International Hospital, Department of Medical Oncology, Ankara, Turkey
| | - Selami Koçak Toprak
- Başkent University School of Medicine, Department of Hematology, Ankara, Turkey
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112
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Metz P, Reuter A, Bender S, Bartenschlager R. Interferon-stimulated genes and their role in controlling hepatitis C virus. J Hepatol 2013; 59:1331-41. [PMID: 23933585 DOI: 10.1016/j.jhep.2013.07.033] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 07/23/2013] [Accepted: 07/24/2013] [Indexed: 12/24/2022]
Abstract
Infections with the hepatitis C virus (HCV) are a major cause of chronic liver disease. While the acute phase of infection is mostly asymptomatic, this virus has the high propensity to establish persistence and in the course of one to several decades liver disease can develop. HCV is a paradigm for the complex interplay between the interferon (IFN) system and viral countermeasures. The virus induces an IFN response within the infected cell and is rather sensitive against the antiviral state triggered by IFNs, yet in most cases HCV persists. Numerous IFN-stimulated genes (ISGs) have been reported to suppress HCV replication, but in only a few cases we begin to understand the molecular mechanisms underlying antiviral activity. It is becoming increasingly clear that blockage of viral replication is mediated by the concerted action of multiple ISGs that target different steps of the HCV replication cycle. This review briefly summarizes the activation of the IFN system by HCV and then focuses on ISGs targeting the HCV replication cycle and their possible mode of action.
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Affiliation(s)
- Philippe Metz
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Heidelberg, Germany
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Carroll K, Hastings C, Miller CL. Amino acids 78 and 79 of Mammalian Orthoreovirus protein µNS are necessary for stress granule localization, core protein λ2 interaction, and de novo virus replication. Virology 2013; 448:133-45. [PMID: 24314644 DOI: 10.1016/j.virol.2013.10.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/01/2013] [Accepted: 10/05/2013] [Indexed: 12/25/2022]
Abstract
At early times in Mammalian Orthoreovirus (MRV) infection, cytoplasmic inclusions termed stress granules (SGs) are formed as a component of the innate immune response, however, at later times they are no longer present despite continued immune signaling. To investigate the roles of MRV proteins in SG modulation we examined non-structural protein µNS localization relative to SGs in infected and transfected cells. Using a series of mutant plasmids, we mapped the necessary μNS residues for SG localization to amino acids 78 and 79. We examined the capacity of a μNS(78-79) mutant to associate with known viral protein binding partners of μNS and found that it loses association with viral core protein λ2. Finally, we show that while this mutant cannot support de novo viral replication, it is able to rescue replication following siRNA knockdown of μNS. These data suggest that μNS association with SGs, λ2, or both play roles in MRV replication.
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Affiliation(s)
- Kate Carroll
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames 50011, IA, USA; Program in Genetics, Iowa State University, Ames 50011, IA, USA
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Pulendran B, Oh JZ, Nakaya HI, Ravindran R, Kazmin DA. Immunity to viruses: learning from successful human vaccines. Immunol Rev 2013; 255:243-55. [PMID: 23947360 PMCID: PMC3748616 DOI: 10.1111/imr.12099] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
For more than a century, immunologists and vaccinologists have existed in parallel universes. Immunologists have for long reveled in using 'model antigens', such as chicken egg ovalbumin or nitrophenyl haptens, to study immune responses in model organisms such as mice. Such studies have yielded many seminal insights about the mechanisms of immune regulation, but their relevance to humans has been questioned. In another universe, vaccinologists have relied on human clinical trials to assess vaccine efficacy, but have done little to take advantage of such trials for studying the nature of immune responses to vaccination. The human model provides a nexus between these two universes, and recent studies have begun to use this model to study the molecular profile of innate and adaptive responses to vaccination. Such 'systems vaccinology' studies are beginning to provide mechanistic insights about innate and adaptive immunity in humans. Here, we present an overview of such studies, with particular examples from studies with the yellow fever and the seasonal influenza vaccines. Vaccination with the yellow fever vaccine causes a systemic acute viral infection and thus provides an attractive model to study innate and adaptive responses to a primary viral challenge. Vaccination with the live attenuated influenza vaccine causes a localized acute viral infection in mucosal tissues and induces a recall response, since most vaccinees have had prior exposure to influenza, and thus provides a unique opportunity to study innate and antigen-specific memory responses in mucosal tissues and in the blood. Vaccination with the inactivated influenza vaccine offers a model to study immune responses to an inactivated immunogen. Studies with these and other vaccines are beginning to reunite the estranged fields of immunology and vaccinology, yielding unexpected insights about mechanisms of viral immunity. Vaccines that have been proven to be of immense benefit in saving lives offer us a new fringe benefit: lessons in viral immunology.
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115
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Silva-García CG, Estela Navarro R. The C. elegans TIA-1/TIAR homolog TIAR-1 is required to induce germ cell apoptosis. Genesis 2013; 51:690-707. [PMID: 23913578 DOI: 10.1002/dvg.22418] [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] [Received: 06/05/2013] [Revised: 07/20/2013] [Accepted: 07/22/2013] [Indexed: 11/11/2022]
Abstract
In Caenorhabditis elegans, physiological germ cell apoptosis eliminates more than half of the cells in the hermaphrodite gonad to support gamete quality and germline homeostasis by a still unidentified mechanism. External factors can also affect germ cell apoptosis. The BH3-only protein EGL-1 induces germ cell apoptosis when animals are exposed to pathogens or agents that produce DNA damage. DNA damage-induced apoptosis also requires the nematode p53 homolog CEP-1. Previously, we found that heat shock, oxidative, and osmotic stresses induce germ cell apoptosis through an EGL-1 and CEP-1 independent mechanism that requires the MAPKK pathway. However, we observed that starvation increases germ cell apoptosis by an unknown pathway. Searching for proteins that participate in stress-induced apoptosis, we found the RNA-binding protein TIAR-1 (a homolog of the mammalian TIA-1/TIAR family of proteins). Here, we show that TIAR-1 in C. elegans is required to induce apoptosis in the germline under several conditions. We also show that TIAR-1 acts downstream of CED-9 (a BCL2 homolog) to induce apoptosis under stress conditions, and apparently does not seem to regulate ced-4 or ced-3 mRNAs accumulation directly. TIAR-1 is expressed ubiquitously in the cytoplasm of the soma as well as the germline, where it sometimes associates with P granules. We show that animals lacking TIAR-1 expression are temperature sensitive sterile due to oogenesis and spermatogenesis defects. Our work shows that TIAR-1 is required for proper germline function and demonstrates that this protein is important to induce germ cell apoptosis under several conditions.
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Affiliation(s)
- Carlos Giovanni Silva-García
- Departamento de Biología Celular y Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México
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116
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Ng SK, Weissbach R, Ronson GE, Scadden ADJ. Proteins that contain a functional Z-DNA-binding domain localize to cytoplasmic stress granules. Nucleic Acids Res 2013; 41:9786-99. [PMID: 23982513 PMCID: PMC3834823 DOI: 10.1093/nar/gkt750] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Long double-stranded RNA may undergo hyper-editing by adenosine deaminases that act on RNA (ADARs), where up to 50% of adenosine residues may be converted to inosine. However, although numerous RNAs may undergo hyper-editing, the role for inosine-containing hyper-edited double-stranded RNA in cells is poorly understood. Nevertheless, editing plays a critical role in mammalian cells, as highlighted by the analysis of ADAR-null mutants. In particular, the long form of ADAR1 (ADAR1p150) is essential for viability. Moreover, a number of studies have implicated ADAR1p150 in various stress pathways. We have previously shown that ADAR1p150 localized to cytoplasmic stress granules in HeLa cells following either oxidative or interferon-induced stress. Here, we show that the Z-DNA-binding domain (ZαADAR1) exclusively found in ADAR1p150 is required for its localization to stress granules. Moreover, we show that fusion of ZαADAR1 to either green fluorescent protein (GFP) or polypyrimidine binding protein 4 (PTB4) also results in their localization to stress granules. We additionally show that the Zα domain from other Z-DNA-binding proteins (ZBP1, E3L) is likewise sufficient for localization to stress granules. Finally, we show that Z-RNA or Z-DNA binding is important for stress granule localization. We have thus identified a novel role for Z-DNA-binding domains in mammalian cells.
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Affiliation(s)
- Siew Kit Ng
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, UK
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117
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Jones BL, VanLoozen J, Kim MH, Miles SJ, Dunham CM, Williams LD, Snell TW. Stress granules form in Brachionus manjavacas (Rotifera) in response to a variety of stressors. Comp Biochem Physiol A Mol Integr Physiol 2013; 166:375-84. [PMID: 23856158 DOI: 10.1016/j.cbpa.2013.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 02/05/2023]
Abstract
Many eukaryotes share a common response to environmental stresses. The responses include reorganization of cellular organelles and proteins. Similar stress responses between divergent species suggest that these protective mechanisms may have evolved early and been retained from the earliest eukaryotic ancestors. Many eukaryotic cells have the capacity to sequester proteins and mRNAs into transient stress granules (SGs) that protect most cellular mRNAs (Anderson and Kedersha, 2008). Our observations extend the phylogenetic range of SGs from trypanosomatids, insects, yeast and mammalian cells, where they were first described, to a species of the lophotrochozoan animal phylum Rotifera. We focus on the distribution of three proteins known to be associated with both ribosomes and SG formation: eukaryotic initiation factors eIF3B, eIF4E and T-cell-restricted intracellular antigen 1. We found that these three proteins co-localize to SGs in rotifers in response to temperature stress, osmotic stress and nutrient deprivation as has been described in other eukaryotes. We have also found that the large ribosomal subunit fails to localize to the SGs in rotifers. Furthermore, the SGs in rotifers disperse once the environmental stress is removed as demonstrated in yeast and mammalian cells. These results are consistent with SG formation in trypanosomatids, insects, yeast and mammalian cells, further supporting the presence of this protective mechanism early in the evolution of eukaryotes.
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Affiliation(s)
- Brande L Jones
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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118
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Fitzgerald KD, Semler BL. Poliovirus infection induces the co-localization of cellular protein SRp20 with TIA-1, a cytoplasmic stress granule protein. Virus Res 2013; 176:223-31. [PMID: 23830997 PMCID: PMC3742715 DOI: 10.1016/j.virusres.2013.06.012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2013] [Revised: 06/21/2013] [Accepted: 06/21/2013] [Indexed: 12/18/2022]
Abstract
Different types of environmental stress cause mammalian cells to form cytoplasmic foci, termed stress granules, which contain mRNPs that are translationally silenced. These foci are transient and dynamic, and contain components of the cellular translation machinery as well as certain mRNAs and RNA binding proteins. Stress granules are known to be induced by conditions such as hypoxia, nutrient deprivation, and oxidative stress, and a number of cellular factors have been identified that are commonly associated with these foci. More recently it was discovered that poliovirus infection also induces the formation of stress granules, although these cytoplasmic foci appear to be somewhat compositionally unique. Work described here examined the punctate pattern of SRp20 (a host cell mRNA splicing protein) localization in the cytoplasm of poliovirus-infected cells, demonstrating the partial co-localization of SRp20 with the stress granule marker protein TIA-1. We determined that SRp20 does not co-localize with TIA-1, however, under conditions of oxidative stress, indicating that the close association of these two proteins during poliovirus infection is not representative of a general response to cellular stress. We confirmed that the expression of a dominant negative version of TIA-1 (TIA-1-PRD) results in the dissociation of stress granules. Finally, we demonstrated that expression of wild type TIA-1 or dominant negative TIA-1-PRD in cells during poliovirus infection does not dramatically affect viral translation. Taken together, these studies provide a new example of the unique cytoplasmic foci that form during poliovirus infection.
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Affiliation(s)
| | - Bert L. Semler
- Corresponding author. Tel.: +1 949 824 7573; fax: +1 949 824 2694.
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119
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Mahboubi H, Seganathy E, Kong D, Stochaj U. Identification of Novel Stress Granule Components That Are Involved in Nuclear Transport. PLoS One 2013; 8:e68356. [PMID: 23826389 PMCID: PMC3694919 DOI: 10.1371/journal.pone.0068356] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Accepted: 05/31/2013] [Indexed: 11/30/2022] Open
Abstract
Background Importin-α1 belongs to a subfamily of nuclear transport adaptors and participates in diverse cellular functions. Best understood for its role in protein transport, importin-α1 also contributes to other biological processes. For instance, arsenite treatment causes importin-α1 to associate with cytoplasmic stress granules (SGs) in mammalian cells. These stress-induced compartments contain translationally arrested mRNAs, small ribosomal subunits and numerous proteins involved in mRNA transport and metabolism. At present, it is not known whether members of all three importin-α subfamilies locate to SGs in response to stress. Results Here, we demonstrate that the oxidant diethyl maleate (DEM), arsenite and heat shock, promote the formation of cytoplasmic SGs that contain nuclear transport factors. Specifically, importin-α1, α4 and α5, which belong to distinct subfamilies, and importin-β1 were targeted by all of these stressors to cytoplasmic SGs, but not to P-bodies. Importin-α family members have been implicated in transcriptional regulation, which prompted us to analyze their ability to interact with poly(A)-RNA in growing cells. Our studies show that importin-α1, but not α4, α5, importin-β1 or CAS, associated with poly(A)-RNA under nonstress conditions. Notably, this interaction was significantly reduced when cells were treated with DEM. Additional studies suggest that importin-α1 is likely connected to poly(A)-RNA through an indirect interaction, as the adaptor did not bind homopolymer RNA specifically in vitro. Significance Our studies establish that members of three importin-α subfamilies are bona fide SG components under different stress conditions. Furthermore, importin-α1 is unique in its ability to interact with poly(A)-RNA in a stress-dependent fashion, and in vitro experiments indicate that this association is indirect. Collectively, our data emphasize that nuclear transport factors participate in a growing number of cellular activities that are modulated by stress.
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Affiliation(s)
- Hicham Mahboubi
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | | | - Dekun Kong
- Department of Physiology, McGill University, Montreal, Quebec, Canada
| | - Ursula Stochaj
- Department of Physiology, McGill University, Montreal, Quebec, Canada
- * E-mail:
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120
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Song Z, Zhao D, Yang L. Molecular mechanisms of neurodegeneration mediated by dysfunctional subcellular organelles in transmissible spongiform encephalopathies. Acta Biochim Biophys Sin (Shanghai) 2013; 45:452-64. [PMID: 23439666 DOI: 10.1093/abbs/gmt014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Transmissible spongiform encephalopathies refer to a group of infectious neurodegenerative diseases with an entirely novel mechanism of transmission and pathophysiology including synaptic damage, dendritic atrophy, vacuolization, and microglial activation. Extensive neuronal loss is the main cause of chronic brain deterioration and fatal outcome of prion diseases. As the final outcome of pathological alterations, neuronal death is a prominent feature of all prion diseases. The mechanisms responsible for prion diseases are not well understood. A more comprehensive understanding of the molecular basis of neuronal damage is essential for the development of an effective therapy for transmissible spongiform encephalopathies and other neurodegenerative diseases sharing similar features. Here, we review the molecular mechanisms of mitochondrial dysfunction and endoplasmic reticulum stress-mediated neuronal death, which play crucial roles in the pathogenisis of prion diseases.
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Affiliation(s)
- Zhiqi Song
- State Key Laboratories for Agrobiotechnology, China Agricultural University, Beijing 100193, China
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121
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Meijer TWH, Kaanders JHAM, Span PN, Bussink J. Targeting hypoxia, HIF-1, and tumor glucose metabolism to improve radiotherapy efficacy. Clin Cancer Res 2013; 18:5585-94. [PMID: 23071360 DOI: 10.1158/1078-0432.ccr-12-0858] [Citation(s) in RCA: 326] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Radiotherapy, an important treatment modality in oncology, kills cells through induction of oxidative stress. However, malignant tumors vary in their response to irradiation as a consequence of resistance mechanisms taking place at the molecular level. It is important to understand these mechanisms of radioresistance, as counteracting them may improve the efficacy of radiotherapy. In this review, we describe how the hypoxia-inducible factor 1 (HIF-1) pathway has a profound effect on the response to radiotherapy. The main focus will be on HIF-1-controlled protection of the vasculature postirradiation and on HIF-1 regulation of glycolysis and the pentose phosphate pathway. This aberrant cellular metabolism increases the antioxidant capacity of tumors, thereby countering the oxidative stress caused by irradiation. From the results of translational studies and the first clinical phase I/II trials, it can be concluded that targeting HIF-1 and tumor glucose metabolism at several levels reduces the antioxidant capacity of tumors, affects the tumor microenvironment, and sensitizes various solid tumors to irradiation.
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Affiliation(s)
- Tineke W H Meijer
- Department of Radiation Oncology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
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122
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Impairment of FOS mRNA stabilization following translation arrest in granulocytes from myelodysplastic syndrome patients. PLoS One 2013; 8:e61107. [PMID: 23593403 PMCID: PMC3625160 DOI: 10.1371/journal.pone.0061107] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/05/2013] [Indexed: 02/06/2023] Open
Abstract
Although quantitative and qualitative granulocyte defects have been described in myelodysplastic syndromes (MDS), the underlying molecular basis of granulocyte dysfunction in MDS is largely unknown. We recently found that FOS mRNA elevation under translation-inhibiting stimuli was significantly smaller in granulocytes from MDS patients than in healthy individuals. The aim of this study is to clarify the cause of the impaired FOS induction in MDS. We first examined the mechanisms of FOS mRNA elevation using granulocytes from healthy donors cultured with the translation inhibitor emetine. Emetine increased both transcription and mRNA stability of FOS. p38 MAPK inhibition abolished the emetine-induced increase of FOS transcription but did not affect FOS mRNA stabilization. The binding of an AU-rich element (ARE)-binding protein HuR to FOS mRNA containing an ARE in 3'UTR was increased by emetine, and the knockdown of HuR reduced the FOS mRNA stabilizing effect of emetine. We next compared the emetine-induced transcription and mRNA stabilization of FOS between MDS patients and healthy controls. Increased rates of FOS transcription by emetine were similar in MDS and controls. In the absence of emetine, FOS mRNA decayed to nearly 17% of initial levels in 45 min in both groups. In the presence of emetine, however, 76.7±19.8% of FOS mRNA remained after 45 min in healthy controls, versus 37.9±25.5% in MDS (P<0.01). To our knowledge, this is the first report demonstrating attenuation of stress-induced FOS mRNA stabilization in MDS granulocytes.
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123
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Kim HS, Headey SJ, Yoga YMK, Scanlon MJ, Gorospe M, Wilce MCJ, Wilce JA. Distinct binding properties of TIAR RRMs and linker region. RNA Biol 2013; 10:579-89. [PMID: 23603827 PMCID: PMC3710364 DOI: 10.4161/rna.24341] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The RNA-binding protein TIAR is an mRNA-binding protein that acts as a translational repressor, particularly important under conditions of cellular stress. It binds to target mRNA and DNA via its RNA recognition motif (RRM) domains and is involved in both splicing regulation and translational repression via the formation of "stress granules." TIAR has also been shown to bind ssDNA and play a role in the regulation of transcription. Here we show, using surface plasmon resonance and nuclear magnetic resonance spectroscopy, specific roles of individual TIAR domains for high-affinity binding to RNA and DNA targets. We confirm that RRM2 of TIAR is the major RNA- and DNA-binding domain. However, the strong nanomolar affinity binding to U-rich RNA and T-rich DNA depends on the presence of the six amino acid residues found in the linker region C-terminal to RRM2. On its own, RRM1 shows preferred binding to DNA over RNA. We further characterize the interaction between RRM2 with the C-terminal extension and an AU-rich target RNA sequence using NMR spectroscopy to identify the amino acid residues involved in binding. We demonstrate that TIAR RRM2, together with its C-terminal extension, is the major contributor for the high-affinity (nM) interactions of TIAR with target RNA sequences.
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Affiliation(s)
- Henry S Kim
- Department of Biochemistry and Molecular Biology, Monash University, Victoria, Australia
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124
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Gupta SK, Carmi S, Waldman Ben-Asher H, Tkacz ID, Naboishchikov I, Michaeli S. Basal splicing factors regulate the stability of mature mRNAs in trypanosomes. J Biol Chem 2013; 288:4991-5006. [PMID: 23283975 DOI: 10.1074/jbc.m112.416578] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gene expression in trypanosomes is mainly regulated post-transcriptionally. Genes are transcribed as polycistronic mRNAs that are dissected by the concerted action of trans-splicing and polyadenylation. In trans-splicing, a common exon, the spliced leader, is added to all mRNAs from a small RNA. In this study, we examined by microarray analysis the transcriptome following RNAi silencing of the basal splicing factors U2AF65, SF1, and U2AF35. The transcriptome data revealed correlations between the affected genes and their splicing and polyadenylation signaling properties, suggesting that differential binding of these factors to pre-mRNA regulates trans-splicing and hence expression of specific genes. Surprisingly, all these factors were shown to affect not only splicing but also mRNA stability. Affinity purification of SF1 and U2AF35 complexes supported their role in mRNA stability. U2AF35 but not SF1 was shown to bind to ribosomes. To examine the role of splicing factors in mRNA stability, mutations were introduced into the polypyrimidine tract located in the 3' UTR of a mini-gene, and the results demonstrate that U2AF65 binds to such a site and controls the mRNA stability. We propose that transcripts carrying splicing signals in their 3' UTR bind the splicing factors and control their stability.
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Affiliation(s)
- Sachin Kumar Gupta
- Mina and Everard Goodman Faculty of Life Sciences, and Advanced Materials and Nanotechnology Institute, Bar-Ilan University, Ramat-Gan 52900, Israel
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125
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Li W, Ivanov P, Anderson P. Fas-activated Ser/Thr phosphoprotein (FAST) is a eukaryotic initiation factor 4E-binding protein that regulates mRNA stability and cell survival. TRANSLATION 2013; 1:e24047. [PMID: 26824015 PMCID: PMC4718062 DOI: 10.4161/trla.24047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2012] [Revised: 02/01/2013] [Accepted: 02/18/2013] [Indexed: 12/02/2022]
Abstract
The recognition of T cell intracellular antigen-1 (TIA-1) by Fas-activated Ser/Thr phosphoprotein (FAST) results in prolonged cell survival by inducing the expression of inhibitors of apoptosis. Here we show that the functional effects of FAST are dependent on its interactions with eukaryotic translation initiation factor 4E (eIF4E) which is the major cytosolic cap binding protein in cells. FAST binds to eIF4E via a consensus motif (428YXXXXLL433) that is also found in eIF4G, 4E-BP1/2/3, 4E-T, and cup. A point mutation within this motif at Y428 dampens the ability of FAST to recognize eIF4E. Wild-type (WT) FAST, but not its Y428G mutant, increases the expression of co-transfected cellular inhibitor of apoptosis-1 (cIAP-1) and β-gal mRNA and protein, but inhibits the Fas-induced activation of caspase-3. Increased expression of the co-transfected proteins results, in part, from stabilization of mRNA, suggesting that FAST:eIF4E interactions can inhibit mRNA decay. We propose that eIF4E:FAST:TIA-1 complexes regulate the translation and stability of specific mRNAs that encode proteins important for cell survival.
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Affiliation(s)
- Wei Li
- Department of Medicine; Division of Rheumatology, Immunology, and Allergy; Brigham and Women's Hospital; Harvard Medical School; Boston, MA USA
| | - Pavel Ivanov
- Department of Medicine; Division of Rheumatology, Immunology, and Allergy; Brigham and Women's Hospital; Harvard Medical School; Boston, MA USA
| | - Paul Anderson
- Department of Medicine; Division of Rheumatology, Immunology, and Allergy; Brigham and Women's Hospital; Harvard Medical School; Boston, MA USA
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Perez-Pepe M, Slomiansky V, Loschi M, Luchelli L, Neme M, Thomas MG, Boccaccio GL. BUHO: a MATLAB script for the study of stress granules and processing bodies by high-throughput image analysis. PLoS One 2012; 7:e51495. [PMID: 23284702 PMCID: PMC3527446 DOI: 10.1371/journal.pone.0051495] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 11/01/2012] [Indexed: 01/15/2023] Open
Abstract
The spontaneous and reversible formation of foci and filaments that contain proteins involved in different metabolic processes is common in both the nucleus and the cytoplasm. Stress granules (SGs) and processing bodies (PBs) belong to a novel family of cellular structures collectively known as mRNA silencing foci that harbour repressed mRNAs and their associated proteins. SGs and PBs are highly dynamic and they form upon stress and dissolve thus releasing the repressed mRNAs according to changes in cell physiology. In addition, aggregates containing abnormal proteins are frequent in neurodegenerative disorders. In spite of the growing relevance of these supramolecular aggregates to diverse cellular functions a reliable automated tool for their systematic analysis is lacking. Here we report a MATLAB Script termed BUHO for the high-throughput image analysis of cellular foci. We used BUHO to assess the number, size and distribution of distinct objects with minimal deviation from manually obtained parameters. BUHO successfully addressed the induction of both SGs and PBs in mammalian and insect cells exposed to different stress stimuli. We also used BUHO to assess the dynamics of specific mRNA-silencing foci termed Smaug 1 foci (S-foci) in primary neurons upon synaptic stimulation. Finally, we used BUHO to analyze the role of candidate genes on SG formation in an RNAi-based experiment. We found that FAK56D, GCN2 and PP1 govern SG formation. The role of PP1 is conserved in mammalian cells as judged by the effect of the PP1 inhibitor salubrinal, and involves dephosphorylation of the translation factor eIF2α. All these experiments were analyzed manually and by BUHO and the results differed in less than 5% of the average value. The automated analysis by this user-friendly method will allow high-throughput image processing in short times by providing a robust, flexible and reliable alternative to the laborious and sometimes unfeasible visual scrutiny.
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127
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Stress granule formation induced by measles virus is protein kinase PKR dependent and impaired by RNA adenosine deaminase ADAR1. J Virol 2012; 87:756-66. [PMID: 23115276 DOI: 10.1128/jvi.02270-12] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
ADAR1, an interferon (IFN)-inducible double-stranded (ds) RNA-specific adenosine deaminase, downregulates host innate responses, including activation of the dsRNA-dependent protein kinase (PKR) and induction of IFN-β mRNA. Conversely, PKR amplifies IFN-β induction by measles virus (MV) and inhibits virus protein synthesis. Formation of stress granules (SGs), cytoplasmic aggregates of stalled translation complexes and RNA-binding proteins, is a host response to virus infection mediated by translation initiation factor eIF2α phosphorylation. We examined the roles of PKR and ADAR1 in SG formation using HeLa cells stably deficient in either PKR (PKR(kd)) or ADAR1 (ADAR1(kd)) compared to control (CON(kd)) cells. Infection with either wild-type (WT) MV or an isogenic mutant lacking C protein expression (C(ko)) comparably induced formation of SG in ADAR1(kd) cells, whereas only the C(ko) mutant was an efficient inducer in control cells. Both ADAR1 and PKR colocalized with SG following infection. MV-induced; SG formation was PKR dependent but impaired by ADAR1. Complementation of ADAR1(kd) cells by expression of either p150 WT isoform or the p150 Zα (Y177A) Z-DNA-binding mutant of ADAR1 restored suppression of host responses, including SG formation and PKR activation. In contrast, neither the p110 WT isoform nor the p150 catalytic (H910A, E912A) mutant of ADAR1 complemented the ADAR1(kd) phenotype. These results further establish ADAR1 as a suppressor of host innate responses, including activation of PKR and the subsequent SG response.
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128
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Abstract
The double-stranded RNA-dependent protein kinase PKR plays multiple roles in cells, in response to different stress situations. As a member of the interferon (IFN)‑Stimulated Genes, PKR was initially recognized as an actor in the antiviral action of IFN, due to its ability to control translation, through phosphorylation, of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). As such, PKR participates in the generation of stress granules, or autophagy and a number of viruses have designed strategies to inhibit its action. However, PKR deficient mice resist most viral infections, indicating that PKR may play other roles in the cell other than just acting as an antiviral agent. Indeed, PKR regulates several signaling pathways, either as an adapter protein and/or using its kinase activity. Here we review the role of PKR as an eIF2α kinase, its participation in the regulation of the NF-κB, p38MAPK and insulin pathways, and we focus on its role during infection with the hepatitis C virus (HCV). PKR binds the HCV IRES RNA, cooperates with some functions of the HCV core protein and may represent a target for NS5A or E2. Novel data points out for a role of PKR as a pro-HCV agent, both as an adapter protein and as an eIF2α-kinase, and in cooperation with the di-ubiquitin-like protein ISG15. Developing pharmaceutical inhibitors of PKR may help in resolving some viral infections as well as stress-related damages.
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Affiliation(s)
- Stéphanie Dabo
- Unit Hepacivirus and Innate Immunity, Department Virology, Institut Pasteur, 28 rue du Dr Roux, 75724 Paris Cedex 15, France.
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129
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Induction of stress granule-like structures in vesicular stomatitis virus-infected cells. J Virol 2012; 87:372-83. [PMID: 23077311 DOI: 10.1128/jvi.02305-12] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Previous studies from our laboratory revealed that cellular poly(C) binding protein 2 (PCBP2) downregulates vesicular stomatitis virus (VSV) gene expression. We show here that VSV infection induces the formation of granular structures in the cytoplasm containing cellular RNA-binding proteins, including PCBP2, T-cell-restricted intracellular antigen 1 (TIA1), and TIA1-related protein (TIAR). Depletion of TIA1 via small interfering RNAs (siRNAs), but not depletion of TIAR, results in enhanced VSV growth and gene expression. The VSV-induced granules appear to be similar to the stress granules (SGs) generated in cells triggered by heat shock or oxidative stress but do not contain some of the bona fide SG markers, such as eukaryotic initiation factor 3 (eIF3) or eIF4A, or the processing body (PB) markers, such as mRNA-decapping enzyme 1A (DCP1a), and thus may not represent canonical SGs or PBs. Our results revealed that the VSV-induced granules, called SG-like structures here, contain the viral replicative proteins and RNAs. The formation and maintenance of the SG-like structures required viral replication and ongoing protein synthesis, but an intact cytoskeletal network was not necessary. These results suggest that cells respond to VSV infection by aggregating the antiviral proteins, such as PCBP2 and TIA1, to form SG-like structures. The functional significance of these SG-like structures in VSV-infected cells is currently under investigation.
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130
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The impact of mRNA turnover and translation on age-related muscle loss. Ageing Res Rev 2012; 11:432-41. [PMID: 22687959 DOI: 10.1016/j.arr.2012.05.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Revised: 05/25/2012] [Accepted: 05/31/2012] [Indexed: 12/21/2022]
Abstract
The deterioration of skeletal muscle that develops slowly with age, termed sarcopenia, often leads to disability and mortality in the elderly population. As the proportion of elderly citizens continues to increase due to the dramatic rise in life expectancy, there are rising concerns about the healthcare cost and social burden of caring for geriatric patients. Thus, there is a growing need to understand the underlying mechanisms of sarcopenic muscle loss so that more efficacious therapies may be developed. Building evidence suggests that the onset of age-related muscle loss is linked to the age-related changes in gene expression that occur during sarcopenia. In recent work, the posttranscriptional regulation of gene expression by RNA-binding proteins (RBPs) and microRNA (miRNA) involved in the turnover and translation of mRNA were shown as key players believed to be involved in the induction of muscle wasting. Furthermore, posttranscriptional regulation may also be linked to the reduced ability of muscle satellite cells to contribute to muscle mass during ageing, a key contributing factor to sarcopenic progression. Here we highlight how the activation of pathways such as the p38 MAPK and the phosphoinositide 3-kinase (PI3K) pathways alter the ability of RBPs to regulate the expression of their target mRNAs encoding proteins involved in cell cycle (p21 and p16), as well as myogenesis (Pax7, myogenin and MyoD). Further investigation into the role of RBPs and miRNA during sarcopenia may provide new insights into the development and progression of this disorder, which may lead to the development of new treatment options for elderly patients suffering from sarcopenia.
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131
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Woldemichael GM, Turbyville TJ, Vasselli JR, Linehan WM, McMahon JB. Lack of a functional VHL gene product sensitizes renal cell carcinoma cells to the apoptotic effects of the protein synthesis inhibitor verrucarin A. Neoplasia 2012; 14:771-7. [PMID: 22952429 PMCID: PMC3431183 DOI: 10.1593/neo.12852] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/13/2012] [Accepted: 07/16/2012] [Indexed: 12/22/2022]
Abstract
Verrucarin A (VA) is a small molecule derived from the fungal plant pathogen Myrothecium verrucaria and was identified as a selective inhibitor of clear cell renal cell carcinoma (CCRCC) cell proliferation in a high-throughput screen of a library of naturally occurring small molecules. CCRCC arises as a result of loss-of-function mutations in the von Hippel-Lindau (VHL) gene. Here we show that VA inhibits protein translation initiation culminating in apoptosis through the extrinsic signaling pathway. Reintroduction of the VHL gene in CCRCC cells afforded resistance to VA's apoptotic effects. This resistance is mediated in part by the formation of stress granules that entrap signaling molecules that initiate the apoptotic signaling cascade. The VHL gene product was found to be a component of stress granules that develop as result of VA treatment. These findings reveal an important role for the VHL gene product in cytotoxic stress response and have important implications for the rational development of VA-related compounds in chemotherapeutic targeting of CCRCC.
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Affiliation(s)
- Girma M Woldemichael
- Basic Science Program, SAIC-Frederick, Inc, Molecular Targets Laboratory, Frederick National Lab, Frederick, MD 21702, USA.
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132
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Reineke LC, Dougherty JD, Pierre P, Lloyd RE. Large G3BP-induced granules trigger eIF2α phosphorylation. Mol Biol Cell 2012; 23:3499-510. [PMID: 22833567 PMCID: PMC3442399 DOI: 10.1091/mbc.e12-05-0385] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Stress granules are large messenger ribonucleoprotein (mRNP) aggregates composed of translation initiation factors and mRNAs that appear when the cell encounters various stressors. Current dogma indicates that stress granules function as inert storage depots for translationally silenced mRNPs until the cell signals for renewed translation and stress granule disassembly. We used RasGAP SH3-binding protein (G3BP) overexpression to induce stress granules and study their assembly process and signaling to the translation apparatus. We found that assembly of large G3BP-induced stress granules, but not small granules, precedes phosphorylation of eIF2α. Using mouse embryonic fibroblasts depleted for individual eukaryotic initiation factor 2α (eIF2α) kinases, we identified protein kinase R as the principal kinase that mediates eIF2α phosphorylation by large G3BP-induced granules. These data indicate that increasing stress granule size is associated with a threshold or switch that must be triggered in order for eIF2α phosphorylation and subsequent translational repression to occur. Furthermore, these data suggest that stress granules are active in signaling to the translational machinery and may be important regulators of the innate immune response.
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Affiliation(s)
- Lucas C Reineke
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX 77584, USA
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133
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Zou T, Rao JN, Liu L, Xiao L, Cui YH, Jiang Z, Ouyang M, Donahue JM, Wang JY. Polyamines inhibit the assembly of stress granules in normal intestinal epithelial cells regulating apoptosis. Am J Physiol Cell Physiol 2012; 303:C102-11. [PMID: 22555848 DOI: 10.1152/ajpcell.00009.2012] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Polyamines regulate multiple signaling pathways and are implicated in many aspects of cellular functions, but the exact molecular processes governed by polyamines remain largely unknown. In response to environmental stress, repression of translation is associated with the assembly of stress granules (SGs) that contain a fraction of arrested mRNAs and are thought to function as mRNA storage. Here we show that polyamines modulate the assembly of SGs in normal intestinal epithelial cells (IECs) and that induced SGs following polyamine depletion are implicated in the protection of IECs against apoptosis. Increasing the levels of cellular polyamines by ectopic overexpression of the ornithine decarboxylase gene decreased cytoplasmic levels of SG-signature constituent proteins eukaryotic initiation factor 3b and T-cell intracellular antigen-1 (TIA-1)-related protein and repressed the assembly of SGs induced by exposure to arsenite-induced oxidative stress. In contrast, depletion of cellular polyamines by inhibiting ornithine decarboxylase with α-difluoromethylornithine increased cytoplasmic eukaryotic initiation factor 3b and TIA-1 related protein abundance and enhanced arsenite-induced SG assembly. Polyamine-deficient cells also exhibited an increase in resistance to tumor necrosis factor-α/cycloheximide-induced apoptosis, which was prevented by inhibiting SG formation with silencing SG resident proteins Sort1 and TIA-1. These results indicate that the elevation of cellular polyamines represses the assembly of SGs in normal IECs and that increased SGs in polyamine-deficient cells are crucial for increased resistance to apoptosis.
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Affiliation(s)
- Tongtong Zou
- Cell Biology Group, Department of Surgery, University of Maryland School of Medicine, Baltimore, USA
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134
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Cap binding-independent recruitment of eIF4E to cytoplasmic foci. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1823:1217-24. [PMID: 22507384 DOI: 10.1016/j.bbamcr.2012.03.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 02/17/2012] [Accepted: 03/26/2012] [Indexed: 01/20/2023]
Abstract
Eukaryotic translation initiation factor 4E (eIF4E) is required for cap-dependent initiation. In addition, eIF4E occurs in cytoplasmic foci such as processing bodies (PB) and stress granules (SG). We examined the role of key functional amino acid residues of eIF4E in the recruitment of this protein to cytoplasmic foci. We demonstrate that tryptophan residues required for mRNA cap recognition are not required for the recruitment of eIF4E to SG or PB. We show that a tryptophan residue required for protein-protein interactions is essential for the accumulation of eIF4E in granules. Moreover, we show, by the analysis of two Drosophila eIF4E isoforms, that the tryptophan residue is the common feature for eIF4E for the transfer of active mRNA from polysomes to other ribonucleoprotein particles in the cytoplasm. This residue resides in a putative interaction domain different than the eIF4E-BP domain. We conclude that protein-protein interactions rather than interactions with the mRNA are essential for the recruitment of eIF4E and for a putative nucleation function.
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135
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Weissbach R, Scadden A. Tudor-SN and ADAR1 are components of cytoplasmic stress granules. RNA (NEW YORK, N.Y.) 2012; 18:462-71. [PMID: 22240577 PMCID: PMC3285934 DOI: 10.1261/rna.027656.111] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Hyperediting by adenosine deaminases that acts on RNA (ADARs) may result in numerous Adenosine-to-Inosine (A-to-I) substitutions within long dsRNA. However, while countless RNAs may undergo hyperediting, the role for inosine-containing hyperedited dsRNA (IU-dsRNA) in cells is poorly understood. We have previously shown that IU-dsRNA binds specifically to various components of cytoplasmic stress granules, as well as to other proteins such as Tudor Staphylococcal Nuclease (Tudor-SN). Tudor-SN has been implicated in diverse roles in mammalian cells, including transcription, splicing, RNAi, and degradation. Moreover, we have shown that Tudor-SN interacts directly with stress granule proteins. Here we show that Tudor-SN localizes to cytoplasmic stress granules in HeLa cells undergoing arsenite-induced oxidative stress, or following transfection with long dsRNA (poly[IC]), which initiates an interferon cascade. We additionally demonstrate a novel interaction between Tudor-SN and ADAR1. Finally, we show that ADAR1 is also localized to stress granules in HeLa cells following various stresses.
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Affiliation(s)
- Rebekka Weissbach
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, United Kingdom
| | - A.D.J. Scadden
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QW, United Kingdom
- Corresponding author.E-mail .
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136
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Bauer WJ, Heath J, Jenkins JL, Kielkopf CL. Three RNA recognition motifs participate in RNA recognition and structural organization by the pro-apoptotic factor TIA-1. J Mol Biol 2011; 415:727-40. [PMID: 22154808 DOI: 10.1016/j.jmb.2011.11.040] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 10/03/2011] [Accepted: 11/22/2011] [Indexed: 01/10/2023]
Abstract
T-cell intracellular antigen-1 (TIA-1) regulates developmental and stress-responsive pathways through distinct activities at the levels of alternative pre-mRNA splicing and mRNA translation. The TIA-1 polypeptide contains three RNA recognition motifs (RRMs). The central RRM2 and C-terminal RRM3 associate with cellular mRNAs. The N-terminal RRM1 enhances interactions of a C-terminal Q-rich domain of TIA-1 with the U1-C splicing factor, despite linear separation of the domains in the TIA-1 sequence. Given the expanded functional repertoire of the RRM family, it was unknown whether TIA-1 RRM1 contributes to RNA binding as well as documented protein interactions. To address this question, we used isothermal titration calorimetry and small-angle X-ray scattering to dissect the roles of the TIA-1 RRMs in RNA recognition. Notably, the fas RNA exhibited two binding sites with indistinguishable affinities for TIA-1. Analyses of TIA-1 variants established that RRM1 was dispensable for binding AU-rich fas sites, yet all three RRMs were required to bind a polyU RNA with high affinity. Small-angle X-ray scattering analyses demonstrated a "V" shape for a TIA-1 construct comprising the three RRMs and revealed that its dimensions became more compact in the RNA-bound state. The sequence-selective involvement of TIA-1 RRM1 in RNA recognition suggests a possible role for RNA sequences in regulating the distinct functions of TIA-1. Further implications for U1-C recruitment by the adjacent TIA-1 binding sites of the fas pre-mRNA and the bent TIA-1 shape, which organizes the N- and C-termini on the same side of the protein, are discussed.
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Affiliation(s)
- William J Bauer
- Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
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137
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Matthews JD, Frey TK. Analysis of subcellular G3BP redistribution during rubella virus infection. J Gen Virol 2011; 93:267-274. [PMID: 21994324 DOI: 10.1099/vir.0.036780-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Rubella virus (RUBV) replicates slowly and to low titre in vertebrate cultured cells, with minimal cytopathology. To determine whether a cellular stress response is induced during such an infection, the formation of Ras-GAP-SH3 domain-binding protein (G3BP)-containing stress granules (SGs) in RUBV-infected cells was examined. Late in infection, accumulation of G3BP granules was detected, albeit in fewer than half of infected cells. Active virus RNA replication was required for induction of these granules, but they were found to differ from SGs induced by arsenite treatment both in composition (they did not uniformly contain other SG proteins, such as PABP and TIA-1) and in resistance to cycloheximide treatment. Thus, bona fide SGs do not appear to be induced during RUBV infection. The distribution of G3BP, either on its own or in granules, did not overlap with that of dsRNA-containing replication complexes, indicating that it played no role in virus RNA synthesis. However, G3BP did co-localize with viral ssRNAs in perinuclear clusters, suggesting an interaction that could possibly be important in a post-replicative role in virus replication, such as encapsidation.
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Affiliation(s)
- Jason D Matthews
- Georgia State University, Department of Biology, Atlanta, GA 30303, USA
| | - Teryl K Frey
- Georgia State University, Department of Biology, Atlanta, GA 30303, USA
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138
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Tollervey JR, Wang Z, Hortobágyi T, Witten JT, Zarnack K, Kayikci M, Clark TA, Schweitzer AC, Rot G, Curk T, Zupan B, Rogelj B, Shaw CE, Ule J. Analysis of alternative splicing associated with aging and neurodegeneration in the human brain. Genome Res 2011; 21:1572-82. [PMID: 21846794 PMCID: PMC3202275 DOI: 10.1101/gr.122226.111] [Citation(s) in RCA: 174] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2011] [Accepted: 07/05/2011] [Indexed: 01/15/2023]
Abstract
Age is the most important risk factor for neurodegeneration; however, the effects of aging and neurodegeneration on gene expression in the human brain have most often been studied separately. Here, we analyzed changes in transcript levels and alternative splicing in the temporal cortex of individuals of different ages who were cognitively normal, affected by frontotemporal lobar degeneration (FTLD), or affected by Alzheimer's disease (AD). We identified age-related splicing changes in cognitively normal individuals and found that these were present also in 95% of individuals with FTLD or AD, independent of their age. These changes were consistent with increased polypyrimidine tract binding protein (PTB)-dependent splicing activity. We also identified disease-specific splicing changes that were present in individuals with FTLD or AD, but not in cognitively normal individuals. These changes were consistent with the decreased neuro-oncological ventral antigen (NOVA)-dependent splicing regulation, and the decreased nuclear abundance of NOVA proteins. As expected, a dramatic down-regulation of neuronal genes was associated with disease, whereas a modest down-regulation of glial and neuronal genes was associated with aging. Whereas our data indicated that the age-related splicing changes are regulated independently of transcript-level changes, these two regulatory mechanisms affected expression of genes with similar functions, including metabolism and DNA repair. In conclusion, the alternative splicing changes identified in this study provide a new link between aging and neurodegeneration.
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Affiliation(s)
- James R. Tollervey
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom
| | - Zhen Wang
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom
| | - Tibor Hortobágyi
- MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, United Kingdom
| | - Joshua T. Witten
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom
| | - Kathi Zarnack
- EMBL–European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, United Kingdom
| | - Melis Kayikci
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom
| | - Tyson A. Clark
- Expression Research, Affymetrix, Inc., Santa Clara, California 95051, USA
| | | | - Gregor Rot
- Faculty of Computer and Information Science, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
| | - Tomaž Curk
- Faculty of Computer and Information Science, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
| | - Blaž Zupan
- Faculty of Computer and Information Science, University of Ljubljana, Tržaška 25, SI-1000 Ljubljana, Slovenia
| | - Boris Rogelj
- MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, United Kingdom
| | - Christopher E. Shaw
- MRC Centre for Neurodegeneration Research, King's College London, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, United Kingdom
| | - Jernej Ule
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom
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139
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Eberhard S, Loiselay C, Drapier D, Bujaldon S, Girard-Bascou J, Kuras R, Choquet Y, Wollman FA. Dual functions of the nucleus-encoded factor TDA1 in trapping and translation activation of atpA transcripts in Chlamydomonas reinhardtii chloroplasts. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 67:1055-66. [PMID: 21623973 DOI: 10.1111/j.1365-313x.2011.04657.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
After endosymbiosis, organelles lost most of their initial genome. Moreover, expression of the few remaining genes became tightly controlled by the nucleus through trans-acting protein factors that are required for post-transcriptional expression (maturation/stability or translation) of a single (or a few) specific organelle target mRNA(s). Here, we characterize the nucleus-encoded TDA1 factor, which is specifically required for translation of the chloroplast atpA transcript that encodes subunit α of ATP synthase in Chlamydomonas reinhardtii. The sequence of TDA1 contains eight copies of a degenerate 38-residue motif, that we named octotrico peptide repeat (OPR), which has been previously described in a few other trans-acting factors targeted to the C. reinhardtii chloroplast. Interestingly, a proportion of the untranslated atpA transcripts are sequestered into high-density, non-polysomic, ribonucleoprotein complexes. Our results suggest that TDA1 has a dual function: (i) trapping a subset of untranslated atpA transcripts into non-polysomic complexes, and (ii) translational activation of these transcripts. We discuss these results in light of our previous observation that only a proportion of atpA transcripts are translated at any given time in the chloroplast of C. reinhardtii.
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Affiliation(s)
- Stephan Eberhard
- Unité Mixte de Recherche (UMR) 7141, Centre National de la Recherche Scientifique (CNRS) and Université Pierre et Marie Curie (UPMC - Paris 06), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, F-75005 Paris, France.
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140
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Towers ER, Kelly JJ, Sud R, Gale JE, Dawson SJ. Caprin-1 is a target of the deafness gene Pou4f3 and is recruited to stress granules in cochlear hair cells in response to ototoxic damage. J Cell Sci 2011; 124:1145-55. [PMID: 21402877 DOI: 10.1242/jcs.076141] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The POU4 family of transcription factors are required for survival of specific cell types in different sensory systems. Pou4f3 is essential for the survival of auditory sensory hair cells and several mutations in human POU4F3 cause hearing loss. Thus, genes regulated by Pou4f3 are likely to be essential for hair cell survival. We performed a subtractive hybridisation screen in an inner-ear-derived cell line to find genes with differential expression in response to changes in Pou4f3 levels. The screen identified the stress-granule-associated protein Caprin-1 as being downregulated by Pou4f3. We demonstrated that this regulation occurs through the direct interaction of Pou4f3 with binding sites in the Caprin-1 5' flanking sequence, and describe the expression pattern of Caprin-1 mRNA and protein in the cochlea. Moreover, we found Caprin-1-containing stress granules are induced in cochlear hair cells following aminoglycoside-induced damage. This is the first report of stress granule formation in mammalian hair cells and suggests that the formation of Caprin-1-containing stress granules is a key damage response to a clinically relevant ototoxic agent. Our results have implications for the understanding of aminoglycoside-induced hearing loss and provide further evidence that stress granule formation is a fundamental cellular stress response.
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Affiliation(s)
- Emily R Towers
- UCL Ear Institute, 332 Gray's Inn Road, London WC1X 8EE, UK
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141
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Idler RK, Yan W. Control of messenger RNA fate by RNA-binding proteins: an emphasis on mammalian spermatogenesis. ACTA ACUST UNITED AC 2011; 33:309-37. [PMID: 21757510 DOI: 10.2164/jandrol.111.014167] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Posttranscriptional status of messenger RNAs (mRNA) can be affected by many factors, most of which are RNA-binding proteins (RBP) that either bind mRNA in a nonspecific manner or through specific motifs, usually located in the 3' untranslated regions. RBPs can also be recruited by small noncoding RNAs (sncRNA), which have been shown to be involved in posttranscriptional regulations and transposon repression (eg, microRNAs or P-element-induced wimpy testis-interacting RNA) as components of the sncRNA effector complex. Non-sncRNA-binding RBPs have much more diverse effects on their target mRNAs. Some can cause degradation of their target transcripts and/or repression of translation, whereas others can stabilize and/or activate translation. The splicing and exportation of transcripts from the nucleus to the cytoplasm are often mediated by sequence-specific RBPs. The mechanisms by which RBPs regulate mRNA transcripts involve manipulating the 3' poly(A) tail, targeting the transcript to polysomes or to other ribonuclear protein particles, recruiting regulatory proteins, or competing with other RBPs. Here, we briefly review the known mechanisms of posttranscriptional regulation mediated by RBPs, with an emphasis on how these mechanisms might control spermatogenesis in general.
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Affiliation(s)
- R Keegan Idler
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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142
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The role of molecular microtubule motors and the microtubule cytoskeleton in stress granule dynamics. Int J Cell Biol 2011; 2011:939848. [PMID: 21760798 PMCID: PMC3132543 DOI: 10.1155/2011/939848] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Accepted: 04/20/2011] [Indexed: 11/18/2022] Open
Abstract
Stress granules (SGs) are cytoplasmic foci that appear in cells exposed to stress-induced translational inhibition. SGs function as a triage center, where mRNAs are sorted for storage, degradation, and translation reinitiation. The underlying mechanisms of SGs dynamics are still being characterized, although many key players have been identified. The main components of SGs are stalled 48S preinitiation complexes. To date, many other proteins have also been found to localize in SGs and are hypothesized to function in SG dynamics. Most recently, the microtubule cytoskeleton and associated motor proteins have been demonstrated to function in SG dynamics. In this paper, we will discuss current literature examining the function of microtubules and the molecular microtubule motors in SG assembly, coalescence, movement, composition, organization, and disassembly.
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143
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Subramaniam K, Kandasamy K, Joseph K, Spicer EK, Tholanikunnel BG. The 3'-untranslated region length and AU-rich RNA location modulate RNA-protein interaction and translational control of β2-adrenergic receptor mRNA. Mol Cell Biochem 2011; 352:125-41. [PMID: 21369731 DOI: 10.1007/s11010-011-0747-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Accepted: 02/17/2011] [Indexed: 12/25/2022]
Abstract
Posttranscriptional controls play a major role in β(2)-adrenergic receptor (β(2)-AR) expression. We recently reported that β(2)-AR mRNA translation is suppressed by elements in its 3'-untranslated region (UTR). We also identified T-cell-restricted intracellular antigen-related protein (TIAR) and HuR as prominent AU-rich (ARE) RNA-binding proteins that associate with β(2)-AR mRNA 3'-UTR. In this study, we identified a poly(U) region at the distal end of the 3'-UTR as critical for TIAR binding to β(2)-AR mRNA and for translational suppression. Here, we also report that the locations of the poly(U) and ARE sequences within the 3'-UTR are important determinants that control the translation of β(2)-AR mRNA. Consistent with this finding, a 20-nucleotide ARE RNA from the proximal 3'-UTR that did not inhibit mRNA translation in its native position was able to suppress translation when re-located to the distal 3'-UTR of the receptor mRNA. Immunoprecipitation and polysome profile analysis demonstrated the importance of 3'-UTR length and the ARE RNA location within the 3'-UTR, as key determinants of RNA/protein interactions and translational control of β(2)-AR mRNA. Further, the importance of 3'-UTR length and ARE location in TIAR and HuR association with mRNA and translational suppression was demonstrated using a chimeric luciferase reporter gene.
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Affiliation(s)
- Kothandharaman Subramaniam
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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Kim HS, Wilce MCJ, Yoga YMK, Pendini NR, Gunzburg MJ, Cowieson NP, Wilson GM, Williams BRG, Gorospe M, Wilce JA. Different modes of interaction by TIAR and HuR with target RNA and DNA. Nucleic Acids Res 2011; 39:1117-30. [PMID: 21233170 PMCID: PMC3035456 DOI: 10.1093/nar/gkq837] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
TIAR and HuR are mRNA-binding proteins that play important roles in the regulation of translation. They both possess three RNA recognition motifs (RRMs) and bind to AU-rich elements (AREs), with seemingly overlapping specificity. Here we show using SPR that TIAR and HuR bind to both U-rich and AU-rich RNA in the nanomolar range, with higher overall affinity for U-rich RNA. However, the higher affinity for U–rich sequences is mainly due to faster association with U-rich RNA, which we propose is a reflection of the higher probability of association. Differences between TIAR and HuR are observed in their modes of binding to RNA. TIAR is able to bind deoxy-oligonucleotides with nanomolar affinity, whereas HuR affinity is reduced to a micromolar level. Studies with U-rich DNA reveal that TIAR binding depends less on the 2′-hydroxyl group of RNA than HuR binding. Finally we show that SAXS data, recorded for the first two domains of TIAR in complex with RNA, are more consistent with a flexible, elongated shape and not the compact shape that the first two domains of Hu proteins adopt upon binding to RNA. We thus propose that these triple-RRM proteins, which compete for the same binding sites in cells, interact with their targets in fundamentally different ways.
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Affiliation(s)
- Henry S Kim
- Department of Biochemistry and Molecular Biology, Monash University, Victoria 3800, Australia
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146
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Abstract
Vaccinia virus (VV) mutants lacking the double-stranded RNA (dsRNA)-binding E3L protein (ΔE3L mutant VV) show restricted replication in most cell types, as dsRNA produced by VV activates protein kinase R (PKR), leading to eIF2α phosphorylation and impaired translation initiation. Here we show that cells infected with ΔE3L mutant VV assemble cytoplasmic granular structures which surround the VV replication factories at an early stage of the nonproductive infection. These structures contain the stress granule-associated proteins G3BP, TIA-1, and USP10, as well as poly(A)-containing RNA. These structures lack large ribosomal subunit proteins, suggesting that they are translationally inactive. Formation of these punctate structures correlates with restricted replication, as they occur in >80% of cells infected with ΔE3L mutant VV but in only 10% of cells infected with wild-type VV. We therefore refer to these structures as antiviral granules (AVGs). Formation of AVGs requires PKR and phosphorylated eIF2α, as mouse embryonic fibroblasts (MEFs) lacking PKR displayed reduced granule formation and MEFs lacking phosphorylatable eIF2α showed no granule formation. In both cases, these decreased levels of AVG formation correlated with increased ΔE3L mutant VV replication. Surprisingly, MEFs lacking the AVG component protein TIA-1 supported increased replication of ΔE3L mutant VV, despite increased eIF2α phosphorylation and the assembly of AVGs that lacked TIA-1. These data indicate that the effective PKR-mediated restriction of ΔE3L mutant VV replication requires AVG formation subsequent to eIF2α phosphorylation. This is a novel finding that supports the hypothesis that the formation of subcellular protein aggregates is an important component of the successful cellular antiviral response.
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147
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Corioni M, Antih N, Tanackovic G, Zavolan M, Krämer A. Analysis of in situ pre-mRNA targets of human splicing factor SF1 reveals a function in alternative splicing. Nucleic Acids Res 2010; 39:1868-79. [PMID: 21062807 PMCID: PMC3061054 DOI: 10.1093/nar/gkq1042] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The conserved pre-mRNA splicing factor SF1 is implicated in 3' splice site recognition by binding directly to the intron branch site. However, because SF1 is not essential for constitutive splicing, its role in pre-mRNA processing has remained mysterious. Here, we used crosslinking and immunoprecipitation (CLIP) to analyze short RNAs directly bound by human SF1 in vivo. SF1 bound mainly pre-mRNAs, with 77% of target sites in introns. Binding to target RNAs in vitro was dependent on the newly defined SF1 binding motif ACUNAC, strongly resembling human branch sites. Surprisingly, the majority of SF1 binding sites did not map to the expected position near 3' splice sites. Instead, target sites were distributed throughout introns, and a smaller but significant fraction occurred in exons within coding and untranslated regions. These data suggest a more complex role for SF1 in splicing regulation. Indeed, SF1 silencing affected alternative splicing of endogenous transcripts, establishing a previously unexpected role for SF1 and branch site-like sequences in splice site selection.
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Affiliation(s)
- Margherita Corioni
- Department of Cell Biology, Faculty of Sciences, University of Geneva, 30 quai Ernest-Ansermet, CH-1211 Geneva
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148
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Abstract
Cellular senescence is a specialized form of growth arrest, confined to mitotic cells, induced by various stressful stimuli and characterized by a permanent growth arrest, resistance to apoptosis, an altered pattern of gene expression and the expression of some markers that are characteristic, although not exclusive, to the senescent state. Senescent cells profoundly modify neighboring and remote cells through the production of an altered secretome, eventually leading to inflammation, fibrosis and possibly growth of neoplastic cells. Mammalian aging has been defined as a reduction in the capacity to adequately maintain tissue homeostasis or to repair tissues after injury. Tissue homeostasis and regenerative capacity are nowadays considered to be related to the stem cell pool present in every tissue. For this reason, pathological and patho-physiological conditions characterized by altered tissue homeostasis and impaired regenerative capacity can be viewed as a consequence of the reduction in stem cell number and/or function. Last, cellular senescence is a double-edged sword, since it may inhibit the growth of transformed cells, preventing the occurrence of cancer, while it may facilitate growth of preneoplastic lesions in a paracrine fashion; therefore, interventions targeting this cell response to stress may have a profound impact on many age-related pathologies, ranging from cardiovascular disease to oncology. Aim of this review is to discuss both molecular mechanisms associated with stem cell senescence and interventions that may attenuate or reverse this process.
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Huichalaf C, Sakai K, Jin B, Jones K, Wang GL, Schoser B, Schneider-Gold C, Sarkar P, Pereira-Smith OM, Timchenko N, Timchenko L. Expansion of CUG RNA repeats causes stress and inhibition of translation in myotonic dystrophy 1 (DM1) cells. FASEB J 2010; 24:3706-19. [PMID: 20479119 DOI: 10.1096/fj.09-151159] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The purpose of this study was to investigate the role of the mutant CUGn RNA in the induction of stress in type 1 myotonic dystrophy (DM1) cells and in the stress-mediated inhibition of protein translation in DM1. To achieve our goals, we performed HPLC-based purification of stress granules (SGs), immunoanalysis of SGs with stress markers TIA-1, CUGBP1, and ph-eIF2, site-specific mutagenesis, and examinations of RNA-protein and protein-protein interactions in myoblasts from control and DM1 patients. The cause-and-effect relationships were addressed in stable cells expressing mutant CUG repeats. We found that the mutant CUGn RNA induces formation of SGs through the increase of the double-stranded RNA-dependent protein kinase (PKR) and following inactivation of eIF2α, one of the substrates of PKR. We show that SGs trap mRNA coding for the DNA repair and remodeling factor MRG15 (MORF4L1), translation of which is regulated by CUGBP1. As the result of the trapping, the levels of MRG15 are reduced in DM1 cells and in CUG-expressing cells. These data show that CUG repeats cause stress in DM1 through the PKR-ph-eIF2α pathway inhibiting translation of certain mRNAs, such as MRG15 mRNA. The repression of protein translation by stress might contribute to the progressive muscle loss in DM1.
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Affiliation(s)
- Claudia Huichalaf
- Department of Molecular Physiology and Biophysics, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, USA
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Fournier MJ, Gareau C, Mazroui R. The chemotherapeutic agent bortezomib induces the formation of stress granules. Cancer Cell Int 2010; 10:12. [PMID: 20429927 PMCID: PMC2873330 DOI: 10.1186/1475-2867-10-12] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2010] [Accepted: 04/29/2010] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND Cytoplasmic stress granules (SGs) are specialized storage sites of untranslated mRNAs whose formation occurs under different stress conditions and is often associated with cell survival. SGs-inducing stresses include radiations, hypoxia, viral infections, and chemical inhibitors of specific translation initiation factors. The FDA-approved drug bortezomib (Velcade(R)) is a peptide boronate inhibitor of the 26S proteasome that is very efficient for the treatment of myelomas and other hematological tumors. Solid tumors are largely refractory to bortezomib. In the present study, we investigated the formation of SGs following bortezomib treatment. RESULTS We show that bortezomib efficiently induces the formation of SGs in cancer cells. This process involves the phosphorylation of translation initiation factor eIF2alpha by heme-regulated inhibitor kinase (HRI). Depletion of HRI prevents bortezomib-induced formation of SGs and promotes apoptosis. CONCLUSIONS This is the first study describing the formation of SGs by a chemotherapeutic compound. We speculate that the activation of HRI and the formation of SGs might constitute a mechanism by which cancer cells resist bortezomib-mediated apoptosis.
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Affiliation(s)
- Marie-Josée Fournier
- Centre de recherche de l'hôpital St-François d'Assise (CHUQ/CRSFA), 10 rue de l'Espinay, Quebec, QC G1L 3L5, Canada.
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