1
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Huang X, Du Z. Possible involvement of three-stemmed pseudoknots in regulating translational initiation in human mRNAs. PLoS One 2024; 19:e0307541. [PMID: 39038036 PMCID: PMC11262651 DOI: 10.1371/journal.pone.0307541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Accepted: 07/08/2024] [Indexed: 07/24/2024] Open
Abstract
RNA pseudoknots play a crucial role in various cellular functions. Established pseudoknots show significant variation in both size and structural complexity. Specifically, three-stemmed pseudoknots are characterized by an additional stem-loop embedded in their structure. Recent findings highlight these pseudoknots as bacterial riboswitches and potent stimulators for programmed ribosomal frameshifting in RNA viruses like SARS-CoV2. To investigate the possible presence of functional three-stemmed pseudoknots in human mRNAs, we employed in-house developed computational methods to detect such structures within a dataset comprising 21,780 full-length human mRNA sequences. Numerous three-stemmed pseudoknots were identified. A selected set of 14 potential instances are presented, in which the start codon of the mRNA is found in close proximity either upstream, downstream, or within the identified three-stemmed pseudoknot. These pseudoknots likely play a role in translational initiation regulation. The probability of their existence gains support from their ranking as the most stable pseudoknot identified in the entire mRNA sequence, structural conservation across homologous mRNAs, stereochemical feasibility as demonstrated by structural modeling, and classification as members of the CPK-1 pseudoknot family, which includes many well-established pseudoknots. Furthermore, in four of the mRNAs, two or three closely spaced or tandem three-stemmed pseudoknots were identified. These findings suggest the frequent occurrence of three-stemmed pseudoknots in human mRNAs. A stepwise co-transcriptional folding mechanism is proposed for the formation of a three-stemmed pseudoknot structure. Our results not only provide fresh insights into the structures and functions of pseudoknots but also unveil the potential to target pseudoknots for treating human diseases.
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Affiliation(s)
- Xiaolan Huang
- School of Computing, Southern Illinois University at Carbondale, IL, United States of America
| | - Zhihua Du
- School of Chemical and Biomolecular Sciences, Southern Illinois University at Carbondale, IL, United States of America
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2
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Kaempfer R. RNA Activators of Stress Kinase PKR within Human Genes That Control Splicing or Translation Create Novel Targets for Hereditary Diseases. Int J Mol Sci 2024; 25:1323. [PMID: 38279321 PMCID: PMC10816128 DOI: 10.3390/ijms25021323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Revised: 01/14/2024] [Accepted: 01/20/2024] [Indexed: 01/28/2024] Open
Abstract
Specific sequences within RNA encoded by human genes essential for survival possess the ability to activate the RNA-dependent stress kinase PKR, resulting in phosphorylation of its substrate, eukaryotic translation initiation factor-2α (eIF2α), either to curb their mRNA translation or to enhance mRNA splicing. Thus, interferon-γ (IFNG) mRNA activates PKR through a 5'-terminal 203-nucleotide pseudoknot structure, thereby strongly downregulating its own translation and preventing a harmful hyper-inflammatory response. Tumor necrosis factor-α (TNF) pre-mRNA encodes within the 3'-untranslated region (3'-UTR) a 104-nucleotide RNA pseudoknot that activates PKR to enhance its splicing by an order of magnitude while leaving mRNA translation intact, thereby promoting effective TNF protein expression. Adult and fetal globin genes encode pre-mRNA structures that strongly activate PKR, leading to eIF2α phosphorylation that greatly enhances spliceosome assembly and splicing, yet also structures that silence PKR activation upon splicing to allow for unabated globin mRNA translation essential for life. Regulatory circuits resulting in each case from PKR activation were reviewed previously. Here, we analyze mutations within these genes created to delineate the RNA structures that activate PKR and to deconvolute their folding. Given the critical role of intragenic RNA activators of PKR in gene regulation, such mutations reveal novel potential RNA targets for human disease.
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Affiliation(s)
- Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, Faculty of Medicine, The Hebrew University, Jerusalem 9112102, Israel
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3
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Kirshina A, Vasileva O, Kunyk D, Seregina K, Muslimov A, Ivanov R, Reshetnikov V. Effects of Combinations of Untranslated-Region Sequences on Translation of mRNA. Biomolecules 2023; 13:1677. [PMID: 38002359 PMCID: PMC10669451 DOI: 10.3390/biom13111677] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 11/16/2023] [Accepted: 11/18/2023] [Indexed: 11/26/2023] Open
Abstract
mRNA-based therapeutics have been found to be a promising treatment strategy in immunotherapy, gene therapy, and cancer treatments. Effectiveness of mRNA therapeutics depends on the level and duration of a desired protein's expression, which is determined by various cis- and trans-regulatory elements of the mRNA. Sequences of 5' and 3' untranslated regions (UTRs) are responsible for translational efficiency and stability of mRNA. An optimal combination of the regulatory sequences allows researchers to significantly increase the target protein's expression. Using both literature data and previously obtained experimental data, we chose six sequences of 5'UTRs (adenoviral tripartite leader [TPL], HBB, rabbit β-globin [Rabb], H4C2, Moderna, and Neo2) and five sequences of 3'UTRs (mtRNR-EMCV, mtRNR-AES, mtRNR-mtRNR, BioNTech, and Moderna). By combining them, we constructed 30 in vitro transcribed RNAs encoding firefly luciferase with various combinations of 5'- and 3'UTRs, and the resultant bioluminescence was assessed in the DC2.4 cell line at 4, 8, 24, and 72 h after transfection. The cellular data enabled us to identify the best seven combinations of 5'- and 3'UTRs, whose translational efficiency was then assessed in BALB/c mice. Two combinations of 5'- and 3'UTRs (5'Rabb-3'mtRNR-EMCV and 5'TPL-3'Biontech) led to the most pronounced increase in the luciferase amount in the in vivo experiment in mice. Subsequent analysis of the stability of the mRNA indicated that the increase in luciferase expression is explained primarily by the efficiency of translation, not by the number of RNA molecules. Altogether, these findings suggest that 5'UTR-and-3'UTR combinations 5'Rabb-3'mtRNR- EMCV and 5'TPL-3'Biontech lead to high expression of target proteins and may be considered for use in preventive and therapeutic modalities based on mRNA.
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Affiliation(s)
- Anna Kirshina
- Translational Medicine Research Center, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Olga Vasileva
- Translational Medicine Research Center, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Dmitry Kunyk
- Translational Medicine Research Center, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Kristina Seregina
- Translational Medicine Research Center, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Albert Muslimov
- Translational Medicine Research Center, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Roman Ivanov
- Translational Medicine Research Center, Sirius University of Science and Technology, 354340 Sochi, Russia
| | - Vasiliy Reshetnikov
- Translational Medicine Research Center, Sirius University of Science and Technology, 354340 Sochi, Russia
- Laboratory of Gene Expression Regulation, Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, 630090 Novosibirsk, Russia
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4
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Ricciardi-Jorge T, da Rocha EL, Gonzalez-Kozlova E, Rodrigues-Luiz GF, Ferguson BJ, Sweeney T, Irigoyen N, Mansur DS. PKR-mediated stress response enhances dengue and Zika virus replication. mBio 2023; 14:e0093423. [PMID: 37732809 PMCID: PMC10653888 DOI: 10.1128/mbio.00934-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 08/01/2023] [Indexed: 09/22/2023] Open
Abstract
IMPORTANCE One of the fundamental features that make viruses intracellular parasites is the necessity to use cellular translational machinery. Hence, this is a crucial checkpoint for controlling infections. Here, we show that dengue and Zika viruses, responsible for nearly 400 million infections every year worldwide, explore such control for optimal replication. Using immunocompetent cells, we demonstrate that arrest of protein translations happens after sensing of dsRNA and that the information required to avoid this blocking is contained in viral 5'-UTR. Our work, therefore, suggests that the non-canonical translation described for these viruses is engaged when the intracellular stress response is activated.
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Affiliation(s)
- Taissa Ricciardi-Jorge
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
- The Pirbright Institute, Woking, United Kingdom
| | - Edroaldo Lummertz da Rocha
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
| | - Edgar Gonzalez-Kozlova
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
- Icahn School of Medicine, New York, USA
| | - Gabriela Flavia Rodrigues-Luiz
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
| | - Brian J. Ferguson
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | | | - Nerea Irigoyen
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Daniel Santos Mansur
- Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina (UFSC), Florianópolis, Brazil
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5
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Prakash S. mRNA-Based Nanomedicine: A New Strategy for Treating Infectious Diseases and Beyond. Eur J Drug Metab Pharmacokinet 2023; 48:515-529. [PMID: 37656402 DOI: 10.1007/s13318-023-00849-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/03/2023] [Indexed: 09/02/2023]
Abstract
Messenger RNA (mRNA) has emerged as a new therapeutic agent for the prevention and treatment of a wide range of diseases. The recent achievement of the two lipid nanoparticle-mRNA vaccines developed by Moderna and Pfizer-BioNTech against coronavirus 2019 (COVID-19) disease in record time highlights the huge potential of mRNA technology and reshaping the landscape of vaccine development and the future of gene therapies. Challenges related to translational efficacy, mRNA stability, immunogenicity, and ensuring the quality of final products have been significantly improved by recent advancements in mRNA engineering and delivery. Thus, the present review aims to provide the latest innovations that incrementally overcome these issues and future directions in the context of ongoing clinical trials against infectious diseases and beyond.
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Affiliation(s)
- Satyendra Prakash
- Centre of Biotechnology, Faculty of Science, University of Allahabad, Allahabad, India.
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Batjargal T, Zappa F, Grant RJ, Piscopio RA, Chialastri A, Dey SS, Acosta-Alvear D, Wilson MZ. Optogenetic control of the integrated stress response reveals proportional encoding and the stress memory landscape. Cell Syst 2023; 14:551-562.e5. [PMID: 37473728 DOI: 10.1016/j.cels.2023.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 12/27/2022] [Accepted: 06/09/2023] [Indexed: 07/22/2023]
Abstract
The integrated stress response (ISR) is a conserved signaling network that detects aberrations and computes cellular responses. Dissecting these computations has been difficult because physical and chemical inducers of stress activate multiple parallel pathways. To overcome this challenge, we engineered a photo-switchable control over the ISR sensor kinase PKR (opto-PKR), enabling virtual, on-target activation. Using light to control opto-PKR dynamics, we traced information flow through the transcriptome and for key downstream ISR effectors. Our analyses revealed a biphasic, proportional transcriptional response with two dynamic modes, transient and gradual, that correspond to adaptive and terminal outcomes. We then constructed an ordinary differential equation (ODE) model of the ISR, which demonstrated the dependence of future stress responses on past stress. Finally, we tested our model using high-throughput light-delivery to map the stress memory landscape. Our results demonstrate that cells encode information in stress levels, durations, and the timing between encounters. A record of this paper's transparent peer review process is included in the supplemental information.
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Affiliation(s)
- Taivan Batjargal
- Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Francesca Zappa
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Ryan J Grant
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Robert A Piscopio
- Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Alex Chialastri
- Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Siddharth S Dey
- Center for BioEngineering, University of California Santa Barbara, Santa Barbara, CA, USA; Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA; Department of Chemical Engineering, University of California Santa Barbara, Santa Barbara, CA, USA
| | - Diego Acosta-Alvear
- Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, CA, USA; Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA, USA; Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
| | - Maxwell Z Wilson
- Center for BioEngineering, University of California Santa Barbara, Santa Barbara, CA, USA; Biomolecular Science and Engineering Program, University of California Santa Barbara, Santa Barbara, CA, USA; Department of Molecular, Cellular, and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA, USA; Neuroscience Research Institute, University of California Santa Barbara, Santa Barbara, CA, USA.
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7
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Kaempfer R. Positive Regulation of Splicing of Cellular and Viral mRNA by Intragenic RNA Elements That Activate the Stress Kinase PKR, an Antiviral Mechanism. Genes (Basel) 2023; 14:genes14050974. [PMID: 37239334 DOI: 10.3390/genes14050974] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 04/03/2023] [Accepted: 04/25/2023] [Indexed: 05/28/2023] Open
Abstract
The transient activation of the cellular stress kinase, protein kinase RNA-activated (PKR), by double-helical RNA, especially by viral double-stranded RNA generated during replication, results in the inhibition of translation via the phosphorylation of eukaryotic initiation factor 2 α-chain (eIF2α). Exceptionally, short intragenic elements within primary transcripts of the human tumor necrosis factor (TNF-α) and globin genes, genes essential for survival, can form RNA structures that strongly activate PKR and thereby render the splicing of their mRNAs highly efficient. These intragenic RNA activators of PKR promote early spliceosome assembly and splicing by inducing phosphorylation of nuclear eIF2α, without impairing the translation of the mature spliced mRNA. Unexpectedly, excision of the large human immunodeficiency virus (HIV) rev/tat intron was shown to require activation of PKR by the viral RNA and eIF2α phosphorylation. The splicing of rev/tat mRNA is abrogated by viral antagonists of PKR and by trans-dominant negative mutant PKR, yet enhanced by the overexpression of PKR. The TNFα and HIV RNA activators of PKR fold into compact pseudoknots that are highly conserved within the phylogeny, supporting their essential role in the upregulation of splicing. HIV provides the first example of a virus co-opting a major cellular antiviral mechanism, the activation of PKR by its RNA, to promote splicing.
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Affiliation(s)
- Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 9112102, Israel
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8
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Manjunath L, Oh S, Ortega P, Bouin A, Bournique E, Sanchez A, Martensen PM, Auerbach AA, Becker JT, Seldin M, Harris RS, Semler BL, Buisson R. APOBEC3B drives PKR-mediated translation shutdown and protects stress granules in response to viral infection. Nat Commun 2023; 14:820. [PMID: 36781883 PMCID: PMC9925369 DOI: 10.1038/s41467-023-36445-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 01/31/2023] [Indexed: 02/15/2023] Open
Abstract
Double-stranded RNA produced during viral replication and transcription activates both protein kinase R (PKR) and ribonuclease L (RNase L), which limits viral gene expression and replication through host shutoff of translation. In this study, we find that APOBEC3B forms a complex with PABPC1 to stimulate PKR and counterbalances the PKR-suppressing activity of ADAR1 in response to infection by many types of viruses. This leads to translational blockage and the formation of stress granules. Furthermore, we show that APOBEC3B localizes to stress granules through the interaction with PABPC1. APOBEC3B facilitates the formation of protein-RNA condensates with stress granule assembly factor (G3BP1) by protecting mRNA associated with stress granules from RNAse L-induced RNA cleavage during viral infection. These results not only reveal that APOBEC3B is a key regulator of different steps of the innate immune response throughout viral infection but also highlight an alternative mechanism by which APOBEC3B can impact virus replication without editing viral genomes.
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Affiliation(s)
- Lavanya Manjunath
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA, USA
- Center for Virus Research, University of California Irvine, Irvine, CA, USA
- Center for Epigenetics and Metabolism, Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA
| | - Sunwoo Oh
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA, USA
- Center for Virus Research, University of California Irvine, Irvine, CA, USA
- Center for Epigenetics and Metabolism, Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA
| | - Pedro Ortega
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA, USA
- Center for Virus Research, University of California Irvine, Irvine, CA, USA
- Center for Epigenetics and Metabolism, Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA
| | - Alexis Bouin
- Center for Virus Research, University of California Irvine, Irvine, CA, USA
- Department of Microbiology & Molecular Genetics, School of Medicine, University of California Irvine, Irvine, CA, USA
| | - Elodie Bournique
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA, USA
- Center for Virus Research, University of California Irvine, Irvine, CA, USA
- Center for Epigenetics and Metabolism, Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA
| | - Ambrocio Sanchez
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA, USA
- Center for Virus Research, University of California Irvine, Irvine, CA, USA
- Center for Epigenetics and Metabolism, Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA
| | - Pia Møller Martensen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Ashley A Auerbach
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, TX, USA
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN, USA
| | - Jordan T Becker
- Institute for Molecular Virology, University of Minnesota - Twin Cities, Minneapolis, MN, USA
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota - Twin Cities, Minneapolis, MN, USA
| | - Marcus Seldin
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA, USA
- Center for Epigenetics and Metabolism, Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA
| | - Reuben S Harris
- Department of Biochemistry and Structural Biology, University of Texas Health San Antonio, San Antonio, TX, USA
- Howard Hughes Medical Institute, University of Texas Health San Antonio, San Antonio, TX, USA
| | - Bert L Semler
- Center for Virus Research, University of California Irvine, Irvine, CA, USA
- Department of Microbiology & Molecular Genetics, School of Medicine, University of California Irvine, Irvine, CA, USA
| | - Rémi Buisson
- Department of Biological Chemistry, School of Medicine, University of California Irvine, Irvine, CA, USA.
- Center for Virus Research, University of California Irvine, Irvine, CA, USA.
- Center for Epigenetics and Metabolism, Chao Family Comprehensive Cancer Center, University of California Irvine, Irvine, CA, USA.
- Department of Pharmaceutical Sciences, School of Pharmacy & Pharmaceutical Sciences, University of California Irvine, Irvine, CA, USA.
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9
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Namer LS, Harwig A, Heynen SP, Das AT, Berkhout B, Kaempfer R. HIV co-opts a cellular antiviral mechanism, activation of stress kinase PKR by its RNA, to enable splicing of rev/tat mRNA. Cell Biosci 2023; 13:28. [PMID: 36774495 PMCID: PMC9922466 DOI: 10.1186/s13578-023-00972-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 01/24/2023] [Indexed: 02/13/2023] Open
Abstract
BACKGROUND Activation of RNA-dependent stress kinase PKR, especially by viral double-stranded RNA, induces eukaryotic initiation factor 2 α-chain (eIF2α) phosphorylation, attenuating thereby translation. We report that this RNA-mediated negative control mechanism, considered a cornerstone of the cell's antiviral response, positively regulates splicing of a viral mRNA. RESULTS Excision of the large human immunodeficiency virus (HIV) rev/tat intron depends strictly on activation of PKR by the viral RNA and on eIF2α phosphorylation. Rev/tat mRNA splicing was blocked by viral PKR antagonists Vaccinia E3L and Ebola VP35, as well as by a trans-dominant negative mutant of PKR, yet enhanced by overexpressing PKR. Expression of non-phosphorylatable mutant eIF2αS51A, but not of wild type eIF2α, abrogated efficient splicing of rev/tat mRNA. By contrast, expression of eIF2αS51D, a phosphomimetic mutant of eIF2α, left rev/tat mRNA splicing intact. Unlike eIF2αS51A, eIF2αS51D does not inhibit eIF2α phosphorylation by activated PKR. All HIV mRNA species contain terminal trans-activation response (TAR) stem-loop sequences that potentially could activate PKR, yet even upon TAR deletion, HIV mRNA production remained sensitive to inhibitors of PKR activation. Bioinformatic and mutational analyses revealed a compact RNA pseudoknot upstream of 3'-terminal TAR that promotes splicing by activating PKR. Supporting its essential role in control of splicing, this pseudoknot is conserved among diverse HIV and nonhuman primate SIVcpz isolates. The pseudoknot and 3'-terminal TAR collaborate in mediating PKR-regulated splicing of rev/tat intron, the pseudoknot being dominant. CONCLUSIONS Our results on HIV provide the first example of a virus co-opting activation of PKR by its RNA, a cellular antiviral mechanism, to promote splicing. They raise the question whether other viruses may use local activation of host kinase PKR through RNA elements within their genome to achieve efficient splicing of their mRNA. Our experiments reveal an indispensable role for eIF2α phosphorylation in HIV rev/tat mRNA splicing that accounts for the need for PKR activation.
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Affiliation(s)
- Lise Sarah Namer
- grid.9619.70000 0004 1937 0538Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, 9112102 Jerusalem, Israel
| | - Alex Harwig
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Stephan P. Heynen
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Atze T. Das
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Ben Berkhout
- grid.509540.d0000 0004 6880 3010Laboratory of Experimental Virology, Department of Medical Microbiology, Amsterdam UMC, 1105 AZ Amsterdam, The Netherlands
| | - Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, 9112102, Jerusalem, Israel.
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10
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Interferon-gamma modulates articular chondrocyte and osteoblast metabolism through protein kinase R-independent and dependent mechanisms. Biochem Biophys Rep 2022; 32:101323. [PMID: 36105611 PMCID: PMC9464860 DOI: 10.1016/j.bbrep.2022.101323] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2022] [Revised: 07/20/2022] [Accepted: 08/01/2022] [Indexed: 11/23/2022] Open
Abstract
Osteoarthritis (OA) affects multiple tissues of the synovial joint and is characterised by articular cartilage degeneration and bone remodelling. Interferon-γ (IFN-γ) is implicated in osteoarthritis pathology exerting its biological effects via various mechanisms including activation of protein kinase R (PKR), which has been implicated in inflammation and arthritis. This study investigated whether treatment of articular cartilage chondrocytes and osteoblasts with IFN-γ could induce a degradative phenotype that was mediated through the PKR signalling pathway. IFN-γ treatment of chondrocytes increased transcription of key inflammatory mediators (TNF-α, IL-6), matrix degrading enzymes (MMP-13), the transcription factor STAT1, and PKR. Activation of PKR was involved in the regulation of TNF-α, IL-6, and STAT1. In osteoblasts, IFN-γ increased human and mouse STAT1, and human IL-6 through a mechanism involving PKR. ALP, COL1A1 (human and mouse), RUNX2 (mouse), and PHOSPHO1 (mouse) were decreased by IFN-γ. The number of PKR positive cells were increased in post-traumatic OA (PTOA). This study has revealed that IFN-γ propagates inflammatory and degenerative events in articular chondrocytes and osteoblasts via PKR activation. Since IFN-γ and PKR signalling are both activated in early PTOA, these mechanisms are likely to contribute to joint degeneration after injury and might offer attractive targets for therapeutic intervention. •IFN-γ treatment of chondrocytes increased transcription of TNF-α, IL-6, and STAT1 via PKR activation. •In osteoblasts, IFN-γ increased STAT1 and IL-6 via PKR activation. •The number of PKR positive cells were increased in post-traumatic OA (PTOA). •IFN-γ propagates inflammatory and degenerative events in articular chondrocytes and osteoblasts via PKR activation. •IFN-γ and PKR signalling are both activated in early PTOA and are likely to contribute to joint degeneration after injury.
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11
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Zappa F, Muniozguren NL, Wilson MZ, Costello MS, Ponce-Rojas JC, Acosta-Alvear D. Signaling by the integrated stress response kinase PKR is fine-tuned by dynamic clustering. J Cell Biol 2022; 221:e202111100. [PMID: 35522180 PMCID: PMC9086502 DOI: 10.1083/jcb.202111100] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Revised: 02/15/2022] [Accepted: 04/05/2022] [Indexed: 12/16/2022] Open
Abstract
The double-stranded RNA sensor kinase PKR is one of four integrated stress response (ISR) sensor kinases that phosphorylate the α subunit of eukaryotic initiation factor 2 (eIF2α) in response to stress. The current model of PKR activation considers the formation of back-to-back PKR dimers as a prerequisite for signal propagation. Here we show that PKR signaling involves the assembly of dynamic PKR clusters. PKR clustering is driven by ligand binding to PKR's sensor domain and by front-to-front interfaces between PKR's kinase domains. PKR clusters are discrete, heterogeneous, autonomous coalescences that share some protein components with processing bodies. Strikingly, eIF2α is not recruited to PKR clusters, and PKR cluster disruption enhances eIF2α phosphorylation. Together, these results support a model in which PKR clustering may limit encounters between PKR and eIF2α to buffer downstream signaling and prevent the ISR from misfiring.
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Affiliation(s)
- Francesca Zappa
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA
| | - Nerea L. Muniozguren
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA
| | - Maxwell Z. Wilson
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA
| | - Michael S. Costello
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA
| | - Jose Carlos Ponce-Rojas
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA
| | - Diego Acosta-Alvear
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA
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12
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Wu B, Song M, Dong Q, Xiang G, Li J, Ma X, Wei F. UBR5 promotes tumor immune evasion through enhancing IFN-γ-induced PDL1 transcription in triple negative breast cancer. Am J Cancer Res 2022; 12:5086-5102. [PMID: 35836797 PMCID: PMC9274738 DOI: 10.7150/thno.74989] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 06/07/2022] [Indexed: 01/12/2023] Open
Abstract
Background: The up-regulation of PD-L1 is recognized as an adaption of cancer cells to evade immune surveillance and attack. However, the intrinsic mechanisms of the induction of PD-L1 by interferon-γ (IFN-γ) in tumor microenvironment remain incompletely characterized. Ubiquitin ligase E3 component N-recognition protein 5 (UBR5) has a critical role in tumorigenesis of triple negative breast cancer (TNBC) by triggering specific immune responses to the tumor. Dual targeting of UBR5 and PD-L1 exhibited superior therapeutic benefits in a preclinical TNBC model in short term. Methods: The regulation of UBR5 to PD-L1 upon IFN-γ stimulation was evaluated through in UBR5 deficiency, reconstitution or overexpression cell line models by quantitative PCR, immunohistochemistry and RNA-seq. The effects of PD-L1 regulation by UBR5 and double blockade of both genes were evaluated in mouse TNBC model. Luciferase reporter assay, chromatin immunoprecipitation-qPCR and bioinformatics analysis were performed to explore the transcription factors involved in the regulation of UBR5 to PD-L1. Results: E3 ubiquitin ligase UBR5 plays a key role in IFN-γ-induced PDL1 transcription in TNBC in an E3 ubiquitination activity-independent manner. RNA-seq-based transcriptomic analyses reveal that UBR5 globally affects the genes in the IFN-γ-induced signaling pathway. Through its poly adenylate binding (PABC) domain, UBR5 enhances the transactivation of PDL1 by upregulating protein kinase RNA-activated (PKR), and PKR's downstream factors including signal transducers and activators of transcription 1 (STAT1) and interferon regulatory factor 1 (IRF1). Restoration of PD-L1 expression in UBR5-deficient tumor cells recoups their malignancy in vivo, whereas CRISPR/Cas9-mediated simultaneous abrogation of UBR5 and PD-L1 expression yields synergistic therapeutic benefits than either blockade alone, with a strong impact on the tumor microenvironment. Conclusions: This study identifies a novel regulator of PDL1 transcription, elucidates the underlying molecular mechanisms and provides a strong rationale for combination cancer immunotherapies targeting UBR5 and PD-L1.
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Affiliation(s)
- Bingbing Wu
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Mei Song
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, New York
| | - Qun Dong
- Department of Bioinformatics and Biostatistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Gang Xiang
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Jing Li
- Department of Bioinformatics and Biostatistics, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Xiaojing Ma
- Department of Microbiology and Immunology, Weill Cornell Medicine, New York, New York.,✉ Corresponding author: Fang Wei, 800 Dongchuan Road, Minghang, Shanghai 200240, China. Phone: 86-21-34205287; Fax: 86-21-34205287; E-mail: ; Xiaojing Ma,
| | - Fang Wei
- Sheng Yushou Center of Cell Biology and Immunology, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.,✉ Corresponding author: Fang Wei, 800 Dongchuan Road, Minghang, Shanghai 200240, China. Phone: 86-21-34205287; Fax: 86-21-34205287; E-mail: ; Xiaojing Ma,
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13
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Marchingo JM, Cantrell DA. Protein synthesis, degradation, and energy metabolism in T cell immunity. Cell Mol Immunol 2022; 19:303-315. [PMID: 34983947 PMCID: PMC8891282 DOI: 10.1038/s41423-021-00792-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 09/24/2021] [Indexed: 01/18/2023] Open
Abstract
T cell activation, proliferation, and differentiation into effector and memory states involve massive remodeling of T cell size and molecular content and create a massive increase in demand for energy and amino acids. Protein synthesis is an energy- and resource-demanding process; as such, changes in T cell energy production are intrinsically linked to proteome remodeling. In this review, we discuss how protein synthesis and degradation change over the course of a T cell immune response and the crosstalk between these processes and T cell energy metabolism. We highlight how the use of high-resolution mass spectrometry to analyze T cell proteomes can improve our understanding of how these processes are regulated.
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Affiliation(s)
- Julia M Marchingo
- Cell Signalling and Immunology Division, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
| | - Doreen A Cantrell
- Cell Signalling and Immunology Division, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK.
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14
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Abstract
In the past 20 years, the mRNA vaccine technology has evolved from the first proof of concept to the first licensed vaccine against emerging pandemics such as SARS-CoV-2. Two mRNA vaccines targeting SARS-CoV-2 have received emergency use authorization by US FDA, conditional marketing authorization by EMA, as well as multiple additional national regulatory authorities. The simple composition of an mRNA encoding the antigen formulated in a lipid nanoparticle enables a fast adaptation to new emerging pathogens. This can speed up vaccine development in pandemics from antigen and sequence selection to clinical trial to only a few months. mRNA vaccines are well tolerated and efficacious in animal models for multiple pathogens and will further contribute to the development of vaccines for other unaddressed diseases. Here, we give an overview of the mRNA vaccine design and factors for further optimization of this new promising technology and discuss current knowledge on the mode of action of mRNA vaccines interacting with the innate and adaptive immune system.
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15
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Seemann SE, Mirza AH, Bang-Berthelsen CH, Garde C, Christensen-Dalsgaard M, Workman CT, Pociot F, Tommerup N, Gorodkin J, Ruzzo WL. OUP accepted manuscript. Nucleic Acids Res 2022; 50:2452-2463. [PMID: 35188540 PMCID: PMC8934657 DOI: 10.1093/nar/gkac067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 01/07/2022] [Accepted: 01/25/2022] [Indexed: 12/01/2022] Open
Abstract
Accelerated evolution of any portion of the genome is of significant interest, potentially signaling positive selection of phenotypic traits and adaptation. Accelerated evolution remains understudied for structured RNAs, despite the fact that an RNA’s structure is often key to its function. RNA structures are typically characterized by compensatory (structure-preserving) basepair changes that are unexpected given the underlying sequence variation, i.e., they have evolved through negative selection on structure. We address the question of how fast the primary sequence of an RNA can change through evolution while conserving its structure. Specifically, we consider predicted and known structures in vertebrate genomes. After careful control of false discovery rates, we obtain 13 de novo structures (and three known Rfam structures) that we predict to have rapidly evolving sequences—defined as structures where the primary sequences of human and mouse have diverged at least twice as fast (1.5 times for Rfam) as nearby neutrally evolving sequences. Two of the three known structures function in translation inhibition related to infection and immune response. We conclude that rapid sequence divergence does not preclude RNA structure conservation in vertebrates, although these events are relatively rare.
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Affiliation(s)
| | - Aashiq H Mirza
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
- Steno Diabetes Center Copenhagen, Gentofte, Denmark
| | - Claus H Bang-Berthelsen
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
- National Food Institute, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Christian Garde
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
| | | | - Christopher T Workman
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
- Center for Biological Sequence Analysis, Technical University of Denmark, Denmark
| | - Flemming Pociot
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
- Steno Diabetes Center Copenhagen, Gentofte, Denmark
| | - Niels Tommerup
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
- Department of Cellular and Molecular Medicine (ICMM), University of Copenhagen, Denmark
| | - Jan Gorodkin
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
- Department of Veterinary and Animal Sciences, University of Copenhagen, Denmark
| | - Walter L Ruzzo
- Center for non-coding RNA in Technology and Health (RTH), University of Copenhagen, Denmark
- Computer Science and Engineering and Genome Sciences, University of Washington, USA
- Fred Hutchinson Cancer Research Center, Seattle, USA
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16
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Kuzmin IV, Ramanathan P, Basler CF, Bukreyev A. Effects of Overexpression of the Egyptian Fruit Bat Innate Immune Genes on Filovirus Infections in the Host Cells. FRONTIERS IN VIROLOGY (LAUSANNE, SWITZERLAND) 2021; 1:759655. [PMID: 36237518 PMCID: PMC9555311 DOI: 10.3389/fviro.2021.759655] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Bats constitute a large and diverse group of mammals with unique characteristics. One of these is the ability of bats to maintain various pathogens, particularly viruses, without evidence of disease. The innate immune system has been implicated as one of the important components involved in this process. However, in contrast to the human innate immune system, little data is available for bats. In the present study we generated 23 fusion constructs of innate immune genes of Egyptian fruit bat (Rousettus aegyptiacus) with mCherry as a fluorescent reporter. We evaluated the effects of overexpressing these genes on the replication of Marburg and Ebola viruses in the Egyptian fruit bat cell line R06EJ. Both viruses were substantially inhibited by overexpression of type I, II and III interferons, as well as by DDX58 (RIG-I), IFIH1, and IRF1. Our observations suggest that the broad antiviral activity of these genes reported previously in human cells is conserved in Egyptian fruit bats and these possess anti-filovirus activities that may contribute to the efficient virus clearance.
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Affiliation(s)
- Ivan V. Kuzmin
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
- Galveston National Laboratory, Galveston, TX, United States
| | - Palaniappan Ramanathan
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
- Galveston National Laboratory, Galveston, TX, United States
| | - Christopher F. Basler
- Center for Microbial Pathogenesis, Institute for Biomedical Sciences, Georgia State University, Atlanta, GA, United States
| | - Alexander Bukreyev
- Department of Pathology, University of Texas Medical Branch, Galveston, TX, United States
- Galveston National Laboratory, Galveston, TX, United States
- Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, TX, United States
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17
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Church MC, Workman JL, Suganuma T. Macrophages, Metabolites, and Nucleosomes: Chromatin at the Intersection between Aging and Inflammation. Int J Mol Sci 2021; 22:10274. [PMID: 34638614 PMCID: PMC8508989 DOI: 10.3390/ijms221910274] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/19/2021] [Accepted: 09/22/2021] [Indexed: 12/24/2022] Open
Abstract
Inflammation is the body's means of defense against harmful stimuli, with the ultimate aim being to restore homeostasis. Controlled acute inflammation transiently activates an immune response and can be beneficial as protection against infection or injury. However, dysregulated inflammatory responses, including chronic inflammation, disrupt the immune system's ability to maintain homeostatic balance, leading to increased susceptibility to infection, continuous tissue damage, and dysfunction. Aging is a risk factor for chronic inflammation; their coincidence is termed "inflammaging". Metabolic disorders including obesity, neurodegenerative diseases, and atherosclerosis are often encountered in old age. Therefore, it is important to understand the mechanistic relationship between aging, chronic inflammation, and metabolism. It has been established that the expression of inflammatory mediators is transcriptionally and translationally regulated. In addition, the post-translational modification of the mediators plays a crucial role in the response to inflammatory signaling. Chromatin regulation responds to metabolic status and controls homeostasis. However, chromatin structure is also changed by aging. In this review, we discuss the functional contributions of chromatin regulation to inflammaging.
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Affiliation(s)
| | | | - Tamaki Suganuma
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA; (M.C.C.); (J.L.W.)
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18
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Freen-van Heeren JJ. Post-transcriptional control of T-cell cytokine production: Implications for cancer therapy. Immunology 2021; 164:57-72. [PMID: 33884612 DOI: 10.1111/imm.13339] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 03/22/2021] [Accepted: 03/30/2021] [Indexed: 01/05/2023] Open
Abstract
As part of the adaptive immune system, T cells are vital for the eradication of infected and malignantly transformed cells. To perform their protective function, T cells produce effector molecules that are either directly cytotoxic, such as granzymes, perforin, interferon-γ and tumour necrosis factor α, or attract and stimulate (immune) cells, such as interleukin-2. As these molecules can also induce immunopathology, tight control of their production is required. Indeed, inflammatory cytokine production is regulated on multiple levels. Firstly, locus accessibility and transcription factor availability and activity determine the amount of mRNA produced. Secondly, post-transcriptional mechanisms, influencing mRNA splicing/codon usage, stability, decay, localization and translation rate subsequently determine the amount of protein that is produced. In the immune suppressive environments of tumours, T cells gradually lose the capacity to produce effector molecules, resulting in tumour immune escape. Recently, the role of post-transcriptional regulation in fine-tuning T-cell effector function has become more appreciated. Furthermore, several groups have shown that exhausted or dysfunctional T cells from cancer patients or murine models possess mRNA for inflammatory mediators, but fail to produce effector molecules, hinting that post-transcriptional events also play a role in hampering tumour-infiltrating lymphocyte effector function. Here, the post-transcriptional regulatory events governing T-cell cytokine production are reviewed, with a specific focus on the importance of post-transcriptional regulation in anti-tumour responses. Furthermore, potential approaches to circumvent tumour-mediated dampening of T-cell effector function through the (dis)engagement of post-transcriptional events are explored, such as CRISPR/Cas9-mediated genome editing or chimeric antigen receptors.
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19
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Zhang XO, Pratt H, Weng Z. Investigating the Potential Roles of SINEs in the Human Genome. Annu Rev Genomics Hum Genet 2021; 22:199-218. [PMID: 33792357 DOI: 10.1146/annurev-genom-111620-100736] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Short interspersed nuclear elements (SINEs) are nonautonomous retrotransposons that occupy approximately 13% of the human genome. They are transcribed by RNA polymerase III and can be retrotranscribed and inserted back into the genome with the help of other autonomous retroelements. Because they are preferentially located close to or within gene-rich regions, they can regulate gene expression by various mechanisms that act at both the DNA and the RNA levels. In this review, we summarize recent findings on the involvement of SINEs in different types of gene regulation and discuss the potential regulatory functions of SINEs that are in close proximity to genes, Pol III-transcribed SINE RNAs, and embedded SINE sequences within Pol II-transcribed genes in the human genome. These discoveries illustrate how the human genome has exapted some SINEs into functional regulatory elements.
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Affiliation(s)
- Xiao-Ou Zhang
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA; .,Current affiliation: School of Life Sciences and Technology, Tongji University, Shanghai 200092, China
| | - Henry Pratt
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA;
| | - Zhiping Weng
- Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA;
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20
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Khan MI, Nur SM, Adhami V, Mukhtar H. Epigenetic regulation of RNA sensors: Sentinels of immune response. Semin Cancer Biol 2021; 83:413-421. [PMID: 33484869 DOI: 10.1016/j.semcancer.2020.12.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 12/17/2020] [Accepted: 12/18/2020] [Indexed: 12/11/2022]
Abstract
Living host system possess mechanisms like innate immune system to combat against inflammation, stress singling, and cancer. These mechanisms are initiated by PAMP and DAMP mediated recognition by PRR. PRR is consist of variety of nucleic acid sensors like-RNA sensors. They play crucial role in identifying exogenous and endogenous RNA molecules, which subsequently mediate pro/inflammatory cytokine, IFN and ISGs response in traumatized or tumorigenic conditions. The sensors can sensitize wide range of nucleic acid particle in term of size and structure, while each category sensors belongs subclasses with differentially expressed in cell and distinguished functioning mechanisms. They are also able to make comparison between self and non-self-nucleic acid molecules through specific mechanisms. Besides exhibiting anti-inflammatory and anti-tumorigenic responses, RNA sensors cover the broad spectrum of response mechanisms. Transcriptionally RNA sensors undergo with tight epigenetic regulations. In this review study, we will be going to discuss about the details of RNA sensors, their functional mechanisms and epi-transactional regulations.
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Affiliation(s)
- Mohammad Imran Khan
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia.
| | - Suza Mohammad Nur
- Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia
| | - Vaqar Adhami
- Department of Dermatology, School of Medicine and Public Health, University of Wisconsin, Madison, USA
| | - Hasan Mukhtar
- Department of Dermatology, School of Medicine and Public Health, University of Wisconsin, Madison, USA.
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21
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Freen-van Heeren JJ. Toll-like receptor-2/7-mediated T cell activation: An innate potential to augment CD8 + T cell cytokine production. Scand J Immunol 2021; 93:e13019. [PMID: 33377182 DOI: 10.1111/sji.13019] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 12/10/2020] [Accepted: 12/26/2020] [Indexed: 12/11/2022]
Abstract
CD8+ T cells are critical to combat pathogens and eradicate malignantly transformed cells. To exert their effector function and kill target cells, T cells produce copious amounts of effector molecules, including the pro-inflammatory cytokines interferon γ, tumour necrosis factor α and interleukin 2. TCR triggering alone is sufficient to induce cytokine secretion by effector and memory CD8+ T cells. However, T cells can also be directly activated by pathogen-derived molecules, such as through the triggering of Toll-like receptors (TLRs). TLR-mediated pathogen sensing by T cells results in the production of only interferon γ. However, in particular when the antigen load on target cells is low, or when TCR affinity to the antigen is limited, antigen-experienced T cells can benefit from costimulatory signals. TLR stimulation can also function in a costimulatory fashion to enhance TCR triggering. Combined TCR and TLR triggering enhances the proliferation, memory formation and effector function of T cells, resulting in enhanced production of interferon γ, tumour necrosis factor α and interleukin 2. Therefore, TLR ligands or the exploitation of TLR signalling could provide novel opportunities for immunotherapy approaches. In fact, CD19 CAR T cells bearing an intracellular TLR2 costimulatory domain were recently employed to treat cancer patients in a clinical trial. Here, the current knowledge regarding TLR2/7 stimulation-induced cytokine production by T cells is reviewed. Specifically, the transcriptional and post-transcriptional pathways engaged upon TLR2/7 sensing and TLR2/7 signalling are discussed. Finally, the potential uses of TLRs to enhance the anti-tumor effector function of T cells are explored.
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22
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Curdy N, Lanvin O, Cadot S, Laurent C, Fournié JJ, Franchini DM. Stress Granules in the Post-transcriptional Regulation of Immune Cells. Front Cell Dev Biol 2021; 8:611185. [PMID: 33520991 PMCID: PMC7841200 DOI: 10.3389/fcell.2020.611185] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 12/07/2020] [Indexed: 12/14/2022] Open
Abstract
Immune cell activation triggers transcriptional and translational programs eliciting cellular processes, such as differentiation or proliferation, essential for an efficient immune response. These dynamic processes require an intricate orchestration of regulatory mechanisms to control the precise spatiotemporal expression of proteins. Post-transcriptional regulation ensures the control of messenger RNA metabolism and appropriate translation. Among these post-transcriptional regulatory mechanisms, stress granules participate in the control of protein synthesis. Stress granules are ribonucleoprotein complexes that form upon stress, typically under control of the integrated stress response. Such structures assemble upon stimulation of immune cells where they control selective translational programs ensuring the establishment of accurate effector functions. In this review, we summarize the current knowledge about post-transcriptional regulation in immune cells and highlight the role of stress sensors and stress granules in such regulation.
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Affiliation(s)
- Nicolas Curdy
- Cancer Research Center of Toulouse (CRCT), INSERM UMR 1037, CNRS ERL 5294, Toulouse, France.,Université Toulouse III Paul Sabatier, Toulouse, France.,Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France
| | - Olivia Lanvin
- Cancer Research Center of Toulouse (CRCT), INSERM UMR 1037, CNRS ERL 5294, Toulouse, France.,Université Toulouse III Paul Sabatier, Toulouse, France.,Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France
| | - Sarah Cadot
- Cancer Research Center of Toulouse (CRCT), INSERM UMR 1037, CNRS ERL 5294, Toulouse, France.,Université Toulouse III Paul Sabatier, Toulouse, France.,Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France
| | - Camille Laurent
- Cancer Research Center of Toulouse (CRCT), INSERM UMR 1037, CNRS ERL 5294, Toulouse, France.,Université Toulouse III Paul Sabatier, Toulouse, France.,Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France.,Département de Pathologie, Centre Hospitalier Universitaire (CHU) de Toulouse, Toulouse, France
| | - Jean-Jacques Fournié
- Cancer Research Center of Toulouse (CRCT), INSERM UMR 1037, CNRS ERL 5294, Toulouse, France.,Université Toulouse III Paul Sabatier, Toulouse, France.,Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France
| | - Don-Marc Franchini
- Cancer Research Center of Toulouse (CRCT), INSERM UMR 1037, CNRS ERL 5294, Toulouse, France.,Université Toulouse III Paul Sabatier, Toulouse, France.,Institut Universitaire du Cancer de Toulouse-Oncopole, Toulouse, France
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23
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Rodenkirchen V, Schettgen T, Rink L. Zinc deficiency impairs interferon-γ production on post-transcriptional level. J Trace Elem Med Biol 2020; 62:126598. [PMID: 32645654 DOI: 10.1016/j.jtemb.2020.126598] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Revised: 06/12/2020] [Accepted: 06/15/2020] [Indexed: 12/18/2022]
Abstract
BACKGROUND Zinc is a trace element and is thus commonly known to be indispensable for regular cellular function. Until today, zinc deficiency is a widespread health problem, affecting approximately one sixth of the world's population. Especially the immune system has proven to be highly dependent on zinc. Interferon-γ (IFN-γ) is a key element in the defense against intracellular pathogens. A lack of this cytokine results in immunological impairment, whereas an excess can lead to autoimmunity, highlighting the importance of a well-regulated IFN-γ expression. In a state of zinc deficiency, the production of this cytokine has long been shown to be reduced. Providing further insight into the molecular mechanisms responsible for this interaction is the primary objective of this study. METHODS Zinc-deficient or -supplemented cell culture, ELISA, quantitative PCR, methylation analysis. RESULTS Promoter methylation is a typical mechanism of gene silencing and a strong regulating factor for IFN-γ production. An analysis of the methylation status of IFN-γ and its transcription factor IRF4 in human PBMC in a state of cellular zinc deficiency or excess showed no dependency on the trace metal. Unexpectedly, zinc-deficient PBMC, which secreted significantly less IFN-γ protein, showed significantly higher mRNA levels of the cytokine compared to cells with high total zinc levels. CONCLUSION This report is the first about this unconventional ratio of IFN-γ mRNA to protein. Such a mismatch is highly relevant to the study of protein production in general and that of IFN-γ in particular. Based on our results and the latest research, we hypothesize a strong post-transcriptional effect of zinc on IFN-γ.
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Affiliation(s)
- Vera Rodenkirchen
- Institute of Immunology, Medical Faculty, RWTH Aachen University, Pauwelsstr. 30, D-52074 Aachen, Germany
| | - Thomas Schettgen
- Institute for Occupational, Social and Environmental Medicine, Medical Faculty, RWTH Aachen University, Pauwelsstr. 30, D-52074 Aachen, Germany
| | - Lothar Rink
- Institute of Immunology, Medical Faculty, RWTH Aachen University, Pauwelsstr. 30, D-52074 Aachen, Germany.
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24
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Eiermann N, Haneke K, Sun Z, Stoecklin G, Ruggieri A. Dance with the Devil: Stress Granules and Signaling in Antiviral Responses. Viruses 2020; 12:v12090984. [PMID: 32899736 PMCID: PMC7552005 DOI: 10.3390/v12090984] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/31/2020] [Accepted: 08/31/2020] [Indexed: 02/07/2023] Open
Abstract
Cells have evolved highly specialized sentinels that detect viral infection and elicit an antiviral response. Among these, the stress-sensing protein kinase R, which is activated by double-stranded RNA, mediates suppression of the host translation machinery as a strategy to limit viral replication. Non-translating mRNAs rapidly condensate by phase separation into cytosolic stress granules, together with numerous RNA-binding proteins and components of signal transduction pathways. Growing evidence suggests that the integrated stress response, and stress granules in particular, contribute to antiviral defense. This review summarizes the current understanding of how stress and innate immune signaling act in concert to mount an effective response against virus infection, with a particular focus on the potential role of stress granules in the coordination of antiviral signaling cascades.
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Affiliation(s)
- Nina Eiermann
- Division of Biochemistry, Mannheim Institute for Innate Immunoscience (MI3), Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany; (N.E.); (K.H.); (G.S.)
| | - Katharina Haneke
- Division of Biochemistry, Mannheim Institute for Innate Immunoscience (MI3), Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany; (N.E.); (K.H.); (G.S.)
| | - Zhaozhi Sun
- Department of Infectious Diseases, Molecular Virology, Center for Integrative Infectious Disease Research (CIID), University of Heidelberg, 69120 Heidelberg, Germany;
| | - Georg Stoecklin
- Division of Biochemistry, Mannheim Institute for Innate Immunoscience (MI3), Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany; (N.E.); (K.H.); (G.S.)
| | - Alessia Ruggieri
- Department of Infectious Diseases, Molecular Virology, Center for Integrative Infectious Disease Research (CIID), University of Heidelberg, 69120 Heidelberg, Germany;
- Correspondence:
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25
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General and Target-Specific DExD/H RNA Helicases in Eukaryotic Translation Initiation. Int J Mol Sci 2020; 21:ijms21124402. [PMID: 32575790 PMCID: PMC7352612 DOI: 10.3390/ijms21124402] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 12/19/2022] Open
Abstract
DExD (DDX)- and DExH (DHX)-box RNA helicases, named after their Asp-Glu-x-Asp/His motifs, are integral to almost all RNA metabolic processes in eukaryotic cells. They play myriad roles in processes ranging from transcription and mRNA-protein complex remodeling, to RNA decay and translation. This last facet, translation, is an intricate process that involves DDX/DHX helicases and presents a regulatory node that is highly targetable. Studies aimed at better understanding this family of conserved proteins have revealed insights into their structures, catalytic mechanisms, and biological roles. They have also led to the development of chemical modulators that seek to exploit their essential roles in diseases. Herein, we review the most recent insights on several general and target-specific DDX/DHX helicases in eukaryotic translation initiation.
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Huynh NP, Gloss CC, Lorentz J, Tang R, Brunger JM, McAlinden A, Zhang B, Guilak F. Long non-coding RNA GRASLND enhances chondrogenesis via suppression of the interferon type II signaling pathway. eLife 2020; 9:49558. [PMID: 32202492 PMCID: PMC7202894 DOI: 10.7554/elife.49558] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 03/21/2020] [Indexed: 12/14/2022] Open
Abstract
The roles of long noncoding RNAs (lncRNAs) in musculoskeletal development, disease, and regeneration remain poorly understood. Here, we identified the novel lncRNA GRASLND (originally named RNF144A-AS1) as a regulator of mesenchymal stem cell (MSC) chondrogenesis. GRASLND, a primate-specific lncRNA, is upregulated during MSC chondrogenesis and appears to act directly downstream of SOX9, but not TGF-β3. We showed that the silencing of GRASLND resulted in lower accumulation of cartilage-like extracellular matrix in a pellet assay, while GRASLND overexpression – either via transgene ectopic expression or by endogenous activation via CRISPR-dCas9-VP64 – significantly enhanced cartilage matrix production. GRASLND acts to inhibit IFN-γ by binding to EIF2AK2, and we further demonstrated that GRASLND exhibits a protective effect in engineered cartilage against interferon type II. Our results indicate an important role of GRASLND in regulating stem cell chondrogenesis, as well as its therapeutic potential in the treatment of cartilage-related diseases, such as osteoarthritis.
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Affiliation(s)
- Nguyen Pt Huynh
- Department of Orthopaedic Surgery, Washington University, St Louis, United States.,Shriners Hospitals for Children, St. Louis, United States.,Department of Cell Biology, Duke University, Durham, United States.,Center of Regenerative Medicine, Washington University, St Louis, United States
| | - Catherine C Gloss
- Department of Orthopaedic Surgery, Washington University, St Louis, United States.,Shriners Hospitals for Children, St. Louis, United States.,Center of Regenerative Medicine, Washington University, St Louis, United States
| | - Jeremiah Lorentz
- Department of Orthopaedic Surgery, Washington University, St Louis, United States.,Shriners Hospitals for Children, St. Louis, United States.,Center of Regenerative Medicine, Washington University, St Louis, United States
| | - Ruhang Tang
- Department of Orthopaedic Surgery, Washington University, St Louis, United States.,Shriners Hospitals for Children, St. Louis, United States.,Center of Regenerative Medicine, Washington University, St Louis, United States
| | - Jonathan M Brunger
- Department of Biomedical Engineering, Vanderbilt University, Nashville, United States
| | - Audrey McAlinden
- Department of Orthopaedic Surgery, Washington University, St Louis, United States.,Shriners Hospitals for Children, St. Louis, United States.,Center of Regenerative Medicine, Washington University, St Louis, United States
| | - Bo Zhang
- Center of Regenerative Medicine, Washington University, St Louis, United States
| | - Farshid Guilak
- Department of Orthopaedic Surgery, Washington University, St Louis, United States.,Shriners Hospitals for Children, St. Louis, United States.,Center of Regenerative Medicine, Washington University, St Louis, United States
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Sun W, Zhang X, Chen D, Murchie AIH. Interactions between the 5' UTR mRNA of the spe2 gene and spermidine regulate translation in S. pombe. RNA (NEW YORK, N.Y.) 2020; 26:137-149. [PMID: 31826924 PMCID: PMC6961545 DOI: 10.1261/rna.072975.119] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 12/10/2019] [Indexed: 05/20/2023]
Abstract
The 5' untranslated regions (5' UTR) of mRNAs play an important role in the eukaryotic translation initiation process. Additional levels of translational regulation may be mediated through interactions between structured mRNAs that can adopt interchangeable secondary or tertiary structures and the regulatory protein/RNA factors or components of the translational apparatus. Here we report a regulatory function of the 5' UTR mRNA of the spe2 gene (SAM decarboxylase) in polyamine metabolism of the fission yeast Schizosaccharomyces pombe Reporter assays, biochemical experiments, and mutational analysis demonstrate that this 5' UTR mRNA of spe2 can bind to spermidine to regulate translation. A tertiary structure transition in the 5' UTR RNA upon spermidine binding is essential for translation regulation. This study provides biochemical evidence for spermidine binding to regulate translation of the spe2 gene through interactions with the 5' UTR mRNA. The identification of such a regulatory RNA that is directly associated with an essential eukaryotic metabolic process suggests that other ligand-binding RNAs may also contribute to eukaryotic gene regulation.
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Affiliation(s)
- Wenxia Sun
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Xuhui Zhang
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Dongrong Chen
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Alastair I H Murchie
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
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Zhang X, Sun W, Chen D, Murchie AIH. Interactions between SAM and the 5' UTR mRNA of the sam1 gene regulate translation in S. pombe. RNA (NEW YORK, N.Y.) 2020; 26:150-161. [PMID: 31767786 PMCID: PMC6961541 DOI: 10.1261/rna.072983.119] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Accepted: 10/14/2019] [Indexed: 05/03/2023]
Abstract
The 5' untranslated region (5' UTR) of eukaryotic mRNA plays an important role in translation. Here we report the function of the 5' UTR mRNA of S-adenosylmethionine synthetase (sam1) in translational modulation in the presence of SAM in fission yeast Schizosaccharomyces pombe Reporter assays, binding and chemical probing experiments, and mutational analysis show that the 5' UTR mRNA of sam1 binds to SAM to effect translation. Translational modulation is dependent on a tertiary structure transition in the RNA upon SAM binding. The characterization of such an RNA that is directly associated with an essential metabolic process in eukaryotes provides additional evidence that ligand binding by RNAs plays an important role in eukaryotic gene regulation.
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Affiliation(s)
- Xuhui Zhang
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Wenxia Sun
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Dongrong Chen
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Alastair I H Murchie
- Fudan University Pudong Medical Center, Pudong and Key Laboratory of Medical Epigenetics and Metabolism, Institute of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 200032, China
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
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29
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Crisler WJ, Eshleman EM, Lenz LL. Ligand-induced IFNGR1 down-regulation calibrates myeloid cell IFNγ responsiveness. Life Sci Alliance 2019; 2:e201900447. [PMID: 31585982 PMCID: PMC6778285 DOI: 10.26508/lsa.201900447] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 09/23/2019] [Accepted: 09/24/2019] [Indexed: 01/04/2023] Open
Abstract
The type II IFN (IFNγ) enhances antimicrobial activity yet also drives expression of genes that amplify inflammatory responses. Hence, excessive IFNγ stimulation can be pathogenic. Here, we describe a previously unappreciated mechanism whereby IFNγ itself dampens myeloid cell activation. Staining of monocytes from Listeria monocytogenes-infected mice provided evidence of type I IFN-independent reductions in IFNGR1. IFNγ was subsequently found to reduce surface IFNGR1 on cultured murine myeloid cells and human CD14+ peripheral blood mononuclear cells. IFNγ-driven reductions in IFNGR1 were not explained by ligand-induced receptor internalization. Rather, IFNγ reduced macrophage Ifngr1 transcription by altering chromatin structure at putative Ifngr1 enhancer sites. This is a distinct mechanism from that used by type I IFNs. Ligand-induced reductions in IFNGR1 altered myeloid cell sensitivity to IFNγ, blunting activation of STAT1 and 3. Our data, thus, reveal a mechanism by which IFNGR1 abundance and myeloid cell sensitivity to IFNγ can be modulated in the absence of type I IFNs. Multiple mechanisms, thus, exist to calibrate macrophage IFNGR1 abundance, likely permitting the fine tuning of macrophage activation and inflammation.
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Affiliation(s)
- William J Crisler
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Emily M Eshleman
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora, CO, USA
| | - Laurel L Lenz
- Department of Immunology & Microbiology, University of Colorado School of Medicine, Aurora, CO, USA
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30
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Piersma SJ, Pak-Wittel MA, Lin A, Plougastel-Douglas B, Yokoyama WM. Activation Receptor-Dependent IFN-γ Production by NK Cells Is Controlled by Transcription, Translation, and the Proteasome. THE JOURNAL OF IMMUNOLOGY 2019; 203:1981-1988. [PMID: 31444264 DOI: 10.4049/jimmunol.1900718] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 07/24/2019] [Indexed: 12/20/2022]
Abstract
NK cells can recognize target cells such as virus-infected and tumor cells through integration of activation and inhibitory receptors. Recognition by NK cells can lead to direct lysis of the target cell and production of the signature cytokine IFN-γ. However, it is unclear whether stimulation through activation receptors alone is sufficient for IFN-γ production. In this study, we show that NK activation receptor engagement requires additional signals for optimal IFN-γ production, which could be provided by IFN-β or IL-12. Stimulation of murine NK cells with soluble Abs directed against NK1.1, Ly49H, Ly49D, or NKp46 required additional stimulation with cytokines, indicating that a range of activation receptors with distinct adaptor molecules require additional stimulation for IFN-γ production. The requirement for multiple signals extends to stimulation with primary m157-transgenic target cells, which triggers the activation receptor Ly49H, suggesting that NK cells do require multiple signals for IFN-γ production in the context of target cell recognition. Using quantitative PCR and RNA flow cytometry, we found that cytokines, not activating ligands, act on NK cells to express Ifng transcripts. Ly49H engagement is required for IFN-γ translational initiation. Results using inhibitors suggest that the proteasome-ubiquitin-IKK-TPL2-MNK1 axis was required during activation receptor engagement. Thus, this study indicates that activation receptor-dependent IFN-γ production is regulated on the transcriptional and translational levels.
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Affiliation(s)
- Sytse J Piersma
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Melissa A Pak-Wittel
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Andrea Lin
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Beatrice Plougastel-Douglas
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
| | - Wayne M Yokoyama
- Division of Rheumatology, Department of Medicine, Washington University School of Medicine, St. Louis, MO 63110
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31
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Klepsch O, Namer LS, Köhler N, Kaempfer R, Dittrich A, Schaper F. Intragenic regulation of SOCS3 isoforms. Cell Commun Signal 2019; 17:70. [PMID: 31238931 PMCID: PMC6593527 DOI: 10.1186/s12964-019-0379-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 05/01/2019] [Indexed: 11/13/2022] Open
Abstract
Background Inflammatory reactions are commonly affected by stress responses. Interleukin-6 signalling is part of the inflammatory response and is stringently regulated by the feedback inhibitor SOCS3 expressed in a short and long isoform. Here, we studied the inhibitory potential of the two SOCS3 isoforms. Furthermore, we analysed the regulation of SOCS3 isoform expression and the role of PKR stress kinase signalling in SOCS3 protein expression. Methods We performed Western blotting, reporter assays, genetic analyses and manipulations for studying SOCS3 isoform expression and activation of signalling components involved in interleukin-6-induced and PKR-dependent signalling. Results Interleukin-6-induced endogenous expression of both SOCS3 isoforms was found in distinct cell types. Forced expression of either the long or short SOCS3 isoform demonstrated equal inhibitory activity of each isoform and confirmed longer half-life of the short isoform. Study of intragenic regulation of SOCS3 isoform expression revealed that (i) the 5′-UTR of SOCS3 mRNA restrains specifically expression of the long SOCS3 isoform, (ii) expression of the long isoform restrains expression of the short isoform, and (iii) signalling through the stress kinase PKR does not impact on SOCS3 isoform ratio. Conclusions Both SOCS3 isoforms show a similar potential for inhibiting interleukin-6 signalling but differ in their half-lives. Relative expression of the isoforms depends on intragenic elements yet is independent of PKR signalling. Graphic abstract ![]()
Electronic supplementary material The online version of this article (10.1186/s12964-019-0379-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Oliver Klepsch
- Department of Systems Biology, Institute of Biology, Otto-von-Guericke University Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany
| | - Lise Sarah Namer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, 9112102, Jerusalem, Israel
| | - Nadine Köhler
- Department of Systems Biology, Institute of Biology, Otto-von-Guericke University Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany
| | - Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, 9112102, Jerusalem, Israel
| | - Anna Dittrich
- Department of Systems Biology, Institute of Biology, Otto-von-Guericke University Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany.
| | - Fred Schaper
- Department of Systems Biology, Institute of Biology, Otto-von-Guericke University Magdeburg, Universitätsplatz 2, 39106, Magdeburg, Germany.
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32
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Lee YS, Kunkeaw N, Lee YS. Protein kinase R and its cellular regulators in cancer: An active player or a surveillant? WILEY INTERDISCIPLINARY REVIEWS-RNA 2019; 11:e1558. [PMID: 31231984 DOI: 10.1002/wrna.1558] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Revised: 05/24/2019] [Accepted: 05/28/2019] [Indexed: 12/12/2022]
Abstract
Protein kinase R (PKR), originally known as an antiviral protein, senses various stresses as well as pathogen-driven double-stranded RNAs. Thereby activated PKR provokes diverse downstream events, including eIF2α phosphorylation and nuclear factor kappa-light-chain-enhancer of activated B cells activation. Consequently, PKR induces apoptosis and inflammation, both of which are highly important in cancer as much as its original antiviral role. Therefore, cellular proteins and RNAs should tightly control PKR activity. PKR and its regulators are often dysregulated in cancer and it is undoubted that such dysregulation contributes to tumorigenesis. However, PKR's precise role in cancer is still in debate, due to incomprehensible and even contradictory data. In this review, we introduce important cellular PKR regulators and discuss about their roles in cancer. Among them, we pay particular attention to nc886, a PKR repressor noncoding RNA that has been identified relatively recently, because its expression pattern in cancer can explain interesting yet obscure oncologic aspects of PKR. Based on nc886 and its regulation of PKR, we have proposed a tumor surveillance model, which reconciles contradictory data about PKR in cancer. This article is categorized under: Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
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Affiliation(s)
- Yong Sun Lee
- Department of Cancer Biomedical Science, Graduate School of Cancer Science and Policy, National Cancer Center, Goyang, Korea
| | - Nawapol Kunkeaw
- Institute of Molecular Biosciences, Mahidol University, Nakhon Pathom, Thailand
| | - Yeon-Su Lee
- Division of Clinical Research, Research Institute, National Cancer Center, Goyang, Korea
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33
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Kaempfer R, Ilan L, Cohen-Chalamish S, Turgeman O, Namer LS, Osman F. Control of mRNA Splicing by Intragenic RNA Activators of Stress Signaling: Potential Implications for Human Disease. Front Genet 2019; 10:464. [PMID: 31139209 PMCID: PMC6527590 DOI: 10.3389/fgene.2019.00464] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 04/30/2019] [Indexed: 11/13/2022] Open
Abstract
A critical step in the cellular stress response is transient activation of the RNA-dependent protein kinase PKR by double-helical RNA, resulting in down-regulation of protein synthesis through phosphorylation of the α chain of translation initiation factor eIF2, a major PKR substrate. However, intragenic elements of 100–200 nucleotides in length within primary transcripts of cellular genes, exemplified by the tumor necrosis factor (TNF)-α gene and fetal and adult globin genes, are capable of forming RNA structures that potently activate PKR and thereby strongly enhance mRNA splicing efficiency. By inducing nuclear eIF2α phosphorylation, these PKR activator elements enable highly efficient early spliceosome assembly yet do not impair translation of the mature spliced mRNA. The TNF-α RNA activator of PKR folds into a compact pseudoknot that is highly conserved within the phylogeny. Upon excision of β-globin first intron, the RNA activator of PKR, located in exon 1, is silenced through strand displacement by a short sequence within exon 2, restricting thereby the ability to activate PKR to the splicing process without impeding subsequent synthesis of β-globin essential for survival. This activator/silencer mechanism likewise controls splicing of α-globin pre-mRNA, but the exonic locations of PKR activator and silencer sequences are reversed, demonstrating evolutionary flexibility. Impaired splicing efficiency may underlie numerous human β-thalassemia mutations that map to the β-globin RNA activator of PKR or its silencer. Even where such mutations change the encoded amino acid sequence during subsequent translation, they carry the potential of first impairing PKR-dependent mRNA splicing or shutoff of PKR activation needed for optimal translation.
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Affiliation(s)
- Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Lena Ilan
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Smadar Cohen-Chalamish
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Orli Turgeman
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Lise Sarah Namer
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Farhat Osman
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem, Israel
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Bou-Nader C, Gordon JM, Henderson FE, Zhang J. The search for a PKR code-differential regulation of protein kinase R activity by diverse RNA and protein regulators. RNA (NEW YORK, N.Y.) 2019; 25:539-556. [PMID: 30770398 PMCID: PMC6467004 DOI: 10.1261/rna.070169.118] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The interferon-inducible protein kinase R (PKR) is a key component of host innate immunity that restricts viral replication and propagation. As one of the four eIF2α kinases that sense diverse stresses and direct the integrated stress response (ISR) crucial for cell survival and proliferation, PKR's versatile roles extend well beyond antiviral defense. Targeted by numerous host and viral regulators made of RNA and proteins, PKR is subject to multiple layers of endogenous control and external manipulation, driving its rapid evolution. These versatile regulators include not only the canonical double-stranded RNA (dsRNA) that activates the kinase activity of PKR, but also highly structured viral, host, and artificial RNAs that exert a full spectrum of effects. In this review, we discuss our deepening understanding of the allosteric mechanism that connects the regulatory and effector domains of PKR, with an emphasis on diverse structured RNA regulators in comparison to their protein counterparts. Through this analysis, we conclude that much of the mechanistic details that underlie this RNA-regulated kinase await structural and functional elucidation, upon which we can then describe a "PKR code," a set of structural and chemical features of RNA that are both descriptive and predictive for their effects on PKR.
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Affiliation(s)
- Charles Bou-Nader
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
| | - Jackson M Gordon
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
| | - Frances E Henderson
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
| | - Jinwei Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland 20892, USA
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35
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Demeter T, Vaskovicova M, Malik R, Horvat F, Pasulka J, Svobodova E, Flemr M, Svoboda P. Main constraints for RNAi induced by expressed long dsRNA in mouse cells. Life Sci Alliance 2019; 2:2/1/e201800289. [PMID: 30808654 PMCID: PMC6391682 DOI: 10.26508/lsa.201800289] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Revised: 02/09/2019] [Accepted: 02/11/2019] [Indexed: 12/13/2022] Open
Abstract
A systematic survey of dsRNA expression in mouse fibroblasts and embryonic stem cells shows main constraints for RNAi. RNAi activity depends on the initial Dicer cleavage of dsRNA, having implications for the evolution of mammalian RNAi functions. RNAi is the sequence-specific mRNA degradation guided by siRNAs produced from long dsRNA by RNase Dicer. Proteins executing RNAi are present in mammalian cells but rather sustain the microRNA pathway. Aiming for a systematic analysis of mammalian RNAi, we report here that the main bottleneck for RNAi efficiency is the production of functional siRNAs, which integrates Dicer activity, dsRNA structure, and siRNA targeting efficiency. Unexpectedly, increased expression of Dicer cofactors TARBP2 or PACT reduces RNAi but not microRNA function. Elimination of protein kinase R, a key dsRNA sensor in the interferon response, had minimal positive effects on RNAi activity in fibroblasts. Without high Dicer activity, RNAi can still occur when the initial Dicer cleavage of the substrate yields an efficient siRNA. Efficient mammalian RNAi may use substrates with some features of microRNA precursors, merging both pathways even more than previously suggested. Although optimized endogenous Dicer substrates mimicking miRNA features could evolve for endogenous regulations, the same principles would make antiviral RNAi inefficient as viruses would adapt to avoid efficacy.
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Affiliation(s)
- Tomas Demeter
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Michaela Vaskovicova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Radek Malik
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Filip Horvat
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic.,Bioinformatics Group, Division of Molecular Biology, Department of Biology, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Josef Pasulka
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Eliska Svobodova
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Matyas Flemr
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Petr Svoboda
- Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Abstract
Interferon gamma, referred to here as IFN-γ, is a major component in immunological cell signaling and is a critical regulatory protein for overall immune system function. First discovered in 1965 (Wheelock Science 149: (3681)310-311, 1965), IFN-γ is the only Type II interferon identified. Its expression is both positively and negatively controlled by different factors. In this chapter, we will review the transcriptional and post-transcriptional control of IFN-γ expression. In the transcriptional control part, the regular activators and suppressors are summarized, we will also focus on the epigenetic control, such as chromosome access, DNA methylation, and histone acetylation. The more we learn about the control of this regulatory protein will allow us to apply this knowledge in the future to effectively manipulate IFN-γ expression for the treatment of infections, cancer, inflammation, and autoimmune diseases.
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37
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Kaempfer R, Namer LS, Osman F, Ilan L. Control of mRNA splicing by noncoding intragenic RNA elements that evoke a cellular stress response. Int J Biochem Cell Biol 2018; 105:20-23. [PMID: 30282053 DOI: 10.1016/j.biocel.2018.09.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 09/25/2018] [Accepted: 09/27/2018] [Indexed: 11/15/2022]
Abstract
Once activated by double-helical RNA, mammalian RNA-dependent stress protein kinase, PKR, phosphorylates its substrate, translation initiation factor eIF2α, to inhibit translation. eIF2α phosphorylation is critical for mounting a cellular stress response. We describe short, 100-200 nucleotide elements within cellular genes that, once transcribed, form RNA structures that potently activate PKR in the vicinity of the RNA and thereby tightly regulate gene expression in cis. Intragenic RNA activators of PKR can (a) attenuate translation of the encoded mRNA by activating PKR and inducing eIF2α phosphorylation, exemplified by the IFN-γ gene, or (b) greatly enhance mRNA splicing efficiency by activating PKR and inducing nuclear eIF2α phosphorylation, thus enabling efficient early spliceosome assembly, exemplified by the adult and fetal globin genes and the TNF-α gene that activates PKR through an RNA pseudoknot conserved from fish to humans. These opposite outcomes considerably extend the potential scope of gene regulation by these novel RNA elements.
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Affiliation(s)
- Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The Hebrew University, Jerusalem, Israel.
| | - Lise Sarah Namer
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Farhat Osman
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
| | - Lena Ilan
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The Hebrew University, Jerusalem, Israel
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Defining the Role of Stress Granules in Innate Immune Suppression by the Herpes Simplex Virus 1 Endoribonuclease VHS. J Virol 2018; 92:JVI.00829-18. [PMID: 29793959 DOI: 10.1128/jvi.00829-18] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 05/16/2018] [Indexed: 12/20/2022] Open
Abstract
In response to virus-induced shutoff host protein synthesis, dynamic aggregates containing mRNA, RNA-binding proteins and translation factors termed stress granules (SGs) often accumulate within the cytoplasm. SGs typically form following phosphorylation and inactivation of the eukaryotic translation initiation factor 2α (eIF2α), a substrate of the double-stranded RNA (dsRNA)-activated kinase protein kinase R (PKR). The detection of innate immune sensors and effectors like PKR at SGs suggests a role in pathogen nucleic acid sensing. However, the functional importance of SGs in host innate responses is unclear and has primarily been examined in response to infection with select RNA viruses. During infection with the DNA virus herpes simplex virus 1 (HSV-1), the virus-encoded virion host shutoff (VHS) endoribonuclease is required to restrict interferon production, PKR activation, and SG formation, although the relationship between these activities remains incompletely understood. Here, we show that in cells infected with a VHS-deficient HSV-1 (ΔVHS) dsRNA accumulated and localized to SGs. Surprisingly, formation of dsRNA and its concentration at SGs was not required for beta interferon mRNA induction, indicating that suppression of type I interferon induction by VHS does not stem from its control of dsRNA accumulation. Instead, STING signaling downstream of cGMP-AMP synthase (cGAS)-dependent DNA sensing is required for beta interferon induction. In contrast, significantly less PKR activation is observed when SG assembly is disrupted by ISRIB, an inhibitor of phosphorylated eIF2α-mediated translation repression, or depleting SG scaffolding proteins G3BP1 or TIA1. This demonstrates that PKR activation is intimately linked to SG formation and that SGs form important hubs to potentiate PKR activation during infection.IMPORTANCE Formation of cytoplasmic stress granules that are enriched for innate immune sensors and effectors is suppressed during many viral infections. It is unclear, however, to what extent this is a side effect of viral efforts to maintain protein synthesis or intentional disruption of a hub for innate immune sensing. In this study, we utilize a herpes simplex virus 1 mutant lacking the RNA nuclease VHS which upon infection induces SGs, PKR activation, and beta interferon to address this question. We show that dsRNA is localized to SGs and that SGs can function to promote PKR activation in the context of a DNA virus infection, but we find no evidence to support their importance for interferon induction during HSV-1 infection.
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Moon SL, Sonenberg N, Parker R. Neuronal Regulation of eIF2α Function in Health and Neurological Disorders. Trends Mol Med 2018; 24:575-589. [PMID: 29716790 DOI: 10.1016/j.molmed.2018.04.001] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/04/2018] [Accepted: 04/05/2018] [Indexed: 12/12/2022]
Abstract
A key site of translation control is the phosphorylation of the eukaryotic translation initiation factor 2α (eIF2α), which reduces the rate of GDP to GTP exchange by eIF2B, leading to altered translation. The extent of eIF2α phosphorylation within neurons can alter synaptic plasticity. Phosphorylation of eIF2α is triggered by four stress-responsive kinases, and as such eIF2α is often phosphorylated during neurological perturbations or disease. Moreover, in some cases decreasing eIF2α phosphorylation mitigates neurodegeneration, suggesting that this could be a therapeutic target. Mutations in the γ subunit of eIF2, the guanine exchange factor eIF2B, an eIF2α phosphatase, or in two eIF2α kinases can cause disease in humans, demonstrating the importance of proper regulation of eIF2α phosphorylation for health.
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Affiliation(s)
- Stephanie L Moon
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80303, USA
| | - Nahum Sonenberg
- Department of Biochemistry and Goodman Cancer Research Centre, McGill University, Montreal, QC H3A 1A3, Canada
| | - Roy Parker
- Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80303, USA; Howard Hughes Medical Institute, University of Colorado, Boulder, CO 80303, USA.
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40
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Namer LS, Osman F, Banai Y, Masquida B, Jung R, Kaempfer R. An Ancient Pseudoknot in TNF-α Pre-mRNA Activates PKR, Inducing eIF2α Phosphorylation that Potently Enhances Splicing. Cell Rep 2018; 20:188-200. [PMID: 28683312 DOI: 10.1016/j.celrep.2017.06.035] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 05/15/2017] [Accepted: 06/12/2017] [Indexed: 12/22/2022] Open
Abstract
Tumor necrosis factor alpha (TNF-α) is expressed promptly during inflammatory responses. Efficient TNF-α mRNA splicing is achieved through a 3' UTR element that activates RNA-dependent eIF2α protein kinase (PKR). The TNF-α RNA activator, we show, folds into a pseudoknot conserved from teleost fish to humans, critical for PKR activation and mRNA splicing. The pseudoknot constrains the RNA into two double-helical stacks having parallel axes, permitting facile PKR dimerization and trans-autophosphorylation needed for kinase activation. Mutations show that the PKR activator potently enhances splicing without inhibiting translation. eIF2α phosphorylation represses translation and is essential for coping with cellular stress, yet PKR-enabled TNF mRNA splicing depends strictly on eIF2α phosphorylation. Indeed, eIF2α phosphorylation at Serine51 is necessary and sufficient to achieve highly efficient splicing, extending its role from negative control of translation to positive control of splicing. This mechanism, operational in human peripheral blood mononuclear cells (PBMCs), links stress signaling to protective immunity through TNF mRNA splicing rendered efficient upon eIF2α phosphorylation.
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Affiliation(s)
- Lise Sarah Namer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 9112102, Israel
| | - Farhat Osman
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 9112102, Israel
| | - Yona Banai
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 9112102, Israel
| | - Benoît Masquida
- Génétique Moléculaire Génomique Microbiologie, CNRS-University of Strasbourg, Strasbourg 67084, France
| | - Rodrigo Jung
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 9112102, Israel
| | - Raymond Kaempfer
- Department of Biochemistry and Molecular Biology, Institute of Medical Research Israel-Canada, The Hebrew University-Hadassah Medical School, Jerusalem 9112102, Israel.
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41
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Leppek K, Das R, Barna M. Functional 5' UTR mRNA structures in eukaryotic translation regulation and how to find them. Nat Rev Mol Cell Biol 2018; 19:158-174. [PMID: 29165424 PMCID: PMC5820134 DOI: 10.1038/nrm.2017.103] [Citation(s) in RCA: 482] [Impact Index Per Article: 80.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
RNA molecules can fold into intricate shapes that can provide an additional layer of control of gene expression beyond that of their sequence. In this Review, we discuss the current mechanistic understanding of structures in 5' untranslated regions (UTRs) of eukaryotic mRNAs and the emerging methodologies used to explore them. These structures may regulate cap-dependent translation initiation through helicase-mediated remodelling of RNA structures and higher-order RNA interactions, as well as cap-independent translation initiation through internal ribosome entry sites (IRESs), mRNA modifications and other specialized translation pathways. We discuss known 5' UTR RNA structures and how new structure probing technologies coupled with prospective validation, particularly compensatory mutagenesis, are likely to identify classes of structured RNA elements that shape post-transcriptional control of gene expression and the development of multicellular organisms.
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Affiliation(s)
- Kathrin Leppek
- Department of Developmental Biology, Stanford University, Stanford, California 94305, USA
- Department of Genetics, Stanford University, Stanford, California 94305, USA
| | - Rhiju Das
- Departments of Biochemistry and Physics, Stanford University, Stanford, California 94305, USA
| | - Maria Barna
- Department of Developmental Biology, Stanford University, Stanford, California 94305, USA
- Department of Genetics, Stanford University, Stanford, California 94305, USA
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42
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Abstract
Metabolism is critical for a host of cellular functions and provides a source of intracellular energy. It has been recognized recently that metabolism also regulates differentiation and effector functions of immune cells. Although initial work in this field has focused largely on T lymphocytes, recent studies have demonstrated metabolic control of innate immune cells, including natural killer (NK) cells. Here, we review what is known regarding the metabolic requirements for NK cell activation, focusing on NK cell production of interferon-gamma (IFN-γ). NK cells are innate immune lymphocytes that are poised for rapid activation during the early immune response. Although their basal metabolic rates do not change with short-term activation, they exhibit specific metabolic requirements for activation depending upon the stimulus received. These metabolic requirements for NK cell activation are altered by culturing NK cells with interleukin-15, which increases NK cell metabolic rates at baseline and shifts them toward aerobic glycolysis. We discuss the metabolic pathways important for NK cell production of IFN-γ protein and potential mechanisms whereby metabolism regulates NK cell function.
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Affiliation(s)
- Annelise Y Mah
- Department of Pediatrics, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO
| | - Megan A Cooper
- Department of Pediatrics, Division of Rheumatology, Washington University School of Medicine, St. Louis, MO
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Marques-Ramos A, Candeias MM, Menezes J, Lacerda R, Willcocks M, Teixeira A, Locker N, Romão L. Cap-independent translation ensures mTOR expression and function upon protein synthesis inhibition. RNA (NEW YORK, N.Y.) 2017; 23:1712-1728. [PMID: 28821580 PMCID: PMC5648038 DOI: 10.1261/rna.063040.117] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 08/15/2017] [Indexed: 06/07/2023]
Abstract
The mechanistic/mammalian target of rapamycin (mTOR) is a conserved serine/threonine kinase that integrates cellular signals from the nutrient and energy status to act, namely, on the protein synthesis machinery. While major advances have emerged regarding the regulators and effects of the mTOR signaling pathway, little is known about the regulation of mTOR gene expression. Here, we show that the human mTOR transcript can be translated in a cap-independent manner, and that its 5' untranslated region (UTR) is a highly folded RNA scaffold capable of binding directly to the 40S ribosomal subunit. We further demonstrate that mTOR is able to bypass the cap requirement for translation both in normal and hypoxic conditions. Moreover, our data reveal that the cap-independent translation of mTOR is necessary for its ability to induce cell-cycle progression into S phase. These results suggest a novel regulatory mechanism for mTOR gene expression that integrates the global protein synthesis changes induced by translational inhibitory conditions.
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Affiliation(s)
- Ana Marques-Ramos
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Marco M Candeias
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan
| | - Juliane Menezes
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Rafaela Lacerda
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
| | - Margaret Willcocks
- Microbial and Cellular Sciences Department, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7TE, United Kingdom
| | - Alexandre Teixeira
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
| | - Nicolas Locker
- Microbial and Cellular Sciences Department, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7TE, United Kingdom
| | - Luísa Romão
- Departamento de Genética Humana, Instituto Nacional de Saúde Doutor Ricardo Jorge, 1649-016 Lisboa, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, 1749-016 Lisboa, Portugal
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Abstract
Although the antiviral kinase PKR was originally characterized as a double-stranded RNA activated enzyme it can be stimulated by RNAs containing limited secondary structure. Single-stranded regions in such RNAs contribute to binding and activation but the mechanism is not understood. Here, we demonstrate that single-stranded RNAs bind to PKR with micromolar dissociation constants and can induce activation. Addition of a 5'-triphosphate slightly enhances binding affinity. Single-stranded RNAs also activate PKR constructs lacking the double-stranded RNA binding domain and bind to a basic region adjacent to the N-terminus of the kinase. However, the isolated kinase is not activated by and does not bind single-stranded RNA. Photocrosslinking measurements demonstrate that that the basic region interacts with RNA in the context of full length PKR. We propose that bivalent interactions with the double stranded RNA binding domain and the basic region underlie the ability of RNAs containing limited structure to activate PKR by enhancing binding affinity and thereby increasing the population of productive complexes containing two PKRs bound to a single RNA.
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45
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Lacerda R, Menezes J, Romão L. More than just scanning: the importance of cap-independent mRNA translation initiation for cellular stress response and cancer. Cell Mol Life Sci 2017; 74:1659-1680. [PMID: 27913822 PMCID: PMC11107732 DOI: 10.1007/s00018-016-2428-2] [Citation(s) in RCA: 87] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2016] [Revised: 11/24/2016] [Accepted: 11/29/2016] [Indexed: 12/11/2022]
Abstract
The scanning model for eukaryotic mRNA translation initiation states that the small ribosomal subunit, along with initiation factors, binds at the cap structure at the 5' end of the mRNA and scans the 5' untranslated region (5'UTR) until an initiation codon is found. However, under conditions that impair canonical cap-dependent translation, the synthesis of some proteins is kept by alternative mechanisms that are required for cell survival and stress recovery. Alternative modes of translation initiation include cap- and/or scanning-independent mechanisms of ribosomal recruitment. In most cap-independent translation initiation events there is a direct recruitment of the 40S ribosome into a position upstream, or directly at, the initiation codon via a specific internal ribosome entry site (IRES) element in the 5'UTR. Yet, in some cellular mRNAs, a different translation initiation mechanism that is neither cap- nor IRES-dependent seems to occur through a special RNA structure called cap-independent translational enhancer (CITE). Recent evidence uncovered a distinct mechanism through which mRNAs containing N 6-methyladenosine (m6A) residues in their 5'UTR directly bind eukaryotic initiation factor 3 (eIF3) and the 40S ribosomal subunit in order to initiate translation in the absence of the cap-binding proteins. This review focuses on the important role of cap-independent translation mechanisms in human cells and how these alternative mechanisms can either act individually or cooperate with other cis-acting RNA regulons to orchestrate specific translational responses triggered upon several cellular stress states, and diseases such as cancer. Elucidation of these non-canonical mechanisms reveals the complexity of translational control and points out their potential as prospective novel therapeutic targets.
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Affiliation(s)
- Rafaela Lacerda
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Av. Padre Cruz, 1649-016, Lisbon, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Juliane Menezes
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Av. Padre Cruz, 1649-016, Lisbon, Portugal
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Luísa Romão
- Department of Human Genetics, Instituto Nacional de Saúde Doutor Ricardo Jorge, Av. Padre Cruz, 1649-016, Lisbon, Portugal.
- Biosystems and Integrative Sciences Institute (BioISI), Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal.
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46
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PKR activation and eIF2α phosphorylation mediate human globin mRNA splicing at spliceosome assembly. Cell Res 2017; 27:688-704. [PMID: 28374749 DOI: 10.1038/cr.2017.39] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 11/20/2016] [Accepted: 12/30/2016] [Indexed: 02/01/2023] Open
Abstract
Short elements in mammalian mRNA can control gene expression by activating the RNA-dependent protein kinase PKR that attenuates translation by phosphorylating cytoplasmic eukaryotic initiation factor 2α (eIF2α). We demonstrate a novel, positive role for PKR activation and eIF2α phosphorylation in human globin mRNA splicing. PKR localizes in splicing complexes and associates with splicing factor SC35. Splicing and early-stage spliceosome assembly on β-globin pre-mRNA depend strictly on activation of PKR by a codon-containing RNA fragment within exon 1 and on phosphorylation of nuclear eIF2α on Serine 51. Nonphosphorylatable mutant eIF2αS51A blocked β-globin mRNA splicing in cells and nuclear extract. Mutations of the β-globin RNA activator abrogated PKR activation and profoundly affected mRNA splicing efficiency. PKR depletion abrogated splicing and spliceosome assembly; recombinant PKR effectively restored splicing. Excision of the first intron of β-globin induces strand displacement within the RNA activator of PKR by a sequence from exon 2, a structural rearrangement that silences the ability of spliced β-globin mRNA to activate PKR. Thus, the ability to activate PKR is transient, serving solely to enable splicing. α-Globin pre-mRNA splicing is controlled likewise but positions of PKR activator and silencer are reversed, demonstrating evolutionary flexibility in how PKR activation regulates globin mRNA splicing through eIF2α phosphorylation.
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47
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Innate Immune Responses of Bat and Human Cells to Filoviruses: Commonalities and Distinctions. J Virol 2017; 91:JVI.02471-16. [PMID: 28122983 DOI: 10.1128/jvi.02471-16] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 01/17/2017] [Indexed: 12/13/2022] Open
Abstract
Marburg (MARV) and Ebola (EBOV) viruses are zoonotic pathogens that cause severe hemorrhagic fever in humans. The natural reservoir of MARV is the Egyptian rousette bat (Rousettus aegyptiacus); that of EBOV is unknown but believed to be another bat species. The Egyptian rousette develops subclinical productive infection with MARV but is refractory to EBOV. Interaction of filoviruses with hosts is greatly affected by the viral interferon (IFN)-inhibiting domains (IID). Our study was aimed at characterization of innate immune responses to filoviruses and the role of filovirus IID in bat and human cells. The study demonstrated that EBOV and MARV replicate to similar levels in all tested cell lines, indicating that permissiveness for EBOV at cell and organism levels do not necessarily correlate. Filoviruses, particularly MARV, induced a potent innate immune response in rousette cells, which was generally stronger than that in human cells. Both EBOV VP35 and VP24 IID were found to suppress the innate immune response in rousette cells, but only VP35 IID appeared to promote virus replication. Along with IFN-α and IFN-β, IFN-γ was demonstrated to control filovirus infection in bat cells but not in human cells, suggesting host species specificity of the antiviral effect. The antiviral effects of bat IFNs appeared not to correlate with induction of IFN-stimulated genes 54 and 56, which were detected in human cells ectopically expressing bat IFN-α and IFN-β. As bat IFN-γ induced the type I IFN pathway, its antiviral effect is likely to be partially induced via cross talk.IMPORTANCE Bats serve as reservoirs for multiple emerging viruses, including filoviruses, henipaviruses, lyssaviruses, and zoonotic coronaviruses. Although there is no evidence for symptomatic disease caused by either Marburg or Ebola viruses in bats, spillover of these viruses into human populations causes deadly outbreaks. The reason for the lack of symptomatic disease in bats infected with filoviruses remains unknown. The outcome of a virus-host interaction depends on the ability of the host immune system to suppress viral replication and the ability of a virus to counteract the host defenses. Our study is a comparative analysis of the host innate immune response to either MARV or EBOV infection in bat and human cells and the role of viral interferon-inhibiting domains in the host innate immune responses. The data are useful for understanding the interactions of filoviruses with natural and accidental hosts and for identification of factors that influence filovirus evolution.
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48
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Superantigens hyperinduce inflammatory cytokines by enhancing the B7-2/CD28 costimulatory receptor interaction. Proc Natl Acad Sci U S A 2016; 113:E6437-E6446. [PMID: 27708164 DOI: 10.1073/pnas.1603321113] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Full T-cell activation requires interaction between the costimulatory receptors B7-2 and CD28. By binding CD28, bacterial superantigens elicit harmful inflammatory cytokine overexpression through an unknown mechanism. We show that, by engaging not only CD28 but also its coligand B7-2 directly, superantigens potently enhance the avidity between B7-2 and CD28, inducing thereby T-cell hyperactivation. Using the same 12-aa β-strand-hinge-α-helix domain, superantigens engage both B7-2 and CD28 at their homodimer interfaces, areas remote from where these coreceptors interact, implying that inflammatory signaling can be controlled through the receptor homodimer interfaces. Short B7-2 dimer interface mimetic peptides bind diverse superantigens, prevent superantigen binding to cell-surface B7-2 or CD28, attenuate inflammatory cytokine overexpression, and protect mice from lethal superantigen challenge. Thus, superantigens induce a cytokine storm not only by mediating the interaction between MHC-II molecule and T-cell receptor but also, critically, by promoting B7-2/CD28 coreceptor engagement, forcing the principal costimulatory axis to signal excessively. Our results reveal a role for B7-2 as obligatory receptor for superantigens. B7-2 homodimer interface mimotopes prevent superantigen lethality by blocking the superantigen-host costimulatory receptor interaction.
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49
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Abstract
In multicellular organisms, the epithelia is a contact surface with the surrounding environment and is exposed to a variety of adverse biotic (pathogenic) and abiotic (chemical) factors. Multi-layered pathways that operate on different time scales have evolved to preserve cellular integrity and elicit stress-specific response. Several stress-response programs are activated until a complete elimination of the stress is achieved. The innate immune response, which is triggered by pathogenic invasion, is rather harmful when active over a prolonged time, thus the response follows characteristic oscillatory trajectories. Here, we review different translation programs that function to precisely fine-tune the time at which various components of the innate immune response dwell between active and inactive. We discuss how different pro-inflammatory pathways are co-ordinated to temporally offset single reactions and to achieve an optimal balance between fighting pathogens and being less harmful for healthy cells.
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50
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Mayo CB, Wong CJ, Lopez PE, Lary JW, Cole JL. Activation of PKR by short stem-loop RNAs containing single-stranded arms. RNA (NEW YORK, N.Y.) 2016; 22:1065-75. [PMID: 27208315 PMCID: PMC4911914 DOI: 10.1261/rna.053348.115] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 04/19/2016] [Indexed: 05/22/2023]
Abstract
Protein kinase R (PKR) is a central component of the innate immunity antiviral pathway and is activated by dsRNA. PKR contains a C-terminal kinase domain and two tandem dsRNA binding domains. In the canonical activation model, binding of multiple PKR monomers to dsRNA enhances dimerization of the kinase domain, leading to enzymatic activation. A minimal dsRNA of 30 bp is required for activation. However, short (∼15 bp) stem-loop RNAs containing flanking single-stranded tails (ss-dsRNAs) are capable of activating PKR. Activation was reported to require a 5'-triphosphate. Here, we characterize the structural features of ss-dsRNAs that contribute to activation. We have designed a model ss-dsRNA containing 15-nt single-stranded tails and a 15-bp stem and made systematic truncations of the tail and stem regions. Autophosphorylation assays and analytical ultracentrifugation experiments were used to correlate activation and binding affinity. PKR activation requires both 5'- and 3'-single-stranded tails but the triphosphate is dispensable. Activation potency and binding affinity decrease as the ssRNA tails are truncated and activation is abolished in cases where the binding affinity is strongly reduced. These results indicate that the single-stranded regions bind to PKR and support a model where ss-dsRNA induced dimerization is required but not sufficient to activate the kinase. The length of the duplex regions in several natural RNA activators of PKR is below the minimum of 30 bp required for activation and similar interactions with single-stranded regions may contribute to PKR activation in these cases.
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Affiliation(s)
- Christopher B Mayo
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA
| | - C Jason Wong
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Prisma E Lopez
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA
| | - Jeffrey W Lary
- National Analytical Ultracentrifugation Facility, University of Connecticut, Storrs, Connecticut 06269, USA
| | - James L Cole
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA National Analytical Ultracentrifugation Facility, University of Connecticut, Storrs, Connecticut 06269, USA
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