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Abstract
Coronaviruses have large positive-strand RNA genomes that are 5' capped and 3' polyadenylated. The 5'-terminal two-thirds of the genome contain two open reading frames (ORFs), 1a and 1b, that together make up the viral replicase gene and encode two large polyproteins that are processed by viral proteases into 15-16 nonstructural proteins, most of them being involved in viral RNA synthesis. ORFs located in the 3'-terminal one-third of the genome encode structural and accessory proteins and are expressed from a set of 5' leader-containing subgenomic mRNAs that are synthesized by a process called discontinuous transcription. Coronavirus protein synthesis not only involves cap-dependent translation mechanisms but also employs regulatory mechanisms, such as ribosomal frameshifting. Coronavirus replication is known to affect cellular translation, involving activation of stress-induced signaling pathways, and employing viral proteins that affect cellular mRNA translation and RNA stability. This chapter describes our current understanding of the mechanisms involved in coronavirus mRNA translation and changes in host mRNA translation observed in coronavirus-infected cells.
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Affiliation(s)
- K Nakagawa
- The University of Texas Medical Branch, Galveston, TX, United States
| | - K G Lokugamage
- The University of Texas Medical Branch, Galveston, TX, United States
| | - S Makino
- The University of Texas Medical Branch, Galveston, TX, United States; Center for Biodefense and Emerging Infectious Diseases, The University of Texas Medical Branch, Galveston, TX, United States; UTMB Center for Tropical Diseases, The University of Texas Medical Branch, Galveston, TX, United States; Sealy Center for Vaccine Development, The University of Texas Medical Branch, Galveston, TX, United States; Institute for Human Infections and Immunity, The University of Texas Medical Branch, Galveston, TX, United States.
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Cruz JLG, Sola I, Becares M, Alberca B, Plana J, Enjuanes L, Zuñiga S. Coronavirus gene 7 counteracts host defenses and modulates virus virulence. PLoS Pathog 2011; 7:e1002090. [PMID: 21695242 PMCID: PMC3111541 DOI: 10.1371/journal.ppat.1002090] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 04/12/2011] [Indexed: 12/14/2022] Open
Abstract
Transmissible gastroenteritis virus (TGEV) genome contains three accessory genes: 3a, 3b and 7. Gene 7 is only present in members of coronavirus genus a1, and encodes a hydrophobic protein of 78 aa. To study gene 7 function, a recombinant TGEV virus lacking gene 7 was engineered (rTGEV-Δ7). Both the mutant and the parental (rTGEV-wt) viruses showed the same growth and viral RNA accumulation kinetics in tissue cultures. Nevertheless, cells infected with rTGEV-Δ7 virus showed an increased cytopathic effect caused by an enhanced apoptosis mediated by caspase activation. Macromolecular synthesis analysis showed that rTGEV-Δ7 virus infection led to host translational shut-off and increased cellular RNA degradation compared with rTGEV-wt infection. An increase of eukaryotic translation initiation factor 2 (eIF2α) phosphorylation and an enhanced nuclease, most likely RNase L, activity were observed in rTGEV-Δ7 virus infected cells. These results suggested that the removal of gene 7 promoted an intensified dsRNA-activated host antiviral response. In protein 7 a conserved sequence motif that potentially mediates binding to protein phosphatase 1 catalytic subunit (PP1c), a key regulator of the cell antiviral defenses, was identified. We postulated that TGEV protein 7 may counteract host antiviral response by its association with PP1c. In fact, pull-down assays demonstrated the interaction between TGEV protein 7, but not a protein 7 mutant lacking PP1c binding motif, with PP1. Moreover, the interaction between protein 7 and PP1 was required, during the infection, for eIF2α dephosphorylation and inhibition of cell RNA degradation. Inoculation of newborn piglets with rTGEV-Δ7 and rTGEV-wt viruses showed that rTGEV-Δ7 virus presented accelerated growth kinetics and pathology compared with the parental virus. Overall, the results indicated that gene 7 counteracted host cell defenses, and modified TGEV persistence increasing TGEV survival. Therefore, the acquisition of gene 7 by the TGEV genome most likely has provided a selective advantage to the virus.
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Affiliation(s)
- Jazmina L. G. Cruz
- Centro Nacional de Biotecnología, CNB, CSIC, Department of Molecular and Cell Biology, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
| | - Isabel Sola
- Centro Nacional de Biotecnología, CNB, CSIC, Department of Molecular and Cell Biology, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
| | - Martina Becares
- Centro Nacional de Biotecnología, CNB, CSIC, Department of Molecular and Cell Biology, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
| | | | | | - Luis Enjuanes
- Centro Nacional de Biotecnología, CNB, CSIC, Department of Molecular and Cell Biology, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
- * E-mail:
| | - Sonia Zuñiga
- Centro Nacional de Biotecnología, CNB, CSIC, Department of Molecular and Cell Biology, Darwin 3, Campus Universidad Autónoma de Madrid, Cantoblanco, Madrid, Spain
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3
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Abstract
Transmissible gastroenteritis virus (TGEV) genome contains three accessory genes: 3a, 3b and 7. Gene 7 is only present in members of coronavirus genus a1, and encodes a hydrophobic protein of 78 aa. To study gene 7 function, a recombinant TGEV virus lacking gene 7 was engineered (rTGEV-Δ7). Both the mutant and the parental (rTGEV-wt) viruses showed the same growth and viral RNA accumulation kinetics in tissue cultures. Nevertheless, cells infected with rTGEV-Δ7 virus showed an increased cytopathic effect caused by an enhanced apoptosis mediated by caspase activation. Macromolecular synthesis analysis showed that rTGEV-Δ7 virus infection led to host translational shut-off and increased cellular RNA degradation compared with rTGEV-wt infection. An increase of eukaryotic translation initiation factor 2 (eIF2α) phosphorylation and an enhanced nuclease, most likely RNase L, activity were observed in rTGEV-Δ7 virus infected cells. These results suggested that the removal of gene 7 promoted an intensified dsRNA-activated host antiviral response. In protein 7 a conserved sequence motif that potentially mediates binding to protein phosphatase 1 catalytic subunit (PP1c), a key regulator of the cell antiviral defenses, was identified. We postulated that TGEV protein 7 may counteract host antiviral response by its association with PP1c. In fact, pull-down assays demonstrated the interaction between TGEV protein 7, but not a protein 7 mutant lacking PP1c binding motif, with PP1. Moreover, the interaction between protein 7 and PP1 was required, during the infection, for eIF2α dephosphorylation and inhibition of cell RNA degradation. Inoculation of newborn piglets with rTGEV-Δ7 and rTGEV-wt viruses showed that rTGEV-Δ7 virus presented accelerated growth kinetics and pathology compared with the parental virus. Overall, the results indicated that gene 7 counteracted host cell defenses, and modified TGEV persistence increasing TGEV survival. Therefore, the acquisition of gene 7 by the TGEV genome most likely has provided a selective advantage to the virus.
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Park SJ, Kim GY, Choy HE, Hong YJ, Saif LJ, Jeong JH, Park SI, Kim HH, Kim SK, Shin SS, Kang MI, Cho KO. Dual enteric and respiratory tropisms of winter dysentery bovine coronavirus in calves. Arch Virol 2007; 152:1885-900. [PMID: 17564760 PMCID: PMC7087358 DOI: 10.1007/s00705-007-1005-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 05/04/2007] [Indexed: 11/29/2022]
Abstract
Although winter dysentery (WD), which is caused by the bovine coronavirus (BCoV) is characterized by the sudden onset of diarrhea in many adult cattle in a herd, the pathogenesis of the WD-BCoV is not completely understood. In this study, colostrum-deprived calves were experimentally infected with a Korean WD-BCoV strain and examined for viremia, enteric and nasal virus shedding as well as for viral antigen expression and virus-associated lesions in the small and large intestines and the upper and lower respiratory tract from 1 to 8 days after an oral infection. The WD-BCoV-inoculated calves showed gradual villous atrophy in the small intestine and a gradual increase in the crypt depth of the large intestine. The WD-BCoV-infected animals showed epithelial damage in nasal turbinates, trachea and lungs, and interstitial pneumonia. The WD-BCoV antigen was detected in the epithelium of the small and large intestines, nasal turbinates, trachea and lungs. WD-BCoV RNA was detected in the serum from post-inoculation day 3. These results show that the WD-BCoV has dual tropism and induces pathological changes in both the digestive and respiratory tracts of calves. To our knowledge, this is the first detailed report of dual enteric and respiratory tropisms of WD-BCoV in calves. Comprehensive studies of the dual tissue pathogenesis of the BCoV might contribute to an increased understanding of similar pneumoenteric CoV infections in humans.
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Affiliation(s)
- S J Park
- Biotherapy Human Resources Center, College of Veterinary Medicine, Chonnam National University, Gwangju, South Korea
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Raaben M, Groot Koerkamp MJA, Rottier PJM, de Haan CAM. Mouse hepatitis coronavirus replication induces host translational shutoff and mRNA decay, with concomitant formation of stress granules and processing bodies. Cell Microbiol 2007; 9:2218-29. [PMID: 17490409 PMCID: PMC7162177 DOI: 10.1111/j.1462-5822.2007.00951.x] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Many viruses, including coronaviruses, induce host translational shutoff, while maintaining synthesis of their own gene products. In this study we performed genome‐wide microarray analyses of the expression patterns of mouse hepatitis coronavirus (MHV)‐infected cells. At the time of MHV‐induced host translational shutoff, downregulation of numerous mRNAs, many of which encode protein translation‐related factors, was observed. This downregulation, which is reminiscent of a cellular stress response, was dependent on viral replication and caused by mRNA decay. Concomitantly, phosphorylation of the eukaryotic translation initiation factor 2α was increased in MHV‐infected cells. In addition, stress granules and processing bodies appeared, which are sites for mRNA stalling and degradation respectively. We propose that MHV replication induces host translational shutoff by triggering an integrated stress response. However, MHV replication per se does not appear to benefit from the inhibition of host protein synthesis, at least in vitro, since viral replication was not negatively affected but rather enhanced in cells with impaired translational shutoff.
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Affiliation(s)
- Matthijs Raaben
- Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
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Enjuanes L, Almazán F, Sola I, Zuñiga S. Biochemical aspects of coronavirus replication and virus-host interaction. Annu Rev Microbiol 2006; 60:211-30. [PMID: 16712436 DOI: 10.1146/annurev.micro.60.080805.142157] [Citation(s) in RCA: 157] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Infection by different coronaviruses (CoVs) causes alterations in the transcriptional and translational patterns, cell cycle, cytoskeleton, and apoptosis pathways of the host cells. In addition, CoV infection may cause inflammation, alter immune and stress responses, and modify the coagulation pathways. The balance between the up- and downregulated genes could explain the pathogenesis caused by these viruses. We review specific aspects of CoV-host interactions. CoV genome replication takes place in the cytoplasm in a membrane-protected microenvironment and may control the cell machinery by locating some of their proteins in the host cell nucleus. CoVs initiate translation by cap-dependent and cap-independent mechanisms. CoV transcription involves a discontinuous RNA synthesis (template switching) during the extension of a negative copy of the subgenomic mRNAs. The requirement for base-pairing during transcription has been formally demonstrated in arteriviruses and CoVs. CoV N proteins have RNA chaperone activity that may help initiate template switching. Both viral and cellular proteins are required for replication and transcription, and the role of selected proteins is addressed.
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Affiliation(s)
- Luis Enjuanes
- Department of Molecular and Cell Biology, CNB, CSIC, 28049 Madrid, Spain.
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7
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Cai Y, Liu Y, Zhang X. Induction of transcription factor Egr-1 gene expression in astrocytoma cells by Murine coronavirus infection. Virology 2006; 355:152-63. [PMID: 16908043 PMCID: PMC1851928 DOI: 10.1016/j.virol.2006.07.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Revised: 05/19/2006] [Accepted: 07/10/2006] [Indexed: 11/22/2022]
Abstract
Mouse hepatitis virus (MHV) causes encephalitis and demyelination in the central nervous system (CNS) of susceptible rodents. Astrocytes are one of the major targets for MHV infection in the CNS, and respond to MHV infection by expressing diverse molecules that may contribute to CNS pathogenesis. Here we characterized the activation of an immediate-early transcription factor Egr-1 by MHV infection in an astrocytoma cell line. We found that the expression of Egr-1 was dramatically increased following virus infection. Using various inhibitors of mitogen-activated protein kinases, we identified that the extracellular signal-regulated kinases 1/2 were involved in the activation of Egr-1 transcription by MHV infection. Experiments with ultraviolet light-inactivated virus revealed that the induction of Egr-1 did not require virus replication and was likely mediated during cell entry. We further found that over-expression of Egr-1 suppressed the expression of BNip3, a pro-apoptotic member of the Bcl-2 family. This finding may provide an explanation for our previously observed down-regulation of BNip3 by MHV infection in astrocytoma cells (Cai, Liu, Yu, and Zhang, Virology 316:104-115, 2003). Furthermore, knockdown of Egr-1 by an siRNA inhibited MHV propagation, suggesting the biological relevance of Egr-1 induction to virus replication. In addition, the persistence/demylinating-positive strains (JHM and A59) induced Egr-1 expression, whereas the persistence/demylinating-negative strain (MHV-2) did not. These results indicate a correlation between the ability of MHVs to induce Egr-1 expression and their ability to cause demyelination in the CNS, which may suggest a potential role for the induction of Egr-1 in viral pathogenesis.
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Affiliation(s)
| | | | - Xuming Zhang
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Slot 511, Little Rock, AR 72205, USA
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Versteeg GA, Slobodskaya O, Spaan WJM. Transcriptional profiling of acute cytopathic murine hepatitis virus infection in fibroblast-like cells. J Gen Virol 2006; 87:1961-1975. [PMID: 16760398 DOI: 10.1099/vir.0.81756-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Understanding the orchestrated genome-wide cellular responses is critical for comprehending the early events of coronavirus infection. Microarray analysis was applied to assess changes in cellular expression profiles during different stages of two independent, highly controlled murine hepatitis virus (MHV) infections in vitro. Fibroblast-like L cells were infected at high multiplicity in order to study the direct effects of a synchronized lytic coronavirus infection. Total RNA was harvested from MHV- or mock-infected L cells at 3, 5 and 6 h post-infection and hybridized to Affymetrix microarrays representing approximately 12,500 murine genes and expressed sequences. The expression data were compared to their respective mock-infected controls. Quantitative RT-PCR of selected transcripts was used to validate the differential expression of transcripts and inter-experiment reproducibility of microarray analysis. It was concluded that MHV-A59 infection in fibroblast-like cells triggers very few transcriptional cellular responses in the first 3 h of infection. Later, after having established a productive infection, a chemokine response is induced together with other cellular changes associated with RNA and protein metabolism, cell cycle and apoptosis. Interferon responses are not triggered during infection, although the L cells can be readily stimulated to produce interferon by dsRNA, a known potent inducer of interferon. Possibly, the interferon response is actively counteracted by a virus-encoded antagonist as has been described previously for other RNA viruses.
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Affiliation(s)
- Gijs A Versteeg
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, E4P, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Olga Slobodskaya
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, E4P, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Willy J M Spaan
- Molecular Virology Laboratory, Department of Medical Microbiology, Center of Infectious Diseases, Leiden University Medical Center, E4P, PO Box 9600, 2300 RC Leiden, The Netherlands
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Bergmann CC, Lane TE, Stohlman SA. Coronavirus infection of the central nervous system: host-virus stand-off. Nat Rev Microbiol 2006; 4:121-32. [PMID: 16415928 PMCID: PMC7096820 DOI: 10.1038/nrmicro1343] [Citation(s) in RCA: 298] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Several viruses infect the mammalian central nervous system (CNS), some with devastating consequences, others resulting in chronic or persistent infections associated with little or no overt pathology. Coronavirus infection of the murine CNS illustrates the contributions of both the innate immune response and specific host effector mechanisms that control virus replication in distinct CNS cell types. Despite T-cell-mediated control of acute virus infection, host regulatory mechanisms, probably designed to protect CNS integrity, contribute to the failure to eliminate virus. Distinct from cytolytic effector mechanisms expressed during acute infection, non-lytic humoral immunity prevails in suppressing infectious virus during persistence.
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Affiliation(s)
- Cornelia C. Bergmann
- Cleveland Clinic Foundation, Neurosciences, 9500 Euclid Avenue NC30, Cleveland, 44195 Ohio USA
| | - Thomas E. Lane
- University of California, Irvine, Molecular Biology & Biochemistry, 3205 McGaugh Hall, Irvine, 92697 California USA
| | - Stephen A. Stohlman
- Cleveland Clinic Foundation, Neurosciences, 9500 Euclid Avenue NC30, Cleveland, 44195 Ohio USA
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Kim TS, Perlman S. Virus-specific antibody, in the absence of T cells, mediates demyelination in mice infected with a neurotropic coronavirus. THE AMERICAN JOURNAL OF PATHOLOGY 2005; 166:801-9. [PMID: 15743792 PMCID: PMC1602352 DOI: 10.1016/s0002-9440(10)62301-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Mice infected with mouse hepatitis virus strain JHM develop an inflammatory demyelinating disease in the central nervous system with many similarities to human multiple sclerosis. The mouse disease is primarily immune-mediated because demyelination is not detected in JHM-infected mice lacking T or B cells but does occur after transfer of JHM-specific T cells. Although less is known about the ability of antibodies to mediate demyelination, the presence of oligoclonally expanded B cells and high concentrations of antibodies (against self or infectious agents) in the central nervous system of many multiple sclerosis patients suggests that antibodies may also contribute to myelin destruction. Here, we show that anti-JHM antibodies, in the absence of T or B cells, caused demyelination in JHM-infected mice. Anti-JHM antibody was detected adjacent to areas of demyelination, consistent with a direct interaction between antibody and infected cells. Demyelination was reduced by 85 to 90% in infected RAG1(-/-) mice lacking normal expression of activating Fc receptors (FcRgamma(-/-)) and by approximately 76% when complement was depleted by treatment with cobra venom factor. These data demonstrate that JHM-specific antibodies are sufficient to cause demyelination and that myelin destruction in the presence of anti-virus antibodies results from a combination of complement- and Fc receptor-dependent mechanisms.
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Affiliation(s)
- Taeg S Kim
- Interdisciplinary Program in Immunology, University of Iowa, Iowa City, IA 52242, USA
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Cai Y, Liu Y, Yu D, Zhang X. Down-regulation of transcription of the proapoptotic gene BNip3 in cultured astrocytes by murine coronavirus infection. Virology 2003; 316:104-15. [PMID: 14599795 PMCID: PMC7125541 DOI: 10.1016/j.virol.2003.07.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2003] [Revised: 06/18/2003] [Accepted: 07/28/2003] [Indexed: 11/30/2022]
Abstract
Murine coronavirus mouse hepatitis virus (MHV) causes encephalitis and demyelination in the central nervous system of susceptible rodents. Astrocytes are the major target for MHV persistence. However, the mechanisms by which astrocytes survive MHV infection and permit viral persistence are not known. Here we performed DNA microarray analysis on differential gene expression in astrocyte DBT cells by MHV infection and found that the mRNA of the proapoptotic gene BNip3 was significantly decreased following MHV infection. This finding was further confirmed by quantitative reverse transcription-polymerase chain reaction, Western blot analysis, and BNip3-promoter-luciferase reporter system. Interestingly, infection with live and ultraviolet light-inactivated viruses equally repressed BNip3 expression, indicating that the down-regulation of BNip3 expression does not require virus replication and is mediated during cell entry. Furthermore, treatment of cells with chloroquine, which blocks the acidification of endosomes, significantly inhibited the repression of the BNip3 promoter activity induced by the acidic pH-dependent MHV mutant OBLV60, which enters cells via endocytosis, indicating that the down-regulation of BNip3 expression is mediated by fusion between viral envelope and cell membranes during entry. Deletion analysis showed that the sequence between nucleotides 262 and 550 of the 588-base-pair BNip3 promoter is necessary and sufficient for driving the BNip3 expression and that it contains signals that are responsible for MHV-induced down-regulation of BNip3 expression in DBT cells. These results may provide insights into the mechanisms by which MHV evades host antiviral defense and promotes cell survival, thereby allowing its persistence in the host astrocytes.
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Affiliation(s)
- Yingyun Cai
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Slot 511, Little Rock, AR 72205, USA
| | - Yin Liu
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Slot 511, Little Rock, AR 72205, USA
| | - Dongdong Yu
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Slot 511, Little Rock, AR 72205, USA
| | - Xuming Zhang
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Slot 511, Little Rock, AR 72205, USA
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Banerjee S, An S, Makino S. Specific cleavage of 28S ribosomal RNA in murine coronavirus-infected cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002; 494:621-6. [PMID: 11774535 DOI: 10.1007/978-1-4615-1325-4_92] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Affiliation(s)
- S Banerjee
- Department of Microbiology and Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas 78712, USA
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Chen H, Wurm T, Britton P, Brooks G, Hiscox JA. Interaction of the coronavirus nucleoprotein with nucleolar antigens and the host cell. J Virol 2002; 76:5233-50. [PMID: 11967337 PMCID: PMC136173 DOI: 10.1128/jvi.76.10.5233-5250.2002] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2001] [Accepted: 02/06/2002] [Indexed: 11/20/2022] Open
Abstract
Coronavirus nucleoproteins (N proteins) localize to the cytoplasm and the nucleolus, a subnuclear structure, in both virus-infected primary cells and in cells transfected with plasmids that express N protein. The nucleolus is the site of ribosome biogenesis and sequesters cell cycle regulatory complexes. Two of the major components of the nucleolus are fibrillarin and nucleolin. These proteins are involved in nucleolar assembly and ribosome biogenesis and act as chaperones for the import of proteins into the nucleolus. We have found that fibrillarin is reorganized in primary cells infected with the avian coronavirus infectious bronchitis virus (IBV) and in continuous cell lines that express either IBV or mouse hepatitis virus N protein. Both N protein and a fibrillarin-green fluorescent protein fusion protein colocalized to the perinuclear region and the nucleolus. Pull-down assays demonstrated that IBV N protein interacted with nucleolin and therefore provided a possible explanation as to how coronavirus N proteins localize to the nucleolus. Nucleoli, and proteins that localize to the nucleolus, have been implicated in cell growth-cell cycle regulation. Comparison of cells expressing IBV N protein with controls indicated that cells expressing N protein had delayed cellular growth. This result could not to be attributed to apoptosis. Morphological analysis of these cells indicated that cytokinesis was disrupted, an observation subsequently found in primary cells infected with IBV. Coronaviruses might therefore delay the cell cycle in interphase, where maximum translation of viral mRNAs can occur.
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Affiliation(s)
- Hongying Chen
- Virology Group, School of Animal and Microbial Sciences, The University of Reading, United Kingdom
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Morales S, Parra B, Ramakrishna C, Blau DM, Stohlman SA. B-cell-mediated lysis of cells infected with the neurotropic JHM strain of mouse hepatitis virus. Virology 2001; 286:160-7. [PMID: 11448169 PMCID: PMC7142306 DOI: 10.1006/viro.2001.0991] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cells expressing the spike (S) glycoprotein of the neurotropic JHM strain (JHMV) of mouse hepatitis virus (MHV) are susceptible to lysis by B cells derived from naïve mice, including B cells from perforin-deficient mice. Cytolysis requires interaction of the virus receptor and the viral S glycoprotein, is independent of other viral-induced components, and is not a unique property of B cells. Neutralizing anti-S-protein monoclonal antibodies (mAb) and a mAb specific for the viral receptor inhibit lysis. However, cells infected with an MHV strain unable to induce cell-cell fusion are resistant to lysis and lysis of JHMV-infected cells is inhibited by an anti-S-protein nonneutralizing mAb which prevents S-protein-mediated cell fusion. These data suggest that B cells may function as antibody-independent innate immune response during JHMV infection in vivo.
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Affiliation(s)
- S Morales
- Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, California 90033, USA
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Banerjee S, An S, Zhou A, Silverman RH, Makino S. RNase L-independent specific 28S rRNA cleavage in murine coronavirus-infected cells. J Virol 2000; 74:8793-802. [PMID: 10982321 PMCID: PMC102073 DOI: 10.1128/jvi.74.19.8793-8802.2000] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We characterized a novel 28S rRNA cleavage in cells infected with the murine coronavirus mouse hepatitis virus (MHV). The 28S rRNA cleavage occurred as early as 4 h postinfection (p.i.) in MHV-infected DBT cells, with the appearance of subsequent cleavage products and a decrease in the amount of intact 28S rRNA with increasing times of infection; almost all of the intact 28S rRNA disappeared by 24 h p.i. In contrast, no specific 18S rRNA cleavage was detected in infected cells. MHV-induced 28S rRNA cleavage was detected in all MHV-susceptible cell lines and all MHV strains tested. MHV replication was required for the 28S rRNA cleavage, and mature cytoplasmic 28S rRNA underwent cleavage. In certain combination of cells and viruses, pretreatment of virus-infected cells with interferon activates a cellular endoribonuclease, RNase L, that causes rRNA degradation. No interferon was detected in the inoculum used for MHV infection. Addition of anti-interferon antibody to MHV-infected cells did not inhibit 28S rRNA cleavage. Furthermore, 28S rRNA cleavage occurred in an MHV-infected mouse embryonic fibroblast cell line derived from RNase L knockout mice. Thus, MHV-induced 28S rRNA cleavage was independent of the activation of RNase L. MHV-induced 28S rRNA cleavage was also different from apoptosis-related rRNA degradation, which usually occurs concomitantly with DNA fragmentation. In MHV-infected 17Cl-1 cells, 28S rRNA cleavage preceded DNA fragmentation by at least 18 h. Blockage of apoptosis in MHV-infected 17Cl-1 cells by treatment with a caspase inhibitor did not block 28S rRNA cleavage. Furthermore, MHV-induced 28S rRNA cleavage occurred in MHV-infected DBT cells that do not show apoptotic signs, including activation of caspase-3 and DNA fragmentation. Thus, MHV-induced 28S rRNA cleavage appeared to differ from any rRNA degradation mechanism described previously.
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Affiliation(s)
- S Banerjee
- Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-1019, USA
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Tahara SM, Dietlin TA, Nelson GW, Stohlman SA, Manno DJ. Mouse hepatitis virus nucleocapsid protein as a translational effector of viral mRNAs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 440:313-8. [PMID: 9782298 DOI: 10.1007/978-1-4615-5331-1_41] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The mouse hepatitis virus (MHV) nucleocapsid protein stimulated translation of a chimeric reporter mRNA containing an intact MHV 5'-untranslated region and the chloramphenicol acetyltransferase (CAT) coding region. The nucleocapsid protein binds specifically the tandemly repeated-UCYAA- of the MHV leader. This RNA sequence is the same as the intergenic motif found in the genome RNA. Preferential translation of viral mRNA in MHV infected cells is stimulated in part by this interaction and represents a specific, positive translational control mechanism employed by coronaviruses.
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Affiliation(s)
- S M Tahara
- Department of Molecular Microbiology and Immunology, USC School of Medicine, Los Angeles 90033, USA
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Okumura A, Machii K, Azuma S, Toyoda Y, Kyuwa S. Maintenance of pluripotency in mouse embryonic stem cells persistently infected with murine coronavirus. J Virol 1996; 70:4146-9. [PMID: 8648758 PMCID: PMC190306 DOI: 10.1128/jvi.70.6.4146-4149.1996] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
A persistently coronavirus-infected embryonic stem (ES) cell line A3/MHV was established by infecting an ES cell line, A3-1, with mouse hepatitis virus type-2. Although almost all A3/MHV cells were found infected, both A3/MHV and A3-1 cells expressed comparable levels of cell surface differentiation markers. In addition, A3/MHV cells retained the ability to form embryoid bodies. These results suggest that persistent coronavirus infection does not affect the differentiation of ES cells.
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Affiliation(s)
- A Okumura
- Department of Animal Pathology, Institute of Medical Science, University of Tokyo, Japan
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Kyuwa S, Machii K, Shibata S. Role of CD4+ and CD8+ T cells in mouse hepatitis virus infection in mice. Exp Anim 1996; 45:81-3. [PMID: 8689585 DOI: 10.1538/expanim.45.81] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Viral growth and histopathological changes in the liver after intraperitoneal infection with mouse hepatitis virus, strain JHM were compared among normal C57BL/6 mice, those depleted of CD4+ T cells, CD8+ T cells and both T cell subsets. Viral growth in mice depleted of CD4+ T cells increased slightly, but pathological changes resembled those in normal mice. In contrast, the hepatitis was exacerbated in mice depleted of CD8+ T cells and those depleted of both T cell subsets. These results suggest that CD8+ T cells play a key role although both T cell subsets are involved in protection against mouse hepatitis virus infection in mice.
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Affiliation(s)
- S Kyuwa
- Department of Animal Pathology, University of Tokyo, Japan
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Stohlman SA, Hinton DR, Cua D, Dimacali E, Sensintaffar J, Hofman FM, Tahara SM, Yao Q. Tumor necrosis factor expression during mouse hepatitis virus-induced demyelinating encephalomyelitis. J Virol 1995; 69:5898-903. [PMID: 7637037 PMCID: PMC189470 DOI: 10.1128/jvi.69.9.5898-5903.1995] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Neutralizing anti-tumor necrosis factor alpha (TNF-alpha) antibody treatment of mice infected with the neurotropic JHMV strain of mouse hepatitis virus showed no reduction of either virus-induced encephalomyelitis or central nervous system demyelination. TNF-alpha-positive cells were present in the central nervous system during infection; however, TNF-alpha could not be colocalized with JHMV-infected cells. In vitro, TNF-alpha mRNA rapidly accumulated following JHMV infection; however, no TNF-alpha was secreted because of inhibition of translation. Both live and UV-inactivated virus inhibited TNF-alpha secretion induced by lipopolysaccharide. These data show that TNF-alpha is not secreted from infected cells and indicate that if contributes to either JHMV-induced acute encephalomyelitis nor primary demyelination.
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Affiliation(s)
- S A Stohlman
- Department of Neurology, University of Southern California School of Medicine, Los Angeles 90033, USA
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Stohlman SA, Bergmann CC, van der Veen RC, Hinton DR. Mouse hepatitis virus-specific cytotoxic T lymphocytes protect from lethal infection without eliminating virus from the central nervous system. J Virol 1995; 69:684-94. [PMID: 7815531 PMCID: PMC188629 DOI: 10.1128/jvi.69.2.684-694.1995] [Citation(s) in RCA: 94] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Acute infection of the central nervous system by the neurotropic JHM strain of mouse hepatitis virus (JHMV) induces nucleocapsid protein specific cytotoxic T lymphocytes (CTL) not found in the periphery (S. Stohlman, S. Kyuwa, J. Polo, D. Brady, M. Lai, and C. Bergmann, J. Virol. 67:7050-7059, 1993). Peripheral induction of CTL specific for the nucleocapsid protein of JHMV by vaccination with recombinant vaccinia viruses was unable to provide significant protection to a subsequent lethal virus challenge. By contrast, the transfer of nucleoprotein-specific CTL protected mice from a subsequent lethal challenge by reducing virus replication within the central nervous system, demonstrating the importance of the CTL response to this epitope in JHMV infection. Transfer of these CTL directly into the central nervous system was at least 10-fold more effective than peripheral transfer. Histological analysis indicated that the CTL reduced virus replication in ependymal cells, astrocytes, and microglia. Although the CTL were relatively ineffective at reducing virus replication in oligodendroglia, survivors showed minimal evidence of virus persistence within the central nervous system and no evidence of chronic ongoing demyelination.
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Affiliation(s)
- S A Stohlman
- Department of Neurology, USC School of Medicine, Los Angeles 90033
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Affiliation(s)
- H Wege
- Institute for Diagnostic Virology, Federal Research Centre for Virus Diseases of Animals, Friedrich-Loeffler-Institutes, Insel Riems, Germany
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