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Kang HR, Han JH, Ng YC, Ryu S, Park JY, Chung WC, Song YJ, Chen ST, Brickey WJ, Ting JPY, Song MJ. Dynamic bidirectional regulation of NLRC3 and gammaherpesviruses during viral latency in B lymphocytes. J Med Virol 2024; 96:e29504. [PMID: 38445794 DOI: 10.1002/jmv.29504] [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: 07/04/2023] [Revised: 02/03/2024] [Accepted: 02/20/2024] [Indexed: 03/07/2024]
Abstract
While most NOD-like receptors (NLRs) are predominately expressed by innate immune cells, NLRC3, an inhibitory NLR of immune signaling, exhibits the highest expression in lymphocytes. The role of NLRC3 or any NLRs in B lymphocytes is completely unknown. Gammaherpesviruses, including human Epstein-Barr virus (EBV) and murine gammaherpesvirus 68 (MHV-68), establish latent infection in B lymphocytes, which requires elevated NF-κB. This study shows that during latent EBV infection of human B cells, viral-encoded latent membrane protein 1 (LMP1) decreases NLRC3 transcript. LMP1-induced-NF-κB activation suppresses the promoter activity of NLRC3 via p65 binding to the promoter. Conversely, NLRC3 inhibits NF-κB activation by promoting the degradation of LMP1 in a proteasome-dependent manner. In vivo, MHV-68 infection reduces Nlrc3 transcripts in splenocytes, and Nlrc3-deficient mice show greater viral latency than controls. These results reveal a bidirectional regulatory circuit in B lymphocytes, where viral latent protein LMP1 reduces NLRC3 expression, while NLRC3 disrupts gammaherpesvirus latency, which is an important step for tumorigenesis.
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Affiliation(s)
- Hye-Ri Kang
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Ji Ho Han
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Yee Ching Ng
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Seungbo Ryu
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Ji-Yeon Park
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Woo-Chang Chung
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Yoon-Jae Song
- Department of Life Science, Gachon University, Seongnam-Si, Kyeonggi-Do, Republic of Korea
| | - Szu-Ting Chen
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan
- Department of Genetics, Lineberger Comprehensive Cancer Center, Center for Translational Immunology and the Institute of Inflammatory Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
- Cancer Progression Research Center, National Yang-Ming University, Taipei, Taiwan
| | - W June Brickey
- Department of Genetics, Lineberger Comprehensive Cancer Center, Center for Translational Immunology and the Institute of Inflammatory Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Jenny P-Y Ting
- Department of Genetics, Lineberger Comprehensive Cancer Center, Center for Translational Immunology and the Institute of Inflammatory Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
| | - Moon Jung Song
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
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Zhang W, Guo J, Chen Q. Role of PARP-1 in Human Cytomegalovirus Infection and Functional Partners Encoded by This Virus. Viruses 2022; 14:2049. [PMID: 36146855 PMCID: PMC9501325 DOI: 10.3390/v14092049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 09/11/2022] [Accepted: 09/12/2022] [Indexed: 11/17/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a ubiquitous pathogen that threats the majority of the world's population. Poly (ADP-ribose) polymerase 1 (PARP-1) and protein poly (ADP-ribosyl)ation (PARylation) regulates manifold cellular functions. The role of PARP-1 and protein PARylation in HCMV infection is still unknown. In the present study, we found that the pharmacological and genetic inhibition of PARP-1 attenuated HCMV replication, and PARG inhibition favors HCMV replication. PARP-1 and its enzymatic activity were required for efficient HCMV replication. HCMV infection triggered the activation of PARP-1 and induced the translocation of PARP-1 from nucleus to cytoplasm. PARG was upregulated in HCMV-infected cells and this upregulation was independent of viral DNA replication. Moreover, we found that HCMV UL76, a true late protein of HCMV, inhibited the overactivation of PARP-1 through direct binding to the BRCT domain of PARP-1. In addition, UL76 also physically interacted with poly (ADP-ribose) (PAR) polymers through the RG/RGG motifs of UL76 which mediates its recruitment to DNA damage sites. Finally, PARP-1 inhibition or depletion potentiated HCMV-triggered induction of type I interferons. Our results uncovered the critical role of PARP-1 and PARP-1-mediated protein PARylation in HCMV replication.
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Affiliation(s)
| | | | - Qiang Chen
- Frontier Science Center for Immunology and Metabolism, Medical Research Institute, Wuhan University, Wuhan 430071, China
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Lytic Replication and Reactivation from B Cells Is Not Required for Establishing or Maintaining Gammaherpesvirus Latency In Vivo. J Virol 2022; 96:e0069022. [PMID: 35647668 PMCID: PMC9215232 DOI: 10.1128/jvi.00690-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gammaherpesviruses (GHVs) are lymphotropic tumor viruses with a biphasic infectious cycle. Lytic replication at the primary site of infection is necessary for GHVs to spread throughout the host and establish latency in distal sites. Dissemination is mediated by infected B cells that traffic hematogenously from draining lymph nodes to peripheral lymphoid organs, such as the spleen. B cells serve as the major reservoir for viral latency, and it is hypothesized that periodic reactivation from latently infected B cells contributes to maintaining long-term chronic infection. While fundamentally important to an understanding of GHV biology, aspects of B cell infection in latency establishment and maintenance are incompletely defined, especially roles for lytic replication and reactivation in this cell type. To address this knowledge gap and overcome limitations of replication-defective viruses, we generated a recombinant murine gammaherpesvirus 68 (MHV68) in which ORF50, the gene that encodes the essential immediate-early replication and transcription activator protein (RTA), was flanked by loxP sites to enable conditional ablation of lytic replication by ORF50 deletion in cells that express Cre recombinase. Following infection of mice that encode Cre in B cells with this virus, splenomegaly and viral reactivation from splenocytes were significantly reduced; however, the number of latently infected splenocytes was equivalent to WT MHV68. Despite ORF50 deletion, MHV68 latency was maintained over time in spleens of mice at levels approximating WT, reactivation-competent MHV68. Treatment of infected mice with lipopolysaccharide (LPS), which promotes B cell activation and MHV68 reactivation ex vivo, yielded equivalent increases in the number of latently infected cells for both ORF50-deleted and WT MHV68, even when mice were simultaneously treated with the antiviral drug cidofovir to prevent reactivation. Together, these data demonstrate that productive viral replication in B cells is not required for MHV68 latency establishment and support the hypothesis that B cell proliferation facilitates latency maintenance in vivo in the absence of reactivation. IMPORTANCE Gammaherpesviruses establish lifelong chronic infections in cells of the immune system and place infected hosts at risk for developing lymphomas and other diseases. It is hypothesized that gammaherpesviruses must initiate acute infection in these cells to establish and maintain long-term infection, but this has not been directly tested. We report here the use of a viral genetic system that allows for cell-type-specific deletion of a viral gene that is essential for replication and reactivation. We employ this system in an in vivo model to reveal that viral replication is not required to initiate or maintain infection within B cells.
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Chung WC, Song MJ. Virus–Host Interplay Between Poly (ADP-Ribose) Polymerase 1 and Oncogenic Gammaherpesviruses. Front Microbiol 2022; 12:811671. [PMID: 35095818 PMCID: PMC8795711 DOI: 10.3389/fmicb.2021.811671] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 12/23/2021] [Indexed: 12/14/2022] Open
Abstract
The gammaherpesviruses, include the Epstein–Barr virus, Kaposi’s sarcoma-associated herpesvirus, and murine gammaherpesvirus 68. They establish latent infection in the B lymphocytes and are associated with various lymphoproliferative diseases and tumors. The poly (ADP-ribose) polymerase-1 (PARP1), also called ADP-ribosyltransferase diphtheria-toxin-like 1 (ARTD1) is a nuclear enzyme that catalyzes the transfer of the ADP-ribose moiety to its target proteins and participates in important cellular activities, such as the DNA-damage response, cell death, transcription, chromatin remodeling, and inflammation. In gammaherpesvirus infection, PARP1 acts as a key regulator of the virus life cycle: lytic replication and latency. These viruses also develop various strategies to regulate PARP1, facilitating their replication. This review summarizes the roles of PARP1 in the viral life cycle as well as the viral modulation of host PARP1 activity and discusses the implications. Understanding the interactions between the PARP1 and oncogenic gammaherpesviruses may lead to the identification of effective therapeutic targets for the associated diseases.
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NAD+-consuming enzymes in immune defense against viral infection. Biochem J 2021; 478:4071-4092. [PMID: 34871367 PMCID: PMC8718269 DOI: 10.1042/bcj20210181] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Revised: 11/03/2021] [Accepted: 11/09/2021] [Indexed: 12/16/2022]
Abstract
The COVID-19 pandemic reminds us that in spite of the scientific progress in the past century, there is a lack of general antiviral strategies. In analogy to broad-spectrum antibiotics as antibacterial agents, developing broad spectrum antiviral agents would buy us time for the development of vaccines and treatments for future viral infections. In addition to targeting viral factors, a possible strategy is to understand host immune defense mechanisms and develop methods to boost the antiviral immune response. Here we summarize the role of NAD+-consuming enzymes in the immune defense against viral infections, with the hope that a better understanding of this process could help to develop better antiviral therapeutics targeting these enzymes. These NAD+-consuming enzymes include PARPs, sirtuins, CD38, and SARM1. Among these, the antiviral function of PARPs is particularly important and will be a focus of this review. Interestingly, NAD+ biosynthetic enzymes are also implicated in immune responses. In addition, many viruses, including SARS-CoV-2 contain a macrodomain-containing protein (NSP3 in SARS-CoV-2), which serves to counteract the antiviral function of host PARPs. Therefore, NAD+ and NAD+-consuming enzymes play crucial roles in immune responses against viral infections and detailed mechanistic understandings in the future will likely facilitate the development of general antiviral strategies.
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Wang Y, Tibbetts SA, Krug LT. Conquering the Host: Determinants of Pathogenesis Learned from Murine Gammaherpesvirus 68. Annu Rev Virol 2021; 8:349-371. [PMID: 34586873 PMCID: PMC9153731 DOI: 10.1146/annurev-virology-011921-082615] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Gammaherpesviruses are an important class of oncogenic pathogens that are exquisitely evolved to their respective hosts. As such, the human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi sarcoma herpesvirus (KSHV) do not naturally infect nonhuman primates or rodents. There is a clear need to fully explore mechanisms of gammaherpesvirus pathogenesis, host control, and immune evasion in the host. A gammaherpesvirus pathogen isolated from murid rodents was first reported in 1980; 40 years later, murine gammaherpesvirus 68 (MHV68, MuHV-4, γHV68) infection of laboratory mice is a well-established pathogenesis system recognized for its utility in applying state-of-the-art approaches to investigate virus-host interactions ranging from the whole host to the individual cell. Here, we highlight recent advancements in our understanding of the processes by which MHV68 colonizes the host and drives disease. Lessons that inform KSHV and EBV pathogenesis and provide future avenues for novel interventions against infection and virus-associated cancers are emphasized.
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Affiliation(s)
- Yiping Wang
- Department of Molecular Genetics and Microbiology, UF Health Cancer Center, College of Medicine, University of Florida, Gainesville, Florida 32610, USA
| | - Scott A Tibbetts
- Department of Molecular Genetics and Microbiology, UF Health Cancer Center, College of Medicine, University of Florida, Gainesville, Florida 32610, USA
| | - Laurie T Krug
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA;
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Chung WC, Lee S, Kim Y, Seo JB, Song MJ. Kaposi's sarcoma-associated herpesvirus processivity factor (PF-8) recruits cellular E3 ubiquitin ligase CHFR to promote PARP1 degradation and lytic replication. PLoS Pathog 2021; 17:e1009261. [PMID: 33508027 PMCID: PMC7872283 DOI: 10.1371/journal.ppat.1009261] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 02/09/2021] [Accepted: 12/30/2020] [Indexed: 12/22/2022] Open
Abstract
Kaposi’s sarcoma–associated herpesvirus (KSHV), which belongs to the gammaherpesvirus subfamily, is associated with the pathogenesis of various tumors. Nuclear enzyme poly(ADP-ribose) polymerase 1 (PARP1) catalyzes the polymerization of ADP-ribose units on target proteins. In KSHV-infected cells, PARP1 inhibits replication and transcription activator (RTA), a molecular switch that initiates lytic replication, through direct interaction. Thus, for efficient replication, KSHV has to overcome the molecular barrier in the form of PARP1. Previously, we have demonstrated that KSHV downregulates the expression of PARP1 through PF-8, a viral processivity factor. PF-8 induces ubiquitin–proteasome system–mediated degradation of PARP1 via direct physical association and enhances RTA transactivation activity. Here, we showed that dimerization domains of PF-8 are crucial not only for PARP1 interaction and degradation but also for enhancement of the RTA transactivation activity. PF-8 recruited CHFR for the PARP1 degradation. A knockdown of CHFR attenuated the PF-8–induced PARP1 degradation and enhancement of the RTA transactivation activity, leading to reduced KSHV lytic replication. These findings reveal a mechanism by which KSHV PF-8 recruits a cellular E3 ligase to curtail the inhibitory effect of PARP1 on KSHV lytic replication. Kaposi’s sarcoma–associated herpesvirus (KSHV), a member of the gammaherpesvirus subfamily, is associated with the pathogenesis of various tumors. Poly(ADP-ribose) polymerase 1 (PARP1), which is involved in various cellular functions, restricts lytic replication of oncogenic gammaherpesviruses by inhibiting replication and transcription activator (RTA), a molecular switch that activates the viral lytic replication. To abrogate the inhibitory effect of PARP1, reactivated KSHV promotes PARP1 degradation via direct interaction between PARP1 and PF-8, a viral processivity factor. Dimerization domains of PF-8 were found to be critical for PARP1 interaction and degradation and for enhancing the RTA transactivation activity. Furthermore, we found that CHFR, an E3 ubiquitin ligase, is required for PF-8–induced PARP1 degradation and efficient lytic replication of KSHV. This is the first study to show the role of CHFR in viral replication or pathogenicity. This study revealed a molecular mechanism via which gammaherpesviruses overcome the PARP1-mediated inhibitory effect on viral replication: by means of PF-8, which recruits a cellular E3 ubiquitin ligase.
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Affiliation(s)
- Woo-Chang Chung
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Seungrae Lee
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Yejin Kim
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
| | - Jong Bok Seo
- Metabolome Analysis Team, Korea Basic Science Institute, Seoul, Republic of Korea
| | - Moon Jung Song
- Virus-Host Interactions Laboratory, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, Republic of Korea
- * E-mail:
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Fehr AR, Singh SA, Kerr CM, Mukai S, Higashi H, Aikawa M. The impact of PARPs and ADP-ribosylation on inflammation and host-pathogen interactions. Genes Dev 2020; 34:341-359. [PMID: 32029454 PMCID: PMC7050484 DOI: 10.1101/gad.334425.119] [Citation(s) in RCA: 144] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Poly-adenosine diphosphate-ribose polymerases (PARPs) promote ADP-ribosylation, a highly conserved, fundamental posttranslational modification (PTM). PARP catalytic domains transfer the ADP-ribose moiety from NAD+ to amino acid residues of target proteins, leading to mono- or poly-ADP-ribosylation (MARylation or PARylation). This PTM regulates various key biological and pathological processes. In this review, we focus on the roles of the PARP family members in inflammation and host-pathogen interactions. Here we give an overview the current understanding of the mechanisms by which PARPs promote or suppress proinflammatory activation of macrophages, and various roles PARPs play in virus infections. We also demonstrate how innovative technologies, such as proteomics and systems biology, help to advance this research field and describe unanswered questions.
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Affiliation(s)
- Anthony R Fehr
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
| | - Sasha A Singh
- Center for Interdisciplinary Cardiovascular Sciences, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Catherine M Kerr
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, USA
| | - Shin Mukai
- Center for Interdisciplinary Cardiovascular Sciences, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Hideyuki Higashi
- Center for Interdisciplinary Cardiovascular Sciences, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Masanori Aikawa
- Center for Interdisciplinary Cardiovascular Sciences, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.,Center for Excellence in Vascular Biology, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.,Department of Human Pathology, I.M. Sechenov First Moscow State Medical University of the Ministry of Health, Moscow 119146, Russian Federation
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Ng YC, Chung WC, Kang HR, Cho HJ, Park EB, Kang SJ, Song MJ. A DNA-sensing-independent role of a nuclear RNA helicase, DHX9, in stimulation of NF-κB-mediated innate immunity against DNA virus infection. Nucleic Acids Res 2019; 46:9011-9026. [PMID: 30137501 PMCID: PMC6158622 DOI: 10.1093/nar/gky742] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Accepted: 08/11/2018] [Indexed: 01/12/2023] Open
Abstract
DExD/H-box helicase 9 (DHX9), or RNA helicase A (RHA), is an abundant multifunctional nuclear protein. Although it was previously reported to act as a cytosolic DNA sensor in plasmacytoid dendritic cells (pDCs), the role and molecular mechanisms of action of DHX9 in cells that are not pDCs during DNA virus infection are not clear. Here, a macrophage-specific knockout and a fibroblast-specific knockdown of DHX9 impaired antiviral innate immunity against DNA viruses, leading to increased virus replication. DHX9 enhanced NF-κB–mediated transactivation in the nucleus, which required its ATPase-dependent helicase (ATPase/helicase) domain, but not the cytosolic DNA-sensing domain. In addition, DNA virus infection did not induce cytoplasmic translocation of nuclear DHX9 in macrophages and fibroblasts. Nuclear DHX9 was associated with a multiprotein complex including both NF-κB p65 and RNA polymerase II (RNAPII) in chromatin containing NF-κB–binding sites. DHX9 was essential for the recruitment of RNAPII rather than NF-κB p65, to the corresponding promoters; this function also required its ATPase/helicase activity. Taken together, our results show a critical role of nuclear DHX9 (as a transcription coactivator) in the stimulation of NF-κB–mediated innate immunity against DNA virus infection, independently of DHX9’s DNA-sensing function.
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Affiliation(s)
- Yee Ching Ng
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Woo-Chang Chung
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Hye-Ri Kang
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Hye-Jeong Cho
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
| | - Eun-Byeol Park
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Suk-Jo Kang
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
| | - Moon Jung Song
- Virus-Host Interactions Laboratory, Department of Biosystems and Biotechnology, Division of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 02841, Republic of Korea
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Abstract
Ovine herpesvirus-2 (OvHV-2) is the causative agent of the sheep-associated form of malignant catarrhal fever, a usually fatal lymphoproliferative disease of bison, deer and cattle. Malignant catarrhal fever is a major cause of cattle loss in Africa with approximately 7% affected annually; and in North America has significant impact on bison farming. Research into the mechanisms by which OvHV-2 induces disease in susceptible species has been hampered by a lack of a cell culture system for the virus. Ov2 is a bZIP protein encoded by OvHV-2. Proteins with bZIP domains in other herpesviruses, such as the Kaposi’s sarcoma-associated herpesvirus K8 protein and the BZLF1 protein of Epstein-Barr virus are known to play important roles in lytic virus replication. Using a reporter based system, we demonstrate that Ov2 can modulate the activity of the major virus transactivator (Replication and Transcriptional Activator protein, RTA) to 1) drive expression of viral genes predicted to be required for efficient reactivation of the virus, including ORF49; and 2) differentially regulate the expression of the two virus encoded Bcl-2 homologues Ov4.5 and Ov9.
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Chung WC, Kim J, Kim BC, Kang HR, Son J, Ki H, Hwang KY, Song MJ. Structure-based mechanism of action of a viral poly(ADP-ribose) polymerase 1-interacting protein facilitating virus replication. IUCRJ 2018; 5:866-879. [PMID: 30443370 PMCID: PMC6211522 DOI: 10.1107/s2052252518013854] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 10/01/2018] [Indexed: 06/09/2023]
Abstract
Poly(ADP-ribose) polymerase 1 (PARP-1), an enzyme that modifies nuclear proteins by poly(ADP-ribosyl)ation, regulates various cellular activities and restricts the lytic replication of oncogenic gammaherpesviruses by inhibiting the function of replication and transcription activator (RTA), a key switch molecule of the viral life cycle. A viral PARP-1-interacting protein (vPIP) encoded by murine gammaherpesvirus 68 (MHV-68) orf49 facilitates lytic replication by disrupting interactions between PARP-1 and RTA. Here, the structure of MHV-68 vPIP was determined at 2.2 Å resolution. The structure consists of 12 α-helices with characteristic N-terminal β-strands (Nβ) and forms a V-shaped-twist dimer in the asymmetric unit. Structure-based mutagenesis revealed that Nβ and the α1 helix (residues 2-26) are essential for the nuclear localization and function of vPIP; three residues were then identified (Phe5, Ser12 and Thr16) that were critical for the function of vPIP and its interaction with PARP-1. A recombinant MHV-68 harboring mutations of these three residues showed severely attenuated viral replication both in vitro and in vivo. Moreover, ORF49 of Kaposi's sarcoma-associated herpesvirus also directly interacted with PARP-1, indicating a conserved mechanism of action of vPIPs. The results elucidate the novel molecular mechanisms by which oncogenic gammaherpesviruses overcome repression by PARP-1 using vPIPs.
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Affiliation(s)
- Woo-Chang Chung
- Virus–Host Interactions Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Junsoo Kim
- Structural Proteomics Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Byung Chul Kim
- Virus–Host Interactions Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Hye-Ri Kang
- Virus–Host Interactions Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - JongHyeon Son
- Structural Proteomics Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Hosam Ki
- Structural Proteomics Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Kwang Yeon Hwang
- Structural Proteomics Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
| | - Moon Jung Song
- Virus–Host Interactions Laboratory, Department of Biosystems and Biotechnology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea
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Gammaherpesvirus Colonization of the Spleen Requires Lytic Replication in B Cells. J Virol 2018; 92:JVI.02199-17. [PMID: 29343572 DOI: 10.1128/jvi.02199-17] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2017] [Accepted: 01/09/2018] [Indexed: 11/20/2022] Open
Abstract
Gammaherpesviruses infect lymphocytes and cause lymphocytic cancers. Murid herpesvirus-4 (MuHV-4), Epstein-Barr virus, and Kaposi's sarcoma-associated herpesvirus all infect B cells. Latent infection can spread by B cell recirculation and proliferation, but whether this alone achieves systemic infection is unclear. To test the need of MuHV-4 for lytic infection in B cells, we flanked its essential ORF50 lytic transactivator with loxP sites and then infected mice expressing B cell-specific Cre (CD19-Cre). The floxed virus replicated normally in Cre- mice. In CD19-Cre mice, nasal and lymph node infections were maintained; but there was little splenomegaly, and splenic virus loads remained low. Cre-mediated removal of other essential lytic genes gave a similar phenotype. CD19-Cre spleen infection by intraperitoneal virus was also impaired. Therefore, MuHV-4 had to emerge lytically from B cells to colonize the spleen. An important role for B cell lytic infection in host colonization is consistent with the large CD8+ T cell responses made to gammaherpesvirus lytic antigens during infectious mononucleosis and suggests that vaccine-induced immunity capable of suppressing B cell lytic infection might reduce long-term virus loads.IMPORTANCE Gammaherpesviruses cause B cell cancers. Most models of host colonization derive from cell cultures with continuous, virus-driven B cell proliferation. However, vaccines based on these models have worked poorly. To test whether proliferating B cells suffice for host colonization, we inactivated the capacity of MuHV-4, a gammaherpesvirus of mice, to reemerge from B cells. The modified virus was able to colonize a first wave of B cells in lymph nodes but spread poorly to B cells in secondary sites such as the spleen. Consequently, viral loads remained low. These results were consistent with virus-driven B cell proliferation exploiting normal host pathways and thus having to transfer lytically to new B cells for new proliferation. We conclude that viral lytic infection is a potential target to reduce B cell proliferation.
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Van Skike ND, Minkah NK, Hogan CH, Wu G, Benziger PT, Oldenburg DG, Kara M, Kim-Holzapfel DM, White DW, Tibbetts SA, French JB, Krug LT. Viral FGARAT ORF75A promotes early events in lytic infection and gammaherpesvirus pathogenesis in mice. PLoS Pathog 2018; 14:e1006843. [PMID: 29390024 PMCID: PMC5811070 DOI: 10.1371/journal.ppat.1006843] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 02/13/2018] [Accepted: 12/27/2017] [Indexed: 12/19/2022] Open
Abstract
Gammaherpesviruses encode proteins with homology to the cellular purine metabolic enzyme formyl-glycinamide-phosphoribosyl-amidotransferase (FGARAT), but the role of these viral FGARATs (vFGARATs) in the pathogenesis of a natural host has not been investigated. We report a novel role for the ORF75A vFGARAT of murine gammaherpesvirus 68 (MHV68) in infectious virion production and colonization of mice. MHV68 mutants with premature stop codons in orf75A exhibited a log reduction in acute replication in the lungs after intranasal infection, which preceded a defect in colonization of multiple host reservoirs including the mediastinal lymph nodes, peripheral blood mononuclear cells, and the spleen. Intraperitoneal infection rescued splenic latency, but not reactivation. The 75A.stop virus also exhibited defective replication in primary fibroblast and macrophage cells. Viruses produced in the absence of ORF75A were characterized by an increase in the ratio of particles to PFU. In the next round of infection this led to the alteration of early events in lytic replication including the deposition of the ORF75C tegument protein, the accelerated kinetics of viral gene expression, and induction of TNFα release and cell death. Infecting cells to deliver equivalent genomes revealed that ORF75A was required for initiating early events in infection. In contrast with the numerous phenotypes observed in the absence of ORF75A, ORF75B was dispensable for replication and pathogenesis. These studies reveal that murine rhadinovirus vFGARAT family members ORF75A and ORF75C have evolved to perform divergent functions that promote replication and colonization of the host. Gammaherpesviruses are infectious agents that cause cancer. The study of viral genes unique to this subfamily may offer insight into the strategies that these viruses use to persist in the host and drive disease. The vFGARATs are a family of viral proteins found only in gammaherpesviruses, and are critical for replication in cell culture. Here we report that a rhadinovirus of rodents requires a previously uncharacterized vFGARAT family member, ORF75A, to support viral growth and persistence in mice. In addition, viruses lacking ORF75A are defective in the production of infectious viral particles. Thus, duplications and functional divergence of the various vFGARATs in the rhadinovirus lineage have likely been driven by selective pressures to disseminate within and colonize the host. Identification of the shared host processes that are targeted by the diverse family of vFGARATs may reveal novel targets for therapeutic agents to prevent life-long infections by these oncogenic viruses.
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Affiliation(s)
- Nick D. Van Skike
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Nana K. Minkah
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Chad H. Hogan
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
- Graduate Program of Genetics, Stony Brook University, Stony Brook, New York, United States of America
| | - Gary Wu
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Peter T. Benziger
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | | | - Mehmet Kara
- Department of Molecular Genetics and Microbiology and UF Shands Cancer Center, College of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Deborah M. Kim-Holzapfel
- Departments of Chemistry and of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Douglas W. White
- Gundersen Health System, La Crosse, Wisconsin, United States of America
| | - Scott A. Tibbetts
- Department of Molecular Genetics and Microbiology and UF Shands Cancer Center, College of Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Jarrod B. French
- Departments of Chemistry and of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York, United States of America
| | - Laurie T. Krug
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
- * E-mail:
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The Epstein-Barr Virus BRRF1 Gene Is Dispensable for Viral Replication in HEK293 cells and Transformation. Sci Rep 2017; 7:6044. [PMID: 28729695 PMCID: PMC5519699 DOI: 10.1038/s41598-017-06413-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 06/14/2017] [Indexed: 12/13/2022] Open
Abstract
The Epstein-Barr virus (EBV) is a gamma-herpesvirus associated with several malignancies. It establishes a latent infection in B lymphocytes and is occasionally reactivated to enter the lytic cycle. Here we examined the role of the EBV gene BRRF1, which is expressed in the lytic state. We first confirmed, using a DNA polymerase inhibitor, that the BRRF1 gene is expressed with early kinetics. A BRRF1-deficient recombinant virus was constructed using a bacterial artificial chromosome system. No obvious differences were observed between the wild-type, BRRF1-deficient mutant and the revertant virus in HEK293 cells in terms of viral lytic protein expression, viral DNA synthesis, progeny production, pre-latent abortive lytic gene expression and transformation of primary B cells. However, reporter assays indicated that BRRF1 may activate transcription in promoter- and cell type-dependent manners. Taken together, BRRF1 is dispensable for viral replication in HEK293 cells and transformation of B cells, but it may have effects on transcription.
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Santana AL, Oldenburg DG, Kirillov V, Malik L, Dong Q, Sinayev R, Marcu KB, White DW, Krug LT. RTA Occupancy of the Origin of Lytic Replication during Murine Gammaherpesvirus 68 Reactivation from B Cell Latency. Pathogens 2017; 6:pathogens6010009. [PMID: 28212352 PMCID: PMC5371897 DOI: 10.3390/pathogens6010009] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 02/10/2017] [Indexed: 02/06/2023] Open
Abstract
RTA, the viral Replication and Transcription Activator, is essential for rhadinovirus lytic gene expression upon de novo infection and reactivation from latency. Lipopolysaccharide (LPS)/toll-like receptor (TLR)4 engagement enhances rhadinovirus reactivation. We developed two new systems to examine the interaction of RTA with host NF-kappaB (NF-κB) signaling during murine gammaherpesvirus 68 (MHV68) infection: a latent B cell line (HE-RIT) inducible for RTA-Flag expression and virus reactivation; and a recombinant virus (MHV68-RTA-Bio) that enabled in vivo biotinylation of RTA in BirA transgenic mice. LPS acted as a second stimulus to drive virus reactivation from latency in the context of induced expression of RTA-Flag. ORF6, the gene encoding the single-stranded DNA binding protein, was one of many viral genes that were directly responsive to RTA induction; expression was further increased upon treatment with LPS. However, NF-κB sites in the promoter of ORF6 did not influence RTA transactivation in response to LPS in HE-RIT cells. We found no evidence for RTA occupancy of the minimal RTA-responsive region of the ORF6 promoter, yet RTA was found to complex with a portion of the right origin of lytic replication (oriLyt-R) that contains predicted RTA recognition elements. RTA occupancy of select regions of the MHV-68 genome was also evaluated in our novel in vivo RTA biotinylation system. Streptavidin isolation of RTA-Bio confirmed complex formation with oriLyt-R in LPS-treated primary splenocytes from BirA mice infected with MHV68 RTA-Bio. We demonstrate the utility of reactivation-inducible B cells coupled with in vivo RTA biotinylation for mechanistic investigations of the interplay of host signaling with RTA.
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Affiliation(s)
- Alexis L Santana
- The Ronald O. Perelman Department of Dermatology, New York University School of Medicine, New York, NY 10016, USA.
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA.
| | | | - Varvara Kirillov
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA.
| | - Laraib Malik
- Department of Computer Science, Stony Brook University, Stony Brook, NY 11794, USA.
| | - Qiwen Dong
- Program in Molecular and Cellular Biology, Stony Brook University, Stony Brook, NY 11794, USA.
| | - Roman Sinayev
- Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY 11794, USA.
| | - Kenneth B Marcu
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA.
- Biomedical Research Foundation Academy of Athens (BRFAA), Athens 115 27, Greece.
- Biochemistry and Cell Biology Dept., Stony Brook University, Stony Brook, NY 11794, USA.
- Department of Pathology, Health Sciences Center, Stony Brook University, Stony Brook, NY 11794, USA.
| | | | - Laurie T Krug
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794, USA.
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Structure of the Open Reading Frame 49 Protein Encoded by Kaposi's Sarcoma-Associated Herpesvirus. J Virol 2017; 91:JVI.01947-16. [PMID: 27807232 DOI: 10.1128/jvi.01947-16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Accepted: 10/25/2016] [Indexed: 01/19/2023] Open
Abstract
Herpesviruses alternate between the latent and the lytic life cycle. Switching into the lytic life cycle is important for herpesviral replication and disease pathogenesis. Activation of a transcription factor replication and transcription activator (RTA) has been demonstrated to govern this switch in Kaposi's sarcoma-associated herpesvirus (KSHV). The protein encoded by open reading frame 49 from KSHV (ORF49KSHV) has been shown to upregulate lytic replication in KSHV by enhancing the activities of the RTA. We have solved the crystal structure of the ORF49KSHV protein to a resolution of 2.4 Å. The ORF49KSHV protein has a novel fold consisting of 12 alpha-helices bundled into two pseudodomains. Most notably are distinct charged patches on the protein surface, which are possible protein-protein interaction sites. Homologs of the ORF49KSHV protein in the gammaherpesvirus subfamily have low sequence similarities. Conserved residues are mainly located in the hydrophobic regions, suggesting that they are more likely to play important structural roles than functional ones. Based on the identification and position of three sulfates binding to the positive areas, we performed some initial protein-DNA binding studies by analyzing the thermal stabilization of the protein in the presence of DNA. The ORF49KSHV protein is stabilized in a dose-responsive manner by double-stranded oligonucleotides, suggesting actual DNA interaction and binding. Biolayer interferometry studies also demonstrated that the ORF49KSHV protein binds these oligonucleotides. IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV) is a tumorigenic gammaherpesvirus that causes multiple cancers and lymphoproliferative diseases. The virus exists mainly in the quiescent latent life cycle, but when it is reactivated into the lytic life cycle, new viruses are produced and disease symptoms usually manifest. Several KSHV proteins play important roles in this reactivation, but their exact roles are still largely unknown. In this study, we report the crystal structure of the open reading frame 49 protein encoded by KSHV (ORF49KSHV). Possible regions for protein interaction that could harbor functional importance were found on the surface of the ORF49KSHV protein. This led to the discovery of novel DNA binding properties of the ORF49KSHV protein. Evolutionary conserved structural elements with the functional homologs of ORF49KSHV were also established with the structure.
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17
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Downregulation of Poly(ADP-Ribose) Polymerase 1 by a Viral Processivity Factor Facilitates Lytic Replication of Gammaherpesvirus. J Virol 2015; 89:9676-82. [PMID: 26157130 DOI: 10.1128/jvi.00559-15] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 07/03/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED In Kaposi's sarcoma-associated herpesvirus (KSHV), poly(ADP-ribose) polymerase 1 (PARP-1) acts as an inhibitor of lytic replication. Here, we demonstrate that KSHV downregulated PARP-1 upon reactivation. The viral processivity factor of KSHV (PF-8) interacted with PARP-1 and was sufficient to degrade PARP-1 in a proteasome-dependent manner; this effect was conserved in murine gammaherpesvirus 68. PF-8 knockdown in KSHV-infected cells resulted in reduced lytic replication upon reactivation with increased levels of PARP-1, compared to those in control cells. PF-8 overexpression reduced the levels of the poly(ADP-ribosyl)ated (PARylated) replication and transcription activator (RTA) and further enhanced RTA-mediated transactivation. These results suggest a novel viral mechanism for overcoming the inhibitory effect of a host factor, PARP-1, thereby promoting the lytic replication of gammaherpesvirus. IMPORTANCE Gammaherpesviruses are important human pathogens, as they are associated with various kinds of tumors and establish latency mainly in host B lymphocytes. Replication and transcription activator (RTA) of Kaposi's sarcoma-associated herpesvirus (KSHV) is a central molecular switch for lytic replication, and its expression is tightly regulated by many host and viral factors. In this study, we investigated a viral strategy to overcome the inhibitory effect of poly(ADP-ribose) polymerase 1 (PARP-1) on RTA's activity. PARP-1, an abundant multifunctional nuclear protein, was downregulated during KSHV reactivation. The viral processivity factor of KSHV (PF-8) directly interacted with PARP-1 and was sufficient and necessary to degrade PARP-1 protein in a proteasome-dependent manner. PF-8 reduced the levels of PARylated RTA and further promoted RTA-mediated transactivation. As this was also conserved in another gammaherpesvirus, murine gammaherpesvirus 68, our results suggest a conserved viral modulation of a host inhibitory factor to facilitate its lytic replication.
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Cho HJ, Song MJ. A gammaherpesvirus establishes persistent infection in neuroblastoma cells. Mol Cells 2014; 37:518-25. [PMID: 25092213 PMCID: PMC4132303 DOI: 10.14348/molcells.2014.0024] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 06/25/2014] [Accepted: 06/25/2014] [Indexed: 11/27/2022] Open
Abstract
Gammaherpesvirus (γHV) infection of the central nervous system (CNS) has been implicated in diverse neurological diseases, and murine γHV-68 (MHV-68) is known to persist in the brain after cerebral infection. The underlying molecular mechanisms of persistency of virus in the brain are poorly understood. Here, we characterized a unique pattern of MHV-68 persistent infection in neuroblastoma cells. On infection with MHV-68, both murine and human neuroblastoma cells expressed viral lytic proteins and produced virions. However, the infected cells survived productive infection and could be cultured for multiple passages without affecting their cellular growth. Latent infection as well as productive replication was established in these prolonged cultures, and lytic replication was further increased by treatment with lytic inducers. Our results provide a novel system to study persistent infection of γHVs in vitro following de novo infection and suggest application of MHV-68 as a potential gene transfer vector to the brain.
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Affiliation(s)
- Hye-Jeong Cho
- Virus-Host Interactions Laboratory, Division of Biotechnology, Department of Biosystems and Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Korea
| | - Moon Jung Song
- Virus-Host Interactions Laboratory, Division of Biotechnology, Department of Biosystems and Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul 136-713, Korea
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Abernathy E, Clyde K, Yeasmin R, Krug LT, Burlingame A, Coscoy L, Glaunsinger B. Gammaherpesviral gene expression and virion composition are broadly controlled by accelerated mRNA degradation. PLoS Pathog 2014; 10:e1003882. [PMID: 24453974 PMCID: PMC3894220 DOI: 10.1371/journal.ppat.1003882] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 11/26/2013] [Indexed: 11/19/2022] Open
Abstract
Lytic gammaherpesvirus infection restricts host gene expression by promoting widespread degradation of cytoplasmic mRNA through the activity of the viral endonuclease SOX. Though generally assumed to be selective for cellular transcripts, the extent to which SOX impacts viral mRNA stability has remained unknown. We addressed this issue using the model murine gammaherpesvirus MHV68 and, unexpectedly, found that all stages of viral gene expression are controlled through mRNA degradation. Using both comprehensive RNA expression profiling and half-life studies we reveal that the levels of the majority of viral mRNAs but not noncoding RNAs are tempered by MHV68 SOX (muSOX) activity. The targeting of viral mRNA by muSOX is functionally significant, as it impacts intracellular viral protein abundance and progeny virion composition. In the absence of muSOX-imposed gene expression control the viral particles display increased cell surface binding and entry as well as enhanced immediate early gene expression. These phenotypes culminate in a viral replication defect in multiple cell types as well as in vivo, highlighting the importance of maintaining the appropriate balance of viral RNA during gammaherpesviral infection. This is the first example of a virus that fails to broadly discriminate between cellular and viral transcripts during host shutoff and instead uses the targeting of viral messages to fine-tune overall gene expression. Many viruses restrict host gene expression during infection, presumably to provide a competitive expression advantage to viral transcripts. Not surprisingly, viruses that induce this ‘host shutoff’ phenotype therefore generally possess mechanisms to selectively spare viral genes. Gammaherpesviruses promote host shutoff by inducing widespread mRNA degradation, a process initiated by the viral SOX nuclease. However, the effect of SOX on viral mRNA during infection was unknown. Here, we reveal that during infection with the murine gammaherpesvirus MHV68, the majority of viral transcripts of all kinetic classes are broadly down regulated through the activity of the MHV68 SOX protein (muSOX). We further demonstrate that in the absence of muSOX-induced control of viral mRNA abundance, viral protein levels increase, thereby affecting the composition of progeny viral particles. Altered virion composition directly impacts early events such as entry and induction of lytic gene expression in subsequent rounds of replication. Furthermore, decreasing both virus and host gene expression via global mRNA degradation is critical for viral replication in a cell type specific manner both in vitro and in vivo. This is the first example of a eukaryotic virus whose host shutoff mechanism similarly tempers viral gene expression, and highlights the degree to which gammaherpesviral gene expression must be fine tuned to ensure replicative success.
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Affiliation(s)
- Emma Abernathy
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, California, United States of America
| | - Karen Clyde
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, California, United States of America
| | - Rukhsana Yeasmin
- Department of Computer Science, Stony Brook University, Stony Brook, New York, United States of America
| | - Laurie T. Krug
- Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, New York, United States of America
| | - Al Burlingame
- Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, United States of America
| | - Laurent Coscoy
- Department of Cell and Molecular Biology, University of California at Berkeley, Berkeley, California, United States of America
| | - Britt Glaunsinger
- Department of Plant and Microbial Biology, University of California at Berkeley, Berkeley, California, United States of America
- Department of Cell and Molecular Biology, University of California at Berkeley, Berkeley, California, United States of America
- * E-mail:
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Amplification of JNK signaling is necessary to complete the murine gammaherpesvirus 68 lytic replication cycle. J Virol 2012; 86:13253-62. [PMID: 23015701 DOI: 10.1128/jvi.01432-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Several studies have previously defined host-derived signaling events capable of driving lytic gammaherpesvirus replication or enhancing immediate-early viral gene expression. Yet signaling pathways that regulate later stages of the productive gammaherpesvirus replication cycle are still poorly defined. In this study, we utilized a mass spectrometric approach to identify c-Jun as an abundant cellular phosphoprotein present in late stages of lytic murine gammaherpesvirus 68 (MHV68) infection. Kinetically, c-Jun phosphorylation was enhanced as infection progressed, and this correlated with enhanced phosphorylation of the c-Jun amino-terminal kinases JNK1 and JNK2 and activation of AP-1 transcription. These events were dependent on progression beyond viral immediate-early gene expression, but not dependent on viral DNA replication. Both pharmacologic and dominant-negative blockade of JNK1/2 activity inhibited viral replication, and this correlated with inhibition of viral DNA synthesis and reduced viral gene expression. These data suggest a model in which MHV68 by necessity amplifies and usurps JNK/c-Jun signaling as infection progresses in order to facilitate late stages of the MHV68 lytic infection cycle.
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