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Aalam F, Totonchy J. Molecular Virology of KSHV in the Lymphocyte Compartment-Insights From Patient Samples and De Novo Infection Models. Front Cell Infect Microbiol 2020; 10:607663. [PMID: 33344267 PMCID: PMC7746649 DOI: 10.3389/fcimb.2020.607663] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Accepted: 11/09/2020] [Indexed: 12/26/2022] Open
Abstract
The incidence of Kaposi’s sarcoma-associated herpesvirus (KSHV)-associated Kaposi Sarcoma has declined precipitously in the present era of effective HIV treatment. However, KSHV-associated lymphoproliferative disorders although rare, have not seen a similar decline. Lymphoma is now a leading cause of death in people living with HIV (PLWH), indicating that the immune reconstitution provided by antiretroviral therapy is not sufficient to fully correct the lymphomagenic immune dysregulation perpetrated by HIV infection. As such, novel insights into the mechanisms of KSHV-mediated pathogenesis in the immune compartment are urgently needed in order to develop novel therapeutics aimed at prevention and treatment of KSHV-associated lymphoproliferations. In this review, we will discuss our current understanding of KSHV molecular virology in the lymphocyte compartment, concentrating on studies which explore mechanisms unique to infection in B lymphocytes.
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Affiliation(s)
- Farizeh Aalam
- Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, United States
| | - Jennifer Totonchy
- Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Irvine, CA, United States
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Stolz ML, McCormick C. The bZIP Proteins of Oncogenic Viruses. Viruses 2020; 12:v12070757. [PMID: 32674309 PMCID: PMC7412551 DOI: 10.3390/v12070757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 07/08/2020] [Accepted: 07/13/2020] [Indexed: 12/20/2022] Open
Abstract
Basic leucine zipper (bZIP) transcription factors (TFs) govern diverse cellular processes and cell fate decisions. The hallmark of the leucine zipper domain is the heptad repeat, with leucine residues at every seventh position in the domain. These leucine residues enable homo- and heterodimerization between ZIP domain α-helices, generating coiled-coil structures that stabilize interactions between adjacent DNA-binding domains and target DNA substrates. Several cancer-causing viruses encode viral bZIP TFs, including human T-cell leukemia virus (HTLV), hepatitis C virus (HCV) and the herpesviruses Marek’s disease virus (MDV), Epstein–Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV). Here, we provide a comprehensive review of these viral bZIP TFs and their impact on viral replication, host cell responses and cell fate.
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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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Abstract
Herpesviruses encode miRNAs that target both virus and host genes; however their role in herpesvirus biology is still poorly understood. We previously identified thirty five miRNAs encoded by OvHV-2; the causative agent of malignant catarrhal fever (MCF) and are investigating the role of these miRNAs in regulating expression of OvHV-2 genes that play important roles in virus biology. Analysis, using RNAHybrid predicted that two OvHV-2 encoded miRNAs, ovhv2-miR-17-10 and ovhv2-miR-61-1, target transcripts coding for the OvHV-2 bZIP protein Ov2. In other herpesvirus bZIP proteins are known to play important roles in lytic virus replication. Here we show by Flow cytometry and western blotting that ovhv2-miR-17-10 and ovhv2-miR-61-1, reduce the expression of Ov2 protein. The predicted target sites for both miRNAs within the Ov2 gene were disrupted whilst retaining the Ov2 coding sequence. Mutation of the ovhv2-miR-61-1 target sequence restored Ov2 protein expression levels to control levels confirming the identity of its target site. However, it was not possible to determine the binding site of ovhv2-miR-17-10 possibly due to potential G:U pairing introduced during the mutation process. The targeting of Ov2 by two virus-encoded miRNAs suggests an important regulatory role for Ov2 in OvHV-2 replication or reactivation.
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Hossain MG, Ohsaki E, Honda T, Ueda K. Importance of Promyelocytic Leukema Protein (PML) for Kaposi's Sarcoma-Associated Herpesvirus Lytic Replication. Front Microbiol 2018; 9:2324. [PMID: 30349510 PMCID: PMC6186782 DOI: 10.3389/fmicb.2018.02324] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 09/11/2018] [Indexed: 12/14/2022] Open
Abstract
Many DNA virus replication-related proteins are associated with promyelocytic leukemia protein (PML), a component of nuclear domain 10 (ND10), which has been investigated for its potential involvement in viral replication. In the case of Kaposi’s sarcoma-associated herpesvirus (KSHV) lytic gene products, K8 (K-bZIP), ORF59, and ORF75 have been shown to colocalize with PML, but its importance in KSHV lytic replication is still unclear. In this study, we analyzed the functional influence of PML on KSHV latency and lytic replication in KSHV-infected primary effusion lymphoma (PEL) cell lines. Stable PML-knockout (BC3-PMLKO) and PML-overexpressing BC3 cells (BC3PML) were successfully generated and the latency and reactivation status were analyzed. The results demonstrated that neither KSHV latency nor the episome copy number was affected in BC3-PMLKO cells. In the reactivation phase, the expression dynamics of KSHV immediate-early or early lytic proteins such as RTA, K9 (vIRF1), K5, K3, ORF59, and K8 (K-bZIP) were comparable between wild-type, control BC3, and BC3-PMLKO cells. Interestingly, KSHV lytic replication, virion production, and expression of late genes were downregulated in BC3-PMLKO cells and upregulated in BC3PML cells, compared to those in control or wild-type BC3 cells. Moreover, exogenous PML increased the size of the PML dots and recruited additional K8 (K-bZIP) to PML-NBs as dots. Therefore, PML would function as a positive regulator for KSHV lytic DNA replication by recruiting KSHV replication factors such as 8 (K-bZIP) or ORF59 to the PML-NBs.
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Affiliation(s)
- Md Golzar Hossain
- Division of Virology, Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Eriko Ohsaki
- Division of Virology, Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Tomoyuki Honda
- Division of Virology, Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University, Osaka, Japan
| | - Keiji Ueda
- Division of Virology, Department of Microbiology and Immunology, Graduate School of Medicine, Osaka University, Osaka, Japan
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Becerra-Artiles A, Santoro T, Stern LJ. Evaluation of a method to measure HHV-6B infection in vitro based on cell size. Virol J 2018; 15:4. [PMID: 29304865 PMCID: PMC5755443 DOI: 10.1186/s12985-017-0917-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 12/21/2017] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Human herpesvirus 6 (HHV-6A and HHV-6B) infection of cell cultures can be measured by different methods, including immunofluorescence microscopy, flow cytometry, or quantification of virus DNA by qPCR. These methods are reliable and sensitive but require long processing times and can be costly. Another method used in the field relies on the identification of enlarged cells in the culture; this method requires little sample processing and is relatively fast. However, visual inspection of cell cultures can be subjective and it can be difficult to establish clear criteria to decide if a cell is enlarged. To overcome these issues, we explored a method to monitor HHV-6B infections based on the systematic and objective measurement of the size of cells using an imaging-based automated cell counter. RESULTS The size of cells in non-infected and HHV-6B-infected cultures was measured at different times post-infection. The relatively narrow size distribution observed for non-infected cultures contrasted with the broader distributions observed in infected cultures. The average size of cultures shifted towards higher values after infection, and the differences were significant for cultures infected with relatively high doses of virus and/or screened at longer times post-infection. Correlation analysis showed that the trend observed for average size was similar to the trend observed for two other methods to measure infection: amount of virus DNA in supernatant and the percentage of cells expressing a viral antigen. In order to determine the performance of the size-based method in differentiating non-infected and infected cells, receiver operating characteristic (ROC) curves were used to analyze the data. Analysis using size of individual cells showed a moderate performance in detecting infected cells (area under the curve (AUC) ~ 0.80-0.87), while analysis using the average size of cells showed a very good performance in detecting infected cultures (AUC ~ 0.99). CONCLUSIONS The size-based method proved to be useful in monitoring HHV-6B infections for cultures where a substantial fraction of cells were infected and when monitored at longer times post-infection, with the advantage of being relatively fast and easy. It is a convenient method for monitoring virus production in-vitro and bulk infection of cells.
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Affiliation(s)
- Aniuska Becerra-Artiles
- Department of Pathology, University of Massachusetts Medical School, 55 Lake Ave North, Worcester, MA, 01655, USA
| | - Tessa Santoro
- Department of Pathology, University of Massachusetts Medical School, 55 Lake Ave North, Worcester, MA, 01655, USA
| | - Lawrence J Stern
- Department of Pathology, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 55 Lake Ave North, Worcester, MA, 01655, USA.
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Gonnella R, Yadav S, Gilardini Montani MS, Granato M, Santarelli R, Garufi A, D'Orazi G, Faggioni A, Cirone M. Oxidant species are involved in T/B-mediated ERK1/2 phosphorylation that activates p53-p21 axis to promote KSHV lytic cycle in PEL cells. Free Radic Biol Med 2017; 112:327-335. [PMID: 28801242 DOI: 10.1016/j.freeradbiomed.2017.08.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 07/31/2017] [Accepted: 08/05/2017] [Indexed: 12/18/2022]
Abstract
KSHV is a gammaherpesvirus strongly associated to human cancers such as Primary Effusion Lymphoma (PEL) and Kaposi's Sarcoma. The naturally virus-infected tumor cells usually display latent infection since a minority of cells undergoes spontaneous viral replication. The lytic cycle can be induced in vitro upon appropriate stimuli such as TPA (T), alone or in combination with butyrate (B), (T/B). In previous studies, Protein Kinase C (PKC) δ, Extracellular Signal-regulated Kinase1/2 (ERK1/2) and p53-p21 axis have been separately reported to play a role in KSHV reactivation from latency. Here, we found that these pathways were interconnected to induce KSHV lytic cycle in PEL cells treated with T/B. T/B also increased H2O2 that played an important role in the activation of these pathways. Oxidant specie production correlated with PKC δ activation, as the PKC δ inhibitor rottlerin reduced both H2O2 and KSHV lytic antigen expression. H2O2 contributed to T/B-mediated ERK1/2 activation that mediated p53 phosphorylation at serine 15 (Ser15) and increased p21 expression. Oxidant specie inhibition by quercetin indeed strongly reduced the activation of these pathways, lytic antigen expression and interestingly it also increased T/B-induced cell death. The use of ERK inhibitor PD98059 or p53 silencing demonstrated the importance of p53Ser15 phosphorylation and of p53-p21 axis in KSHV lytic cycle activation. Understanding the role of oxidant species and the molecular mechanisms involved in KSHV lytic cycle induction is particularly important since oxidant species represent the most physiological stimulus for viral reactivation in vivo and it is known that viral production contributes to the maintenance/progression of KSHV associated malignancies.
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Affiliation(s)
- Roberta Gonnella
- Department of Experimental Medicine, Sapienza University, 00100 Rome, Italy.
| | - Shivangi Yadav
- Department of Experimental Medicine, Sapienza University, 00100 Rome, Italy.
| | | | - Marisa Granato
- Department of Experimental Medicine, Sapienza University, 00100 Rome, Italy.
| | - Roberta Santarelli
- Department of Experimental Medicine, Sapienza University, 00100 Rome, Italy.
| | - Alessia Garufi
- Department of Research, Advanced Diagnostics, and Technological Innovation, Regina Elena National Cancer Institute, 00144 Rome, Italy.
| | - Gabriella D'Orazi
- Department of Research, Advanced Diagnostics, and Technological Innovation, Regina Elena National Cancer Institute, 00144 Rome, Italy; Department of Medical Sciences, University 'G. d'Annunzio', 66013 Chieti, Italy.
| | - Alberto Faggioni
- Department of Experimental Medicine, Sapienza University, 00100 Rome, Italy.
| | - Mara Cirone
- Department of Experimental Medicine, Sapienza University, 00100 Rome, Italy.
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Lowrey AJ, Cramblet W, Bentz GL. Viral manipulation of the cellular sumoylation machinery. Cell Commun Signal 2017; 15:27. [PMID: 28705221 PMCID: PMC5513362 DOI: 10.1186/s12964-017-0183-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 07/07/2017] [Indexed: 12/11/2022] Open
Abstract
Viruses exploit various cellular processes for their own benefit, including counteracting anti-viral responses and regulating viral replication and propagation. In the past 20 years, protein sumoylation has emerged as an important post-translational modification that is manipulated by viruses to modulate anti-viral responses, viral replication, and viral pathogenesis. The process of sumoylation is a multi-step cascade where a small ubiquitin-like modifier (SUMO) is covalently attached to a conserved ΨKxD/E motif within a target protein, altering the function of the modified protein. Here we review how viruses manipulate the cellular machinery at each step of the sumoylation process to favor viral survival and pathogenesis.
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Affiliation(s)
- Angela J Lowrey
- Division of Biomedical Sciences, Mercer University School of Medicine, Macon, Georgia
| | - Wyatt Cramblet
- Division of Biomedical Sciences, Mercer University School of Medicine, Macon, Georgia
| | - Gretchen L Bentz
- Division of Biomedical Sciences, Mercer University School of Medicine, Macon, Georgia.
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Banerjee S, Uppal T, Strahan R, Dabral P, Verma SC. The Modulation of Apoptotic Pathways by Gammaherpesviruses. Front Microbiol 2016; 7:585. [PMID: 27199919 PMCID: PMC4847483 DOI: 10.3389/fmicb.2016.00585] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Accepted: 04/11/2016] [Indexed: 12/11/2022] Open
Abstract
Apoptosis or programmed cell death is a tightly regulated process fundamental for cellular development and elimination of damaged or infected cells during the maintenance of cellular homeostasis. It is also an important cellular defense mechanism against viral invasion. In many instances, abnormal regulation of apoptosis has been associated with a number of diseases, including cancer development. Following infection of host cells, persistent and oncogenic viruses such as the members of the Gammaherpesvirus family employ a number of different mechanisms to avoid the host cell’s “burglar” alarm and to alter the extrinsic and intrinsic apoptotic pathways by either deregulating the expressions of cellular signaling genes or by encoding the viral homologs of cellular genes. In this review, we summarize the recent findings on how gammaherpesviruses inhibit cellular apoptosis via virus-encoded proteins by mediating modification of numerous signal transduction pathways. We also list the key viral anti-apoptotic proteins that could be exploited as effective targets for novel antiviral therapies in order to stimulate apoptosis in different types of cancer cells.
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Affiliation(s)
- Shuvomoy Banerjee
- Amity Institute of Virology and Immunology, Amity University Noida, India
| | - Timsy Uppal
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
| | - Roxanne Strahan
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
| | - Prerna Dabral
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
| | - Subhash C Verma
- Department of Microbiology and Immunology, Center for Molecular Medicine, School of Medicine, University of Nevada, Reno Reno, NV, USA
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Granato M, Santarelli R, Filardi M, Gonnella R, Farina A, Torrisi MR, Faggioni A, Cirone M. The activation of KSHV lytic cycle blocks autophagy in PEL cells. Autophagy 2015; 11:1978-1986. [PMID: 26391343 PMCID: PMC4824593 DOI: 10.1080/15548627.2015.1091911] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
This study confirms that autophagy is activated concomitantly with KSHV lytic cycle induction, and that autophagy inhibition by BECN1 knockdown reduces viral lytic gene expression. In addition, we extend previous observations and show that autophagy is blocked at late steps, during viral replication. This is indicated by the lack of colocalization of autophagosomes and lysosomes and by the LC3-II level that does not increase in the presence of bafilomycin A1 in primary effusion lymphoma (PEL) cells induced to enter the lytic cycle, either by TPA/sodium butyrate (BC3 and BCBL1) or by doxycycline (TRExBCBL1-Rta). The autophagic block correlates with the downregulation of RAB7, whose silencing with specific siRNA results in an autophagic block in the same cells. Finally, by electron microscopy analysis, we observed viral particles inside autophagic vesicles in the cytoplasm of PEL cells undergoing viral replication, suggesting that they may be involved in viral transport.
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Affiliation(s)
- Marisa Granato
- a Department of Experimental Medicine ; "Sapienza" University of Rome ; Rome , Italy
| | - Roberta Santarelli
- a Department of Experimental Medicine ; "Sapienza" University of Rome ; Rome , Italy
| | - Mariarosaria Filardi
- a Department of Experimental Medicine ; "Sapienza" University of Rome ; Rome , Italy
| | - Roberta Gonnella
- a Department of Experimental Medicine ; "Sapienza" University of Rome ; Rome , Italy
| | - Antonella Farina
- a Department of Experimental Medicine ; "Sapienza" University of Rome ; Rome , Italy
| | - Maria Rosaria Torrisi
- b Istituto Pasteur-Fondazione Cenci Bolognetti ; Dipartimento di Medicina Clinica e Molecolare ; Sapienza Università di Roma ; Rome , Italy.,c Azienda Ospedaliera S. Andrea ; Rome , Italy
| | - Alberto Faggioni
- a Department of Experimental Medicine ; "Sapienza" University of Rome ; Rome , Italy
| | - Mara Cirone
- a Department of Experimental Medicine ; "Sapienza" University of Rome ; Rome , Italy
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Yang WS, Hsu HW, Campbell M, Cheng CY, Chang PC. K-bZIP Mediated SUMO-2/3 Specific Modification on the KSHV Genome Negatively Regulates Lytic Gene Expression and Viral Reactivation. PLoS Pathog 2015. [PMID: 26197391 PMCID: PMC4510548 DOI: 10.1371/journal.ppat.1005051] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
SUMOylation is associated with epigenetic regulation of chromatin structure and transcription. Epigenetic modifications of herpesviral genomes accompany the transcriptional switch of latent and lytic genes during the virus life cycle. Here, we report a genome-wide comparison of SUMO paralog modification on the KSHV genome. Using chromatin immunoprecipitation in conjunction with high-throughput sequencing, our study revealed highly distinct landscape changes of SUMO paralog genomic modifications associated with KSHV reactivation. A rapid and widespread deposition of SUMO-2/3, compared with SUMO-1, modification across the KSHV genome upon reactivation was observed. Interestingly, SUMO-2/3 enrichment was inversely correlated with H3K9me3 mark after reactivation, indicating that SUMO-2/3 may be responsible for regulating the expression of viral genes located in low heterochromatin regions during viral reactivation. RNA-sequencing analysis showed that the SUMO-2/3 enrichment pattern positively correlated with KSHV gene expression profiles. Activation of KSHV lytic genes located in regions with high SUMO-2/3 enrichment was enhanced by SUMO-2/3 knockdown. These findings suggest that SUMO-2/3 viral chromatin modification contributes to the diminution of viral gene expression during reactivation. Our previous study identified a SUMO-2/3-specific viral E3 ligase, K-bZIP, suggesting a potential role of this enzyme in regulating SUMO-2/3 enrichment and viral gene repression. Consistent with this prediction, higher K-bZIP binding on SUMO-2/3 enrichment region during reactivation was observed. Moreover, a K-bZIP SUMO E3 ligase dead mutant, K-bZIP-L75A, in the viral context, showed no SUMO-2/3 enrichment on viral chromatin and higher expression of viral genes located in SUMO-2/3 enriched regions during reactivation. Importantly, virus production significantly increased in both SUMO-2/3 knockdown and KSHV K-bZIP-L75A mutant cells. These results indicate that SUMO-2/3 modification of viral chromatin may function to counteract KSHV reactivation. As induction of herpesvirus reactivation may activate cellular antiviral regimes, our results suggest that development of viral SUMO E3 ligase specific inhibitors may be an avenue for anti-virus therapy.
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Affiliation(s)
- Wan-Shan Yang
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Hung-Wei Hsu
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Mel Campbell
- UC Davis Cancer Center, University of California, Davis, Davis, California, United States of America
| | - Chia-Yang Cheng
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China
| | - Pei-Ching Chang
- Institute of Microbiology and Immunology, National Yang-Ming University, Taipei, Taiwan, Republic of China
- Center for Infectious Disease and Cancer Research, Kaohsiung Medical University, Kaohsiung, Taiwan, Republic of China
- * E-mail:
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12
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Avey D, Brewers B, Zhu F. Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis. Virol Sin 2015; 30:130-45. [PMID: 25924994 PMCID: PMC8200917 DOI: 10.1007/s12250-015-3595-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 04/16/2015] [Indexed: 02/07/2023] Open
Abstract
It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus (KSHV; also known as human herpesvirus 8 (HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.
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Affiliation(s)
- Denis Avey
- Department of Biological Science, Florida State University, Tallahassee, 32306 USA
| | - Brittany Brewers
- Department of Biological Science, Florida State University, Tallahassee, 32306 USA
| | - Fanxiu Zhu
- Department of Biological Science, Florida State University, Tallahassee, 32306 USA
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13
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Abstract
Kaposi’s sarcoma-associated herpesvirus (KSHV) primarily persists as a latent episome in infected cells. During latent infection, only a limited number of viral genes are expressed that help to maintain the viral episome and prevent lytic reactivation. The latent KSHV genome persists as a highly ordered chromatin structure with bivalent chromatin marks at the promoter-regulatory region of the major immediate-early gene promoter. Various stimuli can induce chromatin modifications to an active euchromatic epigenetic mark, leading to the expression of genes required for the transition from the latent to the lytic phase of KSHV life cycle. Enhanced replication and transcription activator (RTA) gene expression triggers a cascade of events, resulting in the modulation of various cellular pathways to support viral DNA synthesis. RTA also binds to the origin of lytic DNA replication to recruit viral, as well as cellular, proteins for the initiation of the lytic DNA replication of KSHV. In this review we will discuss some of the pivotal genetic and epigenetic factors that control KSHV reactivation from the transcriptionally restricted latent program.
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Systematic analysis of a xenograft mice model for KSHV+ primary effusion lymphoma (PEL). PLoS One 2014; 9:e90349. [PMID: 24587336 PMCID: PMC3938717 DOI: 10.1371/journal.pone.0090349] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Accepted: 01/28/2014] [Indexed: 11/19/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus is the causative agent of primary effusion lymphoma (PEL), which arises preferentially in the setting of infection with human immunodeficiency virus (HIV). Even with standard cytotoxic chemotherapy, PEL continues to cause high mortality rates, requiring the development of novel therapeutic strategies. PEL xenograft models employing immunodeficient mice have been used to study the in vivo effects of a variety of therapeutic approaches. However, it remains unclear whether these xenograft models entirely reflect clinical presentations of KSHV(+) PEL, especially given the recent description of extracavitary solid tumor variants arising in patients. In addition, effusion and solid tumor cells propagated in vivo exhibit unique biology, differing from one another or from their parental cell lines propagated through in vitro culture. Therefore, we used a KSHV(+) PEL/BCBL-1 xenograft model involving non-obese diabetic/severe-combined immunodeficient (NOD/SCID) mice, and compared characteristics of effusion and solid tumors with their parent cell culture-derived counterparts. Our results indicate that although this xenograft model can be used for study of effusion and solid lymphoma observed in patients, tumor cells in vivo display unique features to those passed in vitro, including viral lytic gene expression profile, rate of solid tumor development, the host proteins and the complex of tumor microenvironment. These items should be carefully considered when the xenograft model is used for testing novel therapeutic strategies against KSHV-related lymphoma.
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15
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Inhibition of Kaposi's sarcoma-associated herpesvirus lytic replication by HIV-1 Nef and cellular microRNA hsa-miR-1258. J Virol 2014; 88:4987-5000. [PMID: 24554664 DOI: 10.1128/jvi.00025-14] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
UNLABELLED Kaposi's sarcoma-associated herpesvirus (KSHV) is causally linked to several AIDS-related malignancies, including Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease. The interaction of human immunodeficiency virus type 1 (HIV-1) and KSHV has a central role in promoting the aggressive manifestations of AIDS-KS. We have previously shown that negative factor (Nef), a secreted HIV-1 protein, synergizes with KSHV viral interleukin-6 (vIL-6) to promote angiogenesis and tumorigenesis by activating the AKT pathway (X. Zhu, et al., Oncogene, 22 April 2013, http://dx.doi.org/10.1038/onc.2013.136). Here, we further demonstrated the role of soluble and ectopic Nef in the regulation of KSHV latency. We found that both soluble Nef protein and ectopic expression of Nef by transfection suppressed the expression of KSHV viral lytic mRNA transcripts and proteins and the production of infectious viral particles. MicroRNA (miRNA) microarray analysis identified a number of Nef-regulated miRNAs. Bioinformatics and luciferase reporter analyses showed that one of the Nef-upregulated miRNAs, cellular miRNA 1258 (hsa-miR-1258), directly targeted a seed sequence in the 3' untranslated region (UTR) of the mRNA encoding the major lytic switch protein (RTA), which controls KSHV reactivation from latency. Ectopic expression of hsa-miR-1258 impaired RTA synthesis and enhanced Nef-mediated inhibition of KSHV replication, whereas repression of hsa-miR-1258 has the opposite effect. Mutation of the seed sequence in the RTA 3'UTR abolished downregulation of RTA by hsa-miR-1258. Collectively, these novel findings demonstrate that, by regulating cellular miRNA, Nef may inhibit KSHV replication to promote viral latency and contribute to the pathogenesis of AIDS-related malignancies. IMPORTANCE This study found that Nef, a secreted HIV-1 protein, suppressed KSHV lytic replication to promote KSHV latency. Mechanistic studies indicated that a Nef-upregulated cellular miRNA, hsa-miR-1258, inhibits KSHV replication by directly targeting a seed sequence in the KSHV RTA 3'UTR. These results illustrate that, in addition to viral miRNAs, cellular miRNAs also play an important role in regulating the life cycle of KSHV. Overall, this is the first study to report the involvement of Nef in KSHV latency, implying its likely important role in the pathogenesis of AIDS-related malignancies.
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Bhatt S, Ashlock BM, Toomey NL, Diaz LA, Mesri EA, Lossos IS, Ramos JC. Efficacious proteasome/HDAC inhibitor combination therapy for primary effusion lymphoma. J Clin Invest 2013; 123:2616-28. [PMID: 23635777 DOI: 10.1172/jci64503] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 02/28/2013] [Indexed: 12/26/2022] Open
Abstract
Primary effusion lymphoma (PEL) is a rare form of aggressive B cell lymphoma caused by Kaposi's sarcoma-associated herpesvirus (KSHV). Current chemotherapy approaches result in dismal outcomes, and there is an urgent need for new PEL therapies. Previously, we established, in a direct xenograft model of PEL-bearing immune-compromised mice, that treatment with the proteasome inhibitor, bortezomib (Btz), increased survival relative to that after treatment with doxorubicin. Herein, we demonstrate that the combination of Btz with the histone deacetylase (HDAC) inhibitor suberoylanilidehydroxamic acid (SAHA, also known as vorinostat) potently reactivates KSHV lytic replication and induces PEL cell death, resulting in significantly prolonged survival of PEL-bearing mice. Importantly, Btz blocked KSHV late lytic gene expression, terminally inhibiting the full lytic cascade and production of infectious virus in vivo. Btz treatment led to caspase activation and induced DNA damage, as evidenced by the accumulation of phosphorylated γH2AX and p53. The addition of SAHA to Btz treatment was synergistic, as SAHA induced early acetylation of p53 and reduced interaction with its negative regulator MDM2, augmenting the effects of Btz. The eradication of KSHV-infected PEL cells without increased viremia in mice provides a strong rationale for using the proteasome/HDAC inhibitor combination therapy in PEL.
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Affiliation(s)
- Shruti Bhatt
- Department of Molecular and Cellular Pharmacology, University of Miami Miller School of Medicine, Miami, Florida, USA
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Chromatin immunoprecipitation and microarray analysis suggest functional cooperation between Kaposi's Sarcoma-associated herpesvirus ORF57 and K-bZIP. J Virol 2013; 87:4005-16. [PMID: 23365430 DOI: 10.1128/jvi.03459-12] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame 57 (ORF57)-encoded protein (Mta) is a multifunctional regulator of viral gene expression. ORF57 is essential for viral replication, so elucidation of its molecular mechanisms is important for understanding KSHV infection. ORF57 has been implicated in nearly every aspect of viral gene expression, including transcription, RNA stability, splicing, export, and translation. Here we demonstrate that ORF57 interacts with the KSHV K-bZIP protein in vitro and in cell extracts from lytically reactivated infected cells. To further test the biological relevance of the interaction, we performed a chromatin immunoprecipitation and microarray (ChIP-chip) analysis using anti-ORF57 antibodies and a KSHV tiling array. The results revealed four specific areas of enrichment, including the ORF4 and K8 (K-bZIP) promoters, as well as oriLyt, all of which interact with K-bZIP. In addition, ORF57 associated with DNA corresponding to the PAN RNA transcribed region, a known posttranscriptional target of ORF57. All of the peaks were RNase insensitive, demonstrating that ORF57 association with the viral genome is unlikely to be mediated exclusively by an RNA tether. Our data demonstrate that ORF57 associates with the viral genome by using at least two modes of recruitment, and they suggest that ORF57 and K-bZIP coregulate viral gene expression during lytic infection.
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Borah S, Nichols LA, Hassman LM, Kedes DH, Steitz JA. Tracking expression and subcellular localization of RNA and protein species using high-throughput single cell imaging flow cytometry. RNA (NEW YORK, N.Y.) 2012; 18:1573-9. [PMID: 22745225 PMCID: PMC3404377 DOI: 10.1261/rna.033126.112] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Accepted: 06/06/2012] [Indexed: 05/25/2023]
Abstract
We report a high-throughput application of multispectral imaging flow cytometry (MIFC) for analyzing the expression and localization of both RNA and protein molecules in a heterogeneous population of cells. The approach was developed using polyadenylated nuclear (PAN) RNA, an abundant, noncoding RNA expressed by Kaposi's sarcoma-associated herpesvirus (KSHV) during the lytic phase of infection. High levels of PAN RNA are, in part, dependent on its interaction with poly(A)-binding protein C1 (PABPC1), which relocalizes from the cytoplasm to the nucleus of lytically infected cells. We quantitatively tracked the cytoplasmic to nuclear translocation of PABPC1 and examined how this translocation relates to the expression and localization of viral RNA and protein molecules in KSHV-infected cells. This high-throughput approach will be useful for other systems in which changes in subcellular localization of RNA and protein molecules need to be monitored simultaneously.
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Affiliation(s)
- Sumit Borah
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06536, USA
| | - Lisa A. Nichols
- Myles H. Thaler Center for AIDS and Human Retrovirus Research and the Department of Microbiology, Immunology and Cancer Biology
| | - Lynn M. Hassman
- Myles H. Thaler Center for AIDS and Human Retrovirus Research and the Department of Microbiology, Immunology and Cancer Biology
| | - Dean H. Kedes
- Myles H. Thaler Center for AIDS and Human Retrovirus Research and the Department of Microbiology, Immunology and Cancer Biology
- Department of Medicine and Department of Microbiology, Immunology and Cancer Biology, University of Virginia, Charlottesville, Virginia 22908, USA
| | - Joan A. Steitz
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06536, USA
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Martínez FP, Tang Q. Leucine zipper domain is required for Kaposi sarcoma-associated herpesvirus (KSHV) K-bZIP protein to interact with histone deacetylase and is important for KSHV replication. J Biol Chem 2012; 287:15622-34. [PMID: 22416134 DOI: 10.1074/jbc.m111.315861] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The Kaposi sarcoma-associated herpesvirus (KSHV; or human herpesvirus-8)-encoded protein called K-bZIP (also named K8) was found to be multifunctional. In this study, we discovered that K-bZIP interacts with histone deacetylase (HDAC) 1/2 in 12-O-tetradecanoylphorbol-13-acetate-stimulated BCBL-1 lymphocyte cells. K-bZIP appears to repress HDAC activity through this interaction, which we determined to be independent of K-bZIP SUMOylation. We dissected the domains of K-bZIP and found that the leucine zipper (LZ) domain is essential for the interaction of K-bZIP and HDAC. In addition, we constructed a KSHV bacterial artificial chromosome (BAC) with LZ domain-deleted K-bZIP (KSHVdLZ) and transfected this mutated KSHV BAC DNA into HEK 293T cells. As a result, it was consistently found that K-bZIP without its LZ domain failed to interact with HDAC2. We also showed that the interaction between K-bZIP and HDAC is necessary for the inhibition of the lytic gene promoters (ORF50 and OriLyt) of KSHV by K-bZIP. Furthermore, we found that the LZ domain is also important for the interaction of K-bZIP with the promoters of ORF50 and OriLyt. Most interestingly, although it was found to have suppressive effects on the promoters of ORF50 and OriLyt, KSHVdLZ replicates at a significantly lower level than its BAC-derived revertant (KSHVdLZRev) or KSHVWT (BAC36) in HEK 293T cells. The defectiveness of KSHVdLZ replication can be partially rescued by siRNA against HDAC2. Our results suggest that the function of K-bZIP interaction with HDAC is two-layered. 1) K-bZIP inhibits HDAC activity generally so that KSHVdLZ replicates at a lower level than does KSHVWT. 2) K-bZIP can recruit HDAC to the promoters of OriLyt and ORF50 through interaction with HDAC for K-bZIP to have a temporary repressive effect on the two promoters.
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Affiliation(s)
- Francisco Puerta Martínez
- Department of Microbiology/Research Centers in Minority Institutions (RCMI) Program, Ponce School of Medicine, Ponce, Puerto Rico
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Zhu X, Zhou F, Qin D, Zeng Y, Lv Z, Yao S, Lu C. Human immunodeficiency virus type 1 induces lytic cycle replication of Kaposi's-sarcoma-associated herpesvirus: role of Ras/c-Raf/MEK1/2, PI3K/AKT, and NF-κB signaling pathways. J Mol Biol 2011; 410:1035-51. [PMID: 21763505 DOI: 10.1016/j.jmb.2011.03.055] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2011] [Revised: 03/20/2011] [Accepted: 03/24/2011] [Indexed: 01/13/2023]
Abstract
Human immunodeficiency virus type 1 (HIV-1) infection significantly increases the risk and development of Kaposi's sarcoma (KS) in individuals infected with KS-associated herpesvirus (KSHV). Previously, we reported that HIV-1 Tat protein induced KSHV replication by modulating the Janus kinase/signal transducers and activators of transcription signaling pathway. Here, we further investigated the possible signaling pathways involved in HIV-1-induced reactivation of KSHV. We showed that HIV-1 infection of primary effusion lymphoma cell lines triggered the reactivation of KSHV, as demonstrated by the expression of KSHV replication and transcription activator, the early viral lytic protein vIL-6 and ORF59 and the production of progeny virions. By utilizing microarray gene expression analyses, transfecting a series of dominant negative mutants, and adding pharmacologic inhibitors, we identified a group of diverse cellular signaling proteins and found that HIV-1 infection of BCBL-1 cells activated phosphatidylinositol 3-kinase/AKT (also called protein kinase B, PKB) pathway and inactivated phosphatase and tensin homolog deleted on chromosome ten and glycogen synthase kinase-3β, which partially modulated HIV-1-induced KSHV reactivation. Furthermore, activation of Ras/c-Raf/MAPK/ERK kinase1/2 pathway contributed to HIV-1-induced KSHV replication. Finally, we discovered that HIV-1 infection activated nuclear factor κB signaling, which exhibits an inhibitory effect on KSHV reactivation in BCBL-1 cells. Collectively, our data demonstrated that HIV-1 infection stimulated these cell signaling pathways that, in turn, contributed to KSHV reactivation, which may be of therapeutic value in acquired immunodeficiency syndrome-related KS patients.
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Affiliation(s)
- Xiaolei Zhu
- State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, People's Republic of China
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Histone demethylase JMJD2A regulates Kaposi's sarcoma-associated herpesvirus replication and is targeted by a viral transcriptional factor. J Virol 2011; 85:3283-93. [PMID: 21228229 DOI: 10.1128/jvi.02485-10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The switch between the latency and lytic cycles of Kaposi's sarcoma-associated herpesvirus (KSHV) is accompanied by specific alterations of histone codes. Recently, comprehensive analysis of histone modifications of KSHV showed the deposition of H3K27me3 across the KSHV genome with two specific regions occupied by the heterochromatin marker H3K9me3. Here, we show that knockdown of JMJD2A, an H3K9me3 demethylase, attenuates viral titers, whereas its overexpression increases KSHV reactivation. JMJD2A is localized in regions of latent viral chromosomes that are deficient in the H3K9me3 mark, indicating that JMJD2A may be responsible for the low level of this mark on viral chromatin. The presence of JMJD2A on the latent genome maintains H3K9 in unmethylated form and signals the readiness of specific sets of viral genes to be reactivated. The demethylase activity of JMJD2A is important for KSHV reactivation, because a demethylase-deficient mutant cannot restore the JMJD2A knockdown phenotype. Interestingly, we found that the KSHV encoded K-bZIP associated with JMJD2A, resulting in the inhibition of demethylase activity of JMJD2A both in vivo and in vitro. Inhibition of JMJD2A by K-bZIP is likely due to a physical interaction which blocks substrate accessibility. A consequence of such an inhibition is increasing global levels of H3K9me3 and gene silencing. Consistently, K-bZIP overexpression resulted in a repression of ∼80% of the ≥2-fold differentially regulated genes compared to results for the uninduced control cells. The consequences of K-bZIP targeting JMJD2A during viral replication will be discussed. To our knowledge, this is the first description of a viral product shown to be a potent inhibitor of a host cellular histone demethylase.
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Abstract
The life cycle of Kaposi's sarcoma-associated herpesvirus (KSHV) consists of latent and lytic replication phases. During latent infection, only a limited number of KSHV genes are expressed. However, this phase of replication is essential for persistent infection, evasion of host immune response, and induction of KSHV-related malignancies. KSHV reactivation from latency produces a wide range of viral products and infectious virions. The resulting de novo infection and viral lytic products modulate diverse cellular pathways and stromal microenvironment, which promote the development of Kaposi's sarcoma (KS). The mechanisms controlling KSHV latency and reactivation are complex, involving both viral and host factors, and are modulated by diverse environmental factors. Here, we review the cellular and molecular basis of KSHV latency and reactivation with a focus on the most recent advancements in the field.
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Lefort S, Gravel A, Flamand L. Repression of interferon-α stimulated genes expression by Kaposi's sarcoma-associated herpesvirus K-bZIP protein. Virology 2010; 408:14-30. [DOI: 10.1016/j.virol.2010.07.027] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2009] [Revised: 05/11/2010] [Accepted: 07/16/2010] [Indexed: 12/24/2022]
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Cloutier N, Flamand L. Kaposi sarcoma-associated herpesvirus latency-associated nuclear antigen inhibits interferon (IFN) beta expression by competing with IFN regulatory factor-3 for binding to IFNB promoter. J Biol Chem 2010; 285:7208-21. [PMID: 20048166 DOI: 10.1074/jbc.m109.018838] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Host cells respond to viral infections by synthesizing and producing antiviral molecules such as type I interferons (IFN). The Kaposi sarcoma-associated herpesvirus (KSHV) encodes multiple proteins expressed during the lytic replication cycle that alter the antiviral response of the host. Considering that in Kaposi sarcoma lesions and primary effusion lymphoma cells KSHV is latent in the vast majority of cells, we were interested in determining whether latently expressed viral proteins have the ability to modulate IFN synthesis. The latency-associated nuclear antigen (LANA-1) is a large nuclear protein that plays a role in the establishment and maintenance of latent KSHV episome in the nucleus of infected cells. LANA-1 is also described to modulate the cellular transcription. Here, we report that LANA-1 inhibits IFN-beta transcription and synthesis by competing with the binding of interferon regulatory factor-3 (IRF3) to the IFNB promoter. Using mutants of LANA-1, we have identified the central acidic repeated region as the domain essential for interfering with the binding of IRF3 to the positive regulatory domains I-III of the IFNB promoter. In addition, the nuclear localization of LANA-1 proved essential for IFN-beta inhibition. Thus, LANA-1 interferes with the formation of IFN-beta enhanceosome by competing with the fixation of IRF3 and by inhibiting the expression of the CREB-binding protein. The ability of LANA-1 to inhibit IFNB gene expression highlights a new role for this protein in cellular gene modulation and immune evasion strategies.
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Affiliation(s)
- Nathalie Cloutier
- Laboratory of Virology, Rheumatology and Immunology Research Center, Centre Hospitalier Universitaire de Québec Research Center and Faculty of Medicine, Laval University, Québec City, Québec G1V 4G2, Canada
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Rennekamp AJ, Lieberman PM. Initiation of lytic DNA replication in Epstein-Barr virus: search for a common family mechanism. Future Virol 2010; 5:65-83. [PMID: 22468146 PMCID: PMC3314400 DOI: 10.2217/fvl.09.69] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Herpesviruses are a complex family of dsDNA viruses that are a major cause of human disease. All family members share highly related viral replication proteins, such as DNA polymerase, ssDNA-binding proteins and processivity factors. Consequently, it is generally thought that lytic replication occurs through a common and conserved mechanism. However, considerable evidence indicates that proteins controlling initiation of DNA replication vary greatly among the herepesvirus subfamilies. In this article, we focus on some of the known mechanisms that regulate Epstein-Barr virus lytic-cycle replication, and compare this to other herpesvirus family members. Our reading of the literature leads us to conclude that diverse viral mechanisms generate a common nucleoprotein prereplication structure that can be recognized by a highly conserved family of viral replication enzymes.
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Affiliation(s)
- Andrew J Rennekamp
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA and The University of Pennsylvania, Biomedical Graduate Program in Cell & Molecular Biology, The School of Medicine, Philadelphia, PA 19104, USA, Tel.: +1 215 898 9523, Fax: +1 251 898 0663,
| | - Paul M Lieberman
- The Wistar Institute, 3601 Spruce Street, Philadelphia, PA 19104, USA, Tel.: +1 215 898 9491, Fax: +1 215 898 0663,
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Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 K-bZIP modulates latency-associated nuclear protein-mediated suppression of lytic origin-dependent DNA synthesis. J Virol 2009; 83:8492-501. [PMID: 19553319 DOI: 10.1128/jvi.00922-09] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The original cotransfection replication assay identified eight human herpesvirus 8 (HHV8)-encoded proteins required for origin-dependent lytic DNA replication. Previously, we demonstrated that under conditions where K-Rta is overexpressed, a K-bZIP knockout bacmid displayed an aberrant subcellular localization pattern for the latency-associated nuclear protein (LANA). Additionally, these same studies demonstrated that K-bZIP interacts with LANA in the absence of K-Rta and that K-bZIP does not directly participate in, but may facilitate, the initiation of lytic DNA synthesis. We developed a modification of the transient cotransfection replication assay wherein both lytic (oriLyt) and latent (terminal repeat) DNA replication are evaluated simultaneously. We now show that LANA represses origin-dependent lytic DNA replication in a dose dependent manner when added to the cotransfection replication assay. This repression was overcome by increasing amounts of a K-bZIP expression plasmid in the cotransfection mixture or by dominant-negative inhibition of the interaction of LANA with K-bZIP by the overexpression of the K-bZIP-LANA binding domain. Chromatin immunoprecipitation assays show that LANA interacts with oriLyt in the absence of K-bZIP expression, suggesting that suppression of lytic replication by LANA is mediated by direct binding. The interaction of K-bZIP with oriLyt was dependent upon the expression of LANA; however, LANA interacted with oriLyt independently of K-bZIP expression. These data suggest that the interaction of LANA with K-bZIP modulates lytic and latent replication and that K-bZIP facilitates lytic DNA replication and modulates the switch from the latent phase of the virus.
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