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Herold K, Ruffin A, Chmura JC, Dellomo AJ, Ehrlich ES. Kaposi's sarcoma herpesvirus viral FLICE inhibitory protein modulates A20 deubiquitinase activity. Access Microbiol 2024; 6:000625.v4. [PMID: 38868372 PMCID: PMC11165616 DOI: 10.1099/acmi.0.000625.v4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 03/19/2024] [Indexed: 06/14/2024] Open
Abstract
KSHV viral FLICE inhibitory protein (vFLIP) is a potent activator of NF-κB signalling and an inhibitor of apoptosis and autophagy. Inhibition of vFLIP function and NF-κB signalling promotes lytic reactivation. Here we provide evidence for a novel function of vFLIP through inhibition of the deubiquitinating (DUB) activity of the negative regulator, A20. We demonstrate direct interaction of vFLIP with Itch and A20 and provide evidence for subsequent loss of A20 DUB activity. Our results provide further insight into the function of vFLIP in the regulation of NF-κB signalling.
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Affiliation(s)
- Kevin Herold
- Department of Biological Sciences, Towson University, Towson, MD, USA
| | - Ayana Ruffin
- Department of Biological Sciences, Towson University, Towson, MD, USA
- Cancer Reserach Institute, Emory University, Atlanta, GA, USA
| | | | - Anna J. Dellomo
- Department of Biological Sciences, Towson University, Towson, MD, USA
| | - Elana S. Ehrlich
- Department of Biological Sciences, Towson University, Towson, MD, USA
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Nakajima KI, Inagaki T, Espera JM, Izumiya Y. Kaposi's sarcoma-associated herpesvirus (KSHV) LANA prevents KSHV episomes from degradation. J Virol 2024; 98:e0126823. [PMID: 38240588 PMCID: PMC10878079 DOI: 10.1128/jvi.01268-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 12/14/2023] [Indexed: 02/21/2024] Open
Abstract
Protein knockdown with an inducible degradation system is a powerful tool for studying proteins of interest in living cells. Here, we adopted the auxin-inducible degron (AID) approach to detail Kaposi's sarcoma-associated herpesvirus (KSHV) latency-associated nuclear antigen (LANA) function in latency maintenance and inducible viral lytic gene expression. We fused the mini-auxin-inducible degron (mAID) tag at the LANA N-terminus with KSHV bacterial artificial chromosome 16 recombination, and iSLK cells were stably infected with the recombinant KSHV encoding mAID-LANA. Incubation with 5-phenyl-indole-3-acetic acid, a derivative of natural auxin, rapidly degraded LANA within 1.5 h. In contrast to our hypothesis, depletion of LANA alone did not trigger lytic reactivation but rather decreased inducible lytic gene expression when we stimulated reactivation with a combination of ORF50 protein expression and sodium butyrate. Decreased overall lytic gene induction seemed to be associated with a rapid loss of KSHV genomes in the absence of LANA. The rapid loss of viral genomic DNA was blocked by a lysosomal inhibitor, chloroquine. Furthermore, siRNA-mediated knockdown of cellular innate immune proteins, cyclic AMP-GMP synthase (cGAS) and simulator of interferon genes (STING), and other autophagy-related genes rescued the degradation of viral genomic DNA upon LANA depletion. Reduction of the viral genome was not observed in 293FT cells that lack the expression of cGAS. These results suggest that LANA actively prevents viral genomic DNA from sensing by cGAS-STING signaling axis, adding novel insights into the role of LANA in latent genome maintenance.IMPORTANCESensing of pathogens' components is a fundamental cellular immune response. Pathogens have therefore evolved strategies to evade such cellular immune responses. KSHV LANA is a multifunctional protein and plays an essential role in maintaining the latent infection by tethering viral genomic DNA to the host chromosome. We adopted the inducible protein knockdown approach and found that depletion of LANA induced rapid degradation of viral genomic DNA, which is mediated by innate immune DNA sensors and autophagy pathway. These observations suggest that LANA may play a role in hiding KSHV episome from innate immune DNA sensors. Our study thus provides new insights into the role of LANA in latency maintenance.
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Affiliation(s)
- Ken-ichi Nakajima
- Department of Dermatology, School of Medicine, University of California Davis, Sacramento, California, USA
| | - Tomoki Inagaki
- Department of Dermatology, School of Medicine, University of California Davis, Sacramento, California, USA
| | - Jonna Magdallene Espera
- Department of Dermatology, School of Medicine, University of California Davis, Sacramento, California, USA
| | - Yoshihiro Izumiya
- Department of Dermatology, School of Medicine, University of California Davis, Sacramento, California, USA
- Department of Biochemistry and Molecular Medicine, School of Medicine, University of California Davis, Sacramento, California, USA
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Ivanišević V, Žilić L, Čunko M, Fadiga H, Munitić I, Jurak I. RNA Editing-Dependent and -Independent Roles of Adenosine Deaminases Acting on RNA Proteins in Herpesvirus Infection-Hints on Another Layer of Complexity. Viruses 2023; 15:2007. [PMID: 37896783 PMCID: PMC10611208 DOI: 10.3390/v15102007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 09/24/2023] [Accepted: 09/25/2023] [Indexed: 10/29/2023] Open
Abstract
The Adenosine Deaminases Acting on RNA (ADAR) catalyze the posttranscriptional deamination of adenosine residues to inosine in double-stranded RNAs (dsRNAs, A-to-I editing), preventing the overactivation of dsRNA sensor molecules and interferons. RNA editing is the cornerstone of innate immunity that distinguishes between self and non-self (virus), and it is essential for normal regulation of cellular homeostasis. Although much is already known about the role of ADAR proteins in RNA virus infection, the role of ADAR proteins in herpesvirus infection remains largely unexplored. In this review, we provide several lines of evidence from studies of different herpesviruses for another level of complexity in regulating the already intricate biphasic life cycle of herpesviruses.
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Affiliation(s)
| | | | | | | | | | - Igor Jurak
- Department of Biotechnology, University of Rijeka, 51000 Rijeka, Croatia (L.Ž.)
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Schlesinger M, McDonald C, Ahuja A, Canete CA, Nuñez del Prado Z, Naipauer J, Lampidis T, Mesri EA. Glucose and mannose analogs inhibit KSHV replication by blocking N-glycosylation and inducing the unfolded protein response. J Med Virol 2023; 95:e28314. [PMID: 36380418 PMCID: PMC9839548 DOI: 10.1002/jmv.28314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 11/10/2022] [Accepted: 11/11/2022] [Indexed: 11/17/2022]
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent for Kaposi's sarcoma (KS), an HIV/AIDS-associated malignancy. Effective treatments against KS remain to be developed. The sugar analog 2-deoxy- d-glucose (2-DG) is an anticancer agent that is well-tolerated and safe in patients and was recently demonstrated to be a potent antiviral, including KSHV and severe acute respiratory syndrome coronavirus 2. Because 2-DG inhibits glycolysis and N-glycosylation, identifying its molecular targets is challenging. Here we compare the antiviral effect of 2-DG with 2-fluoro-deoxy- d-glucose, a glycolysis inhibitor, and 2-deoxy-fluoro- d-mannose (2-DFM), a specific N-glycosylation inhibitor. At doses similar to those clinically achievable with 2-DG, the three drugs impair KSHV replication and virion production in iSLK.219 cells via downregulation of viral structural glycoprotein expression (K8.1 and gB), being 2-DFM the most potent KSHV inhibitor. Consistently with the higher potency of 2-DFM, we found that d-mannose rescues KSHV glycoprotein synthesis and virus production, indicating that inhibition of N-glycosylation is the main antiviral target using d-mannose competition experiments. Suppression of N-glycosylation by the sugar drugs triggers ER stress. It activates the host unfolded protein response (UPR), counteracting KSHV-induced inhibition of the protein kinase R-like endoplasmic reticulum kinase branch, particularly activating transcription factor 4 and C/EBP homologous protein expression. Finally, we demonstrate that sugar analogs induce autophagy (a prosurvival mechanism) and, thus, inhibit viral replication playing a protective role against KSHV-induced cell death, further supporting their direct antiviral effect and potential therapeutic use. Our work identifies inhibition of N-glycosylation leading to ER stress and UPR as an antienveloped virus target and sugar analogs such as 2-DG and the newly identified 2-DFM as antiviral drugs.
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Affiliation(s)
- Mariana Schlesinger
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Miami Center for AIDS Research, Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Christian McDonald
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Miami Center for AIDS Research, Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Anuj Ahuja
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Miami Center for AIDS Research, Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Carolina Alvarez Canete
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Miami Center for AIDS Research, Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Zelmira Nuñez del Prado
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Miami Center for AIDS Research, Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Julian Naipauer
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Miami Center for AIDS Research, Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33136,UM-CFAR/ SCCC Argentina Consortium for AIDS Malignancies,Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), CONICET-Universidad de Buenos Aires, Buenos Aires, Argentina,To whom correspondence should be addressed: Julian Naipauer, Ph.D, IFIBYNE – CONICET – UBA, Pabellón IFIByNE, Ingreso por Av. Costanera, Rafael Obligado – Ciudad Universitaria, CABA – Buenos Aires,
| | - Theodore Lampidis
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Department of Cell Biology, University of Miami Miller School of Medicine, Miami, FL 33136
| | - Enrique A. Mesri
- Tumor Biology Program, Sylvester Comprehensive Cancer Center,Miami Center for AIDS Research, Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL 33136,UM-CFAR/ SCCC Argentina Consortium for AIDS Malignancies
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O’Connor CM, Sen GC. Innate Immune Responses to Herpesvirus Infection. Cells 2021; 10:2122. [PMID: 34440891 PMCID: PMC8394705 DOI: 10.3390/cells10082122] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 08/13/2021] [Accepted: 08/15/2021] [Indexed: 12/24/2022] Open
Abstract
Infection of a host cell by an invading viral pathogen triggers a multifaceted antiviral response. One of the most potent defense mechanisms host cells possess is the interferon (IFN) system, which initiates a targeted, coordinated attack against various stages of viral infection. This immediate innate immune response provides the most proximal defense and includes the accumulation of antiviral proteins, such as IFN-stimulated genes (ISGs), as well as a variety of protective cytokines. However, viruses have co-evolved with their hosts, and as such, have devised distinct mechanisms to undermine host innate responses. As large, double-stranded DNA viruses, herpesviruses rely on a multitude of means by which to counter the antiviral attack. Herein, we review the various approaches the human herpesviruses employ as countermeasures to the host innate immune response.
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Affiliation(s)
- Christine M. O’Connor
- Department of Genomic Medicine, Infection Biology Program, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44106, USA
| | - Ganes C. Sen
- Department of Inflammation and Immunity, Infection Biology Program, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44106, USA
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Brackett K, Mungale A, Lopez-Isidro M, Proctor DA, Najarro G, Arias C. CRISPR Interference Efficiently Silences Latent and Lytic Viral Genes in Kaposi's Sarcoma-Associated Herpesvirus-Infected Cells. Viruses 2021; 13:783. [PMID: 33924938 PMCID: PMC8146339 DOI: 10.3390/v13050783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Revised: 04/22/2021] [Accepted: 04/22/2021] [Indexed: 12/28/2022] Open
Abstract
Uncovering viral gene functions requires the modulation of gene expression through overexpression or loss-of-function. CRISPR interference (CRISPRi), a modification of the CRISPR-Cas9 gene editing technology, allows specific and efficient transcriptional silencing without genetic ablation. CRISPRi has been used to silence eukaryotic and prokaryotic genes at the single-gene and genome-wide levels. Here, we report the use of CRISPRi to silence latent and lytic viral genes, with an efficiency of ~80-90%, in epithelial and B-cells carrying multiple copies of the Kaposi's sarcoma-associated herpesvirus (KSHV) genome. Our results validate CRISPRi for the analysis of KSHV viral elements, providing a functional genomics tool for studying virus-host interactions.
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Affiliation(s)
- Kevin Brackett
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA; (K.B.); (A.M.); (M.L.-I.); (D.A.P.); (G.N.)
| | - Ameera Mungale
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA; (K.B.); (A.M.); (M.L.-I.); (D.A.P.); (G.N.)
| | - Mary Lopez-Isidro
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA; (K.B.); (A.M.); (M.L.-I.); (D.A.P.); (G.N.)
| | - Duncan A. Proctor
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA; (K.B.); (A.M.); (M.L.-I.); (D.A.P.); (G.N.)
| | - Guillermo Najarro
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA; (K.B.); (A.M.); (M.L.-I.); (D.A.P.); (G.N.)
| | - Carolina Arias
- Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, CA 93106, USA; (K.B.); (A.M.); (M.L.-I.); (D.A.P.); (G.N.)
- Neuroscience Research Institute, University of California, Santa Barbara, CA 93106, USA
- Center for Stem Cell Biology and Engineering, University of California, Santa Barbara, CA 93106, USA
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Guven-Maiorov E, Tsai CJ, Ma B, Nussinov R. Interface-Based Structural Prediction of Novel Host-Pathogen Interactions. Methods Mol Biol 2019; 1851:317-335. [PMID: 30298406 PMCID: PMC8192064 DOI: 10.1007/978-1-4939-8736-8_18] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
About 20% of the cancer incidences worldwide have been estimated to be associated with infections. However, the molecular mechanisms of exactly how they contribute to host tumorigenesis are still unknown. To evade host defense, pathogens hijack host proteins at different levels: sequence, structure, motif, and binding surface, i.e., interface. Interface similarity allows pathogen proteins to compete with host counterparts to bind to a target protein, rewire physiological signaling, and result in persistent infections, as well as cancer. Identification of host-pathogen interactions (HPIs)-along with their structural details at atomic resolution-may provide mechanistic insight into pathogen-driven cancers and innovate therapeutic intervention. HPI data including structural details is scarce and large-scale experimental detection is challenging. Therefore, there is an urgent and mounting need for efficient and robust computational approaches to predict HPIs and their complex (bound) structures. In this chapter, we review the first and currently only interface-based computational approach to identify novel HPIs. The concept of interface mimicry promises to identify more HPIs than complete sequence or structural similarity. We illustrate this concept with a case study on Kaposi's sarcoma herpesvirus (KSHV) to elucidate how it subverts host immunity and helps contribute to malignant transformation of the host cells.
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Affiliation(s)
- Emine Guven-Maiorov
- Cancer and Inflammation Program, Leidos Biomedical Research, Inc. Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Chung-Jung Tsai
- Cancer and Inflammation Program, Leidos Biomedical Research, Inc. Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Buyong Ma
- Cancer and Inflammation Program, Leidos Biomedical Research, Inc. Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD, USA
| | - Ruth Nussinov
- Cancer and Inflammation Program, Leidos Biomedical Research, Inc. Frederick National Laboratory for Cancer Research, National Cancer Institute, Frederick, MD, USA.
- Department of Human Genetics and Molecular Medicine, Sackler Inst. of Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.
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EBV and KSHV Infection Dysregulates Autophagy to Optimize Viral Replication, Prevent Immune Recognition and Promote Tumorigenesis. Viruses 2018; 10:v10110599. [PMID: 30384495 PMCID: PMC6266050 DOI: 10.3390/v10110599] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/22/2018] [Accepted: 10/30/2018] [Indexed: 12/12/2022] Open
Abstract
Autophagy is a catabolic process strongly involved in the immune response, and its dysregulation contributes to the onset of several diseases including cancer. The human oncogenic gammaherpesviruses, Epstein—Barr virus (EBV) and Kaposi’s sarcoma-associated herpesvirus (KSHV), manipulate autophagy, either during the de novo infection or during the lytic reactivation, in naturally latently-infected lymphoma cells. In particular, the gammaherpesvirus infection reduces autophagy in immune cells, such as monocytes, resulting in the impairment of cell survival and cell differentiation into dendritic cells (DCs), which are essential for initiating and regulating the immune response. In the case of EBV, the reduction of autophagy in these cells, leading to p62 accumulation, activated the p62-NRF2-antioxidant response, reducing ROS, and further inhibiting autophagy. KSHV inhibits autophagy in monocytes by de-phosphorylating JNK2, altering the calpains–calpastatin balance and increasing the calpain activity responsible for the cleavage of ATG5. To further impair the immune response, KSHV also inhibits autophagy in differentiated DCs by hyper-phosphorylating STAT3. Conversely, when the lytic cycle is induced in vitro in latently-infected lymphoma B cells, both EBV and KSHV promote autophagy to enhance their replication, although the final autophagic steps are blocked through the down-regulation of Rab7. This strategy allows viruses to avoid the destructive environment of lysosomes, and to exploit the autophagic machinery for intracellular transportation. EBV and KSHV encode for proteins that may either inhibit or promote autophagy and, in addition, they can modulate the cellular pathways that control this process. In this review we will discuss the findings that indicate that autophagy is dysregulated by gammaherpesvirus to promote immune suppression, facilitate viral replication and contribute to the onset and maintenance of gammaherpesvirus-associated malignancies.
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Kaposi's Sarcoma-Associated Herpesvirus mRNA Accumulation in Nuclear Foci Is Influenced by Viral DNA Replication and Viral Noncoding Polyadenylated Nuclear RNA. J Virol 2018; 92:JVI.00220-18. [PMID: 29643239 DOI: 10.1128/jvi.00220-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 04/04/2018] [Indexed: 12/20/2022] Open
Abstract
Kaposi's sarcoma-associated herpesvirus (KSHV), like other herpesviruses, replicates within the nuclei of its human cell host and hijacks host machinery for expression of its genes. The activities that culminate in viral DNA synthesis and assembly of viral proteins into capsids physically concentrate in nuclear areas termed viral replication compartments. We sought to better understand the spatiotemporal regulation of viral RNAs during the KSHV lytic phase by examining and quantifying the subcellular localization of select viral transcripts. We found that viral mRNAs, as expected, localized to the cytoplasm throughout the lytic phase. However, dependent on active viral DNA replication, viral transcripts also accumulated in the nucleus, often in foci in and around replication compartments, independent of the host shutoff effect. Our data point to involvement of the viral long noncoding polyadenylated nuclear (PAN) RNA in the localization of an early, intronless viral mRNA encoding ORF59-58 to nuclear foci that are associated with replication compartments.IMPORTANCE Late in the lytic phase, mRNAs from Kaposi's sarcoma-associated herpesvirus accumulate in the host cell nucleus near viral replication compartments, centers of viral DNA synthesis and virion production. This work contributes spatiotemporal data on herpesviral mRNAs within the lytic host cell and suggests a mechanism for viral RNA accumulation. Our findings indicate that the mechanism is independent of the host shutoff effect and splicing but dependent on active viral DNA synthesis and in part on the viral noncoding RNA, PAN RNA. PAN RNA is essential for the viral life cycle, and its contribution to the nuclear accumulation of viral messages may facilitate propagation of the virus.
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Abstract
As the notion of small molecule targeting of regulatory viral and cellular RNAs gathers momentum, understanding their structure, and variations thereof, in the appropriate biological context will play a critical role. This is especially true of the ∼1100-nt polyadenylated nuclear (PAN) long non-coding (lnc) RNA of Kaposi's sarcoma herpesvirus (KSHV), whose interaction with viral and cellular proteins is central to lytic infection. Nuclear accumulation of PAN RNA is mediated via a unique triple helical structure at its 3' terminus (within the expression and nuclear retention element, or ENE) which protects it from deadenylation-dependent decay. Additionally, significant levels of PAN RNA have been reported in both the cytoplasm of KSHV-infected cells and in budding virions, leading us to consider which viral and host proteins might associate with, or dissociate from, this lncRNA during its "journey" through the cell. By combining the power of SHAPE-mutational profiling (SHAPE-MaP) with large scale virus culture facilities of the National Cancer Institute, Frederick MD, Sztuba-Solinska et al. have provide the first detailed description of KSHV PAN nucleoprotein complexes in multiple biological contexts, complementing this by mapping sites of recombinant KSHV proteins on an in vitro-synthesized, polyadenylated counterpart.
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Affiliation(s)
- Joanna Sztuba-Solinska
- a Frederick National Laboratory for Cancer Research, Basic Research Laboratory , National Cancer Institute , Frederick , MD , USA
| | - Stuart F J Le Grice
- b Basic Research Laboratory, National Cancer Institute , Frederick , MD , USA
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Kaposi's Sarcoma-Associated Herpesvirus Increases PD-L1 and Proinflammatory Cytokine Expression in Human Monocytes. mBio 2017; 8:mBio.00917-17. [PMID: 29018115 PMCID: PMC5635685 DOI: 10.1128/mbio.00917-17] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Kaposi’s sarcoma-associated herpesvirus (KSHV) is associated with the human malignancy Kaposi’s sarcoma and the lymphoproliferative disorders primary effusion lymphoma and multicentric Castleman’s disease. KSHV establishes lytic infection of monocytes in vivo, which may represent an important cellular reservoir during KS disease progression. KS tumors consist of latently infected endothelial cells; however, lytic phase gene products are important for KS onset. Early KS lesion progression is driven by proinflammatory cytokines supplied by immune cell infiltrates including T cells and monocytes. KSHV-infected monocytes may supply the lytic viral products and the inflammatory milieu conducive to KS tumor progression. To establish successful infection, KSHV extensively modulates the host immune system. KSHV antigens activate both innate and adaptive immune responses including KSHV-specific T cells, but lifelong infection is still established. Programmed death ligand 1 (PD-L1) is a prosurvival cell surface protein that suppresses T-cell-mediated killing. PD-L1 is variably present on various tumor cells and is a targetable marker for cancer treatment. We show that KSHV infection of human monocytes increases PD-L1 expression and transcription in a dose-dependent manner. We also saw evidence of lytic gene expression in the KSHV-infected monocytes. Intact KSHV is needed for full PD-L1 response in human monocytes. KSHV induces a general proinflammatory cytokine milieu including interleukins 1α, 1β, and 6, which have been implicated in early KS lesion progression. KSHV-mediated PD-L1 increase may represent a novel mechanism of KSHV-mediated immune modulation to allow for virus survival and eventually malignant progression. KSHV is the etiologic agent of Kaposi’s sarcoma and the lymphoproliferative disorders primary effusion lymphoma and multicentric Castleman’s disease. Programmed death ligand 1 (PD-L1) is an immunosuppressive cell surface marker that inhibits T cell activation. We report that KSHV infection of primary human monocytes upregulates PD-L1 transcription and protein expression. Analysis of the cytokine and chemokine milieu following KSHV infection of monocytes revealed that KSHV induces interleukins 1α, 1β, and 6, all of which have been implicated in KS development. Our work has identified another potential immune evasion strategy for KSHV and a potential target for immunotherapy of KSHV-derived disease.
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Kaposi's Sarcoma-Associated Herpesvirus Utilizes and Manipulates RNA N 6-Adenosine Methylation To Promote Lytic Replication. J Virol 2017; 91:JVI.00466-17. [PMID: 28592530 DOI: 10.1128/jvi.00466-17] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Accepted: 05/26/2017] [Indexed: 12/20/2022] Open
Abstract
N6-adenosine methylation (m6A) is the most common posttranscriptional RNA modification in mammalian cells. We found that most transcripts encoded by the Kaposi's sarcoma-associated herpesvirus (KSHV) genome undergo m6A modification. The levels of m6A-modified mRNAs increased substantially upon stimulation for lytic replication. The blockage of m6A inhibited splicing of the pre-mRNA encoding the replication transcription activator (RTA), a key KSHV lytic switch protein, and halted viral lytic replication. We identified several m6A sites in RTA pre-mRNA crucial for splicing through interactions with YTH domain containing 1 (YTHDC1), an m6A nuclear reader protein, in conjunction with serine/arginine-rich splicing factor 3 (SRSF3) and SRSF10. Interestingly, RTA induced m6A and enhanced its own pre-mRNA splicing. Our results not only demonstrate an essential role of m6A in regulating RTA pre-mRNA splicing but also suggest that KSHV has evolved a mechanism to manipulate the host m6A machinery to its advantage in promoting lytic replication.IMPORTANCE KSHV productive lytic replication plays a pivotal role in the initiation and progression of Kaposi's sarcoma tumors. Previous studies suggested that the KSHV switch from latency to lytic replication is primarily controlled at the chromatin level through histone and DNA modifications. The present work reports for the first time that KSHV genome-encoded mRNAs undergo m6A modification, which represents a new mechanism at the posttranscriptional level in the control of viral replication.
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Guven-Maiorov E, Tsai CJ, Nussinov R. Pathogen mimicry of host protein-protein interfaces modulates immunity. Semin Cell Dev Biol 2016; 58:136-45. [DOI: 10.1016/j.semcdb.2016.06.004] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Revised: 06/02/2016] [Accepted: 06/06/2016] [Indexed: 12/21/2022]
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