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Epstein-Barr Virus (EBV) Tegument Protein BGLF2 Suppresses Type I Interferon Signaling To Promote EBV Reactivation.

ABSTRACT: Interferon alpha (IFN-?) and IFN-? are type I IFNs that are induced by virus infection and are important in the host's innate antiviral response. EBV infection activates multiple cell signaling pathways, resulting in the production of type I IFN which inhibits EBV infection and virus-induced B-cell transformation. We reported previously that EBV tegument protein BGLF2 activates p38 and enhances EBV reactivation. To further understand the role of BGLF2 in EBV infection, we used mass spectrometry to identify cellular proteins that interact with BGLF2. We found that BGLF2 binds to Tyk2 and confirmed this interaction by coimmunoprecipitation. BGLF2 blocked type I IFN-induced Tyk2, STAT1, and STAT3 phosphorylation and the expression of IFN-stimulated genes (ISGs) IRF1, IRF7, and MxA. In contrast, BGLF2 did not inhibit STAT1 phosphorylation induced by IFN-?. Deletion of the carboxyl-terminal 66 amino acids of BGLF2 reduced the ability of the protein to repress type I IFN signaling. Treatment of gastric carcinoma and Raji cells with IFN-? blocked BZLF1 expression and EBV reactivation; however, expression of BGLF2 reduced the ability of IFN-? to inhibit BZLF1 expression and enhanced EBV reactivation. In summary, EBV BGLF2 interacts with Tyk2, inhibiting Tyk2, STAT1, and STAT3 phosphorylation and impairs type I IFN signaling; BGLF2 also counteracts the ability of IFN-? to suppress EBV reactivation.IMPORTANCE Type I interferons are important for controlling virus infection. We have found that the Epstein-Barr virus (EBV) BGLF2 tegument protein binds to a protein in the type I interferon signaling pathway Tyk2 and inhibits the expression of genes induced by type I interferons. Treatment of EBV-infected cells with type I interferon inhibits reactivation of the virus, while expression of EBV BGLF2 reduces the ability of type I interferon to inhibit virus reactivation. Thus, a tegument protein delivered to cells during virus infection inhibits the host's antiviral response and promotes virus reactivation of latently infected cells. Therefore, EBV BGLF2 might protect virus-infected cells from the type I interferon response in cells undergoing lytic virus replication.

SUBMITTER: Liu X

PROVIDER: S-EPMC7269453 | biostudies-literature | 2020 May

REPOSITORIES: biostudies-literature

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Epstein-Barr Virus (EBV) Tegument Protein BGLF2 Suppresses Type I Interferon Signaling To Promote EBV Reactivation.

Liu XueQiao X Sadaoka Tomohiko T Krogmann Tammy T Cohen Jeffrey I JI

Journal of virology 20200518 11

Interferon alpha (IFN-α) and IFN-β are type I IFNs that are induced by virus infection and are important in the host's innate antiviral response. EBV infection activates multiple cell signaling pathways, resulting in the production of type I IFN which inhibits EBV infection and virus-induced B-cell transformation. We reported previously that EBV tegument protein BGLF2 activates p38 and enhances EBV reactivation. To further understand the role of BGLF2 in EBV infection, we used mass spectrometry ...[more]

PMID: 32213613

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Project description:Generating oxidative stress is a critical mechanism by which host cells defend against infection by pathogenic microorganisms. Radiation resistance is a critical problem in radiotherapy against cancer. Epstein-Barr virus (EBV) is a cancer-causing virus and its reactivation plays an important role in the development of EBV-related tumors. This study aimed to explore the inner relationship and regulatory mechanism among oxidative stress, EBV reactivation, and radioresistance and to identify new molecular subtyping models and treatment strategies to improve the therapeutic effects of radiotherapy. Methods: ROS, NADP+/NADPH, and GSSG/GSH were detected to evaluate the oxidative stress of cells. 8-OHdG is a reliable oxidative stress marker to evaluate the oxidative stress in patients. Its concentration in serum was detected using an ELISA method and in biopsies was detected using IHC. qPCR array was performed to evaluate the expression of essential oxidative stress genes. qPCR, Western blot, and IHC were used to measure the level of EBV reactivation in vitro and in vivo. A Rta-IgG ELISA kit and EBV DNA detection kit were used to analyze the reactivation of EBV in serum from NPC patients. NPC tumor tissue microarrays was used to investigate the prognostic role of oxidative stress and EBV reactivation. Radiation resistance was evaluated by a colony formation assay. Xenografts were treated with NAC, radiation, or a combination of NAC and radiation. EBV DNA load of tumor tissue was evaluated using an EBV DNA detection kit. Oxidative stress, EBV reactivation, and the apoptosis rate in tumor tissues were detected by using 8-OHdG, EAD, and TUNEL assays, respectively. Results: We found that EBV can induce high oxidative stress, which promotes its reactivation and thus leads to radioresistance. Basically, EBV caused NPC cells to undergo a process of 'Redox Resetting' to acquire a new redox status with higher levels of ROS accumulation and stronger antioxidant systems by increasing the expression of the ROS-producing enzyme, NOX2, and the cellular master antioxidant regulator, Nrf2. Also, EBV encoded driving protein LMP1 promotes EBV reactivation through production of ROS. Furthermore, high oxidative stress and EBV reactivation were positively associated with poor overall survival of patients following radiation therapy and were significant related to NPC patients' recurrence and clinical stage. By decreasing oxidative stress using an FDA approved antioxidant drug, NAC, sensitivity of tumors to radiation was increased. Additionally, 8-OHdG and EBV DNA could be dual prognostic markers for NPC patients. Conclusions: Oxidative stress mediates EBV reactivation and leads to radioresistance. Targeting oxidative stress can provide therapeutic benefits to cancer patients with radiation resistance. Clinically, we, for the first time, generated a molecular subtyping model for NPC relying on 8-OHdG and EBV DNA level. These dual markers could identify patients who are at a high risk of poor outcomes but who might benefit from the sequential therapy of reactive oxygen blockade followed by radiation therapy, which provides novel perspectives for the precise treatment of NPC.

Project description:BackgroundEpstein-Barr virus (EBV) is a universal herpes virus which can cause a life-long and largely asymptomatic infection in the human population. However, the exact pathogenesis of the EBV infection is not well known.ObjectiveA comprehensive bioinformatics prediction was carried out for investigating the molecular properties of the BGLF2 and to afford a foundation for future research of the role and instrument of BGLF2 in the course of EBV infection.Materials and methodsA 1011-base-pair sequence of BGLF2 gene from the Epstein-Barr virus (EBV) Akata strain genome was amplified using polymerase chain reaction and was further characterized by cloning, sequencing, and subcellular localization in the COS-7 cells.ResultsThe bioinformatics analysis demonstrated that EBV BGLF2 gene encodes a putative BGLF2 polypeptide which contains a conservative Herpes_UL16 domain. It was established that the polypeptide shows a close relationship with the Herpes UL16 tegument protein family and is extremely conserved among its homologues proteins encoded by UL16 genes. Multiple sequence alignments of the nucleic acid and amino acid sequence showed that the gene product of EBV BGLF2 contains a comparatively higher homology with the BGLF2-like proteins of the subfamily Gammaherpesvirinae than that of other subfamilies of the herpes virus. Moreover, the phylogenetic analyses suggested that EBV BGLF2 has a close genetic relationship with the member of Gammaherpesvirinae; in particular with the members of Cercopithecine herpesvirus 15 and Callitrichine herpesvirus 3. An antigen epitope analysis indicated that BGLF2 contains several potential B-cell epitopes. In addition, the secondary structure, as well as the three dimensional structure prediction suggests that BGLF2 consists of the both α-helix and β-strand. Besides, the subcellular localization prediction revealed that BGLF2 localizes in both nucleus and cytoplasm.ConclusionsIllustrating the relevance of the molecular properties and genetic evolution of EBV, BGLF2 will offer the perspectives for further study on the role and mechanism of the BGLF2 in course of EBV infection. These works will also conduct our understanding of the EBV at the molecular level as well as enriching the herpesvirus database.

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Epstein-Barr Virus (EBV) Tegument Protein BGLF2 Suppresses Type I Interferon Signaling To Promote EBV Reactivation.

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Epstein-Barr Virus (EBV) Tegument Protein BGLF2 Suppresses Type I Interferon Signaling To Promote EBV Reactivation.

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