scholarly journals Epstein-Barr Virus Immediate-Early Protein BRLF1 Induces the Lytic Form of Viral Replication through a Mechanism Involving Phosphatidylinositol-3 Kinase Activation

2001 ◽  
Vol 75 (13) ◽  
pp. 6135-6142 ◽  
Author(s):  
Catherine Dayle Darr ◽  
Amy Mauser ◽  
Shannon Kenney
Keyword(s):  
Viral Replication ◽  
Transcriptional Activation ◽  
Epstein Barr Virus ◽  
Adenovirus Vector ◽  
Pi3 Kinase ◽  
Immediate Early ◽  
Kinase Activation ◽  
Barr Virus ◽  
Epstein Barr ◽  
Phosphatidylinositol 3

ABSTRACT Expression of the Epstein-Barr virus (EBV) immediate-early (IE) protein BRLF1 induces the lytic form of viral replication in most EBV-positive cell lines. BRLF1 is a transcriptional activator that binds directly to a GC-rich motif present in some EBV lytic gene promoters. However, BRLF1 activates transcription of the other IE protein, BZLF1, through an indirect mechanism which we previously showed to require activation of the stress mitogen-activated protein kinases. Here we demonstrate that BRLF1 activates phosphatidylinositol-3 (PI3) kinase signaling in host cells. We show that the specific PI3 kinase inhibitor, LY294002, completely abrogates the ability of a BRLF1 adenovirus vector to induce the lytic form of EBV infection, while not affecting lytic infection induced by a BZLF1 adenovirus vector. Furthermore, we demonstrate that the requirement for PI3 kinase activation in BRLF1-induced transcriptional activation is promoter dependent. BRLF1 activation of the SM early promoter (which occurs through a direct binding mechanism) does not require PI3 kinase activation, whereas activation of the IE BZLF1 and early BMRF1 promoters requires PI3 kinase activation. Thus, there are clearly two separate mechanisms by which BRLF1 induces transcriptional activation.

scholarly journals Epstein-Barr Virus Immediate-Early Protein BZLF1 Is SUMO-1 Modified and Disrupts Promyelocytic Leukemia Bodies

2001 ◽  
Vol 75 (5) ◽  
pp. 2388-2399 ◽  
Author(s):  
Amy L. Adamson ◽  
Shannon Kenney
Keyword(s):  
Cell Lines ◽  
Transcriptional Activation ◽  
Epstein Barr Virus ◽  
Promyelocytic Leukemia ◽  
Lytic Replication ◽  
Immediate Early ◽  
Barr Virus ◽  
Early Protein ◽  
Pml Bodies ◽  
Epstein Barr

ABSTRACT Although the immediate-early proteins of both herpes simplex virus (HSV) and cytomegalovirus (CMV) are known to modify promyelocytic leukemia (PML) (ND10) bodies in the nucleus of the host cell, it has been unclear whether lytic infection with gamma herpesviruses induces a similar effect. The PML protein is induced by interferon, involved in major histocompatibility complex class I presentation, and necessary for certain types of apoptosis. Therefore, it is likely that PML bodies function in an antiviral capacity. SUMO-1 modification of PML is known to be required for the formation of PML bodies. To examine whether Epstein-Barr virus (EBV) lytic replication interferes with PML bodies, we expressed the EBV immediate-early genes BZLF1 (Z) and BRLF1 (R) in EBV-positive cell lines and examined PML localization. Both Z and R expression resulted in PML dispersion in EBV-positive cells. Z but not R expression is sufficient to disrupt PML bodies in EBV-negative cell lines. We show that dispersion of PML bodies by Z requires a portion of the transcriptional activation domain of Z but not the DNA-binding function. As was previously reported for the HSV-1 ICP0 and CMV IE1 proteins, Z reduces the amount of SUMO-1-modified PML. We also found that Z itself is SUMO-1 modified (through amino acid 12) and that Z competes with PML for limiting amounts of SUMO-1. These results suggest that disruption of PML bodies is important for efficient lytic replication of EBV. Furthermore, Z may potentially alter the function of a variety of cellular proteins by inhibiting SUMO-1 modification.

scholarly journals Use of Adenovirus Vectors Expressing Epstein-Barr Virus (EBV) Immediate-Early Protein BZLF1 or BRLF1 To Treat EBV-Positive Tumors

2002 ◽  
Vol 76 (21) ◽  
pp. 10951-10959 ◽  
Author(s):  
Wen-hai Feng ◽  
Eva Westphal ◽  
Amy Mauser ◽  
Nancy Raab-Traub ◽  
Margaret L. Gulley ◽  
...  
Keyword(s):  
Tumor Cells ◽  
Nude Mice ◽  
Epstein Barr Virus ◽  
Adenovirus Vector ◽  
Immediate Early ◽  
Barr Virus ◽  
Ebv Infection ◽  
Early Protein ◽  
Adenovirus Vectors ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus (EBV) genome is present in a variety of tumor types, including virtually all undifferentiated nasopharyngeal carcinomas (NPC) and a portion of gastric carcinomas. The uniform presence of the EBV genome in certain tumors (versus only a very small number of normal B cells) suggests that novel therapies which specifically target EBV-positive cells for destruction might be effective for treating such tumors. Although the great majority of EBV-positive tumor cells are infected with one of the latent forms of EBV infection, expression of either viral immediate-early protein (BZLF1 or BRLF1) is sufficient to convert the virus to the lytic form of infection. Induction of the lytic form of EBV infection could potentially result in death of the tumor cell. Here we have examined the efficacy of adenovirus vectors expressing the BZLF1 or BRLF1 proteins for treatment of EBV-positive epithelial tumors. The BZLF1 and BRLF1 vectors induced preferential killing of EBV-positive, versus EBV-negative, gastric carcinoma cells in vitro. Infection of C18 NPC tumors (grown in nude mice) with either the BZLF1 or BRLF1 vector, but not a control adenovirus vector, induced expression of early lytic EBV genes in tumor cells. Injection of C18 tumors with the BZLF1 or BRLF1 adenovirus vector, but not the control vector, also significantly inhibited growth of the tumors in nude mice. The addition of ganciclovir did not significantly affect the antitumor effect of the BZLF1 and BRLF1 adenovirus vectors. These results suggest a potential cancer therapy against EBV-related tumors.

scholarly journals Interferon Regulatory Factor 7 Is Negatively Regulated by the Epstein-Barr Virus Immediate-Early Gene, BZLF-1

2005 ◽  
Vol 79 (15) ◽  
pp. 10040-10052 ◽  
Author(s):  
Angela M. Hahn ◽  
Leslie E. Huye ◽  
Shunbin Ning ◽  
Jennifer Webster-Cyriaque ◽  
Joseph S. Pagano
Keyword(s):  
Viral Replication ◽  
Epstein Barr Virus ◽  
Interferon Regulatory Factor ◽  
Lytic Replication ◽  
Immediate Early ◽  
Regulatory Factor ◽  
Barr Virus ◽  
Antiviral Responses ◽  
Interferon Regulatory Factor 7 ◽  
Epstein Barr

ABSTRACT Virus infection stimulates potent antiviral responses; specifically, Epstein-Barr virus (EBV) infection induces and activates interferon regulatory factor 7 (IRF-7), which is essential for production of alpha/beta interferons (IFN-α/β) and upregulates expression of Tap-2. Here we present evidence that during cytolytic viral replication the immediate-early EBV protein BZLF-1 counteracts effects of IRF-7 that are central to host antiviral responses. We initiated these studies by examining IRF-7 protein expression in vivo in lesions of hairy leukoplakia (HLP) in which there is abundant EBV replication but the expected inflammatory infiltrate is absent. This absence might predict that factors involved in the antiviral response are absent or inactive. First, we detected significant levels of IRF-7 in the nucleus, as well as in the cytoplasm, of cells in HLP lesions. IRF-7 activity in cell lines during cytolytic viral replication was examined by assay of the IRF-7-responsive promoters, IFN-α4, IFN-β, and Tap-2, as well as of an IFN-stimulated response element (ISRE)-containing reporter construct. These reporter constructs showed consistent reduction of activity during lytic replication. Both endogenous and transiently expressed IRF-7 and EBV BZLF-1 proteins physically associate in cell culture, although BZLF-1 had no effect on the nuclear localization of IRF-7. However, IRF-7-dependent activity of the IFN-α4, IFN-β, and Tap-2 promoters, as well as an ISRE promoter construct, was inhibited by BZLF-1. This inhibition occurred in the absence of other EBV proteins and was independent of IFN signaling. Expression of BZLF-1 also inhibited activation of IRF-7 by double-stranded RNA, as well as the activity of a constitutively active mutant form of IRF-7. Negative regulation of IRF-7 by BZLF-1 required the activation domain but not the DNA-binding domain of BZLF-1. Thus, EBV may subvert cellular antiviral responses and immune detection by blocking the activation of IFN-α4, IFN-β, and Tap-2 by IRF-7 through the medium of BZLF-1 as a negative regulator.

scholarly journals Epstein-Barr Virus Immediate-Early Protein BRLF1 Interacts with CBP, Promoting Enhanced BRLF1 Transactivation

2001 ◽  
Vol 75 (13) ◽  
pp. 6228-6234 ◽  
Author(s):  
Jennifer J. Swenson ◽  
Elizabeth Holley-Guthrie ◽  
Shannon C. Kenney
Keyword(s):  
Viral Replication ◽  
Epstein Barr Virus ◽  
Immediate Early ◽  
Transcriptional Activators ◽  
Creb Binding Protein ◽  
Raji Cells ◽  
Barr Virus ◽  
Early Protein ◽  
Epstein Barr ◽  
Multiple Domains

ABSTRACT The Epstein-Barr virus (EBV) immediate-early protein BRLF1 is a transcriptional activator that mediates the switch from latent to lytic viral replication. Many transcriptional activators function, in part, due to an interaction with histone acetylases, such as CREB-binding protein (CBP). Here we demonstrate that BRLF1 interacts with the amino and carboxy termini of CBP and that multiple domains of the BRLF1 protein are necessary for this interaction. Furthermore, we show that the interaction between BRLF1 and CBP is important for BRLF1-induced activation of the early lytic EBV gene SM in Raji cells.

scholarly journals The Epstein-Barr Virus EBNA-LP Protein Preferentially Coactivates EBNA2-Mediated Stimulation of Latent Membrane Proteins Expressed from the Viral Divergent Promoter

2005 ◽  
Vol 79 (7) ◽  
pp. 4492-4505 ◽  
Author(s):  
RongSheng Peng ◽  
Stephanie C. Moses ◽  
Jie Tan ◽  
Elisabeth Kremmer ◽  
Paul D. Ling
Keyword(s):  
B Cell ◽  
Transcriptional Activation ◽  
Epstein Barr Virus ◽  
Type I ◽  
Barr Virus ◽  
Cell Immortalization ◽  
Cellular Cofactor ◽  
Epstein Barr ◽  
Transformed Cell Lines ◽  
Stimulation Of

ABSTRACT The mechanistic contribution of the Epstein-Barr virus (EBV) EBNA-LP protein to B-cell immortalization remains an enigma. However, previous studies have indicated that EBNA-LP may contribute to immortalization by enhancing EBNA2-mediated transcriptional activation of the LMP-1 gene. To gain further insight into the potential role EBNA-LP has in EBV-mediated B-cell immortalization, we asked whether it is a global or gene-specific coactivator of EBNA2 and whether coactivation requires interaction between these proteins. In type I Burkitt's lymphoma cells, we found that EBNA-LP strongly coactivated EBNA2 stimulation of LMP-1 and LMP2B RNAs, which are expressed from the viral divergent promoter. Surprisingly, the viral LMP2A gene and cellular CD21 and Hes-1 genes were induced by EBNA2 but showed no further induction after EBNA-LP coexpression. We also found that EBNA-LP did not stably interact with EBNA2 in coimmunoprecipitation assays, even though the conditions were adequate to observe specific interactions between EBNA2 and its cellular cofactor, CBF1. Colocalization between EBNA2 and EBNA-LP was not detectable in EBV-transformed cell lines or transfected type I Burkitt's cells. Finally, no significant interactions between EBNA2 and EBNA-LP were found with mammalian two-hybrid assays. From this data, we conclude that EBNA-LP is not a global coactivator of EBNA2 targets, but it preferentially coactivates EBNA2 stimulation of the viral divergent promoter. While this may require specific transient interactions between these proteins that only occur in the context of the divergent promoter, our data strongly suggest that EBNA-LP also cooperates with EBNA2 through mechanisms that do not require direct or indirect complex formation between these proteins.

scholarly journals Epstein-Barr virus genome packaging factors accumulate in BMRF1-cores within viral replication compartments

PLoS ONE ◽  
2019 ◽  
Vol 14 (9) ◽  
pp. e0222519 ◽  
Author(s):  
Atsuko Sugimoto ◽  
Yoriko Yamashita ◽  
Teru Kanda ◽  
Takayuki Murata ◽  
Tatsuya Tsurumi
Keyword(s):  
Viral Replication ◽  
Epstein Barr Virus ◽  
Virus Genome ◽  
Genome Packaging ◽  
Barr Virus ◽  
Epstein Barr
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