scholarly journals Protein Kinase A Associates with HA95 and Affects Transcriptional Coactivation by Epstein-Barr Virus Nuclear Proteins

2002 ◽  
Vol 22 (7) ◽  
pp. 2136-2146 ◽  
Author(s):  
Innoc Han ◽  
Yong Xue ◽  
Shizuko Harada ◽  
Sigurd Orstavik ◽  
Bjorn Skalhegg ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Epstein Barr Virus ◽  
Nuclear Protein ◽  
Kinase Inhibitor ◽  
Nuclear Bodies ◽  
Barr Virus ◽  
B Lymphoma Cells ◽  
Epstein Barr ◽  
Kinase A

ABSTRACT HA95, a nuclear protein homologous to AKAP95, has been identified in immune precipitates of the Epstein-Barr virus (EBV) coactivating nuclear protein EBNA-LP from EBV-transformed lymphoblastoid cells (LCLs). We now find that HA95 and EBNA-LP are highly associated in LCLs and in B-lymphoma cells where EBNA-LP is expressed by gene transfer. Binding was also evident in yeast two-hybrid assays. HA95 binds to the EBNA-LP repeat domain that is the principal coactivator of transcription. EBNA-LP localizes with HA95 and causes HA95 to partially relocalize with EBNA-LP in promyelocytic leukemia nuclear bodies. Protein kinase A catalytic subunit α (PKAcsα) is significantly associated with HA95 in the presence or absence of EBNA-LP. Although EBNA-LP is not a PKA substrate, HA95 or PKAcsα expression in B lymphoblasts specifically down-regulates the strong coactivating effects of EBNA-LP. The inhibitory effects of PKAcsα are reversed by coexpression of protein kinase inhibitor. PKAcsα also inhibits EBNA-LP coactivation with the EBNA-2 acidic domain fused to the Gal4 DNA binding domain. Furthermore, EBNA-LP- and EBNA-2-induced expression of the EBV oncogene, LMP1, is down-regulated by PKAcsα or HA95 expression in EBV-infected lymphoblasts. These experiments indicate that HA95 and EBNA-LP localize PKAcsα at nuclear sites where it can affect transcription from specific promoters. The role of HA95 as a scaffold for transcriptional regulation is discussed.

scholarly journals Regulation of the Epstein-Barr Virus C Promoter by AUF1 and the Cyclic AMP/Protein Kinase A Signaling Pathway

2000 ◽  
Vol 74 (17) ◽  
pp. 8166-8175 ◽  
Author(s):  
Ezequiel M. Fuentes-Pananá ◽  
RongSheng Peng ◽  
Gary Brewer ◽  
Jie Tan ◽  
Paul D. Ling
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Protein Kinase A ◽  
Epstein Barr Virus ◽  
Barr Virus ◽  
Cell Immortalization ◽  
Hnrnp Protein ◽  
Epstein Barr ◽  
Kinase A ◽  
Stimulation Of

ABSTRACT EBNA2 is an Epstein-Barr virus (EBV)-encoded protein that regulates the expression of viral and cellular genes required for EBV-driven B-cell immortalization. Elucidating the mechanisms by which EBNA2 regulates viral and cellular gene expression is necessary to understand EBV-induced B-cell immortalization and viral latency in humans. EBNA2 targets to the latency C promoter (Cp) through an interaction with the cellular DNA binding protein CBF1 (RBPJk). The EBNA2 enhancer in Cp also binds another cellular factor, C promoter binding factor 2 (CBF2), whose protein product(s) has not yet been identified. Within the EBNA2 enhancer in Cp, we have previously identified the DNA sequence required for CBF2 binding and also determined that this element is required for efficient activation of Cp by EBNA2. In this study, the CBF2 activity was biochemically purified and microsequenced. The peptides sequenced were identical to the hnRNP protein AUF1. Antibodies against AUF1 but not antibodies to related hnRNP proteins reacted with CBF2 in gel mobility shift assays. In addition, stimulation of the cellular cyclic AMP (cAMP)/protein kinase A (PKA) signal transduction pathway results in an increase in detectable CBF2/AUF1 binding activity extracted from stimulated cells. Furthermore, the CBF2 binding site was able to confer EBNA2 responsiveness to a heterologous promoter when transfected cells were treated with compounds that activate PKA or by cotransfection of plasmids expressing a constitutively active catalytic subunit of PKA. EBNA2-mediated stimulation of the latency Cp is also increased in similar cotransfection assays. These results further support an important role for CBF2 in mediating EBNA2 transactivation; they identify the hnRNP protein AUF1 as a major component of CBF2 and are also the first evidence of a cis-acting sequence other than a CBF1 binding element that is able to confer responsiveness to EBNA2.

scholarly journals Epstein-Barr Virus (EBV) Tegument Protein BGLF2 Promotes EBV Reactivation through Activation of the p38 Mitogen-Activated Protein Kinase

2015 ◽  
Vol 90 (2) ◽  
pp. 1129-1138 ◽  
Author(s):  
XueQiao Liu ◽  
Jeffrey I. Cohen
Keyword(s):  
Protein Kinase ◽  
Signaling Pathways ◽  
Epstein Barr Virus ◽  
Virus Production ◽  
Mitogen Activated Protein Kinase ◽  
Tegument Protein ◽  
Barr Virus ◽  
Ebv Reactivation ◽  
Mitogen Activated Protein ◽  
Epstein Barr

ABSTRACTEpstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus associated with both B cell and epithelial cell malignancies. EBV infection of B cells triggers activation of several signaling pathways that are critical for cell survival, virus latency, and growth transformation. To identify EBV proteins important for regulating cell signaling, we used a proteomic approach to screen viral proteins for AP-1 and NF-κB promoter activity in AP-1– and NF-κB–luciferase reporter assays. We found that EBV BGLF2 activated AP-1 but not NF-κB reporter activity. Expression of EBV BGLF2 in cells activated p38 and c-Jun N-terminal kinase (JNK), both of which are important for mitogen-activated protein kinase (MAPK) signaling. Deletion of the carboxyl-terminal 66 amino acids of BGLF2 reduced the ability of BGLF2 to activate JNK and p38. Expression of BGLF2 enhanced BZLF1 expression in latently EBV-infected lymphoblastoid cell lines, and knockdown of BGLF2 reduced EBV reactivation induced by IgG cross-linking. Expression of BGLF2 induced BZLF1 expression and virus production in EBV-infected gastric carcinoma cells. BGLF2 enhanced BZLF1 expression and EBV production by activating p38; chemical inhibition of p38 and MAPK/ERK kinases 1 and 2 (MEK1/2) reduced expression of BZLF1 and virus production induced by BGLF2. In summary, the EBV tegument protein BGLF2, which is delivered to the cell at the onset of virus infection, activates the AP-1 pathway and enhances EBV reactivation and virus production.IMPORTANCEEpstein-Barr virus (EBV) is associated with both B cell and epithelial cell malignancies, and the virus activates multiple signaling pathways important for its persistence in latently infected cells. We identified a viral tegument protein, BGLF2, which activates members of the mitogen-activated protein kinase signaling pathway. Expression of BGLF2 increased expression of EBV BZLF1, which activates a switch from latent to lytic virus infection, and increased production of EBV. Inhibition of BGFL2 expression or inhibition of p38/MAPK, which is activated by BGLF2, reduced virus reactivation from latency. These results indicate that a viral tegument protein which is delivered to cells upon infection activates signaling pathways to enhance virus production and facilitate virus reactivation from latency.

scholarly journals The Epstein-Barr Virus Protein Kinase BGLF4 and the Exonuclease BGLF5 Have Opposite Effects on the Regulation of Viral Protein Production

2009 ◽  
Vol 83 (21) ◽  
pp. 10877-10891 ◽  
Author(s):  
Regina Feederle ◽  
Anja M. Mehl-Lautscham ◽  
Helmut Bannert ◽  
Henri-Jacques Delecluse
Keyword(s):  
Protein Kinase ◽  
Viral Protein ◽  
Epstein Barr Virus ◽  
Protein Production ◽  
Opposite Effect ◽  
Viral Gene ◽  
Virus Protein ◽  
Barr Virus ◽  
Viral Genes ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus BGLF4 and BGLF5 genes encode a protein kinase and an alkaline exonuclease, respectively. Both proteins were previously found to regulate multiple steps of virus replication, including lytic DNA replication and primary egress. However, while inactivation of BGLF4 led to the downregulation of several viral proteins, the absence of BGLF5 had the opposite effect. Using recombinant viruses that lack both viral enzymes, we confirm and extend these initial observations, e.g., by showing that both BGLF4 and BGLF5 are required for proper phosphorylation of the DNA polymerase processivity factor BMRF1. We further found that neither BGLF4 nor BGLF5 is required for baseline viral protein production. Complementation with BGLF5 downregulated mRNA levels and translation of numerous viral genes, though to various degrees, whereas BGLF4 had the opposite effect. BGLF4 and BGLF5 influences on viral expression were most pronounced for BFRF1 and BFLF2, two proteins essential for nuclear egress. For most viral genes studied, cotransfection of BGLF4 and BGLF5 had only a marginal influence on their expression patterns, showing that BGLF4 antagonizes BGLF5-mediated viral gene shutoff. To be able to exert its functions on viral gene expression, BGLF4 must be able to escape BGLF5's shutoff activities. Indeed, we found that BGLF5 stimulated the BGLF4 gene's transcription through an as yet uncharacterized molecular mechanism. The BGLF4/BGLF5 enzyme pair builds a regulatory loop that allows fine-tuning of virus protein production, which is required for efficient viral replication.

A role for protein kinase PKR in the mediation of Epstein–Barr virus latent membrane protein-1-induced IL-6 and IL-10 expression

Cytokine ◽  
2010 ◽  
Vol 50 (2) ◽  
pp. 210-219 ◽  
Author(s):  
San San Lin ◽  
Davy C.W. Lee ◽  
Anna H.Y. Law ◽  
Jun Wei Fang ◽  
Daniel T.T. Chua ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Membrane Protein ◽  
Epstein Barr Virus ◽  
Latent Membrane Protein ◽  
Latent Membrane Protein 1 ◽  
Barr Virus ◽  
Epstein Barr ◽  
Virus Latent Membrane Protein

scholarly journals A Stapled Peptide Mimic of the Pseudosubstrate Inhibitor PKI Inhibits Protein Kinase A

Molecules ◽  
2019 ◽  
Vol 24 (8) ◽  
pp. 1567 ◽  
Author(s):  
Jascha T. Manschwetus ◽  
George N. Bendzunas ◽  
Ameya J. Limaye ◽  
Matthias J. Knape ◽  
Friedrich W. Herberg ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Kinase Inhibitor ◽  
Stapled Peptide ◽  
Peptide Mimic ◽  
Cellular Environment ◽  
Ic50 Values ◽  
Dependent Protein ◽  
Peptide Targeting ◽  
Kinase A

Kinases regulate multiple and diverse signaling pathways and misregulation is implicated in a multitude of diseases. Although significant efforts have been put forth to develop kinase-specific inhibitors, specificity remains a challenge. As an alternative to catalytic inhibition, allosteric inhibitors can target areas on the surface of an enzyme, thereby providing additional target diversity. Using cAMP-dependent protein kinase A (PKA) as a model system, we sought to develop a hydrocarbon-stapled peptide targeting the pseudosubstrate domain of the kinase. A library of peptides was designed from a Protein Kinase Inhibitor (PKI), a naturally encoded protein that serves as a pseudosubstrate inhibitor for PKA. The binding properties of these peptide analogs were characterized by fluorescence polarization and surface plasmon resonance, and two compounds were identified with KD values in the 500–600 pM range. In kinase activity assays, both compounds demonstrated inhibition with 25–35 nM IC50 values. They were also found to permeate cells and localize within the cytoplasm and inhibited PKA activity within the cellular environment. To the best of our knowledge, these stapled peptide inhibitors represent some of the highest affinity binders reported to date for hydrocarbon stapled peptides.

scholarly journals Microtubule depolymerization activates the Epstein–Barr virus lytic cycle through protein kinase C pathways in nasopharyngeal carcinoma cells

2013 ◽  
Vol 94 (12) ◽  
pp. 2750-2758 ◽  
Author(s):  
Yi-Ru Liu ◽  
Sheng-Yen Huang ◽  
Jen-Yang Chen ◽  
Lily Hui-Ching Wang
Keyword(s):  
Protein Kinase C ◽  
Life Cycle ◽  
Protein Kinase ◽  
Nasopharyngeal Carcinoma ◽  
Epstein Barr Virus ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Kinase C ◽  
Epstein Barr ◽  
In Cells

Elevated levels of antibodies against Epstein–Barr virus (EBV) and the presence of viral DNA in plasma are reliable biomarkers for the diagnosis of nasopharyngeal carcinoma (NPC) in high-prevalence areas, such as South-East Asia. The presence of these viral markers in the circulation suggests that a minimal level of virus reactivation may have occurred in an infected individual, although the underlying mechanism of reactivation remains to be elucidated. Here, we showed that treatment with nocodazole, which provokes the depolymerization of microtubules, induces the expression of two EBV lytic cycle proteins, Zta and EA-D, in EBV-positive NPC cells. This effect was independent of mitotic arrest, as viral reactivation was not abolished in cells synchronized at interphase. Notably, the induction of Zta by nocodazole was mediated by transcriptional upregulation via protein kinase C (PKC). Pre-treatment with inhibitors for PKC or its downstream signalling partners p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) abolished the nocodazole-mediated induction of Zta and EA-D. Interestingly, the effect of nocodazole, as well as colchicine and vinblastine, on lytic gene expression occurred only in NPC epithelial cells but not in cells derived from lymphocytes. These results establish a novel role of microtubule integrity in controlling the EBV life cycle through PKC and its downstream pathways, which represents a tissue-specific mechanism for controlling the life-cycle switch of EBV.

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