scholarly journals Epstein–Barr virus Rta-mediated transactivation of p21 and 14-3-3σ arrests cells at the G1/S transition by reducing cyclin E/CDK2 activity

2012 ◽  
Vol 93 (1) ◽  
pp. 139-149 ◽  
Author(s):  
Sheng-Yen Huang ◽  
Min-Jie Hsieh ◽  
Chu-Ying Chen ◽  
Yen-Ju Chen ◽  
Jen-Yang Chen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Epstein Barr Virus ◽  
Cyclin E ◽  
Lytic Replication ◽  
Immediate Early ◽  
Luciferase Reporter ◽  
Barr Virus ◽  
Cycle Arrest ◽  
Epstein Barr

Many herpesviral immediate-early proteins promote their robust lytic phase replications by hijacking the cell cycle machinery. Previously, lytic replication of Epstein–Barr virus (EBV) was found to be concurrent with host cell cycle arrest. In this study, we showed that ectopic expression of EBV immediate-early protein Rta in HEp-2 cells resulted in increased G1/S population, hypophosphorylation of pRb and decreased incorporation of 5-bromo-2′-deoxyuridine. In addition, EBV Rta transcriptionally upregulates the expressions of p21 and 14-3-3σ in HEp-2 cells, 293 cells and nasopharyngeal carcinoma TW01 cells. Although p21 and 14-3-3σ are known targets for p53, Rta-mediated p21 and 14-3-3σ transactivation can be detected in the absence of p53. In addition, results from luciferase reporter assays indicated that direct binding of Rta to either promoter sequences is not required for activation. On the other hand, a special class of Sp1-responsive elements was involved in Rta-mediated transcriptional activation on both promoters. Finally, Rta-induced p21 expression diminished the activity of CDK2/cyclin E complex, and, Rta-induced 14-3-3σ expression sequestered CDK1 and CDK2 in the cytoplasm. Based on these results, we hypothesize that through the disruption of CDK1 and CDK2 activities, EBV Rta might contribute to cell cycle arrest in EBV-infected epithelial cells during viral reactivation.

scholarly journals Radiosensitization Effect of Nedaplatin on Nasopharyngeal Carcinoma Cells in Different Status of Epstein-Barr Virus Infection

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Li Yin ◽  
Jing Wu ◽  
Jianfeng Wu ◽  
Jinjun Ye ◽  
Xuesong Jiang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Nasopharyngeal Carcinoma ◽  
Cell Cycle Arrest ◽  
Cell Lines ◽  
Epstein Barr Virus ◽  
Barr Virus ◽  
Cycle Arrest ◽  
M Phase ◽  
Epstein Barr ◽  
Mts Assay

This study aims to evaluate the radiosensitization effect of nedaplatin on nasopharyngeal carcinoma (NPC) cell lines with different Epstein-Barr virus (EBV) status. Human NPC cell lines CNE-2 (EBV-negative) and C666 (EBV-positive) were treated with 0–100 μg/mL nedaplatin, and inhibitory effects on cell viability and IC50were calculated by MTS assay. We assessed changes in radiosensitivity of cells by MTS and colony formation assays, and detected the apoptosis index and changes in cell cycle by flow cytometry. MTS assay showed that nedaplatin caused significant cytotoxicity in CNE-2 and C666 cells in a time- and dose-dependent manner. After 24 h, nedaplatin inhibited growth of CNE-2 and C666 cells with IC50values of 34.32 and 63.69 μg/mL, respectively. Compared with radiation alone, nedaplatin enhanced the radiation effect on both cell lines. Nedaplatin markedly increased apoptosis and cell cycle arrest in G2/M phase. Nedaplatin radiosensitized human NPC cells CNE-2 and C666, with a significantly greater effect on the former. The mechanisms of radiosensitization include induction of apoptosis and enhancement of cell cycle arrest in G2/M phase.

scholarly journals CCAAT/Enhancer Binding Protein α Interacts with ZTA and Mediates ZTA-Induced p21CIP-1 Accumulation and G1 Cell Cycle Arrest during the Epstein-Barr Virus Lytic Cycle

2003 ◽  
Vol 77 (2) ◽  
pp. 1481-1500 ◽  
Author(s):  
Frederick Y. Wu ◽  
Honglin Chen ◽  
Shizhen Emily Wang ◽  
Collette M. J. apRhys ◽  
Gangling Liao ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Epstein Barr Virus ◽  
Adenovirus Vector ◽  
Lytic Cycle ◽  
Barr Virus ◽  
Cycle Arrest ◽  
Enhancer Binding Protein ◽  
Epstein Barr ◽  
P21 Promoter

ABSTRACT Cellular CCAAT/enhancer binding protein α (C/EBPα) promotes cellular differentiation and has antimitotic activities involving cell cycle arrest at G1/S through stabilization of p21CIP-1/WAF1 and through transcriptional activation of the p21 promoter. The Epstein-Barr virus lytic-cycle transactivator protein ZTA is known to arrest the host cell cycle at G1/S via a p53-independent p21 pathway, but the detailed molecular mechanisms involved have not been defined. To further evaluate the role of ZTA in cell cycle arrest, we constructed a recombinant adenovirus vector expressing ZTA (Ad-ZTA), whose level of expression at a low multiplicity of infection in normal human diploid fibroblast (HF) cells was lower than or equal to the physiological level seen in Akata cells lytically induced by EBV (EBV-Akata cells). Fluorescence-activated cell sorting analysis of HF cells infected with Ad-ZTA confirmed that G1/S cell cycle arrest occurred in the majority of ZTA-positive cells, but not with an adenovirus vector expressing green fluorescent protein. Double-label immunofluorescence assays (IFA) performed with Ad-ZTA-infected HF cells revealed that only ZTA-positive cells induced the expression of both endogenous C/EBPα and p21 and blocked the progression into S phase, as detected by a lack of incorporation of bromodeoxyuridine. The stimulation of endogenous ZTA protein expression either through treatment with tetradecanoyl phorbol acetate in D98/HR1 cells or through B-cell receptor cross-linking with anti-immunoglobulin G antibody in EBV-Akata cells also coincided with the induction of both C/EBPα and p21 and their mRNAs, as assayed by Northern blot, Western blot, and IFA experiments. Mechanistically, the ZTA protein proved to directly interact with C/EBPα by coimmunoprecipitation in EBV-Akata cells and with DNA-bound C/EBPα in electrophoretic mobility shift assay experiments, and the in vitro interaction domain encompassed the basic leucine zipper domain of ZTA. ZTA also specifically protected C/EBPα from degradation in a protein stability assay with a non-EBV-induced Akata cell proteasome extract. Furthermore, both C/EBPα and ZTA were found to specifically associate with the C/EBPα promoter in chromatin immunoprecipitation assays, but the interaction with ZTA appeared to be mediated by C/EBPα because it was abolished by clearing with anti-C/EBPα antibody. ZTA did not bind to or activate the C/EBPα promoter directly but cooperatively enhanced the positive autoregulation of the C/EBPα promoter by cotransfected C/EBPα in transient luciferase reporter gene assays with Vero and HeLa cells as well as with DG75 B lymphocytes. Similarly, ZTA alone had little effect on the p21 promoter in transient reporter gene assays, but in the presence of cotransfected C/EBPα, ZTA enhanced the level of C/EBPα activation. This effect proved to require a previously unrecognized region in the proximal p21 promoter that contains three high-affinity C/EBPα binding sites. Finally, in C/EBPα-deficient mouse embryonic fibroblasts (MEF), Ad-ZTA was unable to induce either p21 or G1 arrest, whereas it was able to induce both in wild-type MEF. Overall, we conclude that C/EBPα is essential for at least one pathway of ZTA-induced G1 arrest during EBV lytic-cycle DNA replication and that this process involves a physical piggyback interaction between ZTA and C/EBPα leading to greatly enhanced C/EBPα and p21 levels through both transcriptional and posttranslational mechanisms.

scholarly journals Inhibition of S-Phase Cyclin-Dependent Kinase Activity Blocks Expression of Epstein-Barr Virus Immediate-Early and Early Genes, Preventing Viral Lytic Replication

2004 ◽  
Vol 78 (1) ◽  
pp. 104-115 ◽  
Author(s):  
Ayumi Kudoh ◽  
Tohru Daikoku ◽  
Yutaka Sugaya ◽  
Hiroki Isomura ◽  
Masatoshi Fujita ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Epstein Barr Virus ◽  
S Phase ◽  
Lytic Replication ◽  
Immediate Early ◽  
Specific Cell ◽  
Cyclin Dependent Kinase ◽  
Barr Virus ◽  
Cellular Environment ◽  
Epstein Barr

ABSTRACT The induction of lytic replication of the Epstein-Barr virus (EBV) completely arrests cell cycle progression, in spite of elevation of S-phase cyclin-dependent kinase (CDK) activity, thereby causing accumulation of hyperphosphorylated forms of retinoblastoma (Rb) protein (A. Kudoh, M. Fujita, T. Kiyono, K. Kuzushima, Y. Sugaya, S. Izuta, Y. Nishiyama, and T. Tsurumi, J. Virol. 77:851-861, 2003). Thus, the EBV lytic program appears to promote specific cell cycle-associated activity involved in the progression from G1 to S phase. We have proposed that this provides a cellular environment that is advantageous for EBV productive infection. Purvalanol A and roscovitine, inhibitors of S-phase CDKs, blocked the viral lytic replication when cells were treated at the early stage of lytic infection, while well-characterized inhibitors of enzymes, such as mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and protein kinase C, known to be involved in BZLF1 gene expression did not. Inhibition of CDK activity resulted in the accumulation of the hypophosphorylated form of Rb protein and inhibition of expression of EBV immediate-early and early proteins. Cycloheximide block-and-release experiments clearly demonstrated that even in the presence of enough amounts of the BZLF1 protein, purvalanol A blocked expression of lytic viral proteins at transcription level. Furthermore, reporter gene experiments confirmed that BZLF1-induced activation of early EBV promoters was impaired in the presence of the CDK inhibitor. We conclude here that the EBV lytic program promotes specific cell cycle-associated activity involved in the progression from G1 to S phase because the S-phase-like cellular environment is essential for the expression of immediate-early and early genes supplying the viral replication proteins and hence for lytic viral replication.

scholarly journals Cell cycle arrest induced by engagement of B7-H4 on Epstein-Barr virus-positive B-cell lymphoma cell lines

Immunology ◽  
2009 ◽  
Vol 128 (3) ◽  
pp. 360-368 ◽  
Author(s):  
Ga Bin Park ◽  
Hyunkeun Song ◽  
Yeong-Seok Kim ◽  
Minjung Sung ◽  
Jeoung W. Ryu ◽  
...  
Keyword(s):  
Cell Cycle ◽  
B Cell ◽  
Cell Cycle Arrest ◽  
Cell Lines ◽  
Epstein Barr Virus ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Barr Virus ◽  
Cycle Arrest ◽  
Epstein Barr

scholarly journals Curcumin Inhibits Proliferation of Epstein–Barr Virus-Associated Human Nasopharyngeal Carcinoma Cells by Inhibiting EBV Nuclear Antigen 1 Expression

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Limei Liu ◽  
Jiaomin Yang ◽  
Wuguang Ji ◽  
Chao Wang
Keyword(s):  
Nasopharyngeal Carcinoma ◽  
Epstein Barr Virus ◽  
Lytic Replication ◽  
Nuclear Antigen ◽  
Mrna Levels ◽  
Curcumin Treatment ◽  
Antitumor Effects ◽  
Barr Virus ◽  
Cycle Arrest ◽  
Epstein Barr

This investigation aims to study the effect of curcumin on the proliferation, cycle arrest, and apoptosis of Epstein–Barr virus- (EBV-) positive nasopharyngeal carcinoma (NPC) cells. EBV+ NPC cells were subjected to curcumin treatment. The cell viability was evaluated with the CCK-8. Cell cycle and apoptosis were analyzed by flow cytometry analysis. Expression (protein and mRNA) levels were detected with western blotting and quantitative real-time PCR, respectively. Curcumin efficiently reduced the viability of EBV+ NPC cells. Curcumin induced the cycle arrest of the HONE1 and HK1-EBV cells positive for EBV. Moreover, curcumin treatment promoted the NPC cell apoptosis, via the mitochondria- and death receptor-mediated pathways. Furthermore, curcumin decreased the expression of EBNA1 in the HONE1 and HK1-EBV cells and inhibited the transcriptional level of EBNA1 in the HeLa cells. Curcumin induced EBNA1 degradation via the proteasome-ubiquitin pathway. In addition, curcumin inhibited the proliferation of HONE1 and HK1-EBV cells positive for EBV, probably by decreasing the expression level of EBNA1. In both the HONE1 and HK1-EBV cells, curcumin inhibited the EBV latent and lytic replication. Curcumin could reduce the EBNA1 expression and exert antitumor effects against NPC in vitro.

74. Dexamethasone activates Epstein Barr Virus lytic replication through immediate early BZLF1 gene expression

2008 ◽  
Vol 22 (4) ◽  
pp. 23
Author(s):  
Seung-jae Kim ◽  
Eric V. Yang ◽  
Min Chen ◽  
Jeanette I. Marketon ◽  
Marshall V. Williams ◽  
...  
Keyword(s):  
Gene Expression ◽  
Epstein Barr Virus ◽  
Lytic Replication ◽  
Immediate Early ◽  
Barr Virus ◽  
Bzlf1 Gene ◽  
Epstein Barr
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