scholarly journals Epstein-Barr Virus Nuclear Antigen 3C Regulates Cyclin A/p27 Complexes and Enhances Cyclin A-Dependent Kinase Activity

2004 ◽  
Vol 78 (4) ◽  
pp. 1981-1991 ◽  
Author(s):  
Jason S. Knight ◽  
Erle S. Robertson
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Cell Transformation ◽  
Cyclin A ◽  
Nuclear Antigen ◽  
Cycle Progression ◽  
Barr Virus ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) is essential for primary B-cell transformation. In this report we show that cyclin A, an activator of S phase progression, bound tightly to EBNA3C. EBNA3C interacted with cyclin A in vitro and associated with cyclin A complexes in EBV-transformed lymphoblastoid cell lines. Importantly, EBNA3C stimulated cyclin A-dependent kinase activity and rescued p27-mediated inhibition of cyclin A/Cdk2 kinase activity by decreasing the molecular association between cyclin A and p27 in cells. Additionally, phosphorylation of the retinoblastoma protein, a major regulator of cell cycle progression, was enhanced both in vitro and in vivo in the presence of EBNA3C. Cyclin A interacted with a region of the carboxy terminus of EBNA3C, shown to be important both for stimulation of cyclin A-dependent kinase activity and for cell cycle progression. This provides the first evidence of an essential EBV latent antigen's directly targeting a cell cycle regulatory protein and suggests a novel mechanism by which EBV deregulates the mammalian cell cycle, which is of critical importance in B-cell transformation.

scholarly journals Epstein-Barr Virus Nuclear Antigen 3C Facilitates Cell Proliferation by Regulating Cyclin D2

2018 ◽  
Vol 92 (18) ◽  
Author(s):  
Yonggang Pei ◽  
Rajnish Kumar Singh ◽  
Sanket Kumar Shukla ◽  
Fengchao Lang ◽  
Shengwei Zhang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Proliferation ◽  
Epstein Barr Virus ◽  
Cell Cycle Progression ◽  
Nuclear Antigen ◽  
Cyclin D2 ◽  
Cycle Progression ◽  
Barr Virus ◽  
Epstein Barr ◽  
Related Proteins

ABSTRACTCell cycle regulation is one of the hallmarks of virus-mediated oncogenesis. Epstein-Barr virus (EBV)-induced lymphomas express a repertoire of essential viral latent proteins that regulate expression of cell cycle-related proteins to dysregulate this process, thereby facilitating the proliferation of infected cells. We now demonstrate that the essential EBV latent protein 3C (EBNA3C) stabilizes cyclin D2 to regulate cell cycle progression. More specifically, EBNA3C directly binds to cyclin D2 and they colocalize together in nuclear compartments. We show that EBNA3C regulates the promoter of cyclin D2 through cooperation with master transcription factor Bcl6 and enhances its stability by inhibiting its ubiquitin-dependent degradation. EBNA3C also promoted cell proliferation in the presence of cyclin D2, suggesting that cyclin D2 contributes to EBNA3C-mediated cell cycle progression. These results provide new clues as to the role of this essential viral latent protein and its ability to regulate expression of cellular factors, which drives the oncogenic process.IMPORTANCEEpstein-Barr virus (EBV) is the first identified human tumor virus and is associated with a range of human cancers. During EBV-induced lymphomas, the essential viral latent proteins modify the expression of cell cycle-related proteins to disturb the cell cycle process, thereby facilitating the proliferative process. The essential EBV nuclear antigen 3C (EBNA3C) plays an important role in EBV-mediated B-cell transformation. Here we show that EBNA3C stabilizes cyclin D2 to regulate cell cycle progression. More specifically, EBNA3C directly binds to cyclin D2, and they colocalize together in nuclear compartments. EBNA3C enhances cyclin D2 stability by inhibiting its ubiquitin-dependent degradation and significantly promotes cell proliferation in the presence of cyclin D2. Our results provide novel insights into the function of EBNA3C on cell progression by regulating the cyclin D2 protein and raise the possibility of the development of new anticancer therapies against EBV-associated cancers.

scholarly journals The ATM/ATR Signaling Effector Chk2 Is Targeted by Epstein-Barr Virus Nuclear Antigen 3C To Release the G2/M Cell Cycle Block

2007 ◽  
Vol 81 (12) ◽  
pp. 6718-6730 ◽  
Author(s):  
Tathagata Choudhuri ◽  
Subhash C. Verma ◽  
Ke Lan ◽  
Masanao Murakami ◽  
Erle S. Robertson
Keyword(s):  
Cell Cycle ◽  
B Lymphocytes ◽  
Epstein Barr Virus ◽  
Cell Cycle Checkpoint ◽  
Nuclear Antigen ◽  
M Cell ◽  
Barr Virus ◽  
Cycle Checkpoint ◽  
Epstein Barr

ABSTRACT Epstein-Barr virus (EBV) infects most of the human population and persists in B lymphocytes for the lifetime of the host. The establishment of latent infection by EBV requires the expression of a unique repertoire of genes. The product of one of these viral genes, the EBV nuclear antigen 3C (EBNA3C), is essential for the growth transformation of primary B lymphocytes in vitro and can regulate the transcription of a number of viral and cellular genes important for the immortalization process. This study demonstrates an associated function of EBNA3C which involves the disruption of the G2/M cell cycle checkpoint. We show that EBNA3C-expressing lymphoblastoid cell lines treated with the drug nocodazole, which is known to block cells at the G2/M transition, did not show a G2/M-specific checkpoint arrest. Analyses of the cell cycles of cells expressing EBNA3C demonstrated that the expression of this essential EBV nuclear antigen is capable of releasing the G2/M checkpoint arrest induced by nocodazole. This G2/M arrest in response to nocodazole was also abolished by caffeine, suggesting an involvement of the ATM/ATR signaling pathway in the regulation of this cell cycle checkpoint. Importantly, we show that the direct interaction of EBNA3C with Chk2, the ATM/ATR signaling effector, is responsible for the release of this nocodazole-induced G2/M arrest and that this interaction leads to the serine 216 phosphorylation of Cdc25c, which is sequestered in the cytoplasm by 14-3-3. Overall, our data suggest that EBNA3C can directly regulate the G2/M component of the host cell cycle machinery, allowing for the release of the checkpoint block.

scholarly journals Retinoids irreversibly inhibit in vitro growth of Epstein-Barr virus- immortalized B lymphocytes

Blood ◽  
1996 ◽  
Vol 88 (8) ◽  
pp. 3147-3159 ◽  
Author(s):  
F Pomponi ◽  
R Cariati ◽  
P Zancai ◽  
P De Paoli ◽  
S Rizzo ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Epstein Barr Virus ◽  
Antigen Expression ◽  
Inhibitory Effect ◽  
Lymphoproliferative Disorders ◽  
Nuclear Antigen ◽  
Barr Virus ◽  
Drug Concentrations ◽  
Epstein Barr

Natural and synthetic retinoids have proved to be effective in the treatment and prevention of various human cancers. In the present study, we investigated the effect of retinoids on Epstein-Barr virus (EBV)-infected lymphoblastoid cell lines (LCLs), since these cells closely resemble those that give rise to EBV-related lymphoproliferative disorders in the immunosuppressed host. All six compounds tested inhibited LCL proliferation with no significant direct cytotoxicity, but 9-cis-retinoic acid (RA), 13-cis-RA, and all-trans-RA (ATRA) were markedly more efficacious than Ro40–8757, Ro13–6298, and etretinate. The antiproliferative action of the three most effective compounds was confirmed in a large panel of LCLs, thus appearing as a generalized phenomenon in these cells. LCL growth was irreversibly inhibited even after 2 days of treatment at drug concentrations corresponding to therapeutically achievable plasma levels. Retinoid-treated cells showed a marked downregulation of CD71 and a decreased S-phase compartment with a parallel accumulation in Gzero/ G1 phases. These cell cycle perturbations were associated with the upregulation of p27 Kip1, a nuclear protein that controls entrance and progression through the cell cycle by inhibiting several cyclin/cyclin-dependent kinase complexes. Unlike what is observed in other systems, the antiproliferative effect exerted by retinoids on LCLs was not due to the acquisition of a terminally differentiated status. In fact, retinoid-induced modifications of cell morphology, phenotype (downregulation of CD19, HLA-DR, and s-Ig, and increased expression of CD38 and c-Ig), and IgM production were late events, highly heterogeneous, and often slightly relevant, being therefore only partially indicative of a drug-related differentiative process. Moreover, EBV-encoded EBV nuclear antigen-2 and latent membrane protein-1 proteins were inconstantly downregulated by retinoids, indicating that their growth-inhibitory effect is not mediated by a direct modulation of viral latent antigen expression. The strong antiproliferative activity exerted by retinoids in our experimental model indicates that these compounds may represent a useful tool in the medical management of EBV-related lymphoproliferative disorders of immunosuppressed patients.

scholarly journals BRCA1 Is Phosphorylated at Serine 1497 In Vivo at a Cyclin-Dependent Kinase 2 Phosphorylation Site

1999 ◽  
Vol 19 (7) ◽  
pp. 4843-4854 ◽  
Author(s):  
Heinz Ruffner ◽  
Wei Jiang ◽  
A. Grey Craig ◽  
Tony Hunter ◽  
Inder M. Verma
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Kinase Activity ◽  
Phosphorylation Site ◽  
Cyclin A ◽  
Dominant Negative ◽  
Protein Kinase Activity ◽  
Cyclin Dependent Kinase

ABSTRACT BRCA1 is a cell cycle-regulated nuclear protein that is phosphorylated mainly on serine and to a lesser extent on threonine residues. Changes in phosphorylation occur in response to cell cycle progression and DNA damage. Specifically, BRCA1 undergoes hyperphosphorylation during late G1 and S phases of the cell cycle. Here we report that BRCA1 is phosphorylated in vivo at serine 1497 (S1497), which is part of a cyclin-dependent kinase (CDK) consensus site. S1497 can be phosphorylated in vitro by CDK2-cyclin A or E. BRCA1 coimmunoprecipitates with an endogenous serine-threonine protein kinase activity that phosphorylates S1497 in vitro. This cellular kinase activity is sensitive to transfection of a dominant negative form of CDK2 as well as the application of the CDK inhibitors p21 and butyrolactone I but not p16. Furthermore, BRCA1 coimmunoprecipitates with CDK2 and cyclin A. These results suggest that the endogenous kinase activity is composed of CDK2-cyclin complexes, at least in part, concordant with the G1/S-specific increase in BRCA1 phosphorylation.

scholarly journals A Cyclin-Binding Motif within the Amino-Terminal Homology Domain of EBNA3C Binds Cyclin A and Modulates Cyclin A-Dependent Kinase Activity in Epstein-Barr Virus-Infected Cells

2004 ◽  
Vol 78 (23) ◽  
pp. 12857-12867 ◽  
Author(s):  
Jason S. Knight ◽  
Nikhil Sharma ◽  
Danielle E. Kalman ◽  
Erle S. Robertson
Keyword(s):  
Amino Acids ◽  
Epstein Barr Virus ◽  
Kinase Activity ◽  
Cyclin A ◽  
Carboxy Terminus ◽  
Barr Virus ◽  
Amino Terminal ◽  
Infected Cells ◽  
Epstein Barr

ABSTRACT The Epstein-Barr virus (EBV) nuclear antigen 3C (EBNA3C) is a virus-encoded latent antigen essential for primary B-cell transformation. In this report we demonstrate that although the carboxy terminus of EBNA3C predominantly regulates cyclin A-dependent kinase activity, the region of greatest affinity for cyclin A lies within the EBNA3 amino-terminal homology domain of EBNA3C. Detailed mapping studies employing both in vitro binding assays and coimmunoprecipitation experiments implicated a small region of EBNA3C, amino acids 130 to 159 within the EBNA3 homology domain, as having the greatest affinity for cyclin A. The EBNA3 homology domain has the highest degree of amino acid similarity (approximately 30%) between the EBNA3 proteins, and, indeed, EBNA3B, but not EBNA3A, showed binding activity with cyclin A. We also show that EBNA3C binds to the α1 helix of the highly conserved mammalian cyclin box, with cyclin A amino acids 206 to 226 required for strong binding to EBNA3C amino acids 130 to 159. Interestingly, EBNA3C also bound human cyclins D1 and E in vitro, although the affinity was approximately 30% of that seen for cyclin A. Previously it was demonstrated that full-length EBNA3C rescues p27-mediated suppression of cyclin A-dependent kinase activity (J. S. Knight and E. S. Robertson, J. Virol. 78:1981-1991, 2004). It was also demonstrated that the carboxy terminus of EBNA3C recapitulates this phenotype. Surprisingly, the amino terminus of EBNA3C with the highest affinity for cyclin A was unable to rescue p27 suppression of kinase activity and actually downregulates cyclin A activity when introduced into EBV-infected cells. The data presented here suggests that the amino terminus of EBNA3C may play an important role in recruiting cyclin A complexes, while the carboxy terminus of EBNA3C is necessary for the functional modulation of cyclin A complex kinase activity.

scholarly journals SCFSkp2 Complex Targeted by Epstein-Barr Virus Essential Nuclear Antigen

2005 ◽  
Vol 25 (5) ◽  
pp. 1749-1763 ◽  
Author(s):  
Jason S. Knight ◽  
Nikhil Sharma ◽  
Erle S. Robertson
Keyword(s):  
Cell Cycle ◽  
Epstein Barr Virus ◽  
Kinase Inhibitor ◽  
Cyclin A ◽  
Cell Cycle Checkpoint ◽  
Nuclear Antigen ◽  
Barr Virus ◽  
Human Cancers ◽  
Cycle Checkpoint ◽  
Epstein Barr

ABSTRACT The stability of cell cycle checkpoint and regulatory proteins is controlled by the ubiquitin-proteasome degradation machinery. A critical regulator of cell cycle molecules is the E3 ubiquitin ligase SCFSkp2, known to facilitate the polyubiquitination and degradation of p27, E2F, and c-myc. SCFSkp2 is frequently deregulated in human cancers. In this study, we have revealed a novel link between the essential Epstein-Barr virus (EBV) nuclear antigen EBNA3C and the SCFSkp2 complex, providing a mechanism for cell cycle regulation by EBV. EBNA3C associates with cyclin A/cdk2 complexes, disrupting the kinase inhibitor p27 and enhancing kinase activity. The recruitment of SCFSkp2 activity to cyclin A complexes by EBNA3C results in ubiquitination and SCFSkp2-dependent degradation of p27. This is the first report of a viral protein usurping the function of the SCFSkp2 cell cycle regulatory machinery to regulate p27 stability, establishing the foundation for a mechanism by which EBV regulates cyclin/cdk activity in human cancers.

scholarly journals Extracellular Signal-Regulated Kinase 2-Dependent Phosphorylation Induces Cytoplasmic Localization and Degradation of p21Cip1

2009 ◽  
Vol 29 (12) ◽  
pp. 3379-3389 ◽  
Author(s):  
Chae Young Hwang ◽  
Cheolju Lee ◽  
Ki-Sun Kwon
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Nuclear Antigen ◽  
Inhibitory Protein ◽  
Cycle Progression ◽  
Double Mutation ◽  
Extracellular Signal Regulated Kinase ◽  
Epidermal Growth Factor Treatment ◽  
Extracellular Signal

ABSTRACT p21Cip1 is an inhibitor of cell cycle progression that promotes G1-phase arrest by direct binding to cyclin-dependent kinase and proliferating cell nuclear antigen. Here we demonstrate that mitogenic stimuli, such as epidermal growth factor treatment and oncogenic Ras transformation, induce p21Cip1 downregulation at the posttranslational level. This downregulation requires the sustained activation of extracellular signal-regulated kinase 2 (ERK2), which directly interacts with and phosphorylates p21Cip1, promoting p21Cip1 nucleocytoplasmic translocation and ubiquitin-dependent degradation, thereby resulting in cell cycle progression. ERK1 is not likely involved in this process. Phosphopeptide analysis of in vitro ERK2-phosphorylated p21Cip1 revealed two phosphorylation sites, Thr57 and Ser130. Double mutation of these sites abolished ERK2-mediated p21Cip1 translocation and degradation, thereby impairing ERK2-dependent cell cycle progression at the G1/S transition. These results indicate that ERK2 activation transduces mitogenic signals, at least in part, by downregulating the cell cycle inhibitory protein p21Cip1.

scholarly journals Epstein–Barr virus-induced B-cell transformation: quantitating events from virus binding to cell outgrowth

2005 ◽  
Vol 86 (11) ◽  
pp. 3009-3019 ◽  
Author(s):  
Claire Shannon-Lowe ◽  
Gouri Baldwin ◽  
Regina Feederle ◽  
Andrew Bell ◽  
Alan Rickinson ◽  
...  
Keyword(s):  
B Cell ◽  
Cell Nucleus ◽  
Epstein Barr Virus ◽  
Cell Activation ◽  
Cell Transformation ◽  
Nuclear Antigen ◽  
Virus Binding ◽  
Barr Virus ◽  
Epstein Barr

Epstein–Barr virus (EBV) infection and growth activation of human B cells is central to virus biology and disease pathogenesis, but is poorly understood in quantitative terms. Here, using virus at defined m.o.i., the different stages of this process at the single-cell level are followed in vitro. Virus binding to the B-cell surface, assayed by quantitative PCR, is highly efficient, particularly at the low m.o.i. values that most likely reflect physiologic events in vivo. However, only 10–15 % of bound virus genomes reach the cell nucleus, as visualized by sensitive fluorescence in situ hybridization (FISH) assay; viral genomes acquired per cell nucleus range from 1 to >10, depending on the m.o.i. Thereafter, despite differences in initial genome load, almost all nuclear genome-positive cells then go on to express the virus-encoded nuclear antigen EBNA2, upregulate the cell activation antigen CD23 and transit the cell cycle. EBNA2-positive cells in the first cycle post-infection then grow out to lymphoblastoid cell lines (LCLs) just as efficiently as do cells limiting-diluted from already established LCLs. This study therefore identifies EBV genome delivery to the nucleus as a key rate-limiting step in B-cell transformation, and highlights the remarkable efficiency with which a single virus genome, having reached the nucleus, then drives the transformation programme.

scholarly journals Stabilization of p18 by deubiquitylase CYLD is pivotal for cell cycle progression and viral replication

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Yueshuo Li ◽  
Feng Shi ◽  
Jianmin Hu ◽  
Longlong Xie ◽  
Lin Zhao ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Viral Replication ◽  
Cell Cycle Progression ◽  
Negative Regulator ◽  
Protein Loss ◽  
Cycle Progression ◽  
Barr Virus ◽  
Cycle Arrest ◽  
Epstein Barr

Abstractp18 is a key negative regulator of cell cycle progression and mediates cell cycle arrest at the G1/S phase. Ubiquitination is the prime mechanism in regulating p18 protein abundance. However, so far no post- translational regulator, especially DUBs, has been identified to regulate the protein stability of p18. In this paper, we identified CYLD as a deubiquitinase of p18, which binds to and removes the K48-linked polyubiquitylation chains conjugated onto p18, thus stabilizing the p18 protein. Loss of CYLD causes the degradation of p18 and induces the G1/S transition. Epstein–Barr virus (EBV), is the human oncovirus etiologically linked to nasopharyngeal carcinoma (NPC). Here we found that EBV drives a replication passive environment by deregulating the CYLD-p18 axis. Functionally, CYLD inhibits cell proliferation and tumorigenesis through p18 in vivo. Restoring CYLD prevents EBV induced viral replication and tumor growth. Collectively, our results identify CYLD directly stabilizes p18 to regulate the cellular G1/S transition. The reconstitution of CYLD-p18 axis could be a promising approach for EBV-positive cancer therapy.

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