|
|
 Previous Article | Table of Contents | Next Article 
Blood, Vol. 90 No. 11 (December 1), 1997:
pp. 4480-4484
Methylation of the Epstein-Barr Virus Genome in Normal Lymphocytes
By
Keith D. Robertson and
Richard F. Ambinder
From the Departments of Oncology, Pharmacology, and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD.
 |
ABSTRACT |
Epstein-Barr virus (EBV) latent infection in B cells persists over years or decades despite a sustained cytotoxic immune response to viral antigens. We present data that methylated EBV DNA can be detected in the normal lymphocytes of healthy volunteers. Whereas methylation of foreign DNA has been recognized as a potential cellular defense mechanism, methylation of EBV DNA may be an essential part of the virus life cycle in vivo, explaining the persistence of virus-infected B cells in the face of immune surveillance. Methylation of the C promoter helps to prevent expression of the immunodominant antigens expressed from this promoter. First recognized in tumors, methylation-associated evasion of immune surveillance is not an aberration restricted to tumor tissue but is detected in normal EBV-infected lymphocytes. Methylation of the viral genome in latency also provides an explanation for the CpG suppression associated with EBV but not other large DNA viruses.
| |
INTRODUCTION |
IN VITRO INFECTION of peripheral blood mononuclear cells (PBMCs) under appropriate conditions generates latently infected B-lymphoblastoid cell lines.1 These Epstein-Barr virus (EBV)-immortalized latently infected lymphoblastoid cell lines express 11 EBV latency genes. Among the proteins expressed by these lymphoblastoid cell lines are the immunodominant EBV nuclear antigens (EBNA-2, -3A, -3B, and -3C) recognized by CD8(+) cytotoxic T cells on a range of HLA backgrounds.2,3 The transcripts for these antigens originate from the major latency promoter, the C promoter (Cp) (Fig 1A). This promoter is silent in EBV(+) Hodgkin's and Burkitt's lymphomas and these immunodominant antigens are not expressed.4-6 The restricted pattern of viral antigen expression in Hodgkin's and in Burkitt's lymphoma is thought to be important for tumor survival insofar as the cytotoxic T-cell response to these proteins is maintained for years and might be expected to eliminate cells expressing these proteins in vivo. C promoter silence is at least in part a function of CpG methylation of a region upstream of the C promoter in the EBNA-2 response region.7,8 Two sequence-specific cellular DNA binding activities footprint in this region.9,10 The first corresponds to CBF1, which interacts with the viral protein EBNA-2 to facilitate activation of the C promoter (Fig 1C). The second corresponds to CBF2. The in vitro binding activity of CBF2 but not CBF1 is inhibited by CpG methylation.7 Sensitivity to methylation-mediated transcriptional repression may be explained in part by inhibition of CBF2 binding.
View larger version (18K):
[in this window]
[in a new window]
| Fig 1.
Aspects of the EBV genome and C promoter regulation. (A) The linear EBV genome. (B) CpG sites upstream of the C promoter whose methylation status was monitored by genomic sequencing (nos. 1 through 9). (C) The EBNA-2 responsive region of the C promoter. The schematic illustrates the nucleotides protected by CBF1 and CBF2 in DNAse protection assays and the interaction of EBNA-2 with CBF1.
|
|
Aberrant methylation of cellular genes and their transcriptional regulatory regions is a well-recognized phenomenon in tumors and tumor cell lines.11 Evidence has recently emerged suggesting that methylation of transcriptional regulatory regions of tumor suppressor genes may be a step in multistep tumorigenesis akin to deletion or mutation of tumor-suppressor genes.12 Methylation of viral promoters suppressing transcription of immunodominant antigens may be another way in which methylation in tumors contributes to tumorigenesis.4 Because primary infection of B lymphocytes in vitro leads to the establishment of EBV-infected B-cell lines in which the viral genome is not methylated, there has been a presumption that methylation of the viral genome was a phenomenon confined to tumors.13,14 However, in light of evidence suggesting that some features of Burkitt's lymphoma, including silence of the C promoter, might reflect the phenotype of latently infected normal lymphocytes in vivo,15-17 we wished to determine whether methylation of the C promoter might also play a role in protecting EBV-infected peripheral blood lymphocytes from immune surveillance.
We wished to determine whether EBV DNA in PBMCs in vivo is methylated. The frequency of EBV-infected cells in PBMCs from healthy seropositives is less than 1/50,000 by virtually all estimates.15,17 EBV genomes in PBMCs are therefore too rare to have their CpG methylation status determined by conventional Southern blot hybridization techniques using methylation-sensitive and -insensitive isoschizomers. The bisulfite genomic sequencing technique yields information about CpG methylation and involves a polymerase chain reaction (PCR) amplification step. We have previously applied this technique to the analysis of the EBV Cp in tumors. By virtue of the PCR amplification step, we thought this technique might allow the analysis of EBV methylation in PBMCs.
| |
MATERIALS AND METHODS |
PBMCs and cell lines.
Peripheral blood was collected from healthy volunteers at Johns Hopkins according to a protocol approved by the institutional human investigations review boards. Mononuclear cells were isolated by density gradient centrifugation in Ficoll-Hypaque. Rael and Akata are EBV-associated Burkitt's-derived cell lines. B95-8 is an EBV-immortalized lymphoblastoid B-cell line. These lines are maintained in RPMI1640 with 10% fetal calf serum. DNA was isolated by standard techniques involving sodium dodecyl sulfate, proteinase K, phenol, and phenol-chloroform extraction.18
Genomic sequencing.
Genomic sequencing was performed on extracted DNA using the bisulfite treatment method, with minor modifications.7,19 Briefly, 1 to 10 µg of genomic DNA was digested with EcoRI, alkali-denatured, neutralized, precipitated, and treated with sodium bisulfite/hydroquinone. After desalting procedures (Wizard DNA Cleanup System; Promega, Madison, WI), PCR was performed and the amplification products were cloned and sequenced. The sequence of the region was also determined without bisulfite modification using the same procedure of PCR followed by cloning. DNA that had incompletely reacted with bisulfite could be recognized by the persistence of cytosines (C's) in the C lane, even in the absence of CpG methylation sites. Such incompletely reacted DNA was not further analyzed. The primers used have been previously described and include the CBF1 and CBF2 binding sites within the EBNA-2 response element of the C promoter.7 As is standard in this technique, the primers bind to regions without CpG sequences and therefore there is no bias during PCR amplification.
Southern blot hybridization.
Genomic DNA samples (5 to 10 µg) prepared after drug treatment were digested with a 10-fold excess of BamHI and Hpa II or BamHI and Msp I (GIBCO-BRL, Gaithersburg, MD) according to the manufacturer's instructions. After digestion, samples were electrophoresed in a 1.5% agarose gel, transferred to nylon membrane (Biotrans; ICN, Irvine, CA), and probed with nick-translated EBV BamHI-C probe (pSL93).20 All quantitative determinations were performed using a Molecular Dynamics Phosphorimager (Molecular Dynamics, Sunnyvale, CA).
| |
RESULTS |
Bisulfite genomic sequencing involves treatment of genomic DNA with sodium bisulfite leading to the conversion of cytosine to uracil. 5-Methylcytosine does not react under these conditions. Bisulfite treatment results in two strands of DNA that are no longer complementary and that can be differentially amplified by PCR. The ability to amplify viral DNA from DNA extracted from PBMCs is a prerequisite for the analysis of methylation patterns. We studied DNA extracted from PBMCs from seven healthy volunteers. Six volunteers were EBV-seropositive and one was seronegative. Using primers to the Cp region of the EBV genome, amplification was successful in four of the seropositive volunteers. Amplification was not detected from the seronegative volunteer or from two of the seropositive donors. Five to six cloned plasmid inserts were sequenced by the dideoxy technique from each donor where amplification yielded an appropriate product (Fig 2 and Table 1). A total of 22 cloned inserts were sequenced and the methylation status at each of 9 CpG sites was analyzed. Of a total of 198 sites examined, 96 (48%) were methylated. In previous investigations, we have suggested that methylation of a particular CpG site (site no. 4) might play a crucial role in the regulation of the C promoter by blocking the binding of CBF2, a cellular DNA binding activity associated with transcriptional activation. This site was methylated in 11 of 22 (50%) cloned inserts. Site no. 2 was usually not methylated (6 of 22). Almost half of the cloned inserts (10 of 22 [45%]) showed a complete absence of methylation.
View larger version (41K):
[in this window]
[in a new window]
| Fig 2.
Representative bisulfite sequencing autoradiogram showing cloned inserts of PCR-amplified bisulfite-treated DNA from PBMCs from donor 2. Examples of cloned inserts with and without methylation of CpG sites in the EBNA-2 responsive region of the C promoter are shown. Arrows indicate CpG dinucleotides. | , a Taq polymerase error. Unmethylated CpG sites are displayed as TpG as a result of the bisulfite treatment, whereas methylated CpG sites are displayed as CpG. CpG sites are numbered as in Table 1. Site no. 1 is not shown. The vector/insert boundary is denoted as vector.
|
|
We also investigated the methylation status of another locus within the BamHI-C fragment of the viral genome, the EBER region. Two genes, EBER-1 and -2, are transcribed by RNA polymerase III and expressed in abundance in latently infected Burkitt's cell lines. Genomic sequencing in a Burkitt's cell line (Rael) showed that, in contrast to the C promoter region that is consistently methylated, there was no methylation in the EBER region (data not shown). This confirms studies using methylation-sensitive and -insensitive restriction enzymes, suggesting that this region of the genome is not methylated.21
We have compared the results of the bisulfite PCR technique as applied to analysis of the EBV Cp with restriction enzyme-based Southern blot techniques and found a close correspondence in EBV cell lines. Thus, using restriction enzyme-Southern blot techniques, the Cp region of Rael (a Burkitt's cell line that is tightly latent) is entirely methylated, that of B95-8 (a lymphoblastoid cell line) is entirely unmethylated, and that of Akata (a Burkitt's cell line with active lytic infection) is a mixture of methylated and unmethylated DNA (data not shown). Using the bisulfite PCR technique, 7 of 7 Rael Cp region clones were completely methylated, 7 of 7 B95-8 region clones were completely unmethylated, and 4 of 8 Akata Cp region clones were completely methylated, whereas 3 were completely unmethylated and 1 was partially methylated. Furthermore, after treatment with inhibitors of DNA methyltransferase such as 5-azacytidine, changes in methylation pattern as determined by genomic sequencing parallel changes in methylation pattern as determined by Southern blot hybridization (K.D.R. and R.F.A., manuscript submitted).
| |
DISCUSSION |
We have shown that methylation of the EBV genome is detectable in PBMCs from healthy individuals. Thus methylation of this region, previously identified in Burkitt's lymphoma, Hodgkin's disease, and nasopharyngeal carcinoma, does not necessarily reflect aberrant methylation associated with malignancy but may reflect a more fundamental interaction of virus and cell. Detection of methylated viral genomes in the peripheral blood is consistent with a growing body of evidence that EBV latency in B cells in the normal host does not resemble EBV latency in immortalized lymphoblastoid cell lines. Other laboratories have shown that the patterns of viral gene expression in PBMCs are different from EBV-immortalized lymphoblastoid cell lines, with a consistent finding being that C promoter transcripts for the EBNAs are not detected in PBMCs.15,22,23 We now demonstrate that, whereas lymphoblastoid cell lines in general do not show methylation of the viral genome, there is methylation of the viral genome in PBMC.
One of the functions that has been ascribed to cytosine methylation is that of a genome-wide defense system that inactivates foreign parasitic sequences such as transposable elements and proviral DNA.24-26 It would appear that EBV has subverted this function. Rather than protecting against viral infection, methylation of the viral genome may ensure that a proportion of infected cells survive cytotoxic T-cell immune surveillance. Evidence to support this hypothesis comes from analysis of the interaction between methylation and CpG content. In vertebrate DNA, the frequency of the CpG dinucleotide is much lower than would be predicted by chance. This CpG suppression is believed to be a consequence of enhanced spontaneous deamination of methylcytosine versus cytosine over evolutionary time.26 A corollary is that CpG methylation should be associated with CpG suppression. In this light, it is interesting to note that there is no significant CpG suppression in large DNA viruses. The exception to the rule is EBV with a CpG relative abundance of 0.60 and its lymphotropic simian cousin, herpesvirus saimiri, with a relative abundance of 0.33.13 The presence of CpG suppression in these lymphotropic herpesviruses is consistent with the hypotheses that methylated EBV genomes detected in PBMCs are (1) susceptible to mutagenesis by deamination of methylcytosines and (2) important in perpetuating the virus over evolutionary time. In contrast, there is no evidence that herpes simplex, varicella zoster, or cytomegalovirus is CpG methylated even in latency.
Is there evidence that the viral genome can reactivate from a methylated latent state? Certainly in Burkitt's tumor cell lines, methylation of viral episomes does not represent a viral dead end. Nearly all potential methylation sites in a region of the C promoter are methylated in the Rael Burkitt's cell line that is a producer cell line that releases infectious virions after lytic induction. Experiments in our laboratory show that lytic replication in methylated Burkitt's cell lines induced by phorbol esters yields unmethylated viral DNA as determined by Southern blot hybridization with methylation-sensitive and methylation-insensitive restriction enzymes (unpublished results). A possible explanation for this observation is that the cellular DNA methyltransferase does not associate with the viral DNA polymerase or is otherwise inactive during lytic viral replication. During latent replication of viral DNA, it is the host cell DNA polymerase rather than the viral DNA polymerase that is active in replicating the EBV episome.
View larger version (17K):
[in this window]
[in a new window]
| Fig 3.
Model of EBV in peripheral blood lymphocytes. Lymphocytes infected by EBV are suggested to exist in three different states. In veiled latency, the immunodominant EBNA's are not expressed, the C promoter is methylated and its silence enforced. In exposed latency, the immunodominant EBNA's are expressed and the C promoter is not methylated. In lytic infection, it is proposed that the C promoter is not methylated.
|
|
Evidence that methylation of the viral genome is regulated or limited so as to preserve select viral functions comes from study of the EBER region. The EBERs are two genes transcribed by RNA polymerase III. Their functions remain ill-defined, but they are expressed in high abundance in Burkitt's cell lines and tumors, in EBV(+) Hodgkin's tumors, and in PBMCs from healthy EBV-seropositive individuals.27 We investigated the methylation status of the EBER region of the viral genome by performing genomic sequencing in a Burkitt's cell line (Rael). Although also located within the BamHI-C fragment of the genome, in contrast to the C promoter region that is consistently methylated, the EBER region showed no methylation (data not shown). This confirms data presented by others using methylation sensitive and insensitive restriction enzymes suggesting that this region of the genome is not methylated.21 The nature of the mechanism that limits the spread of methylation and so protects the EBERs is not known, but it is clear that expression of genes encoding immunodominant proteins driven from the BamHI-C fragment of the genome is suppressed by methylation, whereas the EBER genes that may be important in viral persistence remain unmethylated and their products expressed.
In summary, we have shown the presence of methylated viral genomes in peripheral blood lymphocytes. We propose that these correspond to a reservoir of viral infection in which the immunodominant EBNAs are not expressed and the C promoter is silent (Fig 3). Thus, methylation of the viral episome may play a crucial role in perpetuating viral infection. Intermittently, and by as yet unknown mechanisms, viral episomes in these cells demethylate leading to C promoter activation with expression of latency genes or to lytic activation with production of new virions (lytic cycle). In support of this model, it should be noted that lytic viral gene products have recently been demonstrated in the PBMCs of normal seropositive individuals.28
| |
FOOTNOTES |
Submitted May 21, 1997;
accepted July 24, 1997.
R.F.A. is a Leukemia Society Scholar. This work was supported by Grants No. CA63532 and CA15396 (to R.F.A.).
Address reprint requests to Richard F. Ambinder, MD, PhD, 418 N Bond St, Johns Hopkins Oncology Center, Baltimore, MD 21231.
The publication costs of this article were defrayed in part by page
charge payment. This article must therefore be hearly marked
``advertisment'' in accordance with 18 U.S.C. section 1734 solely to
indicate this fact.
| |
REFERENCES |
1. Rickinson AB, Kieff E: Epstein-Barr Virus, in Fields BN, Knipe DM, Howley PM (eds): Fields Virology. Philadelphia, PA, Lippincott-Raven, 1996, p 2397
2.
Khanna R,
Burrows SR,
Kurilla MG,
Jacob CA,
Misko IS,
Sculley TB,
Kieff E,
Moss DJ:
Localization of Epstein-Barr virus cytotoxic T cell epitopes using recombinant vaccinia: Implications for vaccine development.
J Exp Med
176:169,
1992[Abstract/Free Full Text]
3.
Murray RJ,
Kurilla MG,
Brooks JM,
Thomas WA,
Rowe M,
Kieff E,
Rickinson AB:
Identification of target antigens for the human cytotoxic T cell response to Epstein-Barr virus (EBV): Implications for the immune control of EBV-positive malignancies.
J Exp Med
176:157,
1992[Abstract/Free Full Text]
4.
Robertson KD,
Manns A,
Swinnen LJ,
Zong JC,
Gulley ML,
Ambinder RF:
CpG methylation of the major Epstein-Barr virus latency promoter in Burkitt's lymphoma and Hodgkin's disease.
Blood
88:3129,
1996[Abstract/Free Full Text]
5.
Niedobitek G,
Agathanggelou A,
Rowe M,
Jones EL,
Jones DB,
Turyaguma P,
Oryema J,
Wright DH,
Young LS:
Heterogeneous expression of Epstein-Barr virus latent proteins in endemic Burkitt's lymphoma.
Blood
86:659,
1995[Abstract/Free Full Text]
6.
Deacon EM,
Pallesen G,
Niedobitek G,
Crocker J,
Brooks L,
Rickinson AB,
Young LS:
Epstein-Barr virus and Hodgkin's disease: Transcriptional analysis of virus latency in the malignant cells.
J Exp Med
177:339,
1993[Abstract/Free Full Text]
7.
Robertson KD,
Hayward SD,
Ling PD,
Samid D,
Ambinder RF:
Transcriptional activation of the EBV latency C promoter following 5-azacytidine treatment: Evidence that demethylation at a single CpG site is crucial.
Mol Cell Biol
15:6150,
1995[Abstract]
8.
Robertson KD,
Ambinder RF:
Mapping promoter regions that are hypersensitive to methylation-mediated inhibition of transcription: Application of the methylation cassette assay to the Epstein-Barr virus major latency promoter.
J Virol
71:6445,
1997[Abstract]
9.
Hsieh JJ,
Hayward SD:
Masking of the CBF1/RBPJ kappa transcriptional repression domain by Epstein-Barr virus EBNA2.
Science
268:560,
1995[Abstract/Free Full Text]
10.
Ling PD,
Ryon JJ,
Hayward D:
EBNA-2 of herpesvirus papio diverges significantly from the type A and type B EBNA-2 proteins of Epstein-Barr virus but retains an efficient transactivation domain with a conserved hydrophobic motif.
J Virol
67:2990,
1993[Abstract/Free Full Text]
11.
Counts JL,
Goodman JI:
Alterations in DNA methylation may play a variety of roles in carcinogenesis.
Cell
83:13,
1995[Medline]
[Order article via Infotrieve]
12.
Herman JG,
Latif F,
Weng YK,
Lerman MI,
Zbar B,
Liu S,
Samid D,
Duan DSR,
Gnarra JR,
Linehan WM,
Bavlin SB:
Silencing of the VHL tumor-suppressor gene by DNA methylation in renal carcinoma.
Proc Natl Acad Sci USA
91:9700,
1994[Abstract/Free Full Text]
13.
Karlin S,
Doerfler W,
Cardon LR:
Why is CpG suppressed in the genomes of virtually all small eukaryotic viruses but not in those of large eukaryotic viruses?
J Virol
68:2889,
1994[Abstract/Free Full Text]
14.
Minarovits J,
Minarovits-Kormuta S,
Ehlin-Henriksson B,
Falk K,
Klein G,
Ernberg I:
Host cell phenotype-dependent methylation patterns of Epstein-Barr virus DNA.
J Gen Virol
72:1591,
1991[Abstract/Free Full Text]
15.
Tierney RJ,
Steven N,
Young LS,
Rickinson AB:
Epstein-Barr virus latency in blood mononuclear cells: Analysis of viral gene transcription during primary infection and in the carrier state.
J Virol
68:7374,
1994[Abstract/Free Full Text]
16.
Decker LL,
Klaman LD,
Thorley-Lawson DA:
Detection of the latent form of Epstein-Barr virus DNA in peripheral blood of healthy individuals.
J Virol
70:3286,
1996[Abstract]
17.
Miyashita EM,
Yang B,
Lam KM,
Crawford DH,
Thorley-Lawson DA:
A novel form of Epstein-Barr virus latency in normal B cells in vivo.
Cell
80:593,
1995[Medline]
[Order article via Infotrieve]
18. Sambrook J, Fritsch EF, Maniatis T: Molecular Cloning: A Laboratory Manual. Cold Spring Harbor, NY, Cold Spring Harbor Laboratory, 1989
19.
Frommer M,
McDonald LE,
Millar DS,
Collis CM,
Watt F,
Grigg GW,
Molloy PL,
Paul CL:
A genomic sequencing protocol that yields a positive display of 5-methylcytosine residues in individual DNA strands.
Proc Natl Acad Sci USA
89:1827,
1992[Abstract/Free Full Text]
20.
Ambinder RF,
Shah WA,
Rawlins DR,
Hayward GS,
Hayward SD:
Definition of the sequence requirements for binding of the EBNA-1 protein to its palindromic target sites in Epstein-Barr virus DNA.
J Virol
64:2369,
1990[Abstract/Free Full Text]
21.
Minarovits J,
Hu LF,
Marcsek Z,
Minarovits-Kormuta S,
Klein G,
Ernberg I:
RNA polymerase III-transcribed EBER 1 and 2 transcription units are expressed and hypomethylated in the major Epstein-Barr virus-carrying cell types.
J Gen Virol
73:1687,
1992[Abstract/Free Full Text]
22.
Qu L,
Rowe DT:
Epstein-Barr virus latent gene expression in uncultured peripheral blood lymphocytes.
J Virol
66:3715,
1992[Abstract/Free Full Text]
23.
Chen F,
Zou JZ,
di Renzo L,
Winberg G,
Hu LF,
Klein E,
Klein G,
Ernberg I:
A subpopulation of normal B cells latently infected with Epstein-Barr virus resembles Burkitt lymphoma cells in expressing EBNA-1 but not EBNA-2 or LMP1.
J Virol
69:3752,
1995[Abstract]
24.
Jahner D,
Stuhlmann H,
Stewart CL,
Harbers K,
Lohler J,
Simon I,
Jaenisch R:
De novo methylation and expression of retroviral genomes during mouse embryogenesis.
Nature
298:623,
1982[Medline]
[Order article via Infotrieve]
25.
Bestor TH,
Tycko B:
Creation of genomic methylation patterns.
Nat Genet
12:363,
1996[Medline]
[Order article via Infotrieve]
26.
Bestor TH,
Coxon A:
The pros and cons of cytosine methylation.
Curr Biol
3:384,
1993
27.
Ambinder R,
Mann R:
Epstein-Barr-encoded RNA in situ hybridization.
Hum Pathol
25:602,
1994[Medline]
[Order article via Infotrieve]
28.
Prang NS,
Hornef MW,
Jager M,
Wagner HJ,
Wolf H,
Schwarzmann FM:
Lytic replication of Epstein-Barr virus in the peripheral blood  Analysis of viral gene expression in B lymphocytes during infectious mononucleosis and in the normal carrier state.
Blood
89:1665,
1997[Abstract/Free Full Text]
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati What's this?
This article has been cited by other articles:
|
|
|
|
 
M. Yoshioka, M. M. Crum, and J. T. Sample
Autorepression of Epstein-Barr Virus Nuclear Antigen 1 Expression by Inhibition of Pre-mRNA Processing
J. Virol.,
February 15, 2008;
82(4):
1679 - 1687.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
S. Renaud, D. Loukinov, Z. Abdullaev, I. Guilleret, F. T. Bosman, V. Lobanenkov, and J. Benhattar
Dual role of DNA methylation inside and outside of CTCF-binding regions in the transcriptional regulation of the telomerase hTERT gene
Nucleic Acids Res.,
February 28, 2007;
35(4):
1245 - 1256.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
W.-h. Feng and S. C. Kenney
Valproic Acid Enhances the Efficacy of Chemotherapy in EBV-Positive Tumors by Increasing Lytic Viral Gene Expression.
Cancer Res.,
September 1, 2006;
66(17):
8762 - 8769.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
L.-K. Chang, J.-Y. Chung, Y.-R. Hong, T. Ichimura, M. Nakao, and S.-T. Liu
Activation of Sp1-mediated transcription by Rta of Epstein-Barr virus via an interaction with MCAF1
Nucleic Acids Res.,
November 28, 2005;
33(20):
6528 - 6539.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
P. M. Bhende, W. T. Seaman, H.-J. Delecluse, and S. C. Kenney
BZLF1 Activation of the Methylated Form of the BRLF1 Immediate-Early Promoter Is Regulated by BZLF1 Residue 186
J. Virol.,
June 15, 2005;
79(12):
7338 - 7348.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
J. Elliott, E. B. Goodhew, L. T. Krug, N. Shakhnovsky, L. Yoo, and S. H. Speck
Variable Methylation of the Epstein-Barr Virus Wp EBNA Gene Promoter in B-Lymphoblastoid Cell Lines
J. Virol.,
December 15, 2004;
78(24):
14062 - 14065.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. T.C. Chan, Q. Tao, K. D. Robertson, I. W. Flinn, R. B. Mann, B. Klencke, W. H. Kwan, T. W.-T. Leung, P. J. Johnson, and R. F. Ambinder
Azacitidine Induces Demethylation of the Epstein-Barr Virus Genome in Tumors
J. Clin. Oncol.,
April 15, 2004;
22(8):
1373 - 1381.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
M. Yoshioka, H. Kikuta, N. Ishiguro, X. Ma, and K. Kobayashi
Unique Epstein-Barr virus (EBV) latent gene expression, EBNA promoter usage and EBNA promoter methylation status in chronic active EBV infection
J. Gen. Virol.,
May 1, 2003;
84(5):
1133 - 1140.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Q. Tao, H. Huang, T. M. Geiman, C. Y. Lim, L. Fu, G.-H. Qiu, and K. D. Robertson
Defective de novo methylation of viral and cellular DNA sequences in ICF syndrome cells
Hum. Mol. Genet.,
September 1, 2002;
11(18):
2091 - 2102.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Q N Vo, J Geradts, M L Gulley, D A Boudreau, J C Bravo, and B G Schneider
Epstein-Barr virus in gastric adenocarcinomas: association with ethnicity and CDKN2A promoter methylation
J. Clin. Pathol.,
September 1, 2002;
55(9):
669 - 675.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. J. Tierney, H. E. Kirby, J. K. Nagra, J. Desmond, A. I. Bell, and A. B. Rickinson
Methylation of Transcription Factor Binding Sites in the Epstein-Barr Virus Latent Cycle Promoter Wp Coincides with Promoter Down-Regulation during Virus-Induced B-Cell Transformation
J. Virol.,
November 15, 2000;
74(22):
10468 - 10479.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
A. Krithivas, D. B. Young, G. Liao, D. Greene, and S. D. Hayward
Human Herpesvirus 8 LANA Interacts with Proteins of the mSin3 Corepressor Complex and Negatively Regulates Epstein-Barr Virus Gene Expression in Dually Infected PEL Cells
J. Virol.,
October 15, 2000;
74(20):
9637 - 9645.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
P. J. Jenkins, U. K. Binné, and P. J. Farrell
Histone Acetylation and Reactivation of Epstein-Barr Virus from Latency
J. Virol.,
January 1, 2000;
74(2):
710 - 720.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
E. J. Paulson and S. H. Speck
Differential Methylation of Epstein-Barr Virus Latency Promoters Facilitates Viral Persistence in Healthy Seropositive Individuals
J. Virol.,
December 1, 1999;
73(12):
9959 - 9968.
[Abstract]
[Full Text]
|
|
|
|
|
|
|
H. Chen, J. M. Lee, Y. Wang, D. P. Huang, R. F. Ambinder, and S. D. Hayward
The Epstein-Barr virus latency BamHI-Q promoter is positively regulated by STATs and Zta interference with JAK/STAT activation leads to loss of BamHI-Q promoter activity
PNAS,
August 3, 1999;
96(16):
9339 - 9344.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
Q. Tao, L. J. Swinnen, J. Yang, G. Srivastava, K. D. Robertson, and R. F. Ambinder
Methylation Status of the Epstein-Barr Virus Major Latent Promoter C in Iatrogenic B Cell Lymphoproliferative Disease : Application of PCR-Based Analysis
Am. J. Pathol.,
August 1, 1999;
155(2):
619 - 625.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
R. Singal and G. D. Ginder
DNA Methylation
Blood,
June 15, 1999;
93(12):
4059 - 4070.
[Full Text]
[PDF]
|
|
|
|
|
|
|
Q. Tao, K. D. Robertson, A. Manns, A. Hildesheim, and R. F. Ambinder
The Epstein-Barr Virus Major Latent Promoter Qp Is Constitutively Active, Hypomethylated, and Methylation Sensitive
J. Virol.,
September 1, 1998;
72(9):
7075 - 7083.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
Abstract
Introduction
Abstract