|
|||||||||
|
|
|
|
|
|
|
|
|
|
|
Blood, Vol. 96 No. 2 (July 15), 2000:
pp. 625-634
NEOPLASIA
From the Division of Basic Sciences, Department of Pediatrics,
National Jewish Medical and Research Center, Denver, CO.
Interaction between viral proteins and tumor suppressor p53 is a
common mechanism of viral pathogenesis. The Epstein-Barr virus (EBV)
BZLF-1 ORF-encoded ZEBRA protein (also denoted EB1, Z, Zta) binds to
p53 in vitro and has been associated with the altered transcription of
p53-regulated genes in B lymphocytes and epithelial cells. In this
work, Jurkat T-lymphoblastoid cells that express ZEBRA were
characterized by the use of transiently transfected p53 and p53
reporter genes. Stable expression of ZEBRA was associated with the
activation of p53-dependent transcription and increased p53 dependent
apoptotic cell death. In Jurkat cell lines, stably expressed ZEBRA
protein was apparently localized to the cell cytoplasm, in contrast to
the typical nuclear localization of this protein in other cell types.
Previous studies have suggested that EBV infection of T lymphocytes may
contribute to the malignant transformation of T cells and the increased
replication of human immunodeficiency virus. Our observations suggest a
mechanism through which ZEBRA protein expressed in human T lymphocytes
could alter T-cell proliferation and apoptosis during EBV infection.
(Blood. 2000;96:625-634)
The p53 tumor suppressor serves as a checkpoint for DNA
and cellular damage in many cell types.1-3 p53 is a
transcription factor4-6 that directly activates other genes
such as the cyclin-dependent kinase inhibitor p21.7,8
Levels of p53 protein are regulated in part by binding between p53 and
the mdm2 gene product that targets p53 for ubiquitin-dependent
degradation.9 p53-dependent transcription is controlled by
phosphorylation-regulated conformational changes in the
protein.10 Altered p53 activation that results from
hereditary conditions such as ataxia-telangiectasia11 or that exists in mice lacking p53 expression12 is associated
with increased malignancy. In lymphocytes, p53 may play a particularly important role as a checkpoint for DNA recombination errors because these cells undergo site-specific recombination during generation of
the T- and B-cell repertoire.
Oncogenic viruses often encode proteins that are associated with
altered p53 function and altered cellular apoptosis.13,14 The p53 tumor suppressor interacts with proteins expressed by common
human viruses, including adenovirus,15,16
papillomavirus,17-19 human T-cell lymphoma
virus,20 human immunodeficiency virus (HIV),21-25
and herpes viruses including cytomegalovirus,26
human herpes virus 6,27 and Epstein-Barr virus
(EBV).28-30 Interactions between p53 and viral proteins
have been suggested to regulate viral replication.13,14
Activation or altered regulation of pro-apoptotic proteins, such as
p53, by viral gene products may result in selection for cells lacking
functional p53 or p53-regulated gene products. For example, mutated
transcriptionally inactive p53 is usually present in EBV-associated
Burkitt lymphoma.31
ZEBRA protein (also termed Z, Zta, and EB1) encoded by the EBV-BZLF-1
open reading frame binds physically to p53.28 Binding between ZEBRA and p53 occurs in part through sequences in the carboxyl-terminus dimerization domain of the ZEBRA protein and the
carboxyl terminus of p53. ZEBRA is a site-specific transcription factor
required for activation of the viral lytic cycle in
lymphocytes32 that can bind and activate the transcription
of AP-1 sites in the host genome and viral sequences resembling AP-1
sites.33,34 ZEBRA also binds to other endogenous
transcription factors, including NF- Previously, we showed that the cell cycle-regulated expression of p53
is evident during the activation of primary peripheral human T
cells.39 Detection of EBV genome and gene expression in
T-cell lymphoma40-42 suggests that T cells are targets of
EBV infection. In contrast to most EBV genome-positive T-cell tumors that express latency-associated gene products,41,43 lytic
gene products including ZEBRA are expressed in human
thymocytes.43 We suggested a model of EBV infection of T
cells in which the infection of primary T cells with EBV leads to
the abortive transcription of EBV lytic gene products that can rarely
lead to malignant transformation and stable expression of latent gene
products.44 A clinical syndrome has been described in which
chronic, active EBV infection, including expression of the ZEBRA
protein in T cells, was associated with malignant T-cell
lymphoma.42 Increased lytic replication of EBV in patients
with immunodeficiency caused by HIV45 and congenital
immunodeficiency syndromes or chronic fatigue
syndrome46 could also lead interaction between ZEBRA and
p53 in T cells. Therefore, we characterized the effects of ZEBRA
expression on p53-dependent transcription in Jurkat T-lymphoblastoid
cells that can be infected with EBV in vitro, through a receptor
similar, but not identical, to the CD21 EBV receptor present on B
lymphocytes and thymocytes.47
Jurkat T-lymphoblastoid cell lines stably expressing ZEBRA protein were
established. Both wild-type and mutated p53 were introduced into Jurkat
cells using nontoxic lipid reagents. Transcriptional activity of p53
was monitored with reporter genes, including synthetic reporter genes
regulated by the p53 consensus binding site5,6 and the more
complex endogenous p21 promoter.7 We found that levels of
p53 protein detected by Western blotting were increased in Jurkat cells
stably expressing ZEBRA and that the transcription of p53 reporter
genes was markedly increased. Populations of Jurkat cells expressing
ZEBRA transfected with p53 also exhibited increased apoptotic cell
death that was p53-dependent. Mechanisms through which interaction with
the ZEBRA protein might increase p53 stability and activation are
discussed, such as alterations in the ubiquitin-dependent pathways that
degrade p539,48,49 and the activation of p53 through
regulatory sequences in the p53 carboxyl-terminus.10 We
hypothesize that the activation of p53-dependent transcription in
EBV-infected T lymphocytes may inactivate T cells required for the
control of EBV infection50 as a mechanism of viral pathogenesis.
Plasmids
Cell culture and cell lines
Western blot analysis Whole-cell lysates were generated by the lysis of cells in a hypertonic RIPA buffer containing 25 mmol/L Tris pH 7.5, 2% NP-40, 0.2% sodium dodecyl sulfate (SDS), 150 mmol/L NaCl, 0.5% sodium deoxycholate (SDC), and 10% vol/vol glycerol and protease inhibitors aprotinin (20 µg/mL), leupeptin (10 µg/mL), and phenymethylsulfonyl fluoride (1 mmol/L). For immunoprecipitation, Z+ and Z cells were lysed under nondenaturing conditions in a buffer containing 0.15%
NP-40, 20 mmol/L HEPES pH 7.5, 70 mmol/L KCl, 2 mmol/L
MgCl2, and 1 mmol/L dithiothreitol and protease inhibitors.
Lysates were bound to anti-EBV human sera (1/200 dilution of human
anti-serum) and precipitated with washed protein G plus/A Sephadex
beads (Oncogene Science, Santa Barbara, CA). Lysates of cytoplasmic
protein were generated by the lysis of cells in a hypotonic buffer
containing 25 mmol/L Tris pH 7.5, 2% NP-40, 0.2% SDS, 50 mmol/L NaCl,
and 0.5% SDC. Nuclear extracts were prepared as
described.51 After separation of proteins by 12% SDS-PAGE
and transfer to nitrocellulose as described previously,43
Western blots were bound to antibody (1/1000 dilution of primary
antibody OT20A, 1/10,000 dilution of secondary goat antimouse antiserum
[Amersham, Arlington Heights, IL]). Western blots were developed
using the Renaissance system (NEN, Boston, MA). Anti-ZEBRA murine
monoclonal antibody OT20A was obtained from Dr J. Middledorp
(Organon-Teknika, The Netherlands) and reactivity of OT20A to
ZEBRA protein was confirmed using Akata B-lymphoblastoid cells
induced into the lytic cycle by the ligation of surface IgG (data not
shown). Anti-p53 (whole p53 protein) rabbit antiserum was obtained from
Santa Cruz Biologicals (Santa Cruz, CA).
Cell morphology/immunofluorescence studies For a demonstration of the altered Z+ cell morphology Z+ (Z1) and Z cells were photographed 24 hours after plating in standard polystyrene plastic ware (Falcon; Becton Dickinson, Franklin Lakes, NJ). Cells were plated in fresh media and were not otherwise
stimulated. Under these conditions, both Z+ cell lines (Z1 and ZA) had
a similar adherent phenotype as shown, whereas Z cells and
parental Jurkat cells had a nonadherent phenotype typical of Jurkat
cells (ZA and parental Jurkat cell data not shown). For
immunofluorescence studies, Z+ and Z cells were bound to
poly-D-lysine-coated coverslips as described previously for T
lymphocytes.52 Cells were incubated with rabbit polyclonal
antisera (ZEBRA rabbit antisera generated against bacterially produced
whole ZEBRA protein/TrpE fusion protein; obtained from Dr G. Miller) at
a 1/1000 dilution. Cells were then washed and incubated with
biotinylated donkey antirabbit secondary antibody (Jackson Research,
South Park, PA), washed, and incubated with streptavidin Cy3 (Jackson
Research) used at a 1/180 dilution. Cells were photographed using a
Nikon Diaphot 60× oil immersion lens. Data were collected using
IP Lab Spectrum software (Signal Analytics, Vienna, VA).
Transfection of cells Reporter plasmids and p53 expression plasmids (concentration as indicated in the text) were transiently transfected into 2 × 106 logarithmically growing Z+ Jurkat cells stably expressing ZEBRA and Z-control cells with Superfectin (Qiagen) following the recommended procedure for the transfection of nonadherent cells. After transfection, cells were cultured for 36 hours. In experiments shown, cells were also transfected with a plasmid expressing renilla luciferase to control for cell viability and transformation efficiency. Similar results were obtained without the cotransfection of pRL-SV40 and with luciferase activity normalized to micrograms of total protein, determined by the Bradford protein assay (Bio-Rad, Hercules, CA). Cells were irradiated using a hand-held UVB source (Ultraviolet Products, San Gabriel, CA) 3 cm above the washed cells suspended in 1 mm phosphate-buffered saline in a culture dish. For transient transfection of the Jurkat cells shown, a 2-stage transient transfection was used in which ZEBRA expression plasmid and p53 reporter genes were transfected 24 hours before the transfection of p53 expression plasmid to reduce the potential suppression of ZEBRA expression by the coexpression of p53.Luciferase assay Luciferase activity was determined either using the firefly luciferase or Stop-and-Glo assay systems (Promega Biologicals) and an Analytical Luminescence Laboratory (San Diego, CA) luminometer. Results of at least 3 separate experiments were used to generate each data point in luciferase assay experiments. Mean luciferase activity and standard error were determined, as shown graphically and analyzed using the JMP Statistical Discovery Software Version 3.1 (SAS Institute, Cary, NC). Student t test was used for comparison of experiments, and significance (P < .05) was determined by the JMP program.Detection of apoptosis in Jurkat cells Exponentially growing Z+ and Z cells 2 × 106 were transiently transfected with 1 µg wild-type p53
as described above. Cells were stained with propidium iodide and
annexin-fluorescein isothiocyanate (FITC) of apoptotic cell death
using Apo-alert (Clontech, Palo Alto, CA) as instructed by the
manufacturer. Apoptotic cells were quantitated in 3 independent
experiments for each data point shown by fluorescence-activated cell
sorting (FACS) of 2000 cells using a Coulter (Hialeah, FL) Epics XL. In
some experiments 0.5 µg of a plasmid expressing green fluorescent
protein (Green Lantern; New England Biolabs, Boston, MA) was
transfected into Z+ and Z cells to determine transfection
efficiency, and approximately 10% of transfected cells expressed glial
fibrillary protein under conditions used in these studies (data not shown).
Characterization of Jurkat cells stably expressing ZEBRA protein Jurkat T-lymphoblastoid cell lines stably transfected with the ZEBRA expression plasmid pSV2-neo-WZhet were established by selection for growth in G418 selection medium. pSV2-neo-WZhet has previously been shown to express a functional 43-kd variant of the ZEBRA protein that is sufficient to activate the EBV lytic cycle.32 Jurkat cells transfected with pSV2-neo-WZhet (denoted Z+ cells) grown in G418 expressed a 43-kd protein detected by ZEBRA-specific monoclonal antibody OT20A (Figure 1). This 43-kd putative ZEBRA protein was not detected in Jurkat cells stably transfected with control plasmid pSV2-neo (control cells denoted Z cells; Figure 1A).
Expression of transiently transfected p53 protein in Jurkat cells stably expressing ZEBRA protein Because of the previously described effects of ZEBRA protein on p53-dependent gene transcription,28-30 we determined the effects of ZEBRA expression on p53 stability and p53-dependent gene transcription in Z+ cells in comparison to control Z Jurkat
cells. Endogenous p53 protein was not detected in the parental Jurkat
cells used to generate Z+ and Z cell lines (data not shown). To
introduce p53 expression, Z+ and Z cells were transiently
transfected with 1 µg of expression vectors encoding wild-type p53
(pC53-SN3, denoted p53W), p53 amino acids 1 to 353 (pCEP4-353, deleted
from p53 C-terminal regulatory sequences; denoted p53C), and a DNA
binding null mutant form of p53 (pC53-SCX3, denoted p53N). Expression
of cytoplasmic ZEBRA protein did not vary significantly with transient
transfection of p53 expression vectors (Figure 1D). With the transient
transfection of p53 expression vectors, p53 protein encoded by
wild-type p53 expression plasmid and the pCEP4-353 C-terminal deleted
protein was detected in proteins extracted from the nucleus of Z+ cells in hypertonic buffer (Figure 2A).
Expression of p53C was markedly less than the expression of p53W and
was barely detectable by Western blotting. Remarkably, transiently
expressed p53W or other p53 proteins was not detected in the nuclear
proteins of Z cells under these conditions (Figure 2A).
Transiently expressed p53 proteins were not detected in cytoplasmic
proteins extracted from Z+ or Z cells in hypotonic lysis buffer,
with the possible exception of p53N, which was evident as a very faint
band in the cytoplasm of both Z+ and Z cells (Figure 2B).
Activation of a synthetic p53 reporter gene in Jurkat cells stably expressing ZEBRA protein In the absence of activation, the p53 protein is normally rapidly degraded by a ubiquitin-dependent pathway.9,48,49 Binding between p53 and viral proteins in human cells can either stabilize or destabilize p53 through interference with p53 metabolism. In many instances, p53, stabilized by viral proteins, is not transcriptionally active.13 The transcriptional activity of transiently transfected p53 was further characterized in Jurkat cells stably expressing ZEBRA using a reporter gene pG13PYluc. pG13PYluc is a synthetic reporter gene in which 13 copies of an active p53 response element are fused to a polyoma virus promoter.7 Production of luciferase by this reporter gene has previously been shown to be a sensitive and specific measure of p53-dependent transcriptional activity.8 Two hundred nanograms of pG13PYluc was introduced transiently with 500 ng of p53 expression vectors into Z+ and Z Jurkat cells (Figure 3). As in
Western blotting studies (Figure 2), a nontoxic transfection reagent
(Superfectin; Qiagen) was used to introduce DNA into cells. Cells were
not activated in these experiments by radiation or other stimuli, and
viability of cells was similar to that of control cells cultured
without transfection.
Activation of a p21 promoter reporter gene in Jurkat cells stably expressing ZEBRA protein A luciferase reporter gene regulated by the p21 promoter (plasmid WWP-Luc) was previously used21 to characterize the activation of a physiologic target of the p53 protein in epithelial cells. The p21 promoter is a physiologic target of p53 activation, and it was used in addition to the synthetic reporter, pG13Pyluc, to determine the effects of stable ZEBRA expression in Jurkat cells. Transcription of the p21 promoter was activated by cotransfected wild-type p53 (pC53-SN3, denoted p53W) in Jurkat cells stably expressing ZEBRA but not in Z cells (Figure
4A). In these experiments, synergy was
evident between activation of the p53-responsive p21 promoter in Z+
cells and other stimuli, such as ultraviolet irradiation (Figure 4B). A
small but significant increase in expression of the p21 promoter was
also evident in Z+ cells in the absence of cotransfected p53 (Figure
4B) and also in Z cells, but p53-dependent activation of WWP/Luc
was not evident in Z cells (Z data not shown). These
results demonstrated that stable expression of ZEBRA in Jurkat
T-lymphoblastoid cells was associated with p53-dependent activation of
the physiologic p21 promoter, and this activation could synergize with
other activators of p21 transcription.
Increased apoptosis of cells coexpressing ZEBRA protein and p53 Increased expression of p53 reporter genes including the p21 promoter was demonstrated in cells stably expressing ZEBRA protein transfected with p53W expression plasmid (Figures 3, 4). Although p21 promoter expression was activated by cotransfected p53 (Figure 4A), Western blotting was not sufficiently sensitive to detect a convincing increase in p21 expression in Z+ Jurkat cells transfected with p53W (data not shown), possibly because a small percentage (approximately 10%) of transfected cells expressed transiently transfected genes. Further experiments were designed to determine whether populations of Z+ cells demonstrated evidence of increased apoptosis (programmed cell death) in the presence of p53 expression because p53 induces apoptosis in many cell types through the transcription of gene products, including p21.1-3
RNA transcripts encoding ZEBRA are expressed in EBV-infected T
cells,42,43 but ZEBRA protein expression levels are
low.43 A heterogeneous population of EBV-infected
thymocytes contains infected and uninfected cells.43
Thymocytes from normal patients obtained during surgery43
also have endogenous p53 that may be in variable states of activation,
depending on variable conditions such as the health of the tissue
donor. In contrast, Jurkat cells stably expressing ZEBRA protein are a
homogeneous population of cells lacking significant endogenous
p53-dependent transcriptional activity. Therefore, we characterized
p53-dependent transcription in Jurkat cells stably expressing ZEBRA
protein (Figure 1) to test the hypothesis that ZEBRA expression
modulates p53-dependent transcription in T cells. Remarkably, ZEBRA
protein detected in these cells using several ZEBRA-specific antibodies
(mouse monoclonal antibody, human and rabbit polyclonal antisera) was
localized to the cell cytoplasm, as determined by both
immunofluorescence (Figure 1C) and protein fractionation (Figure 1D).
These small amounts of cytoplasmic ZEBRA protein were associated with
an altered cellular morphology (Figure 1E).
We thank Drs James F. Jones, Shannon Kenney, and Lucy Ghoda for helpful
discussions. We also thank Dr Avi Kupfer and Hannah Kupfer for their
assistance with immunofluorescence studies. We thank Diana Nabighian
for her assistance in the preparation of the manuscript.
Submitted November 5, 1999; accepted February 27, 2000.
Supported by National Institutes of Health training grant
T32-AI07365 (D.H.D.).
Reprints: Erwin W. Gelfand, Division of Basic Sciences,
Department of Pediatrics, National Jewish Medical and Research Center,
1400 Jackson St, Denver, CO 80206.
The publication costs of this
article were defrayed in part by
page charge payment. Therefore,
and solely to indicate this fact,
this article is hereby marked
"advertisement"
in accordance with 18 U.S.C.
section 1734.
1.
Ko LJ, Prives C.
p53: puzzle and paradigm.
Genes Dev.
1996;10:1054
2.
Levine AJ.
p53, the cellular gatekeeper for growth and division.
Cell.
1997;88:323[Medline]
[Order article via Infotrieve].
3.
Hawley RS, Friend SH.
Strange bedfellows in even stranger places: the role of ATM in meiotic cells, lymphocytes, tumors, and its functional links to p53.
Genes Dev.
1996;10:2383
4.
el-Deiry WS, Kern SE, Pietenpol JA, Kinzler KW, Vogelstein B.
Definition of a consensus binding site for p53.
Nat Genet.
1992;1:45[Medline]
[Order article via Infotrieve].
5.
Kern SE, Pietenpol JA, Thiagalingam S, Seymor A, Kinzler KW, Vogelstein B.
Oncogenic forms of p53 inhibit p53-regulated gene expression.
Science.
1992;256:827
6.
Pietenpol JA, Tokino T, Thiagalingam S, el-Deiry WS, Kinzler KW, Vogelstein B.
Sequence-specific transcriptional activation is essential for growth suppression by p53.
Proc Natl Acad Sci U S A.
1994;91:1998
7.
el-Deiry WS, Tokino T, Velculescu VE, et al.
WAF1, a potential mediator of p53 tumor suppression.
Cell.
1993;75:817[Medline]
[Order article via Infotrieve].
8.
Macleod KF, Sherry N, Hannon G, et al.
p53-dependent and independent expression of p21 during cell growth, differentiation, and DNA damage.
Genes Dev.
1995;9:935
9.
Shieh SY, Ikeda M, Taya Y, Prives C.
DNA damage-induced phosphorylation of p53 alleviates inhibition by MDM2.
Cell.
1997;91:325[Medline]
[Order article via Infotrieve].
10.
Hupp TR, Sparks A, Lane DP.
Small peptides activate the latent sequence-specific DNA binding function of p53.
Cell.
1995;83:237[Medline]
[Order article via Infotrieve].
11.
Shiloh Y.
Ataxia-telangectasia and the nijmegen breakage syndrome: related disorders but genes apart.
Annu Rev Genet.
1997;31:635[Medline]
[Order article via Infotrieve].
12.
Harris CC, Hollstein M.
Clinical implications of the p53 tumor-suppressor gene.
N Engl J Med.
1993;329:1318
13.
Teodoro JG, Branton PE.
Regulation of apoptosis by viral gene products.
J Virol.
1997;71:1739[Medline]
[Order article via Infotrieve].
14.
Kieff E, Shenk T.
Modulation of apoptosis by herpes viruses.
Semin Virol.
1998;8:471.
15.
Sarnow P, Ho YS, Williams J, Levine AJ.
Adenovirus E1b-58 kd tumor antigen and SV40 large tumor antigen are physically associated with the same 54 kd cellular protein in transformed cells.
Cell.
1982;28:387[Medline]
[Order article via Infotrieve].
16.
Martin MED, Berk AJ.
Adenovirus E1B 55K represses p53 activation in vitro.
J Virol.
1998;72:3146
17.
Werness BA, Levine AJ, Howley PM.
Association of human papillomavirus types 16 and 18 E6 proteins with p53.
Science.
1990;248:76
18.
Jones DL, Thompson DA, Munger K.
Destabilization of the RB tumor suppressor protein and stabilization of p53 contribute to HPV type 16 E7-induced apoptosis.
Virology.
1997;239:97[Medline]
[Order article via Infotrieve].
19.
Daniels PR, Sanders CM, Maitland NJ.
Characterization of the interactions of human papillomavirus type 16 E6 with p53 and E6-associated protein in insect and human cells.
J Gen Virol.
1998;79:489[Abstract].
20.
Pise-Masison CA, Choi KS, Radonovich M, Dittmer J, Kim SJ, Brady JN.
Inhibition of p53 transactivation function by the human T-cell lymphotropic virus type 1 tax protein.
J Virol.
1998;72:1165
21.
Duan L, Ozaki I, Oakes JW, Taylor JP, Khalili K, Pomeranz RJ.
The tumor suppressor p53 strongly alters human immunodeficiency virus type 1 replication.
J Virol.
1994;68:4302
22.
Subler MA, Martin DW, Deb S.
Activation of the human immunodeficiency virus type 1 long terminal repeat by transforming mutants of human p53.
J Virol.
1994;68:103
23.
Greenway A, Azad A, McPhee D.
Human immunodeficiency virus type 1 Nef protein inhibits activation pathways in peripheral blood mononuclear cells and T-cell lines.
J Virol.
1995;69:1842[Abstract].
24.
Li CJ, Wang C, Friedman DJ, Pardee AB.
Reciprocal modulations between p53 and Tat of human immunodeficiency virus type 1.
Proc Natl Acad Sci U S A
1995;92:5461
25.
Longo F, Marchetti MA, Castagnolli L, Battaglia PA, Gigliani F.
A novel approach to protein-protein interaction: complex formation between the p53 tumor suppressor and the HIV TAT proteins.
Biochem Biophys Res Comm.
1995;206:326[Medline]
[Order article via Infotrieve].
26.
Fortunato EA, Spector DH.
p53 and RPA are sequestered in viral replication centers in the nuclei of cells infected with human cytomegalovirus.
J Virol.
1998;72:2033
27.
Kashanchi F, Araujo J, Doniger J, et al.
Human herpes virus 6 (HHV-6) ORF-1 transactivating gene exhibits malignant transforming activity and its protein binds to p53.
Oncogene.
1997;14:359[Medline]
[Order article via Infotrieve].
28.
Zhang Q, Gutsch D, Kenney S.
Functional and physical interaction between p53 and BZLF-1: implications for Epstein-Barr virus latency.
Mol Cell Biol.
1994;14:1929
29.
Cayrol C, Flemington EK.
The Epstein-Barr virus bZIP transcription factor Zta causes G0/G1 cell cycle arrest through induction of cyclin dependent kinase inhibitors.
EMBO J.
1996;15:2748[Medline]
[Order article via Infotrieve].
30.
Chen W, Cooper NR.
Epstein-Barr virus nuclear antigen 2 and latent membrane protein independently transactivate p53 through induction of NF-kB activity.
J Virol.
1996;70:4849[Abstract].
31.
Farrell PJ, Allan GJ, Shanahan F, Vousdan KH, Crook T.
p53 is frequently mutated in Burkitt's lymphoma cell lines.
EMBO J.
1991;10:2879[Medline]
[Order article via Infotrieve].
32.
Countryman J, Jenson H, Seibl R, Wolf H, Miller G.
Polymorphic proteins encoded within BZLF-1 of defective and standard Epstein-Barr viruses disrupt latency.
J Virol.
1987;61:3672
33.
Farrell PJ, Rowe DT, Rooney CM, Kouzarides T.
Epstein-Barr virus BZLF-1 trans-activator specifically binds to a consensus AP-1 site and is related to c-fos.
EMBO J.
1989;8:127[Medline]
[Order article via Infotrieve].
34.
Flemington E, Speck SH.
Epstein-Barr virus BZLF1 trans-activator induces the promoter of a cellular cognate gene, c-fos.
J Virol.
1990;64:4549
35.
Gutsch DE, Holley-Guthrie EA, Zhang Q, et al.
The bZIP transactivator of Epstein-Barr virus, BZLF-1, functionally and physically interacts with the p65 subunit of NF-
36.
Sista ND, Barry C, Sampson K, Pagano JS.
Physical and functional interaction of the Epstein- Barr virus BZLF1 transactivator with the retinoic acid receptors RARa and RXRa.
Nucl Acids Res.
1995;23:1729
37.
Lieberman PM, Berk AJ.
The Zta trans-activator protein stabilizes TFIID association with promoter DNA by direct protein-protein interaction.
Genes Dev.
1991;5:2441
38.
Kouzarides T, Packham C, Cook A, Farrell PJ.
The BZLF-1 protein of EBV has a coiled coil dimerisation domain without a heptad leucine repeat but with homology to the C/EBP leucine zipper.
Oncogene.
1991;6:195[Medline]
[Order article via Infotrieve].
39.
Terada N, Lucas JJ, Gelfand EW.
Differential regulation of the tumor suppressor molecules, retinoblastoma susceptibility gene product (Rb) and p53, during cell cycle progression of normal human T cells.
J Immunol.
1991;147:698[Abstract].
40.
Jones JF, Shurin S, Abramowsky C, et al.
T-cell lymphomas containing Epstein-Barr viral DNA in patients with chronic Epstein-Barr virus infections.
N Engl J Med.
1988;318:733[Abstract].
41.
Chen C, Sadler RH, Walling DM, Su I, Hsieh H, Raab-Traub N.
Epstein-Barr virus (EBV) gene expression in EBV-positive peripheral T-cell lymphomas.
J Virol.
1993;67:6303
42.
Kanegane H, Bhatia K, Gutierrez M, et al.
A syndrome of peripheral blood T-cell infection with Epstein-Barr virus (EBV) followed by EBV-positive T-cell lymphoma.
Blood.
1998;91:2085
43.
Kelleher CA, Kaufman-Patterson R, Dreyfus DH, et al.
Epstein-Barr virus replicative gene transcription during de novo infection of human thymocytes: simultaneous early expression of BZLF-1 and its repressor RAZ.
Virology.
1995;208:685[Medline]
[Order article via Infotrieve].
44.
Dreyfus DH, Kelleher CA, Jones JF, Gelfand EW.
Epstein-Barr virus infection of T cells: implicationsfor altered T-lymphocyte activation, repertoire development, and autoimmunity.
Immunol Rev.
1996;152:89[Medline]
[Order article via Infotrieve].
45.
Guan M, Zhang RD, Wu B, Henderson EE.
Infection of primary CD4+ and CD8+ T lymphocytes by Epstein-Barr virus enhances human immunodeficiency virus expression.
J Virol.
1996;70:7341
46.
Katz BZ, Berkman AB, Shapiro ED.
Serologicevidence of active Epstein-Barr virus infection in Epstein-Barr virus-associated lymphoproliferative disorders of children with acquired immunodeficiency syndrome.
J Pediatr.
1992;120:228[Medline]
[Order article via Infotrieve].
47.
Sinha SK, Todd SC, Hedrick JA, Speiser CL, Lambris JD, Tsoukas CD.
Characterization of the EBV/C3d receptor on the human Jurkat T cell line.
J Immunol.
1993;150:5311[Abstract].
48.
Li X, Coffino P.
Identification of a region of p53 that confers lability.
J Biol Chem.
1996;271:4447
49.
Ciechanover A, Shkedy D, Oren M, Bercovich B.
Degradation of the tumor suppressor protein p53 by the ubiquitin-mediated proteolytic system requires a novel species of ubiquitin-carrier protein E2.
J Biol Chem.
1994;269:9582
50.
Rickinson AB, Kieff E.
Epstein-Barr virus. Fields Virology. Philadelphia: Lippincott-Raven; 1996:2397-2446.
51.
Schreiber E, Matthias P, Muller MM, Schaffner W.
Rapid detection of octamer binding proteins with "mini-extracts"prepared from a small number of cells.
Nucl Acids Res.
1989;17:6419
52.
Monks CR, Kupfer H, Tamir I, Barlow A, Kupfer A.
Selective modulation of protein kinase C during T-cell activation.
Nature.
1997;385:83[Medline]
[Order article via Infotrieve].
53.
Daibata M, Humphreys RE, Sairenji T.
Phosphorylation of the Epstein-Barr virus immediate-early gene product BZLF-1.
Virology.
1992;188:916[Medline]
[Order article via Infotrieve].
54.
Dreyfus DH, Nagasawa M, Pratt JC, Kelleher CA, Gelfand EW.
Inactivation of NF-
55.
Furnari FB, Zacny V, Quinlivan EB, Kenney S, Pagano JS.
RAZ, an Epstein-Barr virus transdominant repressor that modulates the viral reactivation mechanism.
J Virol.
1994;68:1827
56.
Selivanova G, Iotsova V, Okan I, et al.
Restoration of the growth suppression function of mutant p53 by a synthetic peptide derived from the p53 C-terminal domain.
Nat Med.
1997;3:632[Medline]
[Order article via Infotrieve].
57.
Gu W, Shi XL, Roeder RG.
Synergistic activation of transcription by CBP and p53.
Nature.
1997;387:819[Medline]
[Order article via Infotrieve].
58.
Lill NL, Grossman SR, Ginsberg D, Decaprio J, Livingston DM.
Binding and modulation of p53 by p300/CBP coactivators.
Nature.
1997;387:823[Medline]
[Order article via Infotrieve].
59.
Avantaggiati ML, Ogryzko V, Gardner K, Giordano A, Levine AS, Kelly K.
Recruitment of p300/CBP in p53-dependent signal pathways.
Cell.
1997;89:1175[Medline]
[Order article via Infotrieve].
60.
Flamand L, Menezes J.
Cyclic AMP-responsive element-dependent activation of Epstein-Barr virus Zebra promoter by human herpes virus 6.
J Virol.
1996;70:1784[Abstract].
61.
Coffey AJ, Brooksbank RA, Brandau O, et al.
Host response to EBV infection in X-linked lymphoproliferative disease results from mutations in an SH2-domain encoding gene.
Nat Genet.
1999;20:129.
This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 |
 |
 |
|||||||
 |
 |
 |
 |
 |
 |
 |
 |
||
| Copyright © 2000 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||
Top
Abstract
Introduction
B p65,
the LMP-1 and
EBNA-2 proteins expressed during viral latency
