Phosphorylation of the epstein-barr virus nuclear antigen 2

Grässer, Friedrich A.; Göttel, Susanne; Haiss, Peter; Boldyreff, Brigitte; Issinger, O.-G.; Mueller‐Lantzsch, Nikolaus

doi:10.1016/s0006-291x(05)81604-3

Cited by 30 publications

(34 citation statements)

References 21 publications

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“…Zone Velocity Sedimentation-Extracts of 1.5 ϫ 10 7 EBV-positive and EBV-negative cells were separated by centrifugation through a 15-30% sucrose gradient as described (39). Fifteen fractions collected by bottom puncture were precipitated in ethanol and subjected to 10% SDS-PAGE (polyacrylamide gel electrophoresis) followed by immunoblotting with mAbs 2G7 and 1H4 directed against Rch1 and EBNA1, respectively.…”

Section: Leumentioning

confidence: 99%

“…For this purpose, cell extracts were analyzed by sucrose gradient centrifugation as described previously (39). We compared the EBV-negative cell lines BL41 and BJAB (both cell lines were isolated from patients diagnosed with Burkitt's lymphoma) with the EBNA1-expressing cell lines BL41-P3HR1 (BL41 cells infected with the P3HR1 strain of EBV) and the human lymphoblastoid cell line iB4 (generated from uninfected primary human lymphoid cells by infection with the B95-8 virus).…”

Section: Inhibition Of Nuclear Transport Of Ebna1 By N-terminally Trumentioning

confidence: 99%

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Epstein-Barr Virus Nuclear Antigen 1 Forms a Complex with the Nuclear Transporter Karyopherin α2

Fischer

Kremmer²,

Lautscham

et al. 1997

Journal of Biological Chemistry

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The Epstein-Barr virus (EBV) is implicated in the induction of several malignancies. The nuclear antigen 1 (EBNA1) is the only viral protein that is expressed consistently in all EBV-associated tumors. EBNA1 is involved in the replication and maintenance of the viral episome in the infected cell and exhibits oncogenic activity in transgenic mice. Here we report the identification of the nuclear transporter karyopherin ␣2 as a cellular partner of EBNA1 using the yeast "two-hybrid system." Karyopherin ␣2 is also called importin ␣ or Rch1. The binding to karyopherin ␣2 was mediated through a C-terminal region of EBNA1 encompassing the nuclear localization signal, whereas clones of EBNA1 devoid of the nuclear localization signal failed to bind to karyopherin ␣2. The interaction was biochemically confirmed by far-Western analysis using bacterially expressed karyopherin ␣2 and karyopherin ␣2-specific monoclonal antibodies. The nuclear transport of EBNA1 was impaired by expression of N-terminally truncated karyopherin ␣2. Zone velocity sedimentation in a sucrose gradient indicated that: (i) EBNA1 and Rch1 colocalize; and (ii) the association of karyopherin ␣2 with high molecular weight protein complexes might be impeded by the presence of EBNA1.The Epstein-Barr virus (EBV) 1 is the etiological agent of infectious mononucleosis and is implicated in the induction of several malignancies including Burkitt's lymphoma, nasopharyngeal carcinoma, Hodgkin's disease, T-cell lymphoma, and polyclonal B-cell lymphoma that arise under immunosuppression (reviewed in Ref. 1). The expression of EBV-encoded proteins is most stringently restricted in primary Burkitt's lymphoma in that only EBNA1 and the nontranslated EpsteinBarr virus-encoded small nuclear RNAs are transcribed. EBNA1 binds to the viral origin of replication (oriP)(2, 3) and is the only virus protein necessary and sufficient to replicate and maintain the EBV genome in the infected cell (4). In addition, experiments using transgenic animals show that EBNA1 by itself is able to induce tumors in vivo (5, 6). EBNA1 is a multifunctional phosphoprotein (7) with a variety of properties, including sequence-specific binding to DNA (8, 9), formation of homodimers (10), nuclear localization (11), and stimulation of cellular gene expression (12).Import of proteins into the nucleus is an active process that can be divided into at least two steps: 1) binding of proteins with a nuclear localization signal (NLS) to a cytosolic NLSreceptor and translocation to the nuclear pore complex; and 2) transport of NLS-bearing proteins into the nucleus. The NLSreceptor consists of two subunits, a 60-kDa protein that is called karypherin ␣2 (alternatively, it is called importin ␣ in vertebrates and Srp1 in yeast) and a 95-kDa protein, called karyopherin ␤ (also known as importin ␤ in vertebrates and Kap95p in yeast). Karyopherin ␣2 serves as the NLS-receptor, whereas karyopherin ␤ functions as an adapter that mediates binding to nucleoporins. Two additional proteins, GTPase Ran/ TC4 and p15 (NTF2...

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Section: Leumentioning

confidence: 99%

Section: Inhibition Of Nuclear Transport Of Ebna1 By N-terminally Trumentioning

confidence: 99%

Epstein-Barr Virus Nuclear Antigen 1 Forms a Complex with the Nuclear Transporter Karyopherin α2

Fischer

Kremmer²,

Lautscham

et al. 1997

Journal of Biological Chemistry

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“…Only this fusion protein exhibits tyrosine kinase activity that results in autophosphorylation and tyrosine phosphorylation of other cellular proteins. Finally, there are known viral phosphoproteins such as the EBV protein ENBA-2 that has phosphorylation at Ser 469 and Ser 470 (37), EBV latent membrane protein 1 at Ser 313 and Thr 324 (38), and EBV BZLF1 at Ser 173 (39). Indeed, phosphorylated peptides could be directly purified from MHC molecules derived from several different EBV-transformed B lymphoblastoid cell lines, exposing the repertoire of naturally processed and phosphorylated peptides that are presented by MHC class I molecules (26).…”

Section: Discussionmentioning

confidence: 99%

Reduced KIR2DL1 Recognition of MHC Class I Molecules Presenting Phosphorylated Peptides

Betser-Cohen¹,

Katz²,

Gonen‐Gross³

et al. 2006

The Journal of Immunology

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As initially described by K. Karre and colleagues in the missing self hypothesis, cells expressing self-MHC class I proteins are protected from NK cells attack. In contrast, reduction in the expression of MHC class I molecules due to viral infection or tumor transformation result in the killing of these “abnormal” cells by NK cells via NK-activating receptors. Thus, NK killing of target cells is determined by both negative signals coming from MHC class I proteins and by positive signals derived from the activating ligands. The bound peptide in MHC class I play an important role in the balanced recognition of NK cells. The peptide stabilizes the MHC complex and interacts directly with the NK inhibitory receptors, thus participating in the determination of the fate of the target cells. In this study we demonstrate that posttranslational modifications such as phosphorylation of the presented peptide altered the ability of NK cells to recognize MHC class I molecules. By using a consensus peptide (QYDDAVYKL) that binds HLA-Cw4 in which different positions in the bound peptide were modified by serine phosphorylation, we observed a reduction in KIR2DL1 binding that led to decreased protection from NK killing. Therefore, it might be possible that alteration in the phosphorylation pattern during tumor transformation or viral infection may result in less inhibition and, consequently, improved NK cell killing.

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“…This is consistent with the long lifetime of other EBNAs. [30][31][32][33] EBNA-5 expression delays the activation of p53-dependent genes after DNA damage…”

Section: Binding Of Ebna-5 To Mdm2 Prevents Polyubiquitination and 26mentioning

confidence: 99%

Epstein‐Barr virus‐encoded EBNA‐5 forms trimolecular protein complexes with MDM2 and p53 and inhibits the transactivating function of p53

Kashuba

Yurchenko

Yenamandra

et al. 2010

Intl Journal of Cancer

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We report that MDM2, a negative regulator of p53, can bind to EBNA-5. Using GST pull-down assay, immunoprecipitation, surface plasmon resonance and immunostaining of lymphoblastoid cells, we found that trimolecular complexes are formed between EBNA-5, MDM2 and p53, where MDM2 serves as a bridge. The EBNA-5 binding to MDM2 counteracted destabilizing effect of the latter on the p53. In ubiquitination and degradation assays in vitro, EBNA-5 inhibited p53 polyubiquitination (but not monoubiquitination) in a concentration-dependent manner. This resembles the effect of p14ARF on p53. Moreover, EBNA-5 was found to inhibit the degradation of p53 in vitro. High levels of p53 expression were maintained in LCLs. The binding of EBNA-5 to MDM2 also could impair the functional activity of p53. The p53-dependent genes P21 and VDR were not induced in EBV-infected, in contrast to mitogen-activated cells. This may explain the tolerance of established LCLs to high levels of p53 without undergoing apoptosis.

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Phosphorylation of the epstein-barr virus nuclear antigen 2

Cited by 30 publications

References 21 publications

Epstein-Barr Virus Nuclear Antigen 1 Forms a Complex with the Nuclear Transporter Karyopherin α2

Epstein-Barr Virus Nuclear Antigen 1 Forms a Complex with the Nuclear Transporter Karyopherin α2

Reduced KIR2DL1 Recognition of MHC Class I Molecules Presenting Phosphorylated Peptides

Epstein‐Barr virus‐encoded EBNA‐5 forms trimolecular protein complexes with MDM2 and p53 and inhibits the transactivating function of p53

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