Abstract
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.
Copyright © 2010 UICC.
MeSH terms
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B-Lymphocytes / metabolism*
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B-Lymphocytes / pathology
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Blotting, Western
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Breast Neoplasms / genetics
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Breast Neoplasms / metabolism*
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Breast Neoplasms / pathology
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Cells, Cultured
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Chromatin Immunoprecipitation
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Epstein-Barr Virus Nuclear Antigens / genetics
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Epstein-Barr Virus Nuclear Antigens / metabolism*
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Female
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Humans
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Protein Binding
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Proto-Oncogene Proteins c-mdm2 / genetics
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Proto-Oncogene Proteins c-mdm2 / metabolism*
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RNA, Messenger / genetics
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Reverse Transcriptase Polymerase Chain Reaction
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Surface Plasmon Resonance
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Trans-Activators*
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Tumor Suppressor Protein p14ARF / genetics
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Tumor Suppressor Protein p14ARF / metabolism
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Tumor Suppressor Protein p53 / antagonists & inhibitors
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Tumor Suppressor Protein p53 / genetics*
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Tumor Suppressor Protein p53 / metabolism*
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Ubiquitination
Substances
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EBNA-5 protein, Epstein-Barr virus
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Epstein-Barr Virus Nuclear Antigens
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RNA, Messenger
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TP53 protein, human
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Trans-Activators
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Tumor Suppressor Protein p14ARF
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Tumor Suppressor Protein p53
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MDM2 protein, human
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Proto-Oncogene Proteins c-mdm2