Epstein-Barr virus-encoded EBNA-5 forms trimolecular protein complexes with MDM2 and p53 and inhibits the transactivating function of p53.
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.
Kashuba
Elena
E
Department of Microbiology, Karolinska Institute, Stockholm, Sweden. Elena.Kashuba@ki.se
Yurchenko
Mariya
M
Yenamandra
Surya Pavan
SP
Snopok
Boris
B
Szekely
Laszlo
L
Bercovich
Beatrice
B
Ciechanover
Aaron
A
Klein
George
G
D001402:B-Lymphocytes / Q000378:metabolism* / Q000473:pathology; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D019309:Epstein-Barr Virus Nuclear Antigens / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D011485:Protein Binding; D051736:Proto-Oncogene Proteins c-mdm2 / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020349:Surface Plasmon Resonance; D015534:Trans-Activators; D025803:Tumor Suppressor Protein p14ARF / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D054875:Ubiquitination
C421621:EBNA-5 protein, Epstein-Barr virus; D019309:Epstein-Barr Virus Nuclear Antigens; D012333:RNA, Messenger; C495901:TP53 protein, human; D015534:Trans-Activators; D025803:Tumor Suppressor Protein p14ARF; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2