MDM2 is a target of simian virus 40 in cellular transformation and during lytic infection.
Phosphopeptide analyses of the simian virus 40 (SV40) large tumor antigen (LT) in SV40-transformed rat cells, as well as in SV40 lytically infected monkey cells, showed that gel-purified LT that was not complexed to p53 (free LT) and p53-complexed LT differed substantially in their phosphorylation patterns. Most significantly, p53-complexed LT contained phosphopeptides not found in free LT. We show that these additional phosphopeptides were derived from MDM2, a cellular antagonist of p53, which coprecipitated with the p53-LT complexes, probably in a trimeric LT-p53-MDM2 complex. MDM2 also quantitatively bound the free p53 in SV40-transformed cells. Free LT, in contrast, was not found in complex with MDM2, indicating a specific targeting of the MDM2 protein by SV40. This specificity is underscored by significantly different phosphorylation patterns of the MDM2 proteins in normal and SV40-transformed cells. Furthermore, the MDM2 protein, like p53, becomes metabolically stabilized in SV40-transformed cells. This suggests the possibility that the specific targeting of MDM2 by SV40 is aimed at preventing MDM2-directed proteasomal degradation of p53 in SV40-infected and -transformed cells, thereby leading to metabolic stabilization of p53 in these cells.
Henning
W
W
Heinrich-Pette-Institut für Experimentelle Virologie und Immunologie, Hamburg, Germany.
Rohaly
G
G
Kolzau
T
T
Knippschild
U
U
Maacke
H
H
Deppert
W
W
D016475:3T3 Cells; D000818:Animals; D000957:Antigens, Viral, Tumor / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D002522:Chlorocebus aethiops; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism; D009687:Nuclear Proteins; D010449:Peptide Mapping; D010748:Phosphopeptides / Q000737:chemistry / Q000302:isolation & purification; D014176:Protein Biosynthesis; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051736:Proto-Oncogene Proteins c-mdm2; D051381:Rats; D013539:Simian virus 40 / Q000472:pathogenicity / Q000502:physiology*; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism
D000957:Antigens, Viral, Tumor; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D010748:Phosphopeptides; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497207:Mdm2 protein, mouse; C497208:Mdm2 protein, rat; D051736:Proto-Oncogene Proteins c-mdm2