Complex formation between the lymphotropic papovavirus large tumor antigen and the tumor suppressor protein p53.
The simian B-lymphotropic papovavirus (LPV) encodes a large tumor antigen (T antigen) which is 45% identical to both the simian virus 40 (SV40) and the polyomavirus (PyV) large T antigens. In transgenic mice, the transforming properties of the LPV T antigen are similar to those of the SV40 T antigen. However, little is known about its biochemical activities. Since SV40 T antigen forms a complex with and stabilizes the host cell tumor suppressor protein p53 while the PyV large T antigen does not, we characterized the LPV T antigen for its ability to complex p53. We demonstrate an association between LPV T antigen and p53 in both a tumor-derived cell line and BALB/c 3T3 cells transformed in culture. A third protein of approximately 68 kDa which was found associated with the LPV T antigen-p53 complex in tumor-derived cells appears to be heat shock protein 70 (hsp70). The half-life of p53 in all LPV T-antigen-transformed cells was extended significantly; i.e., it was 3 to 7 h compared with 19 minutes in BALB/c 3T3 cells. The half-life of the LPV T antigen itself was 5 to 9 h depending on the cell line origin. That p53 was stabilized because of association with LPV T antigen and not because of mutation was demonstrated with the p53 conformation-dependent monoclonal antibody PAb246. This antibody distinguishes between wild-type p53 (PAb246+) and mutant, oncogenic p53 (PAb246-). Sequential immunoprecipitation showed all detectable p53 to be of the PAb246+ class in each LPV-transformed cell line, suggesting that the stable p53 was indeed wild type.
Symonds
H
H
Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260.
Chen
J D
JD
Van Dyke
T
T
D000595:Amino Acid Sequence; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D007700:Kinetics; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D027383:Papillomaviridae / Q000235:genetics*; D027382:Polyomaviridae; D011485:Protein Binding; D012689:Sequence Homology, Nucleic Acid; D016159:Tumor Suppressor Protein p53 / Q000302:isolation & purification / Q000378:metabolism*
D000952:Antigens, Polyomavirus Transforming; D016159:Tumor Suppressor Protein p53