Structural prerequisites of simian virus 40 large T antigen for the maintenance of cell transformation.
We have investigated the functional roles of two structural subsets of simian virus 40 (SV40) large T antigen, namely homo-oligomers and complexes with the host cellular p53 protein, for the transformed phenotype. We examined T antigen produced in cells transformed by temperature-sensitive SV40 large T mutants: heat-sensitive or unrestricted SV40 tsA58-transformed rat cells and unrestricted tsA1499 transformants. In both unrestricted cell lines, T antigen was temperature-sensitive only for the formation of fast sedimenting homo-oligomers. Corresponding to our recent observations obtained with tsA1499-infected monkey cells, in tsA1499 transformants large T was competent to form stable T-p53 complexes independently of the temperature. However, T antigen coded for by tsA58, which is heat-sensitive for binding to p53, occurred in stable complexes with this protein in unrestricted tsA58 transformants under all conditions. Furthermore, in both unrestricted transformants T-p53 complexes arise in the absence of homo-oligomers of T antigen. In conclusion, T antigen homo-oligomers are not involved in cell transformation, whereas T-p53 complexes may be involved in the maintenance of this phenotype.
D000818:Animals; D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor / Q000235:genetics* / Q000302:isolation & purification; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D006224:Cricetinae; D008647:Mesocricetus; D009154:Mutation; D009856:Oncogene Proteins, Viral / Q000235:genetics* / Q000302:isolation & purification; D010641:Phenotype; D011494:Protein Kinases / Q000235:genetics*; D013539:Simian virus 40 / Q000201:enzymology / Q000235:genetics*; D013696:Temperature
D000952:Antigens, Polyomavirus Transforming; D000957:Antigens, Viral, Tumor; D009856:Oncogene Proteins, Viral; D011494:Protein Kinases