Recombinant retroviruses that transduce middle T antigen cDNAs derived from polyomavirus mutants: separation of focus formation and soft-agar growth in transformation assays and correlations with kinase activities in vitro.
To study correlations between cellular transformation and the biochemical properties of polyomavirus middle T antigen, middle T cDNAs have been derived from the polyomavirus mutants dl1015, dl23, and NG59b and have been introduced into rodent fibroblast cell lines by using a retrovirus vector. It was found that all three mutants are completely defective in inducing growth in soft agar but possess a range of activities in assays of focus formation on cell monolayers. Furthermore, when assays of middle T antigen-associated kinase activities were performed in vitro, a correlation between the level of associated phosphatidylinositol kinase activity and the ability of mutant middle T antigens to induce focus formation was observed. However, the association of this activity with middle T antigen does not appear to be sufficient to bring about full transformation, since the middle T antigen derived from dl1015 is completely defective for soft-agar growth but is associated with a level of phosphatidylinositol kinase activity which is comparable to that of the wild type. Therefore, some other unidentified middle T antigen function may also be required for full transformation.
Morgan
W C
WC
Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
Kaplan
D R
DR
Pallas
D C
DC
Roberts
T M
TM
D019870:1-Phosphatidylinositol 4-Kinase; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002472:Cell Transformation, Viral; D003001:Cloning, Molecular; D004279:DNA, Viral / Q000235:genetics; D005347:Fibroblasts; D005822:Genetic Vectors; D007118:Immunoassay; D051379:Mice; D009154:Mutation; D010770:Phosphotransferases / Q000378:metabolism*; D011120:Polyomavirus / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000276:immunology*; D012190:Retroviridae / Q000235:genetics; D014162:Transfection
D000952:Antigens, Polyomavirus Transforming; D004279:DNA, Viral; D010770:Phosphotransferases; D019870:1-Phosphatidylinositol 4-Kinase