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

J Virol. 1988 Sep;62(9):3407-14. doi: 10.1128/JVI.62.9.3407-3414.1988.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 1-Phosphatidylinositol 4-Kinase
  • Animals
  • Antigens, Polyomavirus Transforming / genetics*
  • Cell Line
  • Cell Transformation, Neoplastic*
  • Cell Transformation, Viral*
  • Cloning, Molecular
  • DNA, Viral / genetics
  • Fibroblasts
  • Genetic Vectors
  • Immunoassay
  • Mice
  • Mutation
  • Phosphotransferases / metabolism*
  • Polyomavirus / enzymology
  • Polyomavirus / genetics
  • Polyomavirus / growth & development
  • Polyomavirus / immunology*
  • Retroviridae / genetics
  • Transfection


  • Antigens, Polyomavirus Transforming
  • DNA, Viral
  • Phosphotransferases
  • 1-Phosphatidylinositol 4-Kinase