Götz, C3; Koenig, M G3; Issinger, O G4; Montenarh, M3
1 Faculty of Science, SDU2 Department of Biochemistry and Molecular Biology, Faculty of Science, SDU3 unknown4 Department of Biochemistry and Molecular Biology, Faculty of Science, SDU
The simian virus 40 (SV40) large T antigen is a multifunctional protein involved in SV40 cell transformation and lytic virus infection. Some of its activities are regulated by interaction with cellular proteins and/or by phosphorylation of T antigen by various protein kinases. In this study, we show that immuno-purified T antigen from SV40-transformed cells and from baculovirus-infected insect cells is tightly associated with a protein kinase that phosphorylates T antigen in vitro. In the presence of heparin or a peptide resembling a protein kinase CK2 recognition site, the phosphorylation of T antigen by the associated kinase is reduced whereas a p34cdc2-kinase-specific peptide has no influence. In addition, the T-antigen-associated protein kinase can use GTP and ATP as phosphate donors. These properties together with the observation that immunopurified T antigen can be phosphorylated by the addition of protein kinase CK2 suggest that at least one of the T-antigen-associated protein kinases is CK2 or a protein-kinase-CK2-related enzyme. The association of recombinant CK2 with T antigen was strongly confirmed by in vitro binding studies. Experiments with temperature-sensitive SV40-transformed cells provide evidence for a close correlation between cell transformation and phosphorylation of T antigen by the associated protein kinase.
European Journal of Biochemistry, 1995, Vol 233, Issue 1, p. 327-34