Simian virus 40 T antigen is detected only in cells in the G2 phase of the cell cycle in one group of rat transformants.

The relationship between the cell cycle and the presence of the nuclear T antigen in simian virus 40-transformed rat cells independently derived from FR 3T3 cells has been investigated using a fluorescence-activated cell sorter and a combination of stainings for cellular DNA (4',6-diamidine-2-phenylindole dihydrochloride, DAPI) and for the viral T antigen (fluorescein-labeled IgG). Such an analysis revealed that in three out of six lines, T antigen could be detected only in the G2 phase of the cell cycle. In the other three lines, the accumulation of T antigen appeared to be independent of the position of the cell in the cycle. The emergence of either phenotype was strictly correlated with the physiological state of the cell (growing versus resting, respectively) at the time the transformants were established.