Deoxyribonucleoside Triphosphate Pools of Normal and Transformed Baby‐Hamster‐Kidney Cells

Pools of the four deoxyribonucleoside triphosphates were determined during growth in tissue culture of baby hamster kidney normal cells and cells transformed either by wild‐type polyoma virus or a temperature‐sensitive mutant of polyoma (ts‐3). The cells are transformed by ts‐3 at 31°C but lose most of their transformed character at 39°C. The three cell lines did not show any major differences with respect to pool sizes at 39°C: during rapid growth, dCTP formed the largest and dGTP the smallest pool, while the dATP and dTTP pools were of intermediate size. On cessation of growth all pools decrease in size; the decrease was very pronounced for dCTP but slight for dATP. The results at 31°C were similar to those at 39°C with one exception: the two transformed lines contained about twice as much dTTP as the normal cell line under comparable growth conditions. Our results suggest that after transformation a change occurs in the control of one or several of the enzymes leading to the synthesis of dTTP. This change is manifested only at the lower temperature.