DNA polymerase alpha and beta activity in gamma-irradiated HeLa S3 cells

The acute effects (less than 2 hours) of gamma-irradiation on DNA polymerase alpha and beta activity in HeLa S3 cells were studied. The enzyme activities were measured in sonicates of the irradiated cells, using an exogenous DNA as template. Both DNA alpha- and beta-polymerase activities decreased following irradiation of the cells. Doses as low as 100 rad significantly reduced the activities of the enzymes. While the activities of both DNA polymerases decreased as the dose received by the cells increased, the major reduction in enzyme activity occurred with doses of 100--200 rad. The reduction in DNA alpha- and beta-polymerase activities was maximal by 30 min post-irradiation and recovered to control values by 2 hours post-irradiation.