Activity of Thymidine Kinase in Mouse Embryo Cells infected with Polyoma Virus

INFECTION of cells with DNA viruses is known to cause an increase in the activity of several enzymes involved in the synthesis of DNA1–3. Kit and Dubbs4 reported that infection of mouse fibroblasts with vaccinia or herpes virus determines the induction of a thymidine kinase (TK), which differs from that of uninfected cells in certain chemico-physical properties, including the resistance to thermal inactivation. Dulbecco et al.5 observed that infection of mouse kidney cells with polyoma virus causes an increase in the activity of TK and DNA polymerase, and suggested that this phenomenon may be related to the enhanced synthesis of cellular DNA.