Thymidine Kinase Activity and DNA Synthesis in Cells Infected with the Parvovirus,H-1 1

Summary

Infection of SV40-transformed newborn human kidney (NB) cell cultures with H-1 virus resulted in a marked drop in the rate of incorporation of ³H-thymidine into DNA relatively late in infection. Autoradiographic measurements revealed that the inhibition of total DNA synthesis was due to a decrease in the capacity of an infected cell to synthesize DNA. Thymidine kinase activity increased 1.5- to 2.6-fold during a period of virus maturation (20–48 hr), but, later in infection, it decreased to 11–43% of the control cell activity. A similar decline in enzyme activity was also observed in “Salk monkey heart” (SMH) cells late after H-1 infection. Extracts prepared from NB cells infected for different times had no effect on the enzyme activity from uninfected cells. The decrease in thymidine kinase activity found after H-1 infection relative to control cell activity was apparently dependent on de novo protein and DNA-dependent RNA synthesis.