Interferon inhibition of thymidine incorporation into DNA through effects on thymidine transport and uptake

Publisher Website
Google Scholar
Abstract
Replenishment of medium after 72 hr of growth of HeLa‐S3 cells in dense suspension cultures increased [3H]‐thymidine uptake into cells and incorporation into DNA, with the levels reaching a peak ∼ 12 hr following medium change; β interferon inhibits the enhanced uptake of [3H]‐thymidine and labeling of DNA in a dose‐dependent manner. Some reduction in these processes is observed at a concentration as low as 1 u/ml, and ∼ 75% inhibition at 640 u/ml. Kinetic analysis has revealed that the rate of labeling of the acid‐soluble pool with [3H]‐thymidine, measured either at 22°C, or 37°C, is reduced in interferon‐treated (640 u/ml, 24 hr) HeLa‐S3 cells. At 22°C, the initial rate of thymidine transport at a high (500 μM) thymidine concentration, determined within the first 30 sec of [3H]‐thymidine addition was depressed by 44% in interferon‐treated HeLa cells. At 37°C, labeled precursors accumulate in acid‐soluble material for ∼ 8 min after the addition of [3H]‐thymidine, after which an apparent equilibrium level is attained. At this temperature, the rate of thymidine uptake and the apparent equilibrium level attained were depressed by 70% in interferon‐treated HeLa cells. The reduced incorporation of [3H]‐thymidine into DNA in interferon‐treated HeLa‐S3 cells can be largely explained by interferon inhibition of thymidine transport and phosphorylation.