Cell cycle study on the effect of interferon on synchronized mouse embryo fibroblasts

Mouse embryo fibroblasts synchronized by controlling cultural conditions were used to examine the effects of interferon (IFN) while undergoing a single synchronous cycle of division at the tertiary stage. IFN was added early in G1 and at the G1-S boundary and the duration of specific phases of the cycle were investigated together with biochemical events related to cell cycle progression. Assessment of population distribution by fluorimetric quantitation of DNA content showed that IFN extended G1 and G2 but had no effect on the duration of S phase. Assessment of transport and uptake of exogenous TdR and measurements of specific kinase activity under conditions where DNA synthesis and S phase were not altered showed that IFN had no effect on TdR transport but could markedly reduce TdR uptake, and delay the S phase associated increase of TdR-kinase activity.