Synthesis of DNA-like RNA in synchronized cultures of mammalian cells

Abstract

1. Cultures of KB cells, synchronized by excess thymidine treatment were used to study the synthesis of DNA-like RNA (D-RNA) and total RNA during the various periods of the mammalian cell cycle. The rate of incorporation of [8- 14C]hypoxanthine into RNA was used as a measure of the rate of total RNA synthesis. D-RNA was assayed by the hybridization of 3H-labeled RNA with DNA. 2. The results obtained indicate that D-RNA is a relatively constant fraction of the RNA synthesized at all times in the cell cycle. On the basis of this result, together with the observation that total RNA synthesis continues throughout interphase, it is concluded that D-RNA is synthesized during all 3 periods of interphase, G 1, S and G 2.