Treatment of cultured normal human fibroblasts with an adenosine analog (aminonucleoside of puromycin) rapidly inhibits the appearance of cytoplasmic messenger RNA, identified by its polyadenylate sequence. Similar treatment of SV40-transformed fibroblasts does not lead to such an inhibition. Cordycepin. another analog of adenosine. inlhibits polyadenylate-containing cytoplasmic RNA in both types of cell.
Human embryonic lung fibroblasts (IMR-90 and WI-38) were arrested in the G1 phase of the cell cycle by serum deprivation and high population density. Within 1 hr after the addition of medium containing fresh serum, these cells showed an increase in rRNA synthesis. The inclusion of 100 micrograms per ml aminonucleoside of puromycin (AMS) in the fresh medium eliminated the serum stimulation of rRNA synthesis and prevented the cells from making the G1-resting phase to G1-prereplicative phase transition. AMS also prevented the synthesis of HnRNA normally found within 10 hr after serum stimulation. Serum-stimulated RNA synthesis in starved, SV-40 transformed fibroblasts (WI-38-VA-13 cells) was inhibited, but not completely prevented, by AMS indicating that transformed cells may produce specific RNA's that are not AMS-sensitive and that may be responsible for the failure of transformed cells to be arrested in G1.
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