Effect of inhibitors of RNA and protein synthesis on the course of mitosis in a synchronized culture of Chinese hamster cells

Abstract

The period of synthesis of different types of RNA and proteins related to the first mitosis after synchronization in interphase was investigated by means of inhibitors in a synchronized culture of Chinese hamster cells. Analysis of the mitotic index and forms of pathology of mitosis showed that proteins functionally connected with cell division are mainly synthesized in the second half of interphase. The most essential factor for the action of puromycin during this period is induction of C mitoses by suppression of synthesis of the protein responsible for spiralization of the chromosomes in prophase. Suppression of rRNA transcription at any stage affected cytotomy and reconstruction of the daughter nuclei, and was accompanied by delay in the emergency of the cells from mitosis. A high dose of actinomycin D, as an inhibitor of synthesis of total nuclear RNA, by contrast with puromycin, was most effective in the first half of interphase. It is suggested that at least three types of RNA, differing in their functional connections with the next mitosis, are synthesized during this period: an RNA for replication of the genome, an RNA for tubulin synthesis and, finally, an RNA which is a structural component of the division spindle.