[Effect of the inhibition of a synthesis processes in the S-period on the subsequent course of mitosis in a synchronized Chinese hamster cell culture]

Abstract

The transcription of all nuclear RNA and rRNA was inhibited in the synchronized Chinese hamster cell culture by actinomycin D and protein synthesis was suppressed by pyromycin during the first and the second parts of the S period of the mitotic cycle. A decrease of the mitotic cell activity was revealed during the first and second waves of cell proliferation after the synchronization irrespective of the time of the antibiotic administration. At the same time there was noticed an increase of such pathological mitoses as C-mitoses and chromosome scattering in the metaphase, whereas suppression of rRNA synthesis determined the delay of cell going out of mitosis (an increase of the anaphase and telophase cell portion) mostly correlated with such type of pathological mitoses as chromatid and chromosome bridges. The protein synthesis depression during the first half of the S-period failed to influence the mitotic regimen of the cell culture during the first, nearest division, but suppressed considerably the cell proliferation during the distant proliferation wave. It is suggested that the cells entered the S-period having in store the proteins for initiation and supporting the genom reduplication at least during the first stage of this process.