RNA synthesis in Tetrahymena: Temperature-pressure studies

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RNA has been extracted from whole cells of heat-synchronized Tetrahymena and fractionated by methylated albumin Kieselguhr chromatography (MAK). It was found that ribosomal precursor RNA (Q 1) and ribosomal RNA are synthesized during the period between the end of the heat treatment and cytokinesis. Moreover, there is an increase in the synthesis of Q 1 RNA during the later half of cell cycle. The synthesis of DNA-like RNA is maintained during the cycle, however the amount of DNA-like RNA associated with cytoplasmic ribosomes increases at later stages during the cycle. The effects of two physical agents, high temperature and high hydrostatic pressure, on RNA synthesis were also investigated. It was established that these agents markedly inhibit the synthesis of both ribosomal RNA and DNA-like RNA. It is proposed that transfer of messenger RNA from the nucleus to the cytoplasm increases as the cells approach cytokinesis and this is related to the synthesis of ‘division protein’. Moreover, the temperature and pressure treatments result in the inhibition of the supply of messenger RNA.