The synthesis of ribosomal 5 S RNA in cultured hamster cells during the inhibition of protein synthesis

Ribosomal 5 S RNA synthesis in Chinese hamster V79 cells treated with an inhibitory antibiotic of protein synthesis, cycloheximide, was quantitated by hybridization of RNA preparations with plasmid ColE1-pSC101 DNA carrying Xenopus 5 S DNA. In V79 cells, cycloheximide produced a notable decrease in the production of the higher molecular weight ribosomal RNA (rRNA) fraction, whereas the accumulation of both 5 S RNA and polyadenylate-containing messenger RNA was much less affected. When the cellular protein synthesis was inhibited by over 85% of the control, accumulation of 5 S RNA and of rRNA was respectively 40–50% and about 10% of the control. The size distribution analysis of RNA species revealed that 5 S RNAs obtained from V79 cells after treatment with 0.1 μg/ml or 2.0 μg/ml cycloheximide were indistinguishable from control. Inhibition of precursor uptake into 5 S RNA by cycloheximide was apparently phase-specific during the cell cycle and was 44–67% and 78–85% of the control for the S and the M phase, respectively. The responses of RNA polymerase III activities to cycloheximide in isolated nuclei from each phase of the cell cycle correlated very well with those of precursor uptake into 5 S RNA observed in vivo, while total solubilized RNA polymerase activities showed no inhibition by the drug at any phase of the cell cycle. Cytosine arabinoside, a specific inhibitor of DNA synthesis, did not cause any decrease in the cellular level of 5 S RNA.