On the mechanism of phenethyl alcohol-induced loss of polyribosomes and their re-formation after reversal in rat hepatoma cells.

Treatment of exponentially growing Novikoff rat hepatoma cells with cytostatic concentrations of phenethyl alcohol causes a rapid disappearance of both the free and the membrane-bound polyribosomes, with the concomitant appearance of 80 S and 110 S ribosomal particles. This is accompanied by an 80 to 90% reduction in the rate of protein synthesis by the cells. The phenethyl alcohol-induced loss of polyribosomes is prevented by treating cells with actidione (cycloheximide) before phenethyl alcohol. This result suggests that the loss of polyribosomes after treatment with phenethyl alcohol probably results from the normal release of ribosomes from the messenger upon completion of polypeptide chains and a simultaneous interference by phenethyl alcohol with the reattachment of ribosomes to messenger RNA. Messenger RNA is conserved during treatment with phenethyl alcohol, since upon removal of the chemical from the cells protein synthesis resumes in the presence of actinomycin D at about 80% of the normal rate with the concomitant re-formation of the polyribosomes. Experiments were undertaken to elucidate the fate of messenger RNA after treatment with phenethyl alcohol. Cells were pulse labeled with 3H-uridine and then incubated with phenethyl alcohol plus actinomycin D. Cytoplasmic extracts from these cells were analyzed by sucrose density gradient centrifugation. The results indicate that the phenethyl alcoholinduced disaggregation of polyribosomes is accompanied by a loss of about one-half of the pulse-labeled messenger RNA from the cytoplasm. The remainder remains associated with cytoplasmic membranous structures. Re-formation of polyribosomes after removal of phenethyl alcohol appears to proceed via a direct attachment of 80 S or 110 S ribosomes to conserved messenger RNA.