Effect of the Vinca alkaloids on RNA synthesis in human cells in vitro.

The Vinca alkaloids vinblastine sulfate and vincrystine sulfate, which are mitotic poisons, inhibit RNA synthesis in human (HEp-2) cells cultured in vitro. Analyses of RNA synthesis by cells treated with these drugs by acrylamide gel electrophoresis show that 28s rRNA and to a lesser extent 18s rRNA are preferentially inhibited. The synthesis of tRNA is affected much less than that of rRNA. The present experiments suggest that the drugs inhibit both the synthesis and processing of the nucleolar RNA precursors of rRNA. An explanation is also given for previous reports that these alkaloids preferentially inhibit the synthesis of tRNA in animal cells in vitro.