Multiple Effects of Rifamycin Derivatives on Animal‐Cell Metabolism of Macromolecules

Abstract

A group of rifamycin derivatives were tested against the nucleolar and nucleoplasmic RNA polymerases from three types of animal cells. It was found that several compounds effectively inhibited such enzymes without substantial discrimination. In addition, the same derivatives inhibited polyphenylalanine synthesis in an animal cell‐free system. Experiments with intact Hela cells showed that the synthesis of RNA, the processing of rRNA, the synthesis of DNA and the uptake of nucleosides were inhibited by rifamycins. It is concluded that the specificity of rifamycin effects obtained at the concentrations that appear to be necessary to interfere with normal (or virus‐directed) processes in animal cells can be seriously questioned.