Inhibition by Puromycin of Incorporation of Tritiated Uridine into Nucleolar and Cytoplasmic Ribonucleic Acids

Abstract

PUROMYCIN is a specific inhibitor of protein synthesis in bacterial and mammalian cells^1,2 and can therefore be used as a tool for investigating the dependence of various processes on concomitant synthesis of protein^3,4. It has already been shown that the action of puromycin results in the depression of DNA (refs. 4–6) and RNA (refs. 6–8) synthesis in mammalian cells. These effects are thought to be due to secondary consequences of the interference with protein synthesis, rather than to a direct effect of puromycin on the synthesis of nucleic acids. Density gradient centrifugation of nucleic acids extracted from HeLa cells has shown that the molecular species of RNA most markedly affected by puromycin is the ribosomal⁷ or ribosomal precursor type⁸. Correlation of this finding with the results of autoradiography reported here gives further support to the belief that the nucleolus is the site of production, or at least the site of accumulation, of the ribosomal types of RNA (refs. 9–12).