SUMMARY The effect of adniamycin on DNA, RNA

and protein syn thesis was investigated in cell-free systems and intact cells. In studies with purified mammalian cell enzymes, adniamy cm produced a greater inhibition of DNA-dependent DNA polymerase than of RNA polymerase. The extent of inhibi tion of both these enzymes was decreased by increasing the concentration of the DNA template in the reaction mixture. In studies with isolated nuclei, adniamycin was also a more potent inhibitor of DNA synthesis than of RNA synthesis. However, with intact cells, adniamycin inhibited both DNA and RNA synthesis to about the same extent. The inhibition produced by adniamycin on RNA synthesis in intact cells was greater than that observed in the cell-free systems. Adniamycin inhibited protein synthesis in a cell-free system consisting of polynibosomes, transfer RNA, and enzymes but did not inhibit protein synthesis in intact cells. These differencesinthe patternof inhibitionmay be due to bio transformation of the drug and/or preferential binding to chromosomal DNA in the intact cell