Inhibition of the synthesis of Moloney leukemia virus structural proteins by N-methylisatin-beta-4',4'-diethylthiosemicarbazone.

The mechanism of inhibition of Moloney leukemia virus by N-methylisatin-beta-4',4'-diethylthiosemicarbazone was studied. Experiments that used [3H]leucine for short-pulse labeling in the presence of the drug resulted in a 71% inhibition in the synthesis of Pr-80, the polypeptide precursor of the gag viral proteins. The radioactive pulse products of the polypeptide precursors after a further 2-h chase period showed a normal cleavage of the precursors, with the formation of a reduced amount of final mature viral structural proteins. The experimental evidence indicated that at the inhibitory concentration of 17 microM N-methylisatin-beta-4',4'-diethylthiosemicarbazone, the amount of intracellular viral RNA was not affected, whereas the activities of reverse transcriptase and the other viral protein syntheses were suppressed.