Effect of azacytidine on Simian Virus 40 nucleoprotein complexes.

Simian virus 40 nucleoprotein complexes synthesized in the presence of 5-azacytidine showed small differences in sedimentation rate on neutral sucrose and buoyant density in metrizamide and cesium chloride. Simian virus 40 deoxyribonucleic acid (DNA) I, isolated from the nucleoprotein complexes of drug-treated cultures, was found to band at a higher buoyant density and therefore had a decreased ability to bind ethidium bromide. The data indicated that these molecules were deficient in superhelical turns. Treatment with 5-azacytidine was shown to inhibit protein synthesis, which preceded the inhibition of DNA synthesis. Under the same conditions, protein synthesis was inhibited to a greater degree and occurred much faster than inhibition of DNA syntheses. Upon removal of the drug, resumption of protein and DNA synthesis occurred slowly. It is concluded that the inhibition of simian virus 40 DNA synthesis and the conformational alterations in DNA I isolated from nucleoprotein complexes result from the inhibition of protein synthesis.