[Decrease in the transforming action of Rous sarcoma virus produced by avian cells grown in the presence of 5'-deoxy-5'-S-isobutyladenosine (SIBA)].

Treatment of Rous Sarcoma virus transformed chick embryo fibroblasts with 1 mM 5'-deoxy-5'-S-isobutyladenosine for 24 hrs. leads to the inhibition of transforming virus production. A kinetic analysis of the inhibition of active virion production revealed that the effect of the drug was time and concentration dependent. After 24 hrs. with 1 mM SIBA, the production of transforming virus was inhibited 165 fold. However, under these conditions there was only a 2 fold inhibition in viral particle production. Thus, these viral particles were either non infective (non adsorbed on cell membrane) or non transforming. The majority of viral particles produced by cells cultured with the drug have a decreased density. Analysis of these virions showed a decrease of protein P19 and an accumulation of proteins with high molecular weight.