Aloni, Y., Dept. Genet., Weizmann Inst. Sci., Rehovot, Israel
Shani, M., Dept. Genet., Weizmann Inst. Sci., Rehovot, Israel
Reuveni, Y., Dept. Genet., Weizmann Inst. Sci., Rehovot, Israel

The usefulness of cytochalasin B enucleate cells for the study of the metabolism of cytoplasmic mRNA and for determining its half life in animal cells is demonstrated. Simian virus 40 infected monkey cells in which the RNA had been labeled with [3H]uridine were enucleated, and the decay of the two prominent RNAs of simian virus 40, the 19S and 16S species, was measured by analysis on sucrose gradients. The results of these experiments, together with kinetic analysis of nuclear and cytoplasmic viral RNA, indicate a precursor product relationship between the 19S and 16S cytoplasmic viral RNA species, which decay by first order kinetics with a mean half life of about 3 hr and 6 hr, respectively.