Abstract
1.
1. The synthesis of RNA in Ehrlich ascites tumor cells was studied during the inhibition of protein synthesis by cycloheximide. When the cells were preincubated in presence of cycloheximide to inhibit protein synthesis and subsequently labeled with [
3H]uridine, there was little difference in the specific activity of the RNA isolated from the control and the drug-treated cells.
2.
2. Examination of the isolated labeled RNA by sucrose density gradient centrifugation, however, revealed that whereas the 45-S precursor rRNA and 28-S rRNA were labeled in both the cases, the labeling of the 16-S rRNA was inhibited in the cycloheximide treated cells.
3.
3. Labeling with [
Me-
14C]methionine showed that the methylation of rRNA was considerably inhibited in the cycloheximide-inhibited cells. In this case also, the 16-S rRNA from the treated cells was not appreciably labeled.
4.
4. These results indicated that although precursor rRNA synthesis can take place in absence of protein synthesis, continued synthesis of protein is needed for subsequent maturation of this RNA into stable rRNA.