Effects of thioacetamide on labeling of ribonucleic acid of isolated nucleoli in vitro

The conditions that were optimal for incorporation of [¹⁴C]uridine triphosphate into RNA of nucleoli of normal liver cells were found to be optimal for incorporation of [¹⁴C]uridine triphosphate into nucleoli of thioacetamide-treated rat livers. Maximum incorporation of isotope was found at 15–30 min after the incubation was begun. Thioacetamide produced a marked increase in the rate of uptake of total isotope into RNA and in the specific activity of the RNA despite the increased amount of RNA in the nucleoli obtained from thioacetamide-treated animals. These data suggest that thioacetamide may derepress the genomic segments involved in biosynthesis of nucleolar RNA.