Induction of ornithine decarboxylase activity in a temperature-sensitive cell cycle mutant of Chinese hamster cells.

We have investigated the induction of ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) activity in a temperature-sensitive cell cycle mutant of Chinese hamster fibroblasts. This activity is not induced at the nonpermissive temperature, although the synthesis of the majority of proteins is normal. From a combination of studies with inhibitors of mRNA synthesis and maturation (alpha-amanitin, and cordycepin) and of proteins synthesis (cycloheximide, diphtheria toxin, and emetine), we conclude that the temperature-sensitive block is at the level of translation of one or more specific mRNAs.