Transcriptional activation of mammalian ornithine decarboxylase during stimulated growth.

Cloned ornithine decarboxylase (ODC) (EC 4.1.1.17) cDNA was used to investigate the mechanisms which mediate the mitogenic induction of mammalian ODC. Stimulation of quiescent BALB/c 3T3 mouse fibroblasts with purified fibroblast and platelet-derived growth factors and with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate results in a rapid and dramatic increase in ODC mRNA, similar to the increase caused by serum stimulation. Using nuclear runoff transcriptional analysis, we demonstrate that an increase in ODC transcription accounts for the mitogenic induction of ODC mRNA, and using cycloheximide together with the stimulating mitogen, we found that the mitogenic induction of ODC is dependent on ongoing protein synthesis in the stimulated cells.