Posttranscriptional regulation of ornithine decarboxylase in Chinese hamster ovary cells

rnithine decarboxylase (ODC) is the first and rate-limiting step in the synthesis of polyamines in mammalian cells. We have analyzed the regulation of ODC activity in Chinese hamster ovary cells during the cell cycle and in response to variations in intracellular polyamine levels. We have shown that the level of ODC activity is regulated posttranscriptionally, primarily by modulation of the rate of translation, in response to fluctuations in the intracellular putrescine concentration. Putrescine depletion has been shown to lead to elevated levels of ODC expression, while supplementation of cells with exogenous putrescine or ornithine suppresses ODC induction. The gene and the cDNA for ODC from hamster cells have been cloned. Comparisons of these sequences to those for ODC from other organisms reveals that the overall structure of the gene has been conserved and that the coding sequence for ODC from hamster is...