Abundance of tubulin mRNA on polysomes following deciliation and during the synchronous cell cycle of Tetrahymena.

The protozoan, Tetrahymena pyriformis GL, was used as a model system for studying polysomal mRNA during the cell cycle and during cilia regeneration. Our previous work has shown a substantial induction of tubulin synthesis following deciliation and during G2 of the synchronous cell cycle. In the present study, the abundance of tubulin mRNA on polysomes was examined in order to determine whether more tubulin mRNA was being translated during the periods of peak tubulin synthesis. Polysomes isolated at sequential times following deciliation and during the synchronous cell cycle were translated in a cell-free translation system derived from wheat germ. The abundance of tubulin mRNA on polysomes was inferred from the amount of tubulin translated in vitro. Following deciliation and prior to the peak period of tubulin synthesis, the abundance of tubulin mRNA (at 140 min post-deciliation) increases to 25 times the initial value observed (at 20 min post-deciliation). Since the increase in tubulin mRNA abundance precedes the peak in tubulin synthesis, induction of tubulin synthesis appears to be mRNA-dependent. A similar analysis of tubulin mRNA abundance on polysomes during the synchronous cell cycle revealed a peak of tubulin mRNA prior to each peak of tubulin synthesis. These studies suggest that the periodic fluctuations in the synthesis of tubulin are dependent upon fluctuating levels of tubulin mRNA on polysomes.