Stability of division‐related protein and nucleic acid fractions in synchronized Tetrahymena

The kinetics of RNA synthesis have been studied under various growth conditions using synchronized Tetrahymena pyriformis GL. The curves obtained are approximately linear in growth-supporting media but vary under other circumstances. The presence of amino acids in the medium stimulates RNA synthesis in Tetrahymena as it does in bacteria. Since these induced variations do not influence the essential features of the pre-cytokinetic period it is inferred that fluctuations in the rate of RNA synthesis described by others are probably not essential features of temperature-induced synchrony. In addition, the translational stability of division-related templates at synchronizing temperatures has been investigated. The synthesis of proteins necessary for cytokinesis is shown to be greatly reduced under conditions simulating a heat-shock. Inhibitor studies using cycloheximide indicate that protein synthesis is required longer into the cytokinetic phase than had previously been thought. Collectively the data are all compatible with the hypothesis that synthesis of division-related proteins is drastically reduced in heat-shocked Tetrahymena and that the basis for this reduction is hydrolysis of template RNA without concurrent translation.