The Relation of Protein Synthesis to Radiation-Induced Division Delay in Chinese Hamster Cells

We have studied the effects of x rays on the progression toward division and on the synthesis of proteins in Chinese hamster cells in G2 phase, with the aim of clarifying the role played by protein synthesis in radiation-induced division delay. The results have been compared with those obtained in similar experiments with cycloheximide, an inhibitor of protein synthesis. We have observed that the terminal point of action of x rays in arresting the progression of G2 cells occurs at 90-60 minutes before division and is dose-independent over the range 200-710 rads. However, the terminal point of action of cycloheximide is concentration-dependent and occurs at 120-90 minutes before division for concentrations of 2 and 5 μg/ml, and at 90-60 minutes before division for 50 μg/ml. Therefore, only at the higher concentration is there coincidence with x rays in the time of the terminal points of action. The two agents, moreover, have opposite effects on the synthesis of proteins. We have observed a stimulation of t...