Effect of X-Irradiation at Different Stages in the Cell Cycle on Individual Cell-Based Kinetics in an Asynchronous Cell Population.

Using an asynchronously growing cell population, we investigated how X-irradiation at different stages of the cell cycle influences individual cell-based kinetics. To visualize the cell-cycle phase, we employed the fluorescent ubiquitination-based cell cycle indicator (Fucci). After 5 Gy irradiation, HeLa cells no longer entered M phase in an order determined by their previous stage of the cell cycle, primarily because green phase (S and G2) was less prolonged in cells irradiated during the red phase (G1) than in those irradiated during the green phase.