Influence of p53 on the progression of irradiated cells through the S-phase

Abstract

Objectives: Many pathways seem to be involved in the regulation of the intra-S-phase checkpoint after exposure to ionizing radiation, but the role of p53 has proven to be rather elusive. Here we have a closer look at the progression of irradiated cells through S-phase in dependence of their p53 status.

Materials and methods: Three pairs of cell lines were used, each consisting of one p53 functional and one p53 non-functional line. Cells were labelled with BrdU immediately after irradiation, they were then incubated in label-free medium, and at different times afterwards their position within the S-phase was determined flow cytometrically.

Results: While in the p53 deficient cells progression through S-phase was slowed significantly over at least a few hours, it was halted for just about an hour in the p53 proficient cells and then proceeded without further delay or even at a slightly accelerated pace.

Conclusions: It is clear from the experiments presented here that p53 does play a role for the progress of cells through the S-phase after X-ray exposure, but the exact mechanisms by which replicon initiation and elongation is controlled in irradiated cells remain to be elucidated.