electron accelerator providing pulsed irradiation separated by timeintervals of a second to a few minutes, the V. Favaudon’s groupobserved a tetraphasic, W-shaped time-dependent dose-responsecurve strongly dependent on the cell line and on the PARP status,suggesting again the influence of chromatin organization (Ponetteet al., 1996). Questions about synergy between these particulareffects with HRS phenomenon (described in the section above) areof clinical interest. Since it is long known that time between split-dose conditions the chromatin recondensation and the DSB repair(see for instance (Wierowski et al., 1984)), a better understanding ofthe dynamics of chromatin condensation/decondensation in theseparticular but clinically relevant conditions would be therefore avery useful research axis.