Theoretical requirements for the experimentally observed DNA damage-induced PRCs with small delays in circadian clock models.

We removed the autocatalytic positive feedback from our simple model and added positive feedback into the Leloup and Goldbeter's model as discussed in the text. In all cases, we checked the maxima and minima from PRCs after the Chk2-dependent degradations of PER. In the last column, we report the ratio of these values (larger value indicates most advance with least delay). See text for analysis and Table S1 for detailed results. In all cases we assume that Chk2 acts only on the free forms of PER.