Figure 5.

Model for the primary TTFL of the mammalian clock in the mouse liver. (A) Expression patterns of the four core clock proteins in mouse liver nuclei over a circadian period revealing different peak expression times of CRY1 and PER2. (ZT) Zeitgeber time; (ZT0) light on; (ZT12) light off for mice under a 12-h light:12-h dark cycle. (B) New model for the mammalian circadian clock. The figure shows a semiquantitative heat map representation of CRY1 and PER2 protein expression as well as the ChIP data for CLOCK–BMAL1 and CRY1 over a circadian cycle and its consequences with regard to interactions of core clock proteins with the E-box and the effects of these interactions on transcription of genes (Nr1d1 and Dbp) regulated exclusively by the core TTFL.