Figure 2.

The core molecular clock system from Hardman et al. [23]. The figure shown describes a peripheral system in which the key elements in maintaining oscillations are shown. (1) The transcribed protein CLOCK and BMAL1 form a heterodimer, which translocates to the nucleus where it binds to genes containing an E-box motif in the promoter region or clock controlled genes (CCGs); (2) this binding leads to the transcription of CCGs and two families of proteins, the Period (PER) and Cryptochrome (CRY) family; (3) proteins PER and CRY form a second heterodimer, which prevents the formation of the first heterodimer and thereby inhibits their own transcription; (4) this cycle leads to an approximately 24 h oscillatory rhythm (5). Used with permission.