Figure 10.

Synchronization readily occurs when two modes of coupling of the cell cycle to the circadian clock and two modes of coupling of the circadian clock to the cell cycle are considered simultaneously. The cell cycle and the circadian clock respectively have a period of T_CC = 20 h and T_CR = 24 h before coupling. Upon bidirectional coupling, the synchronized circadian clock and the cell cycle oscillate at a period of T_syn=23 h. The circadian clock is coupled to the cell cycle via mitotic repression of transcription and REV-ERBα phosphorylation, both under the control of CDK1. The cell cycle is coupled to the circadian clock via BMAL1 induction of Wee1 and negative regulation of Cyclin E by BMAL1. The coupling strengths are K_Icdk1 = 0.5 µM, v_sw = 0.1 µMh⁻¹, V_Cdk1 = 3.16 nMh⁻¹ and v_sce = 0.005 µMh⁻¹. (Online version in colour.)