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. Author manuscript; available in PMC: 2011 Jun 18.
Published in final edited form as: FEBS Lett. 2010 Mar 15;584(12):2618–2625. doi: 10.1016/j.febslet.2010.03.017

Figure 6.

Figure 6

Two models for coupling the circadian clock to the cell cycle/checkpoint response. (A) Serial coupling. The XPA repair factor, the p21 and Wee1 cell cycle proteins, and the c-Myc transcription factor, which are involved in DNA repair, the cell cycle, and cellular proliferation, respectively, are encoded by clock-controlled genes (CCG), and hence DNA repair, checkpoint activation, cell cycle regulation, and cellular proliferation are gated by the clock (solid line). Conversely, the cell cycle influences the circadian cycle by halting transcription during mitosis, thus causing a phase shift of the circadian rhythm (broken line). (B) Direct coupling. The core circadian clock protein Cry, in conjunction with Tim participates in the ATR-Chk1 signaling pathway in response to UV and UV-mimetic agents. Similarly, Per1 participates in the ATM-Chk2 signaling pathway in response to IR and radiomimetic agents.