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. Author manuscript; available in PMC: 2011 Aug 1.
Published in final edited form as: Biochim Biophys Acta. 2009 Nov 6;1804(8):1584–1590. doi: 10.1016/j.bbapap.2009.10.024

Fig. 3.

Fig. 3

A novel NAMPT/NAD-driven feedback loop through SIRT1 and CLOCK:BMAL1. Whereas CLOCK:BMAL1-mediated circadian transcription comprises a positive limb of the transcription-translation circadian feedback loop, the complex of PER and CRY proteins inhibits the function of CLOCK:BMAL1, forming the negative limb of this feedback loop. NAMPT/NAD/SIRT1 comprises a novel circadian feedback cycle that mediates rhythmic regulation of many physiological events. In this NAMPT/NAD-driven feedback loop, NAD functions as a “metabolic oscillator.” See text for details.