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. Author manuscript; available in PMC: 2011 Feb 19.
Published in final edited form as: Circ Res. 2010 Feb 19;106(3):447–462. doi: 10.1161/CIRCRESAHA.109.208355

Fig 1. The core molecular clock components.

Fig 1

The mammalian circadian clock consists of a series of interlocking transcription/translation feedback loops. The positive limb of the clock is composed of the transcription factors CLOCK/NPAS2 and BMAL1, which heterodimerize and activate transcription of downstream clock target genes, including the period (Per1, 2, and 3) and cryptochrome (Cry1 and 2) genes, Rev-erba, Rora, and other clock-controlled genes. Upon translation, the PERs and CRYs heterodimerize, translocate back to the nucleus, and inhibit CLOCK/BMAL1. Multiple additional interlocking loops are shown and are described within the text.