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Science 326 (5951): 378-379

Copyright © 2009 by the American Association for the Advancement of Science


Feeding the Clock

David M. Suter, and Ueli Schibler

In mammals, sleeping, feeding, and most other physiological processes are influenced by a circadian system and therefore display daily oscillations. These rhythms are generated by self-sustained and cell-autonomous molecular clocks that exist in virtually all cell types. A "master clock" located in the brain's suprachiasmatic nucleus (SCN) can synchronize these peripheral clocks, but for many organs, feeding-fasting rhythms are the dominant zeitgebers (timing cues) (1, 2). On page 437 of this issue, Lamia et al. propose a molecular mechanism through which metabolic cycles may interact with the circadian clockwork circuitry. They show that an enzyme that responds to nutrient availability—adenosine monophosphate–activated protein kinase (AMPK)—directly phosphorylates the core clock protein cryptochrome 1 (CRY1), thereby marking it for degradation (3).

Department of Molecular Biology, Sciences III, University of Geneva, and National Centre of Competence in Research Frontiers in Genetics, 30 Quai Ernest Ansermet, 1211 Geneva, Switzerland.

E-mail: david.suter{at}; ueli.schibler{at}

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