PerspectiveCircadian Rhythms

Chronobiology--Reducing Time

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Science  20 Jul 2001:
Vol. 293, Issue 5529, pp. 437-438
DOI: 10.1126/science.1063296

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The physiology and behavior of mammals are subject to daily oscillations. These oscillations are driven by a master clock in the suprachiasmatic nucleus (SCN) of the brain's hypothalamus and by clocks in most other cell types that contain many of the same protein components. But what regulates the activity of these clocks? The answer, according to Schibler et al. , reporting in their Perspective on new work from McKnight's group, may lie in cellular metabolism. It turns out that two crucial clock proteins (transcription factors that switch on target genes involved in circadian oscillations) are regulated in vitro by the ratio between reduced and oxidized forms of the respiratory chain electron carrier NAD that fluctuate according to the metabolic state of the cell.