The pentose phosphate pathway regulates the circadian clock

The circadian clock is a ubiquitous timekeeping system that organizes the behavior and physiology of organisms over the day and night. The clockwork orchestrates a multitude of metabolic processes as illustrated by previous global transcriptomics and proteomics studies, and the existence of daily rhythms of reduction and oxidation (redox) in a range of diverse species. However, the reciprocal question of whether metabolism can alter the clockwork remains largely unaddressed. Here we identify the pentose phosphate pathway (PPP), a critical source of cellular reducing power in the form of NADPH, as an important modulator of circadian oscillations. We show that genetic and pharmacologic inhibition of the PPP perturbs circadian gene expression and metabolic rhythms in human cells. Pharmacologic inhibition of the PPP caused similar effects in mouse tissues, and altered the pattern of rhythmic behavior in Drosophila. These manipulations also altered genome wide DNA-binding activity of the circadian transcription factors BMAL1 and CLOCK through a mechanism likely involving the redox-sensitive histone acetyltransferase p300. Thus, disruption of the PPP regulates circadian rhythms via modulation of NADPH metabolism, highlighting redox reactions as a novel connector of metabolic cycles and transcriptional oscillations in nucleated cells. RNA-Seq time-course experiment in U2OS cells treated with 6AN or control over 48 hours at 4h resolution. ChIP-Seq of BMAL1, CLOCK, H3K4me3 and H3K9ac in U2OS cells treated with 6AN or control for 24h.