Regulation of circadian behaviour and metabolism by REV-ERB-α and REV-ERB-β

The circadian clock acts at the genomic level to coordinate internal behavioural and physiological rhythms via the CLOCK-BMAL1 transcriptional heterodimer. Although the nuclear receptors REV-ERB-alpha and REV-ERB-beta have been proposed to form an accessory feedback loop that contributes to clock function(1,2), their precise roles and importance remain unresolved. To establish their regulatory potential, we determined the genome-wide cis-acting targets (cistromes) of both REV-ERB isoforms in murine liver, which revealed shared recognition at over 50% of their total DNA binding sites and extensive overlap with the master circadian regulator BMAL1. Although REV-ERB-alpha has been shown to regulate Bmal1 expression directly(1,2), our cistromic analysis reveals a more profound connection between BMAL1 and the REV-ERB-alpha and REV-ERB-beta genomic regulatory circuits than was previously suspected. Genes within the intersection of the BMAL1, REV-ERB-alpha and REV-ERB-beta cistromes are highly enriched for both clock and metabolic functions. As predicted by the cistromic analysis, dual depletion of Rev-erb-alpha and Rev-erb-beta function by creating double-knockout mice profoundly disrupted circadian expression of core circadian clock and lipid homeostatic gene networks. As a result, double-knockout mice show markedly altered circadian wheel-running behaviour and deregulated lipid metabolism. These data now unite REV-ERB-alpha and REV-ERB-beta with PER, CRY and other components of the principal feedback loop that drives circadian expression and indicate a more integral mechanism for the coordination of circadian rhythm and metabolism.