Figure 1.

Circadian regulation of the human body. External signals entrain the body’s central clock, the SCN in the brain, which in turn synchronizes peripheral clocks in organs and results in the molecular regulation of each cellular clock. Transcriptional/translational feedback loops coordinate rhythmic gene expression, and proteasomal degradation of the components restarts the system. BMAL1:CLOCK binds to E-Boxes and activates the expression of REV-ERB, RORα, and PER:CRY, which then directly inhibit BMAL1:CLOCK or act on Bmal1 promoter activity. SCN = suprachiasmatic nucleus; BMAL = brain and muscle ARNT-like 1; CLOCK = circadian locomotor output cycles kaput; ROR = related orphan receptor; PER = Period; CRY = Cryptochrome. Created with BioRender.com