Figure 2.

Interaction between the aryl hydrocarbon receptor (AhR) and the molecular clock. (A) In normal circadian clock function, CLOCK and BMAL heterodimerise and bind the E-box promotor, to transcribe Per1. (B) AhR shares sequence homology with CLOCK. Ligand-bound AhR heterodimerises with aryl hydrocarbon receptor nuclear translocator (ARNT) in the nucleus leading to transcription of enzyme superfamilies. (C) Ligand-bound AhR can also heterodimerise to BMAL1, which disrupts normal binding of CLOCK/BMAL to the Per1 promoter, leading to circadian disruption.