
This gene encodes a basic helix-loop-helix transcription factor belonging to the PAS (PER| ARNT| SIM) superfamily. The PAS proteins play important roles in adaptation to low atmospheric and cellular oxygen levels| exposure to certain environmental pollutants| and diurnal oscillations in light and temperature. This protein forms a transcriptionally active heterodimer with the circadian CLOCK protein| the structurally related MOP4| and hypoxia-inducible factors| such as HIF1alpha. Consistent with its role as a biologically relevant partner of circadian and hypoxia factors| this protein is coexpressed in regions of the brain such as the thalamus| hypothalamus| and amygdala. Alternatively spliced transcript variants encoding different isoforms have been described for this gene.
