. These protein-DNA interactions are associated with alterations in both chromatin structure and protein binding at the CYP1A1 promoter. AhR's transactivation domain communicates the induction signal from enhancer to promoter probably via protein-protein interactions, thereby facilitating the binding of general transcription factors to the promoter.
Arnt can also interact with other bHLH/PAS proteins, thereby mediating responses to additional environmental stimuli. In particular, Arnt heterodimerizes with hypoxia-inducible factor 1 alpha (HIF1 alpha) in response to low oxygen tension, and the HIF1 alpha/Arnt heterodimer alters the transcription of hypoxia-responsive genes.