Aryl hydrocarbon receptor interacting protein, may play a positive role in AHR-mediated signalling possibly by influencing its receptivity for ligand and/or its nuclear targeting. AIP is the cellular negative regulator of the HBV X protein.The aryl hydrocarbon receptor (AHR) is found in a multiprotein complex that includes the 90-kD heat shock protein (HSP90). The AHR is a ligand-activated transcription factor that is a member of the basic helix-loop-helix PAS superfamily. In response to ligand binding in the cytosol, the AHR-HSP90 complex translocates to the nucleus where the molecular chaperone HSP90 dissociates and the activated AHR heterodimerizes with ARNT. The resulting complex attains binding specificity for its cognate enhancer elements to regulate transcription of a variety of xenobiotic metabolizing enzymes.