Aryl hydrocarbon receptor (AHR) interacting protein (AIP) may have a positive role in AHR-mediated (aromatic hydrocarbon receptor) signaling, probably by influencing its receptivity for ligand and/or its nuclear targeting. AIP is a Cellular negative regulator of the hepatitis B virus (HBV) X protein. Furthermore, AIP is a ubiquitously expressed protein, which binds to HSP 90 and AHR through a highly conserved carboxy-terminal tetraticopeptide repeat domain.