Isolation and characterization of AINT: a novel ARNT interacting protein expressed during murine embryonic development.

Basic helix-loop-helix-PER-ARNT-SIM (bHLH-PAS) proteins form dimeric transcription factors to mediate diverse biological functions including xenobiotic metabolism, hypoxic response, circadian rhythm and central nervous system midline development. The Ah receptor nuclear translocator protein (ARNT) plays a central role as a common heterodimerization partner. Herein, we describe a novel, embryonically expressed, ARNT interacting protein (AINT) that may be a member of a larger coiled-coil PAS interacting protein family. The AINT C-terminus mediates interaction with the PAS domain of ARNT in yeast and interacts in vitro with ARNT and ARNT2 specifically. AINT localizes to the cytoplasm and overexpression leads to non-nuclear localization of ARNT. A dynamic pattern of AINT mRNA expression during embryogenesis and cerebellum ontogeny supports a role for AINT in development.