Facilitates protein transport into the nucleus. Interacts with various nucleoporins and with Ran-GDP. Could be part of a multicomponent system of cytosolic factors that assemble at the pore complex during nuclear import. Interacts with RAN1. Accumulates at the nuclear rim. Excluded from the nucleolus. A number of isoforms are produced. According to EST sequences. Expressed in roots, stems, leaves and flowers, and, at low levels, in siliques.