Karyopherin, a cytosolic and heterodimeric protein complex consisting of alpha and beta subunits, is responsible for targeting proteins with nuclear localization signals to the nuclear pore complex by an energy requiring, Ran-dependent mechanism. The alpha subunit and imported substrate enter the nucleus and accumulate in the nucleoplasm, while the beta subunit accumulates at the NPC. Molecules containing the classical nuclear localization signal (NLS) are transported into the nucleus by alpha/beta heterodimers. KPNA3 has been shown to be important in the TNF-alpha-induced nuclear import of NF-kappaB. It is also involved in the stress-mediated nuclear stabilization of p53 and the nuclear import and replication of HIV-1 in both dividing and non-dividing cells.Synonyms: Importin alpha Q1, Karyopherin subunit alpha-4, QIP1