Nup50 is a nucleoplasmically oriented component of the nuclear pore complex with a role in protein export. Npap60 (Nup50) is a nucleoporin that binds directly to importin alpha. In humans, there are two Npap60 isoforms: the long (Npap60L) and short (Npap60S) forms. Nucleoporin 50 kDa (NUP50), a component of the nuclear pore complex, is highly expressed in male germ cells. NUP50 plays an essential role in the survival of primordial germ cells (PGCs) during embryonic development. Nup50 is a mobile Nup with a pronounced presence both at the NPC and in the nucleoplasm that can move between these different localizations. Strikingly, the dynamic behavior of Nup50 in both locations is dependent on active transcription by RNA polymerase II and requires the N-terminal half of the protein, which contains importin α- and Nup153-binding domains.