Nudeocytoplasmic shuttling by protein nuclear import factors

Protein nuclear import factors are not, in general, believed to function in the nuclear export of macromolecules and their reutilization therefore requires their recycling from the nucleus to the cytoplasm. Two possible mechanisms for recycling have been proposed. On the one hand, protein import factors such as importin beta and transportin (Trn) could continuously shuttle between cytoplasm and nucleoplasm. On the other hand, these proteins …