The nuclear pore complex (NPC) is a structure that spans the nuclear envelope and provides a conduit between the nucleus and cytoplasm for the nucleocytoplasmic transport of macromolecules. The main components of the NPC are nucleoporins. About 30 different human Nups have been identified and appear to serve non-redundant functions. Nup153 contains four RanBP2-type zinc fingers and an RNA binding domain. The zinc-fingers of Nup153 can bind the small GTPase, Ran. The RNA binding domain has been shown to have an affinity for single-stranded RNA.