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. Nup160 forms a subcomplex with Nup107. This subcomplex has been found to be important to bipolar spindle assembly and kinetochore function.