The nuclear pore complex (NPC) is a large proteinaceous structure through which 
bidirectional transport of macromolecules across the nuclear envelope (NE) takes 
place. Nup153 is a peripheral NPC component that has been implicated in protein 
and RNP transport and in the interaction of NPCs with the nuclear lamina. Here, 
Nup153 is localized by immunogold electron microscopy to a position on the 
nuclear ring of the NPC. Nuclear reconstitution is used to investigate the role 
of Nup153 in nucleo- cytoplasmic transport and NPC architecture. NPCs assembled 
in the absence of Nup153 lacked several nuclear basket components, were unevenly 
distributed in the NE and, unlike wild-type NPCs, were mobile within the NE. 
Importin alpha/beta-mediated protein import into the nucleus was strongly 
reduced in the absence of Nup153, while transportin-mediated import was 
unaffected. This was due to a reduction in import complex translocation rather 
than to defective receptor recycling. Our results therefore reveal functions for 
Nup153 in NPC assembly, in anchoring NPCs within the NE and in mediating 
specific nuclear import events.