Nuclear pore complexes (NPCs) control the directed transport of macromolecules across the nuclear envelope. To establish a functional barrier for transport and a firm integration into the double membrane of the envelope requires the coordinated assembly of over 30 multi-copy nucleoporins (Nups). To date, the detailed assembly steps and membrane interactions of Nups are not fully understood. In their Research Article (jcs208538), Wolfram Antonin and colleagues focus on the inner ring NPC component Nup155 and show that direct membrane binding of Nup155 through its N-terminus is required for NPC assembly in Xenopus egg extracts. Furthermore, this domain of Nup155 is sufficient for formation of the nuclear envelope and the NPC, but not for assembly of a fully functional NPC. Interestingly, the authors show the existence of an autoinhibitory role of the C-terminus of Nup155 towards its N-terminus, which severely weakens its binding to Nup53. The Nup155–Nup53 interaction is needed for NPC assembly. Autoinhibition is overcome when another inner ring component, Nup93, is present, which leads to formation of the inner ring of the NPC and transport-competent pores. Taken together, this work establishes the N-terminus of Nup155 as crucial for nuclear envelope and NPC assembly, and uncovers an unexpected autoregulation of Nup155 in the sequential assembly steps of the inner ring of the NPC.
