NEP-A and NEP-B both contribute to nuclear pore formation in Xenopus eggs and oocytes

Georgia Salpingidou, Ryszard Rzepecki, Elena Kiseleva, Carol Lyon, Birgit Lane, Kasia Fusiek, Anja Golebiewska, Shoena Drummond, Terry Allen, Juliet A. Ellis, Carl Smythe, Martin W. Goldberg, Christopher J. Hutchison*

*Corresponding author for this work

Research output: Contribution to journalArticleResearchpeer-review

15 Citations (Scopus)


In vertebrates, the nuclear envelope (NE) assembles and disassembles during mitosis. As the NE is a complex structure consisting of inner and outer membranes, nuclear pore complexes (NPCs) and the nuclear lamina, NE assembly must be a controlled and systematic process. In Xenopus egg extracts, NE assembly is mediated by two distinct membrane vesicle populations, termed NEP-A and NEP-B. Here, we re-investigate how these two membrane populations contribute to NPC assembly. In growing stage III Xenopus oocytes, NPC assembly intermediates are frequently observed. High concentrations of NPC assembly intermediates always correlate with fusion of vesicles into preformed membranes. In Xenopus egg extracts, two integral membrane proteins essential for NPC assembly, POM121 and NDC1, are exclusively associated with NEP-B membranes. By contrast, a third integral membrane protein associated with the NPCs, gp210, associates only with NEP-A membranes. During NE assembly, fusion between NEP-A and NEP-B led to the formation of fusion junctions at which >65% of assembling NPCs were located. To investigate how each membrane type contributes to NPC assembly, we preferentially limited NEP-A in NE assembly assays. We found that, by limiting the NEP-A contribution to the NE, partially formed NPCs were assembled in which protein components of the nucIeoplasmic face were depleted or absent. Our data suggest that fusion between NEP-A and NEP-B membranes is essential for NPC assembly and that, in contrast to previous reports, both membranes contribute to NPC assembly.

Original languageEnglish
Pages (from-to)706-716
Number of pages11
JournalJournal of Cell Science
Issue number5
Publication statusPublished - 1 Mar 2008
Externally publishedYes


  • LAP2
  • Nuclear Envelope Assembly
  • Nuclear Pore Complexes


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