NDC1 is necessary for stable assembly of the nuclear pore scaffold to establish nuclear transport in early C. elegans embryos
Nuclear pore complexes (NPCs) are large protein assemblies that facilitate transport of macromolecules across the nuclear envelope (NE) [1, 2]. How thousands of NPCs rapidly assemble to form a functional NE after open mitosis is not known. Recruitment of the outer ring Nup107-160 complex to the NE initiates NPC assembly. The Nup53/93 complex bridges the outer ring to the central channel to form a functional pore [3-6]. Nup53 interacts with the conserved transmembrane nucleoporin Ndc1; however, how Ndc1 contributes to post-mitotic NPC assembly is unclear [7-9]. Here, we use C. elegans embryos to show that the timely formation of a functional NE after mitosis depends on Ndc1. Endogenously tagged Ndc1 is recruited early to the reforming NE and is highly mobile in the nuclear rim. 3D analysis of NE reformation revealed a significant decrease in NPC density in ndc1 deleted embryos: continuous nuclear membranes contained few holes where NPCs are normally located. Nup160 is highly mobile in NEs depleted of Ndc1 and outer ring scaffold components are less enriched at the rim. Nup160 is not recruited to the nuclear rim when both ndc1 and nup53 are absent and nuclear assembly fails. This suggests that Ndc1 and Nup53 function in part in parallel pathways to drive post-mitotic nuclear assembly in vivo. Together, we show that Ndc1 dynamically associates with the NE and promotes stable association of the outer ring scaffold with nascent NEs to facilitate NPC assembly after open mitosis, revealing a previously uncharacterized role for Ndc1 in forming functional NE.