From studies with Xenopus and human model systems, the transmembrane nucleoporins POM121 and NDC1 recruit the NUP93 complex to nascent nuclear pore complexes (NPCs) due to interaction with the NUP93 complex components NUP155 (Mitchell et al. 2010) and, potentially, NUP35 (Mansfield et al. 2006). This is consistent with order-of-assembly seen in live cell imaging (Dultz et al. 2008).