Based on studies in Xenopus (Fichtman et al. 2010) and human (Schwartz et al. 2015) models, POM121 binds the Nup107-160 complex through direct interaction with NUP133, a subunit of the Nup107-160 complex. Binding of POM121 to the Nup107-160 complex precedes formation of the nuclear pore diffusion barrier (Dultz et al. 2008), and is followed by recruitment of FG repeat nucleoporins (Fichtman et al. 2010). FG nucleoporins contain phenylalanine-glycine repeats needed for interaction with soluble nuclear import and export receptors (Frey et al. 2006).