Functions as a component of the nuclear pore complex (NPC). NPC components, collectively referred to as nucleoporins (NUPs), can play the role of both NPC structural components and of docking or interaction partners for transiently associated nuclear transport factors. Active directional transport is assured by both, a Phe-Gly (FG) repeat affinity gradient for these transport factors across the NPC and a transport cofactor concentration gradient across the nuclear envelope (GSP1 and GSP2 GTPases associated predominantly with GTP in the nucleus, with GDP in the cytoplasm). NUP53 may play an important role in cell cycle regulation by inhibiting PSE1 transport functions during mitosis and sequestration of MAD1-MAD2 in a cell cycle-dependent manner. It also seems to play an important role in de novo NPC assembly by associating with nuclear membranes and driving their proliferation. Component of the nuclear pore complex (NPC). NPC constitutes the exclusive means of nucleocytoplasmic transport. NPCs allow the passive diffusion of ions and small molecules and the active, nuclear transport receptor-mediated bidirectional transport of macromolecules such as proteins, RNAs, ribonucleoparticles (RNPs), and ribosomal subunits across the nuclear envelope. Due to its 8-fold rotational symmetry, all subunits are present with 8 copies or multiples thereof. NUP53 interacts with MAD1-MAD2. During mitosis NUP53 changes its binding partner within the NPC from NUP170 to NIC96, exposing a high affinity binding site for the karyopherin PSE1, and retaining it in the NPC, while MAD2 is released. It forms a subcomplex with ASM4 and NDC1. Symmetric distribution. Contains FG repeats. FG repeats are interaction sites for karyopherins (importins, exportins) and form probably an affinity gradient, guiding the transport proteins unidirectionally with their cargo through the NPC. FG repeat regions are highly flexible and lack ordered secondary structure. The overall conservation of FG repeats regarding exact sequence, spacing, and repeat unit length is limited. FG repeat types and their physico-chemical environment change across the NPC from the nucleoplasmic to the cytoplasmic side. The RRM Nup35-type domain might be involved in the control of mitosis. Phosphorylated by CDC28. Present with 2060 molecules/cell in log phase SD medium.