Karyopherins remodel the dynamic organization of the nuclear pore complex transport barrier.

Nuclear pore complexes (NPCs) mediate selective exchange of macromolecules between the nucleus and cytoplasm, but the organization of their transport barrier has been a matter of debate. Here we used high-speed atomic force microscopy, complemented with orthogonal in vitro and in vivo approaches, to probe the dynamic behaviour of the NPC central channel at millisecond resolution. We found that nuclear transport factors dynamically remodel intrinsically disordered phenylalanine-glycine (FG) domains tethered within the NPC channel, partitioning the barrier into two zones: a rapidly fluctuating annular region and a highly mobile central plug. Increased FG-repeat density in mutant NPCs dampened barrier dynamics and impaired transport. Notably, NPC-like behaviour was recapitulated in DNA origami nanopores bearing transport factors and correctly tethered FG domains but not in in vitro FG hydrogels. Thus, the rotationally symmetric architecture of NPCs supports a nanoscopic barrier organization that contrasts with many of the bulk properties of in vitro FG-domain assemblies.