Nup98 FG domains from diverse species spontaneously phase-separate into particles with nuclear pore-like permselectivity.

Dirk Görlich,Hermann Broder Schmidt

doi:10.7554/elife.04251

Dirk Görlich, Hermann Broder Schmidt

Open Access

https://doi.org/10.7554/elife.04251

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Journal: eLife	Publication Date: Jan 6, 2015
Citations: 291	License type: CC BY 4.0

Affiliation: Max Planck Institute for Biophysical Chemistry

Abstract

Nuclear pore complexes (NPCs) conduct massive transport mediated by shuttling nuclear transport receptors (NTRs), while keeping nuclear and cytoplasmic contents separated. The NPC barrier in Xenopus relies primarily on the intrinsically disordered FG domain of Nup98. We now observed that Nup98 FG domains of mammals, lancelets, insects, nematodes, fungi, plants, amoebas, ciliates, and excavates spontaneously and rapidly phase-separate from dilute (submicromolar) aqueous solutions into characteristic 'FG particles'. This required neither sophisticated experimental conditions nor auxiliary eukaryotic factors. Instead, it occurred already during FG domain expression in bacteria. All Nup98 FG phases rejected inert macromolecules and yet allowed far larger NTR cargo complexes to rapidly enter. They even recapitulated the observations that large cargo-domains counteract NPC passage of NTR⋅cargo complexes, while cargo shielding and increased NTR⋅cargo surface-ratios override this inhibition. Their exquisite NPC-typical sorting selectivity and strong intrinsic assembly propensity suggest that Nup98 FG phases can form in authentic NPCs and indeed account for the permeability properties of the pore.

Highlights

Cell nuclei lack protein synthesis and import required proteins from the cytoplasm
Larger objects are essentially excluded from passage but may traverse the pore when bound to an appropriate nuclear transport receptor (NTR)
One possible explanation for the observed permselectivity of Nuclear pore complexes (NPCs) is given by the hypothesis that the barrier-critical FG domains assemble into a sieve-like meshwork, whose contact points can be temporarily and locally resolved by translocating NTRs

Summary

Introduction

Cell nuclei lack protein synthesis and import required proteins from the cytoplasm. Numerous FG domains can form hydrogels that behave like the NPC's permeability barrier, i.e. they exclude inert macromolecules but allow rapid influx of NTRs and NTR⋅cargo complexes (Frey and Görlich, 2007, 2009; Milles and Lemke, 2011).

Results

Conclusion