Abstract
Multiple export receptors passage bound pre-ribosomes through nuclear pore complexes (NPCs) by transiently interacting with the Phe-Gly (FG) meshwork of their transport channels. Here, we reveal how the non-FG interacting yeast mRNA export factor Gly-Leu-FG lethal 2 (Gle2) functions in the export of the large pre-ribosomal subunit (pre-60S). Structure-guided studies uncovered conserved platforms used by Gle2 to export pre-60S: an uncharacterized basic patch required to bind pre-60S, and a second surface that makes non-FG contacts with the nucleoporin Nup116. A basic patch mutant of Gle2 is able to function in mRNA export, but not pre-60S export. Thus, Gle2 provides a distinct interaction platform to transport pre-60S to the cytoplasm. Notably, Gle2’s interaction platforms become crucial for pre-60S export when FG-interacting receptors are either not recruited to pre-60S or are impaired. We propose that large complex cargos rely on non-FG as well as FG-interactions for their efficient translocation through the nuclear pore complex channel.
Highlights
A fundamental feature of all eukaryotes is the rapid exchange of diverse macromolecules between the nucleus and cytoplasm
Gly-Leu-FG lethal 2 (Gle2) genetically interacts with pre-60S subunit export receptors
We began our investigation by testing whether Gle2 genetically interacts with other factors that directly participate in pre-60S subunit export
Summary
A fundamental feature of all eukaryotes is the rapid exchange of diverse macromolecules between the nucleus and cytoplasm. Transport between the two compartments takes place through nuclear pore complexes (NPCs) that are embedded within the double bi-layered nuclear envelope. Shuttling receptors facilitate nucleo-cytoplasmic exchange by binding diverse cargos and simultaneously engaging in transient interactions with Phe-Gly (FG)rich nucleoporins that line the transport channel of the NPC. Import and export receptors include members of the importin-b-like family, termed as karyopherins, which recognize either a nuclear localization signal or a nuclear export signal (NES) on cargoes that need to be imported or exported, respectively. Karyopherin-cargo complexes bind to 11 different FGrepeat nucleoporins along the central transport channel [1]. The GTPase Ran and its nuclear and cytoplasmic localized regulators (Ran-GAP and Ran-GEF) ensure directionality of karyopherin-mediated transport [2,3,4]
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