The RNA export factor Mex67 functions as a mobile nucleoporin

J Cell Biol. 2019 Dec 2;218(12):3967-3976. doi: 10.1083/jcb.201909028. Epub 2019 Nov 21.


The RNA export factor Mex67 is essential for the transport of mRNA through the nuclear pore complex (NPC) in yeast, but the molecular mechanism of this export process remains poorly understood. Here, we use quantitative fluorescence microscopy techniques in live budding yeast cells to investigate how Mex67 facilitates mRNA export. We show that Mex67 exhibits little interaction with mRNA in the nucleus and localizes to the NPC independently of mRNA, occupying a set of binding sites offered by FG repeats in the NPC. The ATPase Dbp5, which is thought to remove Mex67 from transcripts, does not affect the interaction of Mex67 with the NPC. Strikingly, we find that the essential function of Mex67 is spatially restricted to the NPC since a fusion of Mex67 to the nucleoporin Nup116 rescues a deletion of MEX67 Thus, Mex67 functions as a mobile NPC component, which receives mRNA export substrates in the central channel of the NPC to facilitate their translocation to the cytoplasm.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus
  • Binding Sites
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • DEAD-box RNA Helicases / metabolism
  • Gene Deletion
  • Microscopy, Fluorescence
  • Nuclear Pore Complex Proteins / metabolism*
  • Nuclear Proteins / metabolism*
  • Nucleocytoplasmic Transport Proteins / metabolism*
  • Protein Binding
  • RNA Transport
  • RNA, Messenger / metabolism
  • RNA-Binding Proteins / metabolism*
  • Ribosomes / metabolism
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*


  • MEX67 protein, S cerevisiae
  • NUP116 protein, S cerevisiae
  • Nuclear Pore Complex Proteins
  • Nuclear Proteins
  • Nucleocytoplasmic Transport Proteins
  • RNA, Messenger
  • RNA-Binding Proteins
  • Saccharomyces cerevisiae Proteins
  • DBP5 protein, S cerevisiae
  • DEAD-box RNA Helicases