A new role for nuclear transport factor 2 and Ran: nuclear import of CapG.
The small GTPase Ran plays a central role in nucleocytoplasmic transport. Nuclear transport of Ran itself depends on nuclear transport factor 2 (NTF2). Here, we report that NTF2 and Ran control nuclear import of the filamentous actin capping protein CapG. In digitonin-permeabilized cells, neither GTPgammaS nor the GTP hydrolysis-deficient Ran mutant RanQ69L affect transit of CapG to the nucleus in the presence of cytosol. Obstruction of nucleoporins prevents nuclear transport of CapG, and we show that CapG binds to nucleoporin62. In addition, CapG interacts with NTF2, associates with Ran and is furthermore able to bind the NTF2-Ran complex. NTF2-Ran interaction is required for CapG nuclear import. This is corroborated by a NTF2 mutant with reduced affinity for Ran and a Ran mutant that does not bind NTF2, both of which prevent CapG import. Thus, a ubiquitously expressed protein shuttles to the nucleus through direct association with NTF2 and Ran. The role of NTF2 may therefore not be solely confined to sustaining the Ran gradient in cells.
Van Impe
Katrien
K
Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium.
Hubert
Thomas
T
De Corte
Veerle
V
Vanloo
Berlinda
B
Boucherie
Ciska
C
Vandekerckhove
Joël
J
Gettemans
Jan
J
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D011257:Pregnancy Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; C038965:NUTF2 protein, human; D019913:Nuclear Localization Signals; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D010455:Peptides; D011257:Pregnancy Proteins; D011994:Recombinant Proteins; C049312:nuclear pore protein p62; C066575:CAPG protein, human; D020931:ran GTP-Binding Protein