Steady-state nuclear localization of exportin-t involves RanGTP binding and two distinct nuclear pore complex interaction domains.
Vertebrate tRNA export receptor exportin-t (Xpo-t) binds to RanGTP and mature tRNAs cooperatively to form a nuclear export complex. Xpo-t shuttles bidirectionally through nuclear pore complexes (NPCs) but is mainly nuclear at steady state. The steady-state distribution of Xpo-t is shown to depend on its interaction with RanGTP. Two distinct Xpo-t NPC interaction domains that bind differentially to peripherally localized nucleoporins in vitro are identified. The N terminus binds to both Nup153 and RanBP2/Nup358 in a RanGTP-dependent manner, while the C terminus binds to CAN/Nup214 independently of Ran. We propose that these interactions increase the concentration of tRNA export complexes and of empty Xpo-t in the vicinity of NPCs and thus increase the efficiency of the Xpo-t transport cycle.
Gene Expression Programme, European Molecular Biology Laboratory, D-69117 Heidelberg, Germany.
Scott
S
Kuersten
Gert-Jan
GJ
Arts
Tobias C
TC
Walther
Ludwig
L
Englmeier
Iain W
IW
Mattaj
D021581:Active Transport, Cell Nucleus / Q000502:physiology*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008845:Microinjections; D008954:Models, Biological; D022022:Nuclear Pore / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D009865:Oocytes; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012343:RNA, Transfer / Q000378:metabolism; D014982:Xenopus laevis; D020931:ran GTP-Binding Protein / Q000378:metabolism*
D002352:Carrier Proteins; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; C503618:XPOT protein, human; D012343:RNA, Transfer; D020931:ran GTP-Binding Protein