title: Nuclear transport factor p10/NTF2 functions as a Ran-GDP dissociation inhibitor (Ran-GDI).
abstract: The cytosolic nuclear transport factor p10/NTF2 is required for the translocation of karyophilic molecules through nuclear pores [1] [2] [3], and the small GTPase Ran is a key regulator of protein transport between the nucleus and cytoplasm [4] [5]. It has been reported that p10/NTF2 interacts directly and specifically with Ran-GDP but not with Ran-GTP [6]. The precise role(s) of p10/NTF2 in the Ran GTP/GDP cycle are thus far unclear, however. In this study, we show that mammalian p10/NTF2 dramatically inhibits the dissociation of [3H]GDP from Ran and the binding of [35S]GTPgammaS to Ran following the dissociation of non-radioactive GDP by RCC1, the only known mammalian guanine nucleotide exchange factor for Ran (Ran-GEF) [7]. In contrast, the dissociation of [35S]GTP gamma S from Ran, which was also catalyzed by RCC1, was not affected by p10/NTF2. Furthermore, the activities of wild-type p10/NTF2 and the mutant forms M84T and D92G in an assay of nuclear protein import in a digitonin-permeabilized cell-free system correlated with their level of inhibition of the dissociation of nucleotide from Ran-GDP. These results suggest that p10/NTF2 acts as a GDP dissociation inhibitor for Ran (Ran-GDI), thereby coordinating the Ran-dependent reactions that underlie nuclear protein import.
authors.affiliation: Department of Anatomy and Cell Biology Osaka University Medical School 2-2 Yamada-oka Suita Osaka 565-0871 Japan.
authors.forename: M
authors.initials: M
authors.lastname: Yamada
authors.forename: T
authors.initials: T
authors.lastname: Tachibana
authors.forename: N
authors.initials: N
authors.lastname: Imamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Yoneda
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D018797:Cell Cycle Proteins; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002474:Cell-Free System; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D017354:Point Mutation; D020931:ran GTP-Binding Protein; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D020730:Guanine Nucleotide Dissociation Inhibitors; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D062947:rho-Specific Guanine Nucleotide Dissociation Inhibitors; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019204:GTP-Binding Proteins; D020931:ran GTP-Binding Protein