title: The interaction between importin-α and Nup153 promotes importin-α/β-mediated nuclear import.
abstract: Nuclear transport is mediated by transport factors, including the importin β family members. The directionality of nuclear transport is governed by the asymmetrical distribution of the small GTPase Ran. Of note, importin α/β-mediated import of classical nuclear localization signal (cNLS)--containing cargo is more efficient than other Ran-dependent import pathways that do not require importin α. In this study, we characterized the role of importin α in nuclear transport by examining import efficiencies of cNLS-cargo/importin α/β complexes. We first depleted digitonin-permeabilized semi-intact cells of endogenous importin α and used the cells to show that the interaction between importin α and Nup153--a component of the nuclear pore complex (NPC)--is essential for efficient import of importin β-binding domain containing substrates, but not other cargoes that directly bind to importin β. Moreover, we found that the binding of importin α to Nup153 facilitates cNLS-mediated import, and demonstrated that importin α in import complexes and cargo-free importin α prebound to Nup153 promote efficient import of cNLS-containing proteins. This is the first in vitro study showing that in conjunction with Nup153, importin α contributes to directionally biased exit of cNLS-containing cargo to the nuclear side of NPCs.
authors.affiliation: Department of Frontier Biosciences, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-oka, Suita, Osaka, 565-0871, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Miyamoto
authors.forename: Masahiro
authors.initials: M
authors.lastname: Oka
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yoneda
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D019913:Nuclear Localization Signals; D022022:Nuclear Pore / Q000378:metabolism*; D028861:Nuclear Pore Complex Proteins / Q000378:metabolism*; D011485:Protein Binding; D028901:alpha Karyopherins / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*
chemical_list: C079377:NUP153 protein, human; D019913:Nuclear Localization Signals; D028861:Nuclear Pore Complex Proteins; D028901:alpha Karyopherins; D028961:beta Karyopherins