title: The nuclear import of RNA helicase A is mediated by importin-alpha3.
abstract: RNA helicase A (RHA), an ATPase/helicase, regulates the gene expression at various steps including transcriptional activation and RNA processing. RHA is known to shuttle between the nucleus and cytoplasm. We identified the nuclear localization signal (NLS) of RHA and analyzed the nuclear import mechanisms. The NLS of RHA (RHA-NLS) consisting of 19 amino acid residues is highly conserved through species and does not have the consensus classical NLS. In vitro nuclear import assays revealed that the nuclear import of RHA was Ran-dependent and mediated with the classical importin-alpha/beta-dependent pathway. The binding assay indicated that the basic residues in RHA-NLS were used for interaction with importin-alpha. Furthermore, the nuclear import of RHA-NLS was supported by importin-alpha1 and preferentially importin-alpha3. Our results indicate that the nuclear import of RHA is mediated by the importin-alpha3/importin-beta-dependent pathway and suggest that the specificity for importin may regulate the functions of cargo proteins.
authors.affiliation: Department of Genome Science, Institute of Medical Science, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan.
authors.forename: Satoko
authors.initials: S
authors.lastname: Aratani
authors.forename: Takayuki
authors.initials: T
authors.lastname: Oishi
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Fujita
authors.forename: Minako
authors.initials: M
authors.lastname: Nakazawa
authors.forename: Ryouji
authors.initials: R
authors.lastname: Fujii
authors.forename: Naoko
authors.initials: N
authors.lastname: Imamoto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yoneda
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Fukamizu
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nakajima
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism*; D053487:DEAD-box RNA Helicases; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000378:metabolism*; D019913:Nuclear Localization Signals / Q000378:metabolism*; D028901:alpha Karyopherins / Q000378:metabolism*
chemical_list: C106259:KPNA4 protein, human; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D019913:Nuclear Localization Signals; D028901:alpha Karyopherins; C098487:DHX9 protein, human; D053487:DEAD-box RNA Helicases