title: The double-stranded RNA binding domain of human Dicer functions as a nuclear localization signal.
abstract: Dicer is a key player in microRNA (miRNA) and RNA interference (RNAi) pathways, processing miRNA precursors and double-stranded RNA into ∼21-nt-long products ultimately triggering sequence-dependent gene silencing. Although processing of substrates in vertebrate cells occurs in the cytoplasm, there is growing evidence suggesting Dicer is also present and functional in the nucleus. To address this possibility, we searched for a nuclear localization signal (NLS) in human Dicer and identified its C-terminal double-stranded RNA binding domain (dsRBD) as harboring NLS activity. We show that the dsRBD-NLS can mediate nuclear import of a reporter protein via interaction with importins β, 7, and 8. In the context of full-length Dicer, the dsRBD-NLS is masked. However, duplication of the dsRBD localizes the full-length protein to the nucleus. Furthermore, deletion of the N-terminal helicase domain results in partial accumulation of Dicer in the nucleus upon leptomycin B treatment, indicating that CRM1 contributes to nuclear export of Dicer. Finally, we demonstrate that human Dicer has the ability to shuttle between the nucleus and the cytoplasm. We conclude that Dicer is a shuttling protein whose steady-state localization is cytoplasmic.
authors.affiliation: Friedrich Miescher Institute for Biomedical Research, CH-4058 Basel, Switzerland. michael.doyle@meduniwien.ac.at
authors.forename: Michael
authors.initials: M
authors.lastname: Doyle
authors.forename: Lukas
authors.initials: L
authors.lastname: Badertscher
authors.forename: Lukasz
authors.initials: L
authors.lastname: Jaskiewicz
authors.forename: Stephan
authors.initials: S
authors.lastname: Güttinger
authors.forename: Sabine
authors.initials: S
authors.lastname: Jurado
authors.forename: Tabea
authors.initials: T
authors.lastname: Hugenschmidt
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kutay
authors.forename: Witold
authors.initials: W
authors.lastname: Filipowicz
mesh_terms: D021581:Active Transport, Cell Nucleus; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000378:metabolism*; D021381:Protein Transport; D012330:RNA, Double-Stranded / Q000737:chemistry* / Q000378:metabolism*; D043244:Ribonuclease III / Q000737:chemistry* / Q000378:metabolism; D014162:Transfection
chemical_list: D019913:Nuclear Localization Signals; D012330:RNA, Double-Stranded; C408087:DICER1 protein, human; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases
keywords: Dicer; NLS; RNAi; dsRBD; helicase