title: Importin-β negatively regulates multiple aspects of mitosis including RANGAP1 recruitment to kinetochores.
abstract: Importin-β is the main vector for interphase nuclear protein import and plays roles after nuclear envelope breakdown. Here we show that importin-β regulates multiple aspects of mitosis via distinct domains that interact with different classes of proteins in human cells. The C-terminal region (which binds importin-α) inhibits mitotic spindle pole formation. The central region (harboring nucleoporin-binding sites) regulates microtubule dynamic functions and interaction with kinetochores. Importin-β interacts through this region with NUP358/RANBP2, which in turn binds SUMO-conjugated RANGAP1 in nuclear pores. We show that this interaction continues after nuclear pore disassembly. Overexpression of importin-β, or of the nucleoporin-binding region, inhibited RANGAP1 recruitment to mitotic kinetochores, an event that is known to require microtubule attachment and the exportin CRM1. Co-expressing either importin-β-interacting RANBP2 fragments, or CRM1, restored RANGAP1 to kinetochores and rescued importin-β-dependent mitotic dynamic defects. These results reveal previously unrecognized importin-β functions at kinetochores exerted via RANBP2 and opposed by CRM1.
authors.affiliation: Institute of Molecular Biology and Pathology, CNR National Research Council, 00185 Rome, Italy.
authors.forename: Emanuele
authors.initials: E
authors.lastname: Roscioli
authors.forename: Laura
authors.initials: L
authors.lastname: Di Francesco
authors.forename: Alessio
authors.initials: A
authors.lastname: Bolognesi
authors.forename: Maria
authors.initials: M
authors.lastname: Giubettini
authors.forename: Serena
authors.initials: S
authors.lastname: Orlando
authors.forename: Amnon
authors.initials: A
authors.lastname: Harel
authors.forename: Maria Eugenia
authors.initials: ME
authors.lastname: Schininà
authors.forename: Patrizia
authors.initials: P
authors.lastname: Lavia
mesh_terms: D021581:Active Transport, Cell Nucleus; D015153:Blotting, Western; D005455:Fluorescent Antibody Technique; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins / Q000235:genetics / Q000378:metabolism*; D018386:Kinetochores / Q000502:physiology*; D008938:Mitosis / Q000502:physiology*; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D025841:Small Ubiquitin-Related Modifier Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism; D028961:beta Karyopherins / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
chemical_list: D020690:GTPase-Activating Proteins; D049452:Green Fluorescent Proteins; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D025841:Small Ubiquitin-Related Modifier Proteins; D028961:beta Karyopherins; D000097606:Exportin 1 Protein; C092317:RANGAP1 protein, human; C485184:enhanced green fluorescent protein