title: NuSAP, a novel microtubule-associated protein involved in mitotic spindle organization.
abstract: Here, we report on the identification of nucleolar spindle-associated protein (NuSAP), a novel 55-kD vertebrate protein with selective expression in proliferating cells. Its mRNA and protein levels peak at the transition of G2 to mitosis and abruptly decline after cell division. Microscopic analysis of both fixed and live mammalian cells showed that NuSAP is primarily nucleolar in interphase, and localizes prominently to central spindle microtubules during mitosis. Direct interaction of NuSAP with microtubules was demonstrated in vitro. Overexpression of NuSAP caused profound bundling of cytoplasmic microtubules in interphase cells, and this relied on a COOH-terminal microtubule-binding domain. In contrast, depletion of NuSAP by RNA interference resulted in aberrant mitotic spindles, defective chromosome segregation, and cytokinesis. In addition, many NuSAP-depleted interphase cells had deformed nuclei. Both overexpression and knockdown of NuSAP impaired cell proliferation. These results suggest a crucial role for NuSAP in spindle microtubule organization.
authors.affiliation: Laboratory for Experimental Medicine and Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium.
authors.forename: Tim
authors.initials: T
authors.lastname: Raemaekers
authors.forename: Katharina
authors.initials: K
authors.lastname: Ribbeck
authors.forename: Joel
authors.initials: J
authors.lastname: Beaudouin
authors.forename: Wim
authors.initials: W
authors.lastname: Annaert
authors.forename: Mark
authors.initials: M
authors.lastname: Van Camp
authors.forename: Ingrid
authors.initials: I
authors.lastname: Stockmans
authors.forename: Nico
authors.initials: N
authors.lastname: Smets
authors.forename: Roger
authors.initials: R
authors.lastname: Bouillon
authors.forename: Jan
authors.initials: J
authors.lastname: Ellenberg
authors.forename: Geert
authors.initials: G
authors.lastname: Carmeliet
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D002460:Cell Line; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000473:pathology; D020090:Chromosome Segregation / Q000235:genetics; D018076:DNA, Complementary / Q000032:analysis; D005057:Eukaryotic Cells / Q000378:metabolism; D016195:G2 Phase / Q000235:genetics; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis / Q000235:genetics*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D018076:DNA, Complementary; D008869:Microtubule-Associated Proteins; C478323:NuSAP protein, mouse; D009687:Nuclear Proteins; D012333:RNA, Messenger