NuSAP, a novel microtubule-associated protein involved in mitotic spindle organization.
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.
Raemaekers
Tim
T
Laboratory for Experimental Medicine and Endocrinology, Katholieke Universiteit Leuven, Leuven, Belgium.
Ribbeck
Katharina
K
Beaudouin
Joel
J
Annaert
Wim
W
Van Camp
Mark
M
Stockmans
Ingrid
I
Smets
Nico
N
Bouillon
Roger
R
Ellenberg
Jan
J
Carmeliet
Geert
G
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
D018076:DNA, Complementary; D008869:Microtubule-Associated Proteins; C478323:NuSAP protein, mouse; D009687:Nuclear Proteins; D012333:RNA, Messenger