Title: NuSAP, a mitotic RanGTP target that stabilizes and cross-links microtubules
Authors: Ribbeck, Katharina ×
Groen, Aaron C
Santarella, Rachel
Bohnsack, Markus T
Raemaekers, Tim
Köcher, Thomas
Gentzel, Marc
Görlich, Dirk
Wilm, Matthias
Carmeliet, Geert
Mitchison, Timothy J
Ellenberg, Jan
Hoenger, Andreas
Mattaj, Iain W #
Issue Date: Jun-2006
Publisher: American Society for Cell Biology
Series Title: Molecular Biology of the Cell vol:17 issue:6 pages:2646-2660
Abstract: Nucleolar and spindle-associated protein (NuSAP) was recently identified as a microtubule- and chromatin-binding protein in vertebrates that is nuclear during interphase. Small interfering RNA-mediated depletion of NuSAP resulted in aberrant spindle formation, missegregation of chromosomes, and ultimately blocked cell proliferation. We show here that NuSAP is enriched on chromatin-proximal microtubules at meiotic spindles in Xenopus oocytes. When added at higher than physiological levels to Xenopus egg extract, NuSAP induces extensive bundling of spindle microtubules and causes bundled microtubules within spindle-like structures to become longer. In vitro reconstitution experiments reveal two direct effects of NuSAP on microtubules: first, it can efficiently stabilize microtubules against depolymerization, and second, it can cross-link large numbers of microtubules into aster-like structures, thick fibers, and networks. With defined components we show that the activity of NuSAP is differentially regulated by Importin (Imp) alpha, Impbeta, and Imp7. While Impalpha and Imp7 appear to block the microtubule-stabilizing activity of NuSAP, Impbeta specifically suppresses aspects of the cross-linking activity of NuSAP. We propose that to achieve full NuSAP functionality at the spindle, all three importins must be dissociated by RanGTP. Once activated, NuSAP may aid to maintain spindle integrity by stabilizing and cross-linking microtubules around chromatin.
ISSN: 1059-1524
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Molecular Genetics Section (-)
Clinical and Experimental Endocrinology
Biomedical Sciences Group Management - miscellaneous
× corresponding author
# (joint) last author

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