NuSAP, a Mitotic RanGTP Target That Stabilizes and Cross-links Microtubules

摘要: Nucleolar and spindle-associated protein (NuSAP) was recently identified as a microtubule- chromatin-binding in vertebrates that is nuclear during interphase. Small interfering RNA-mediated depletion of NuSAP resulted aberrant spindle formation, missegregation chromosomes, ultimately blocked cell proliferation. We show here enriched on chromatin-proximal microtubules at meiotic spindles Xenopus oocytes. When added higher than physiological levels to egg extract, induces extensive bundling causes bundled within spindle-like structures become longer. In vitro reconstitution experiments reveal two direct effects microtubules: first, it can efficiently stabilize against depolymerization, second, cross-link large numbers into aster-like structures, thick fibers, networks. With defined components we the activity differentially regulated by Importin (Imp) , Imp, Imp7. While Imp Imp7 appear block microtubule-stabilizing NuSAP, specifically suppresses aspects cross-linking NuSAP. propose achieve full functionality spindle, all three importins must be dissociated RanGTP. Once activated, may aid maintain integrity stabilizing around chromatin.