title: Compartmentalized Toxoplasma EB1 bundles spindle microtubules to secure accurate chromosome segregation.
abstract: Toxoplasma gondii replicates asexually by a unique internal budding process characterized by interwoven closed mitosis and cytokinesis. Although it is known that the centrosome coordinates these processes, the spatiotemporal organization of mitosis remains poorly defined. Here we demonstrate that centrosome positioning around the nucleus may signal spindle assembly: spindle microtubules (MTs) are first assembled when the centrosome moves to the basal side and become extensively acetylated after the duplicated centrosomes reposition to the apical side. We also tracked the spindle MTs using the MT plus end-binding protein TgEB1. Endowed by a C-terminal NLS, TgEB1 resides in the nucleoplasm in interphase and associates with the spindle MTs during mitosis. TgEB1 also associates with the subpellicular MTs at the growing end of daughter buds toward the completion of karyokinesis. Depletion of TgEB1 results in escalated disintegration of kinetochore clustering. Furthermore, we show that TgEB1's MT association in Toxoplasma and in a heterologous system (Xenopus) is based on the same principles. Finally, overexpression of a high-MT-affinity TgEB1 mutant promotes the formation of overstabilized MT bundles, resulting in avulsion of otherwise tightly clustered kinetochores. Overall we conclude that centrosome position controls spindle activity and that TgEB1 is critical for mitotic integrity.
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.
authors.forename: Chun-Ti
authors.initials: CT
authors.lastname: Chen
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.
authors.forename: Megan
authors.initials: M
authors.lastname: Kelly
authors.affiliation: Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697.
authors.forename: Jessica de
authors.initials: Jd
authors.lastname: Leon
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.
authors.forename: Belinda
authors.initials: B
authors.lastname: Nwagbara
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.
authors.forename: Patrick
authors.initials: P
authors.lastname: Ebbert
authors.affiliation: Nuffield Department of Clinical Laboratory Science, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: David J P
authors.initials: DJ
authors.lastname: Ferguson
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.
authors.forename: Laura Anne
authors.initials: LA
authors.lastname: Lowery
authors.affiliation: Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697 nmorriss@uci.edu gubbelsj@bc.edu.
authors.forename: Naomi
authors.initials: N
authors.lastname: Morrissette
authors.affiliation: Department of Biology, Boston College, Chestnut Hill, MA 02467.
authors.forename: Marc-Jan
authors.initials: MJ
authors.lastname: Gubbels
mesh_terms: D000818:Animals; D002451:Cell Compartmentation / Q000235:genetics*; D018385:Centrosome; D020090:Chromosome Segregation / Q000235:genetics*; D018386:Kinetochores; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D008870:Microtubules / Q000235:genetics; D008938:Mitosis / Q000235:genetics; D015800:Protozoan Proteins / Q000235:genetics*; D008941:Spindle Apparatus / Q000235:genetics*; D014122:Toxoplasma / Q000235:genetics; D014982:Xenopus laevis / Q000235:genetics
chemical_list: D008869:Microtubule-Associated Proteins; D015800:Protozoan Proteins