title: Poleward transport of Eg5 by dynein-dynactin in Xenopus laevis egg extract spindles.
abstract: Molecular motors are required for spindle assembly and maintenance during cell division. How motors move and interact inside spindles is unknown. Using photoactivation and photobleaching, we measure mitotic motor movement inside a dynamic spindle. We find that dynein-dynactin transports the essential motor Eg5 toward the spindle poles in Xenopus laevis egg extract spindles, revealing a direct interplay between two motors of opposite directionality. This transport occurs throughout the spindle except at the very spindle center and at the spindle poles, where Eg5 remains stationary. The variation of Eg5 dynamics with its position in the spindle is indicative of position-dependent functions of this motor protein. Our results suggest that Eg5 drives microtubule flux by antiparallel microtubule sliding in the spindle center, whereas the dynein-dependent concentration of Eg5 outside the spindle center could contribute to parallel microtubule cross-linking. These results emphasize the importance of spatially differentiated functions of motor proteins and contribute to our understanding of spindle organization.
authors: Cell Biology and Biophysics Unit, European Molecular Biology Laboratory, Heidelberg, Germany.
authors: Marianne
authors: M
authors: Uteng
authors: Christian
authors: C
authors: Hentrich
authors: Kota
authors: K
authors: Miura
authors: Peter
authors: P
authors: Bieling
authors: Thomas
authors: T
authors: Surrey
mesh_terms: D000818:Animals; D002021:Buffers; D002232:Carbocyanines; D002457:Cell Extracts; D016764:Cell Polarity; D000072159:Dynactin Complex; D004398:Dyneins / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D016547:Kinesins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D010063:Ovum / Q000166:cytology*; D038761:Photobleaching; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*; D029867:Xenopus Proteins / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D002021:Buffers; D002232:Carbocyanines; D002457:Cell Extracts; D000072159:Dynactin Complex; C088335:KIF11 protein, Xenopus; D008869:Microtubule-Associated Proteins; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; C085321:cyanine dye 5; D049452:Green Fluorescent Proteins; D004398:Dyneins; D016547:Kinesins