Kinesin-5 motors are essential to separate mitotic spindle poles and assemble a bipolar spindle in many organisms. These motors crosslink and slide apart antiparallel microtubules via microtubule plus-end-directed motility. However, kinesin-5 localization is enhanced away from antiparallel overlaps. Increasing evidence suggests this localization occurs due to bidirectional motility or trafficking. Purified fission-yeast kinesin-5 Cut7p moves bidirectionally, but bidirectionality has not been shown in cells and the function of the minus-end-directed movement is unknown. We characterized the motility of Cut7p on bipolar and monopolar spindles and observed movement toward both plus and minus ends of microtubules. Notably, the activity of the motor increases at anaphase B onset. Perturbations to microtubule dynamics only modestly changed Cut7p movement, while Cut7p mutation reduced movement. These results suggest that the directed motility of Cut7p contributed to the movement of the motor. Comparison of Cut7 mutant and human Eg5 localization suggest a new hypothesis for the function of minus-end-directed motility and spindle-pole localization of kinesin-5s.
Kinesin-5 motor proteins play essential roles during mitosis in most organisms. Their tetrameric structure and plus-end-directed motility allow them to bind to and move along antiparallel microtubules, thereby pushing spindle poles apart to assemble a bipolar spindle. Recent work has shown that the C-terminal tail is particularly important to kinesin-5 function: the tail affects motor domain structure, ATP hydrolysis, motility, clustering, and sliding force measured for purified motors, as well as motility, clustering, and spindle assembly in cells. Because previous work has focused on presence or absence of the entire tail, the functionally important regions of the tail remain to be identified. We have therefore characterized a series of kinesin-5/Cut7 tail truncation alleles in fission yeast. Partial truncation causes mitotic defects and temperature-sensitive growth, while further truncation that removes the conserved BimC motif is lethal. We compared the sliding force generated bycuts7mutants using a kinesin-14 mutant background in which some microtubules detach from the spindle poles and are pushed into the nuclear envelope. These Cut7 driven protrusions decreased as more of the tail was truncated, and the most severe truncations produced no observable protrusions. Our observations suggest that the BimC motif and adjacent C-terminal amino acids are essential for sliding force, while the residues N-terminal to the BimC motif are more important for midzone localization. Spindle microtubule protrusions may be a useful tool to study sliding force generated by kinesin-5 motors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.