Distinct regions of the kinesin-5 C-terminal tail are essential for mitotic spindle midzone localization and sliding force

Abstract

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 by cut7 mutants 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 C-terminal tail of Cut7p contributes to both sliding force and midzone localization. In the context of sequential tail truncation, the BimC motif and adjacent C-terminal amino acids are particularly important for sliding force. In addition, moderate tail truncation increases midzone localization, but further truncation of residues N-terminal to the BimC motif decreases midzone localization.

Computational Studies Reveal How Passive Cross-Linkers Regulate Anaphase Spindle Elongation

“…Here, we use the model for the processive stepping of the full-length kinesin-5 Eg5 motor as proposed before, which was modified from the general model for the N-terminal kinesin dimers. − In the model for the full-length Eg5 motor, the effect of the tail domain on the motor dynamics was considered (see Section S1 in the Supporting Information). ,− Upon binding to a MT filament, each pair of MT-bound heads of the Eg5 motor can move along the filament with the period of the binding sites being d = 8.2 nm . The pair of heads of the Eg5 motor can take a forward (plus-ended-directed) step with rate k F (m) and a backward (minus-ended-directed) step with rate k B (m) (see Section S1 in the Supporting Information).…”

Mitotic Functions and Characters of KIF11 in Cancers

“…Moreover, by facilitating the interaction between KIF11 and MTs, the tail domain promotes their crosslinking and sliding to ensure the effective alignment of MTs during metaphase without substantially hindering movement [70]. The tail domain interacts with the motor to decelerate ATP hydrolysis, generating a stable, powerful force to confirm the crosslinking and sliding of MTs [71,72].…”