Kinesin-8 and Dis1/TOG collaborate to limit spindle elongation from prophase to anaphase A for proper chromosome segregation in fission yeast

Abstract

High-fidelity chromosome segregation relies on proper microtubule regulation. Kinesin-8 has been shown to destabilise microtubules to reduce metaphase spindle length and chromosome movements in multiple species. XMAP215/chTOG polymerases catalyse microtubule growth for spindle assembly, elongation and kinetochore-microtubule attachment. Understanding of their biochemical activity has advanced, but little work directly addresses the functionality and interplay of these conserved factors. We utilised the synthetic lethality of fission yeast kinesin-8 (Klp5-Klp6) and XMAP215/chTOG (Dis1) to study their individual and overlapping roles. We found that the non-motor kinesin-8 tailbox is essential for mitotic function; mutation compromises plus-end-directed processivity. Klp5-Klp6 induces catastrophes to control microtubule length and, surprisingly, Dis1 collaborates with kinesin-8 to slow spindle elongation. Together, they enforce a maximum spindle length for a viable metaphase–anaphase transition and limit elongation during anaphase A to prevent lagging chromatids. Our work provides mechanistic insight into how kinesin-8 negatively regulates microtubules and how this functionally overlaps with Dis1 and highlights the importance of spindle length control in mitosis.

Two XMAP215/TOG microtubule polymerases, Alp14 and Dis1, play non-exchangeable, distinct roles in microtubule organisation in fission yeast

“…For instance, during the first meiotic division, Dis1 plays a role in microtubule shortening to pull kinetochores polewards: this protein appears to promote MT depolymerisation under this condition [26]. In addition, we recently showed that Dis1 potentiates spindle shortening in the absence of the Klp5-Klp6 kinesin-8 complex to ensure kinetochore capture by spindle MTs for proper mitotic progression [27]. Furthermore, Dis1, but not Alp14, plays a role in epigenetic regulation at centromeric chromatin [55].…”

Loss of Kinesin-8 improves the robustness of the acentrosomal spindle

“…Most of klp6Δ SPB-dependent spindles segregate parental chromosomes into two masses (84%), although a minority exhibits three to six masses, consistent with chromosome segregation defects intrinsic to the loss of Klp5/6 (Fig. 7 G, n=69) (Pinder et al, 2019; Syrovatkina et al, 2013; Garcia et al, 2002; West et al, 2001). Self-assembled spindles present severe segregation defects: nearly a third (32%) of the spindles do not segregate chromosomes, leaving the parental nucleus as a single mass, while another third (36%) segregate chromosomes up to three to six masses and only a minority (32%) segregates into two masses i.e., normal segregation (Fig.…”

“…7 B, 20’ arrowhead, 70’ top arrowhead) as well as lagging chromosomes (Fig. 7 B, 70’ bottom arrowhead) (Pinder et al, 2019; Syrovatkina et al, 2013). Remarkably, in the case of self-assembled spindles, deletion of Klp6 rendered MI and MII self-assembled spindles thicker and brighter respect to klp6 + (compare Fig.…”

Two XMAP215/TOG Microtubule Polymerases, Alp14 and Dis1, Play Non-Exchangeable, Distinct Roles in Microtubule Organisation in Fission Yeast

“…Whether or not Dis1 could also promote MT nucleation remains to be determined. By contrast, we and others have recently shown that Dis1 is capable of promoting MT depolymerisation, rather than polymerisation, under some physiological circumstances [26,27].…”

“…For instance, during the first meiotic division, Dis1 plays a role in microtubule shortening to pull kinetochores polewards: this protein appears to promote MT depolymerisation under this condition [26]. In addition, we recently showed that Dis1 potentiates spindle shortening in the absence of the Klp5-Klp6 kinesin-8 complex to ensure kinetochore capture by spindle MTs for proper mitotic progression [27]. Furthermore, Dis1, but not Alp14, plays a role in epigenetic regulation at centromeric chromatin [56].…”