SKAP interacts with Aurora B to guide end-on capture of spindle microtubules via phase separation

Abstract

Chromosome segregation in mitosis is orchestrated by the dynamic interactions between the kinetochore and spindle microtubules. Our recent studies show that mitotic motor CENP-E cooperates with SKAP and forms a link between kinetochore core MIS13 complex and spindle microtubule plus-ends to achieve accurate chromosome alignment in mitosis. However, it remains elusive how SKAP regulates kinetochore attachment from lateral association to end-on attachment during metaphase alignment. Here, we identify a novel interaction between Aurora B and SKAP that orchestrates accurate interaction between the kinetochore and dynamic spindle microtubules. Interestingly, SKAP spontaneously phase-separates in vitro via weak, multivalent interactions into droplets with fast internal dynamics. SKAP and Aurora B form heterogeneous coacervates in vitro, which recapitulate the dynamics and behavior of SKAP comets in vivo. Importantly, SKAP interaction with Aurora B via phase separation is essential for accurate chromosome segregation and alignment. Based on those findings, we reason that SKAP–Aurora B interaction via phase separation constitutes a dynamic pool of Aurora B activity during the lateral to end-on conversion of kinetochore–microtubule attachments to achieve faithful cell division.

Phosphorylation of CENP-R by Aurora B regulates kinetochore–microtubule attachment for accurate chromosome segregation

“…The NDC80 complex is extensively investigated as the main microtubule receptor at outer kinetochore ( Cheeseman et al., 2006 ; DeLuca et al., 2006 ). In addition, the astrin–SKAP complex and Ska1/2/3 complex selectively localize to the kinetochores with correct microtubule attachment to stabilize the linkage ( Fang et al., 2009 ; Schmidt et al., 2010 ; Chan et al., 2012 ; Zhang et al., 2021 ). Besides the aforementioned complex, the CENP-OPQUR complex is reported to have microtubule-binding activity ( Pesenti et al., 2018 ).…”

Sgo1 interacts with CENP-A to guide accurate chromosome segregation in mitosis

“…GST-tagged full-length Sgo1 and the truncated mutants were purified as described previously ( Liu et al., 2020 ; Zhang et al., 2022 ). Basically, the plasmids were transformed into E scherichia coli strain Rosetta (DE3), and protein expression was induced with 0.2 mM IPTG at 16°C.…”