A bifunctional kinase-phosphatase module integrates mitotic checkpoint and error-correction signalling to ensure mitotic fidelity

Abstract

Two major mechanisms have evolved to safeguard genome stability during mitosis: the mitotic checkpoint delays mitosis until all chromosomes have attached to microtubules, and the kinetochore-microtubule error-correction pathway keeps this attachment process free from errors. We demonstrate here that the optimal strength and dynamics of both processes is set by a kinase-phosphatase pair (PLK1-PP2A) that engage in negative feedback on the BUB complex. Uncoupling this homeostatic feedback to skew the balance towards PLK1 produces a strong checkpoint, weak microtubule attachments, and mitotic delays. Conversely, skewing the balance towards PP2A causes a weak checkpoint, strong microtubule attachments, and chromosome segregation errors. The number of MELT motifs on the KNL1 signalling scaffold sets the optimal levels of each enzyme, because engineering KNL1 to recruit too many BUB complexes increases KNL1-PLK1/PP2A levels, and enhances checkpoint/microtubule attachment strength. In contrast, recruiting too few BUB complexes lowers KNL1-PLK1/PP2A, and decreases checkpoint/microtubule attachment strength. Both of these situations are associated with chromosome segregation errors. Together, these data demonstrate how a single bifunctional kinase-phosphatase module integrates two major mitotic processes to help preserve genome stability.

A cytological and functional framework of the meiotic spindle assembly checkpoint inArabidopsis thaliana

“…The step-wise (dis-)assembly of the SAC argued for a strict regulation of protein interactions at the level of the kinetochore, possibly through post-translational modifications. Phosphorylation is well known to control the interaction of SAC components and finetune the strength of the SAC in mammals for instance by promoting the interaction of Bub3-Bub1 and Bub3-BubR1 dimers with Knl1 (preprint: Corno et al, 2022;Espert et al, 2014;Vleugel et al, 2013).…”