Biology subjects

Cordeiro, M. H.

Publications and source records attributed to Cordeiro, M. H..

3 recordsLinked to original sources

bioRxiv2022

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

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.

cell biology↗

bioRxiv2019

Kinetochore phosphatases suppress autonomous kinase activity to control the spindle assembly checkpoint

AO_SCPLOWBSTRACTC_SCPLOWLocal phosphatase regulation is critical for determining when phosphorylation signals are activated or deactivated. A typical example is the spindle assembly checkpoint (SAC) during mitosis, which regulates kinetochore PP1 and PP2A-B56 activities to switch-off signalling events at the correct time. In this case, kinetochore phosphatase activation dephosphorylates MELT motifs on KNL1 to remove SAC proteins, including the BUB complex. We show here that, surprisingly, neither PP1 or PP2A are required to dephosphorylate the MELT motifs. Instead, they remove polo-like kinase 1 (PLK1) from the BUB complex, which can otherwise maintain MELT phosphorylation in an autocatalytic manner. This is their principle role in the SAC, because both phosphatases become redundant if PLK1 is inhibited or BUB-PLK1 interaction is prevented. Therefore, phosphatase regulation is critical for the SAC, but primarily to restrain and extinguish autonomous kinase activity. We propose that these circuits have evolved to generate a semi-autonomous SAC signal that can be synchronously silenced following kinetochore-microtubule tension.

cell biology↗

bioRxiv2019

PP1 and PP2A use opposite phospho-dependencies to control distinct processes at the kinetochore

PP1 and PP2A-B56 are major serine/threonine phosphatase families that achieve specificity by colocalising with substrates. At the kinetochore, however, both phosphatases localise to an almost identical molecular space and yet they still manage to regulate unique pathways and processes. By switching or modulating the positions of PP1/PP2A-B56 at kinetochores, we show that their unique downstream effects are not due to either the identity of the phosphatase or its precise location. Instead, these phosphatases signal differently because their kinetochore recruitment can be either inhibited (PP1) or enhanced (PP2A) by phosphorylation inputs. Mathematical modelling explains how these inverse phospho-dependencies elicit unique forms of cross-regulation and feedback, which allows otherwise indistinguishable phosphatases to produce distinct network behaviours and control different mitotic processes. Therefore, the kinetochore uses PP1 and PP2A-B56 because their binding motifs respond to kinase inputs in opposite ways. Genome-wide motif analysis suggests that many other pathways also select for these same key features, implying that these similar catalytic enzymes may have diverged during evolution to allow opposite modes of phospho-regulation.

cell biology↗