Biology subjects

Cunha-Silva, S.

Publications and source records attributed to Cunha-Silva, S..

2 recordsLinked to original sources

bioRxiv2024

POLO kinase inhibits Protein Phosphatase 1 to promote the Spindle Assembly Checkpoint and prevent aneuploidy

Protein phosphatase 1 (PP1) is essential for spindle assembly checkpoint (SAC) silencing and mitotic exit, but its regulation during mitosis remains ill-defined. Here, we demonstrate in vitro and in Drosophila cells that the mitotic kinase POLO phosphorylates PP187B at a conserved residue (T286) within a pocket implicated in the recognition of RVxF-containing target proteins. Phosphorylation of T286 inhibits PP187B binding to the RVxF motif of the SAC kinase MPS1, dampening the dephosphorylation of MPS1 T-loop. Phosphorylation of T286 is dynamically regulated during mitosis. It occurs at unattached/tensionless kinetochores and decreases as chromosomes congress. Expression of phosphomimetic PP187BT286D prevents MPS1 inactivation in metaphase and causes a SAC-dependent delay of anaphase onset. Conversely, an unphosphorylatable PP187BT286A mutant impairs MPS1 activation at unattached kinetochores and weakens the SAC. In vivo, larval neuroblasts expressing PP187BT286 phosphomutants exhibit frequent chromosome mis-segregation and aneuploidy. Thus, our findings identify POLO-mediated phosphorylation of PP187B as a critical regulatory strategy that fine-tunes phosphatase activity to ensure a robust and timely SAC and prevent genome instability.

cell biology↗

bioRxiv2019

Mps1 releases Mad1 from nuclear pores to ensure a robust mitotic checkpoint and accurate chromosome segregation

The strength of the Spindle Assembly Checkpoint (SAC) depends on the amount of the Mad1-C-Mad2 heterotetramer at kinetochores but also on its binding to Megator/Tpr at nuclear pore complexes (NPCs) during interphase. However, the molecular underpinnings controlling the spatiotemporal redistribution of Mad1-C-Mad2 as cells progress into mitosis remain elusive. Here, we show that Mps1-mediated phosphorylation of Megator/Tpr abolishes its interaction with Mad1 in vitro and in Drosophila cells. Timely activation of Mps1 during prophase triggers Mad1 release from NPCs, which we find to be required for competent kinetochore recruitment of Mad1-C-Mad2 and robust checkpoint response. Importantly, preventing Mad1 binding to Megator/Tpr rescues the fidelity of chromosome segregation and aneuploidy in larval neuroblasts of Drosophila mps1-null mutants. Our findings demonstrate that the subcellular localization of Mad1 is stringently coordinated with cell cycle progression by kinetochore-extrinsic activity of Mps1. This ensures that both NPCs in interphase and kinetochores in mitosis can generate anaphase inhibitors to efficiently preserve genomic stability.

cell biology↗