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Kinetochores attached to microtubule-ends are stabilised by Astrin bound PP1 to ensure proper chromosome segregation.

eLife (2019-12-07)
Duccio Conti, Parveen Gul, Asifa Islam, José M Martín-Durán, Richard W Pickersgill, Viji M Draviam
RÉSUMÉ

Microtubules segregate chromosomes by attaching to macromolecular kinetochores. Only microtubule-end attached kinetochores can be pulled apart; how these end-on attachments are selectively recognised and stabilised is not known. Using the kinetochore and microtubule-associated protein, Astrin, as a molecular probe, we show that end-on attachments are rapidly stabilised by spatially-restricted delivery of PP1 near the C-terminus of Ndc80, a core kinetochore-microtubule linker. PP1 is delivered by the evolutionarily conserved tail of Astrin and this promotes Astrin's own enrichment creating a highly-responsive positive feedback, independent of biorientation. Abrogating Astrin:PP1-delivery disrupts attachment stability, which is not rescued by inhibiting Aurora-B, an attachment destabiliser, but is reversed by artificially tethering PP1 near the C-terminus of Ndc80. Constitutive Astrin:PP1-delivery disrupts chromosome congression and segregation, revealing a dynamic mechanism for stabilising attachments. Thus, Astrin-PP1 mediates a dynamic 'lock' that selectively and rapidly stabilises end-on attachments, independent of biorientation, and ensures proper chromosome segregation.

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Ampicilline sodium salt, powder or crystals, BioReagent, suitable for cell culture
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Paclitaxel, from semisynthetic, ≥98%
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Anticorps monoclonal anti-tubuline, acétylée antibody produced in mouse, clone 6-11B-1, ascites fluid
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Z-Leu-Leu-Leu-al, ≥90% (HPLC)
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IPTG, ≥99% (TLC), ≤0.1% Dioxane
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PP1, ≥98% (HPLC)