Polo regulates Spindly to prevent premature stabilization of kinetochore–microtubule attachments. (18th December 2019)

• Record Type: Journal Article
• Authors: Barbosa, João; Martins, Torcato; Bange, Tanja; Tao, Li; Conde, Carlos; Sunkel, Claudio
• Is Part Of: EMBO journal. Volume 39:Number 2(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-12-18
• Subjects: kinetochore attachments -- mitosis -- Polo -- RZZ -- Spindly; Molecular biology -- Periodicals; 572.805
• DOI: 10.15252/embj.2018100789
• Languages: English
• ISSNs: 0261-4189

Abstract

Abstract: Accurate chromosome segregation in mitosis requires sister kinetochores to bind to microtubules from opposite spindle poles. The stability of kinetochore–microtubule attachments is fine‐tuned to prevent or correct erroneous attachments while preserving amphitelic interactions. Polo kinase has been implicated in both stabilizing and destabilizing kinetochore–microtubule attachments. However, the mechanism underlying Polo–destabilizing activity remains elusive. Here, resorting to an RNAi screen in Drosophila for suppressors of a constitutively active Polo mutant, we identified a strong genetic interaction between Polo and the Rod–ZW10–Zwilch (RZZ) complex, whose kinetochore accumulation has been shown to antagonize microtubule stability. We find that Polo phosphorylates Spindly and impairs its ability to bind to Zwilch. This precludes dynein‐mediated removal of the RZZ from kinetochores and consequently delays the formation of stable end‐on attachments. We propose that high Polo‐kinase activity following mitotic entry directs the RZZ complex to minimize premature stabilization of erroneous attachments, whereas a decrease in active Polo in later mitotic stages allows the formation of stable amphitelic spindle attachments. Our findings demonstrate that Polo tightly regulates the RZZ–Spindly–dynein module during mitosis to ensure the fidelity of chromosome segregation. Synopsis: Polo kinase is involved in both stabilizing and destabilizing kinetochore‐microtubule attachments during mitosis. A Drosophila RNAi screen identifies the RZZ complex as mediator of Polo‐dependent destabilization of early mitotic spindle mis‐attachments. Constitutively‐active Polo kinase delays formation of stable end‐on kinetochore‐microtubule attachments in an RZZ‐dependent manner. Polo phosphorylates the dynein adaptor Spindly at prometaphase kinetochores, decreasing its affinity towards the RZZ complex. Dynein promptly strips phosphorylated Spindly from kinetochores, leaving the RZZ behind to reduce the stability of microtubule attachments. Decreasing Spindly phosphorylation as chromosomes congress enables efficient dynein‐mediated removal of RZZ from kinetochores and consequent stabilization of microtubule attachments. Preventing Polo from phosphorylating Spindly during early mitosis leads to premature stabilization of merotelic attachments. Abstract : RNAi screening identifies the RZZ complex as mediator of early mitotic spindle attachment destabilization via high Polo kinase activity in Drosophila .