Journal of Biological Chemistry
Volume 291, Issue 34, 19 August 2016, Pages 17579-17592
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Cell Biology
Phosphorylation of Astrin Regulates Its Kinetochore Function*

https://doi.org/10.1074/jbc.M115.712745Get rights and content
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The error-free segregation of chromosomes, which requires the precisely timed search and capture of chromosomes by spindles during early mitotic and meiotic cell division, is responsible for genomic stability and is achieved by the spindle assembly checkpoint in the metaphase-anaphase transition. Mitotic kinases orchestrate M phase events, such as the reorganization of cell architecture and kinetochore (KT) composition with the exquisite phosphorylation of mitotic regulators, to ensure timely and temporal progression. However, the molecular mechanisms underlying the changes of KT composition for stable spindle attachment during mitosis are poorly understood. Here, we show that the sequential action of the kinase Cdk1 and the phosphatase Cdc14A control spindle attachment to KTs. During prophase, the mitotic spindle protein Spag5/Astrin is transported into centrosomes by Kinastrin and phosphorylated at Ser-135 and Ser-249 by Cdk1, which, in prometaphase, is loaded onto the spindle and targeted to KTs. We also demonstrate that Cdc14A dephosphorylates Astrin, and therefore the overexpression of Cdc14A sequesters Astrin in the centrosome and results in aberrant chromosome alignment. Mechanistically, Plk1 acts as an upstream kinase for Astrin phosphorylation by Cdk1 and targeting phospho-Astrin to KTs, leading to the recruitment of outer KT components, such as Cenp-E, and the stable attachment of spindles to KTs. These comprehensive findings reveal a regulatory circuit for protein targeting to KTs that controls the KT composition change of stable spindle attachment and chromosome integrity.

cell cycle
cell division
cyclin-dependent kinase (Cdk)
kinetochore
phosphorylation
mitosis

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*

This work was supported by Institute for Basic Science Grant IBS-R015-D1 and National Research Foundation of Korea grants NRF-2015R1A2A2A01003975 and 2011-0030074 funded by the Korea government. The authors declare that they have no conflicts of interest with the contents of this article.

1

These authors contributed equally to this work.