Phosphorylation of PP1 Regulator Sds22 by PLK1 Ensures Accurate Chromosome Segregation

Hequan Duan,Gregory Barrett,Chunli Wang,Youjun Chu,Xing Liu,Ming Wang,Fangjun Wang,Wenwen Wang,Zhen Dou,Saima Akram,Ping He,Wei Peng,Dong Wang,Xuebiao Yao,Ruijun Tian,Maomao Yan,Hadiyah-Nichole Green,Hanfa Zou,Xiaolan Gao ,Jiajia Zhang

doi:10.1074/jbc.m116.745372

Abstract

During cell division, accurate chromosome segregation is tightly regulated by Polo-like kinase 1 (PLK1) and opposing activities of Aurora B kinase and protein phosphatase 1 (PP1). However, the regulatory mechanisms underlying the aforementioned hierarchical signaling cascade during mitotic chromosome segregation have remained elusive. Sds22 is a conserved regulator of PP1 activity, but how it regulates PP1 activity in space and time during mitosis remains elusive. Here we show that Sds22 is a novel and cognate substrate of PLK1 in mitosis, and the phosphorylation of Sds22 by PLK1 elicited an inhibition of PP1-mediated dephosphorylation of Aurora B at threonine 232 (Thr232) in a dose-dependent manner. Overexpression of a phosphomimetic mutant of Sds22 causes a dramatic increase in mitotic delay, whereas overexpression of a non-phosphorylatable mutant of Sds22 results in mitotic arrest. Mechanistically, the phosphorylation of Sds22 by PLK1 strengthens the binding of Sds22 to PP1 and inhibits the dephosphorylation of Thr232 of Aurora B to ensure a robust, error-free metaphase-anaphase transition. These findings delineate a conserved signaling hierarchy that orchestrates dynamic protein phosphorylation and dephosphorylation of critical mitotic regulators during chromosome segregation to guard chromosome stability.

Highlights

During cell division, accurate chromosome segregation is tightly regulated by Polo-like kinase 1 (PLK1) and opposing activities of Aurora B kinase and protein phosphatase 1 (PP1)
We show that Sds22 is a novel and cognate substrate of PLK1 in mitosis, and the phosphorylation of Sds22 by PLK1 elicited an inhibition of PP1-mediated dephosphorylation of Aurora B at threonine 232 (Thr232) in a dose-dependent manner
Our studies revealed that PLK1 physically interacts with Sds22, both in vitro and in vivo, and that Sds22 is a cognate substrate of PLK1 in mitosis

Summary

Introduction

Accurate chromosome segregation is tightly regulated by Polo-like kinase 1 (PLK1) and opposing activities of Aurora B kinase and protein phosphatase 1 (PP1). The phosphorylation of Sds by PLK1 strengthens the binding of Sds to PP1 and inhibits the dephosphorylation of Thr232 of Aurora B to ensure a robust, error-free metaphase-anaphase transition These findings delineate a conserved signaling hierarchy that orchestrates dynamic protein phosphorylation and dephosphorylation of critical mitotic regulators during chromosome segregation to guard chromosome stability. Bipolar attachment of spindle microtubules to kinetochores is monitored by the spindle assembly checkpoint (SAC) and dynamically regulated by phosphorylation and dephosphorylation to allow correction of improper attachment and stabilization of correct attachments [2,3,4] Key elements of this regulation are PLK1, Aurora B, and PP1/Sds, whose opposing activities need to be tightly balanced [5,6,7]. PLK1-PP1/Sds22-Aurora B Orchestrates Chromosome Segregation is critical for orchestrating Aurora B activity in centromeres, which Phosphatase specificity of PP1 is achieved through associais essential for accurate chromosome segregation and faithful tion with accessory subunits that control the specificity and completion of cytokinesis [20]

Methods

Results

Conclusion