Aurora-A promotes the establishment of spindle assembly checkpoint by priming the Haspin-Aurora-B feedback loop in late G2 phase

Fazhi Yu,Zhenye Yang,Jing Guo,Dan Liu,Xing Liu,Xuebiao Yao,Terry Van Dyke,Lucy Lu,Yulong Qiao,Fangwei Wang,Mimi Cao,Ya Jiang

doi:10.1038/celldisc.2016.49

Abstract

Aurora-A kinase functions mainly in centrosome maturation, separation and spindle formation. It has also been found to be amplified or overexpressed in a range of solid tumors, which is linked with tumor progression and poor prognosis. Importantly, Aurora-A inhibitors are being studied in a number of ongoing clinical trials. However, whether and how Aurora-A has a role in the regulation of the mitotic checkpoint is controversial. Additionally, the function of nuclear-accumulated Aurora-A in late G2 phase is not clear. Here we show that knockout, inhibition or blockade of the nuclear entry of Aurora-A severely decreased the centromere localization of Aurora-B and the phosphorylation of histone H3 threonine 3 (H3T3-ph) mediated by the kinase Haspin in late G2 phase. We further reveal that nuclear-accumulated Aurora-A phosphorylates Haspin at multiple sites at its N-terminus and that this promotes H3T3-ph and the rapid recruitment to the centromere of the chromosomal passenger complex. In addition, Aurora-A facilitates the association of Aurora-B with their common substrates: Haspin and Plk1. Notably, these functions of Aurora-A are mostly independent of Plk1. Thus we demonstrate that, in late G2 and prophase, Aurora-A phosphorylates Haspin to trigger the Haspin-H3T3-ph-Aurora-B positive feedback loop that supports the timely establishment of the chromosomal passenger complex and the mitotic checkpoint before spindle assembly.

Highlights

Using different approaches, including selective inhibitors, genetic KO and ectopic expression, we demonstrate that Aurora-A phosphorylates and activates Haspin kinase independently of Plk1 to facilitate histone H3T3-ph, which promotes timely assembly of chromosomal passenger complex (CPC) and spindle assembly checkpoint (SAC) proteins before nuclear envelope breakdown (NEBD)
We first visualized the initial recruitment of Mad2, one of the key components of the SAC, to the kinetochores in live cells with or without Aurora-A kinase activity
As there is no quality control that monitors the integrity of the SAC assembly, cells must evolve highly efficient ways to ensure the rapid generation of the SAC before NEBD, after which the chromosomes are immediately encountered with highly dynamic microtubules

Summary

Introduction

The centromere accumulation of CPC is required for the efficiency of the Aurora-B–Mps feedback loop [6, 7, 9]. The centromeric localization of CPC is initially mediated by survivin, which recognizes the phosphorylation of histone H3 threonine 3 (H3T3-ph) and anchors the CPC to the chromatin including centromere [10,11,12,13]. In late G2 phase and prophase, cyclindependent kinase 1 (CDK1) and Plk phosphorylate Haspin at multiple sites, which triggers its activation and may release it from autoinhibitory conformation [15, 16]. Phosphorylation of H2A threonine 120 (H2AT120ph) and the signaling axis: Bub1-H2AT120ph-Sgo, promote the centromere establishment of CPC at kinetochore proximal side [5, 11, 12]

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Results

Conclusion