Regulation of NDR1 activity by PLK1 ensures proper spindle orientation in mitosis.

Maomao Yan,Bo Qin,Zhengjun Chen,Xuebiao Yao,Lingluo Chu,Xinjiao Gao,Ping He,Xing Liu,Zhikai Wang,Guanglan Zhang,Marta Gomez,Alexander Hergovich,Changjiang Jin

doi:10.1038/srep10449

Abstract

Accurate chromosome segregation during mitosis requires the physical separation of sister chromatids which depends on correct position of mitotic spindle relative to membrane cortex. Although recent work has identified the role of PLK1 in spindle orientation, the mechanisms underlying PLK1 signaling in spindle positioning and orientation have not been fully illustrated. Here, we identified a conserved signaling axis in which NDR1 kinase activity is regulated by PLK1 in mitosis. PLK1 phosphorylates NDR1 at three putative threonine residues (T7, T183 and T407) at mitotic entry, which elicits PLK1-dependent suppression of NDR1 activity and ensures correct spindle orientation in mitosis. Importantly, persistent expression of non-phosphorylatable NDR1 mutant perturbs spindle orientation. Mechanistically, PLK1-mediated phosphorylation protects the binding of Mob1 to NDR1 and subsequent NDR1 activation. These findings define a conserved signaling axis that integrates dynamic kinetochore-microtubule interaction and spindle orientation control to genomic stability maintenance.

Highlights

Accurate development of multicellular organism requires well-orchestrated symmetric and asymmetric cell division
Consistent with previous studies[15,16], we found that the phosphorylation of NDR1 on Thr[444], a readout of NDR1 kinase activity, is much lower in mitosis than that in interphase judged by quantitative Western blotting (Fig. 1a; p < 0 .001)
We examined whether PLK1-elicited phosphorylation at Thr[7], Thr[183] and Thr[407] impairs NDR1 kinase activity

Summary

Introduction

Accurate development of multicellular organism requires well-orchestrated symmetric and asymmetric cell division. The cell division axis is ruled by mitotic spindle orientation, which is mainly mediated by LGN-NuMA-Dynein-Dynactin signaling axis. Extrinsic cues orchestrate LGN-NuMA complex position at cell cortex via dynamic interaction with other cortical polarity proteins. A recent study showed that mitotic kinase PLK1 controled the cortical pulling forces via orchestrating the dynamic interaction between Dynein-Dynactin and LGN-NuMA7. The precise mechanism underlying PLK1 regulation in spindle orientation has remained to be characterized. To explore the molecular mechanism underlying NDR1 function and regulation in mitosis, we characterized the activity profile of NDR1 during cell division. PLK1 interacts with and phosphorylates NDR1 by which NDR1 kinase activity is negatively regulated in mitosis. Our study provides a novel insight into the temporal control of NDR1 kinase activity by PLK1-elicited phosphorylation in mitosis

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Results

Conclusion