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Nek9 Phosphorylation Defines a New Role for TPX2 in Eg5-Dependent Centrosome Separation before Nuclear Envelope Breakdown.

Current biology : CB | 2018

Centrosomes [1, 2] play a central role during spindle assembly in most animal cells [3]. In early mitosis, they organize two symmetrical microtubule arrays that upon separation define the two poles of the forming spindle. Centrosome separation is tightly regulated [4, 5], occurring through partially redundant mechanisms that rely on the action of microtubule-based dynein and kinesin motors and the actomyosin system [6]. While centrosomes can separate in prophase or in prometaphase after nuclear envelope breakdown (NEBD), prophase centrosome separation optimizes spindle assembly and minimizes the occurrence of abnormal chromosome attachments that could end in aneuploidy [7, 8]. Prophase centrosome separation relies on the activity of Eg5/KIF11, a mitotic kinesin [9] that accumulates around centrosomes in early mitosis under the control of CDK1 and the Nek9/Nek6/7 kinase module [10-17]. Here, we show that Eg5 localization and centrosome separation in prophase depend on the nuclear microtubule-associated protein TPX2 [18], a pool of which localizes to the centrosomes before NEBD. This localization involves RHAMM/HMMR [19] and the kinase Nek9 [20], which phosphorylates TPX2 nuclear localization signal (NLS) preventing its interaction with importin and nuclear import. The pool of centrosomal TPX2 in prophase has a critical role for both microtubule aster organization and Eg5 localization, and thereby for centrosome separation. Our results uncover an unsuspected role for TPX2 before NEBD and define a novel regulatory mechanism for centrosome separation in prophase. They furthermore suggest NLS phosphorylation as a novel regulatory mechanism for spindle assembly factors controlled by the importin/Ran system.

Pubmed ID: 29276125 RIS Download

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Goat Anti-Mouse IgG HRP Affinity Purified PAb (antibody)

RRID:AB_357234

This polyclonal targets Goat Mouse IgG HRP Affinity Purified PAb

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Eg5 antibody (antibody)

RRID:AB_625879

This polyclonal targets Human Eg5

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Eg5 (antibody)

RRID:AB_398720

This monoclonal targets Eg5

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NTF97/Importin beta antibody (antibody)

RRID:AB_881759

This polyclonal targets NTF97/Importin beta antibody

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Purified Rabbit Anti-GFP, Anti-GFP (antibody)

RRID:AB_10013661

This polyclonal targets Citrine, EGFP, GFP, YFP

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RHAMM (H-90) (antibody)

RRID:AB_2118510

This polyclonal targets HMMR

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GAPDH Antibody (0411) (antibody)

RRID:AB_627678

This monoclonal targets GAPDH

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HeLa (cell line)

RRID:CVCL_0030

Cell line HeLa is a Cancer cell line with a species of origin Homo sapiens

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HEK293T (cell line)

RRID:CVCL_0063

Cell line HEK293T is a Transformed cell line with a species of origin Homo sapiens (Human)

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