Prophase-Specific Perinuclear Actin Coordinates Centrosome Separation and Positioning to Ensure Accurate Chromosome Segregation

Tom Stiff,Fabio R Echegaray-Iturra,Harry J Pink,Alex Herbert,Constantino Carlos Reyes-Aldasoro,Helfrid Hochegger

doi:10.1016/j.celrep.2020.107681

Tom Stiff, Fabio R Echegaray-Iturra + Show 4 more

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https://doi.org/10.1016/j.celrep.2020.107681

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Journal: Cell Reports	Publication Date: May 1, 2020
Citations: 27	License type: cc-by

Affiliation: University of Sussex, University of London

Abstract

SummaryCentrosome separation in late G2/ early prophase requires precise spatial coordination that is determined by a balance of forces promoting and antagonizing separation. The major effector of centrosome separation is the kinesin Eg5. However, the identity and regulation of Eg5-antagonizing forces is less well characterized. By manipulating candidate components, we find that centrosome separation is reversible and that separated centrosomes congress toward a central position underneath the flat nucleus. This positioning mechanism requires microtubule polymerization, as well as actin polymerization. We identify perinuclear actin structures that form in late G2/early prophase and interact with microtubules emanating from the centrosomes. Disrupting these structures by breaking the interactions of the linker of nucleoskeleton and cytoskeleton (LINC) complex with perinuclear actin filaments abrogates this centrosome positioning mechanism and causes an increase in subsequent chromosome segregation errors. Our results demonstrate how geometrical cues from the cell nucleus coordinate the orientation of the emanating spindle poles before nuclear envelope breakdown.

Highlights

Centrosomes are the microtubule (MT) organizing centers in animal cells
We find that centrosome separation before nuclear envelope breakdown (NEBD) is antagonized by forces that push the centrosomes toward a central position underneath the nucleus
Centrosome Position before NEBD Is Stabilized by Eg5Antagonizing Forces To analyze the dynamics of centrosome separation prior to NEBD, we used U2OS cells that carry a Cdk1-analog-sensitive mutation. These cells arrest in late G2 phase with separated centrosomes before NEBD following Cdk1 inhibition by the bulky ATP analog 1NM-PP1 (Hochegger et al, 2007; Rata et al, 2018)

Summary

Introduction

Centrosomes are the microtubule (MT) organizing centers in animal cells. Centrosome numbers are restricted to one in G1/S and two in G2/M phase but are often amplified in cancer cells (Godinho, 2014). Sufficient separation during prophase is not essential for bipolar spindle formation but is important for the establishment of accurate sister chromatid alignment. Both premature and insufficient separation of centrosomes before NEBD can cause an increase in sister chromatid attachment and segregation errors that may contribute to aneuploidy and tumorigenesis (Kaseda et al, 2012; Nam et al, 2015; Nam and van Deursen, 2014; Silkworth et al, 2012). Understanding the balance of forces impacting on prophase centrosome separation is a critical question for our understanding of genome stability (Agircan et al, 2014)

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