Author response: Spatiotemporal control of mitotic exit during anaphase by an aurora B-Cdk1 crosstalk

Ki-67 and RepoMan have key roles during mitotic exit. Previously, we showed that Ki-67 organizes the mitotic chromosome periphery and recruits protein phosphatase 1 (PP1) to chromatin at anaphase onset, in a similar manner as RepoMan (<xref ref-type="bibr" rid="bib2">Booth et al., 2014</xref>). Here we show how Ki-67 and RepoMan form mitotic exit phosphatases by recruiting PP1, how they distinguish between distinct PP1 isoforms and how the assembly of these two holoenzymes are dynamically regulated by Aurora B kinase during mitosis. Unexpectedly, our data also reveal that Ki-67 and RepoMan bind PP1 using an identical, yet novel mechanism, interacting with a PP1 pocket that is engaged only by these two PP1 regulators. These findings not only show how two distinct mitotic exit phosphatases are recruited to their substrates, but also provide immediate opportunities for the design of novel cancer therapeutics that selectively target the Ki-67:PP1 and RepoMan:PP1 holoenzymes.

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Aurora B spatially regulates EB3 phosphorylation to coordinate daughter cell adhesion with cytokinesis

The Journal of Cell Biology ◽

10.1083/jcb.201301131 ◽

2013 ◽

Vol 201 (5) ◽

pp. 709-724 ◽

Cited By ~ 40

Author(s):

Jorge G. Ferreira ◽

António J. Pereira ◽

Anna Akhmanova ◽

Helder Maiato

Keyword(s):

Cell Adhesion ◽

Daughter Cell ◽

Cortical Microtubule ◽

Focal Adhesions ◽

Mitotic Exit ◽

Aurora B ◽

Microtubule Stability ◽

Spatiotemporal Regulation ◽

Cytoskeleton Remodeling ◽

Microtubule Growth

During mitosis, human cells round up, decreasing their adhesion to extracellular substrates. This must be quickly reestablished by poorly understood cytoskeleton remodeling mechanisms that prevent detachment from epithelia, while ensuring the successful completion of cytokinesis. Here we show that the microtubule end-binding (EB) proteins EB1 and EB3 play temporally distinct roles throughout cell division. Whereas EB1 was involved in spindle orientation before anaphase, EB3 was required for stabilization of focal adhesions and coordinated daughter cell spreading during mitotic exit. Additionally, EB3 promoted midbody microtubule stability and, consequently, midbody stabilization necessary for efficient cytokinesis. Importantly, daughter cell adhesion and cytokinesis completion were spatially regulated by distinct states of EB3 phosphorylation on serine 176 by Aurora B. This EB3 phosphorylation was enriched at the midbody and shown to control cortical microtubule growth. These findings uncover differential roles of EB proteins and explain the importance of an Aurora B phosphorylation gradient for the spatiotemporal regulation of microtubule function during mitotic exit and cytokinesis.

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PRC1 controls spindle polarization and recruitment of cytokinetic factors during monopolar cytokinesis

Molecular Biology of the Cell ◽

10.1091/mbc.e11-12-1008 ◽

2012 ◽

Vol 23 (7) ◽

pp. 1196-1207 ◽

Cited By ~ 34

Author(s):

Sanjay Shrestha ◽

Lori Jo Wilmeth ◽

Jarrett Eyer ◽

Charles B. Shuster

Keyword(s):

Mitotic Exit ◽

Aurora B ◽

Gtpase Activating Protein ◽

Contractile Ring ◽

Rac Gtpase ◽

Principal Role ◽

Central Spindle ◽

Ring Assembly ◽

Diffuse Distribution ◽

Kinesin Family

The central spindle is a postanaphase array of microtubules that plays an essential role in organizing the signaling machinery for cytokinesis. The model by which the central spindle organizes the cytokinetic apparatus is premised on an antiparallel arrangement of microtubules, yet cells lacking spindle bipolarity are capable of generating a distal domain of ectopic furrowing when forced into mitotic exit. Because protein regulator of cytokinesis (PRC1) and kinesin family member 4A (KIF4A) are believed to play a principal role in organizing the antiparallel midzone array, we sought to clarify their roles in monopolar cytokinesis. Although both factors localized to the distal ends of microtubules during monopolar cytokinesis, depletion of PRC1 and KIF4A displayed different phenotypes. Cells depleted of PRC1 failed to form a polarized microtubule array or ectopic furrows following mitotic exit, and recruitment of Aurora B kinase, male germ cell Rac GTPase-activating protein, and RhoA to the cortex was impaired. In contrast, KIF4A depletion impaired neither polarization nor ectopic furrowing, but it did result in elongated spindles with a diffuse distribution of cytokinetic factors. Thus, even in the absence of spindle bipolarity, PRC1 appears to be essential for polarizing parallel microtubules and concentrating the factors responsible for contractile ring assembly, whereas KIF4A is required for limiting the length of anaphase microtubules.

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Author response: The Mitotic Exit Network integrates temporal and spatial signals by distributing regulation across multiple components

10.7554/elife.41139.020 ◽

2018 ◽

Author(s):

Ian Winsten Campbell ◽

Xiaoxue Zhou ◽

Angelika Amon

Keyword(s):

Mitotic Exit ◽

Author Response ◽

Multiple Components ◽

Mitotic Exit Network ◽

Temporal And Spatial

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Spatiotemporal control of mitotic exit during anaphase by an aurora B-Cdk1 crosstalk

eLife ◽

10.7554/elife.47646 ◽

2019 ◽

Vol 8 ◽

Cited By ~ 10

Author(s):

Olga Afonso ◽

Colleen M Castellani ◽

Liam P Cheeseman ◽

Jorge G Ferreira ◽

Bernardo Orr ◽

...

Keyword(s):

Spindle Assembly Checkpoint ◽

Cyclin B1 ◽

Mitotic Exit ◽

Aurora B ◽

Dependent Manner ◽

Slowing Down ◽

Molecular Rulers ◽

Spindle Midzone ◽

Chromosome Separation ◽

Chromosome Motion

According to the prevailing ‘clock’ model, chromosome decondensation and nuclear envelope reformation when cells exit mitosis are byproducts of Cdk1 inactivation at the metaphase-anaphase transition, controlled by the spindle assembly checkpoint. However, mitotic exit was recently shown to be a function of chromosome separation during anaphase, assisted by a midzone Aurora B phosphorylation gradient - the ‘ruler’ model. Here we found that Cdk1 remains active during anaphase due to ongoing APC/CCdc20- and APC/CCdh1-mediated degradation of B-type Cyclins in Drosophila and human cells. Failure to degrade B-type Cyclins during anaphase prevented mitotic exit in a Cdk1-dependent manner. Cyclin B1-Cdk1 localized at the spindle midzone in an Aurora B-dependent manner, with incompletely separated chromosomes showing the highest Cdk1 activity. Slowing down anaphase chromosome motion delayed Cyclin B1 degradation and mitotic exit in an Aurora B-dependent manner. Thus, a crosstalk between molecular ‘rulers’ and ‘clocks’ licenses mitotic exit only after proper chromosome separation.

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Mitotic exit is controlled during anaphase by an Aurora B-Cyclin B1/Cdk1 crosstalk

10.1242/prelights.10372 ◽

2019 ◽

Author(s):

Gautam Dey

Keyword(s):

Cyclin B1 ◽

Mitotic Exit ◽

Aurora B

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Chk2 prevents mitotic exit when the majority of kinetochores are unattached

The Journal of Cell Biology ◽

10.1083/jcb.201310071 ◽

2014 ◽

Vol 205 (3) ◽

pp. 339-356 ◽

Cited By ~ 17

Author(s):

Eleni Petsalaki ◽

George Zachos

Keyword(s):

Spindle Checkpoint ◽

Mitotic Exit ◽

Aurora B ◽

Anaphase Onset ◽

Chromosome Alignment ◽

Essential Function ◽

In Cells

The spindle checkpoint delays exit from mitosis in cells with spindle defects. In this paper, we show that Chk2 is required to delay anaphase onset when microtubules are completely depolymerized but not in the presence of relatively few unattached kinetochores. Mitotic exit in Chk2-deficient cells correlates with reduced levels of Mps1 protein and increased Cdk1–tyrosine 15 inhibitory phosphorylation. Chk2 localizes to kinetochores and is also required for Aurora B–serine 331 phosphorylation in nocodazole or unperturbed early prometaphase. Serine 331 phosphorylation contributed to prometaphase accumulation in nocodazole after partial Mps1 inhibition and was required for spindle checkpoint establishment at the beginning of mitosis. In addition, expression of a phosphomimetic S331E mutant Aurora B rescued chromosome alignment or segregation in Chk2-deficient cells. We propose that Chk2 stabilizes Mps1 and phosphorylates Aurora B–serine 331 to prevent mitotic exit when most kinetochores are unattached. These results highlight mechanisms of an essential function of Chk2 in mitosis.

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