scholarly journals Tension on kinetochore substrates is insufficient to prevent Aurora-triggered detachment

2018 ◽  
Author(s):  
Anna K. de Regt ◽  
Charles L. Asbury ◽  
Sue Biggins
Keyword(s):  
Chromosome Segregation ◽  
Direct Evidence ◽  
Underlying Mechanism ◽  
Aurora B ◽  
Trial And Error ◽  
Spindle Poles ◽  
Pulling Forces ◽  
Low Tension

Introduction / AbstractChromosome segregation requires large macromolecular structures called kinetochores to attach dynamic microtubules from opposite spindle poles1,2. Attachments are made iteratively, through a trial-and-error process, and proper attachments come under tension from the pulling forces of microtubules3,4. However, if sister kinetochores bind microtubules from the same pole1,2, these defective attachments lack tension and must be destabilized to give another chance for proper attachments to form. This vital error correction process requires Aurora B kinase, which phosphorylates kinetochores lacking tension to reduce their affinity for microtubules5-11. An unresolved question is how Aurora B distinguishes the level of tension on kinetochores. There are conflicting reports on the underlying mechanism12-16, owing in part to the difficulties of manipulating kinetochore tension in vivo and distinguishing kinase from opposing phosphatase activity. To address these issues, we have reconstituted Aurora B-triggered kinetochore detachment in an in vitro optical trapping-based flow assay. Here, we test an outstanding model by determining whether kinetochore tension is sufficient to prevent kinase-triggered detachments. Strikingly, Aurora B detaches kinetochores from microtubules under both high and low tension, providing direct evidence that the kinase does not distinguish correct versus incorrect attachments by recognizing tension-dependent changes in the conformation of its kinetochore substrates.

scholarly journals chTOG is a conserved mitotic error correction factor

2020 ◽  
Author(s):  
Jacob A. Herman ◽  
Matthew P. Miller ◽  
Sue Biggins
Keyword(s):  
Protein Kinase ◽  
Error Correction ◽  
Chromosome Segregation ◽  
Correction Factor ◽  
Budding Yeast ◽  
Aurora B ◽  
Spindle Poles ◽  
Low Tension ◽  
Intrinsic Error

AbstractAccurate chromosome segregation requires kinetochores on duplicated chromatids to biorient by attaching to dynamic microtubules from opposite spindle poles, which exerts forces to bring kinetochores under tension. However, kinetochores initially bind to MTs indiscriminately, resulting in errors that must be corrected. While the Aurora B protein kinase destabilizes low-tension attachments by phosphorylating kinetochores, low-tension attachments are intrinsically less stable than those under higher tension in vitro independent of Aurora activity. Intrinsic tensionsensitive behavior requires the microtubule regulator Stu2 (budding yeast Dis1/XMAP215 ortholog), which we demonstrate here is likely a conserved function for the TOG protein family. The human TOG protein, chTOG, localizes to kinetochores independent of microtubules by interacting with Hec1. We identify a chTOG mutant that regulates microtubule dynamics but accumulates erroneous kinetochore-microtubule attachments that Aurora B fails to destabilize. Thus, TOG proteins confer a unique, intrinsic error correction activity to kinetochores that ensures accurate chromosome segregation.

scholarly journals chTOG is a conserved mitotic error correction factor

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Jacob A Herman ◽  
Matthew P Miller ◽  
Sue Biggins
Keyword(s):  
Protein Kinase ◽  
Error Correction ◽  
Chromosome Segregation ◽  
Correction Factor ◽  
Aurora B ◽  
Spindle Poles ◽  
Low Tension ◽  
Intrinsic Error ◽  
Sensitive Behavior

Accurate chromosome segregation requires kinetochores on duplicated chromatids to biorient by attaching to dynamic microtubules from opposite spindle poles, which exerts forces to bring kinetochores under tension. However, kinetochores initially bind to microtubules indiscriminately, resulting in errors that must be corrected. While the Aurora B protein kinase destabilizes low-tension attachments by phosphorylating kinetochores, low-tension attachments are intrinsically less stable than those under higher tension in vitro independent of Aurora activity. Intrinsic tension-sensitive behavior requires the microtubule regulator Stu2 (budding yeast Dis1/XMAP215 ortholog), which we demonstrate here is likely a conserved function for the TOG protein family. The human TOG protein, chTOG, localizes to kinetochores independent of microtubules by interacting with Hec1. We identify a chTOG mutant that regulates microtubule dynamics but accumulates erroneous kinetochore-microtubule attachments that are not destabilized by Aurora B. Thus, TOG proteins confer a unique, intrinsic error correction activity to kinetochores that ensures accurate chromosome segregation.

scholarly journals A Stu2-mediated intrinsic tension-sensing pathway promotes chromosome biorientation in vivo

2018 ◽  
Author(s):  
Matthew P. Miller ◽  
Rena K. Evans ◽  
Alex Zelter ◽  
Elisabeth A. Geyer ◽  
Michael J. MacCoss ◽  
...  
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Aurora B ◽  
Critical Aspect ◽  
Daughter Cells ◽  
Low Tension ◽  
Kinetochore Function ◽  
Segregation Of Chromosomes

ABSTRACTAccurate segregation of chromosomes to daughter cells is a critical aspect of cell division. It requires the kinetochores on duplicated chromosomes to biorient, attaching to microtubules from opposite poles of the cell. Bioriented attachments come under tension, while incorrect attachments lack tension and must be destabilized. A well-studied error correction pathway is mediated by the Aurora B kinase, which destabilizes low tension-bearing attachments. We recently discovered that in vitro, kinetochores display an additional intrinsic tension-sensing pathway that utilizes Stu2. This pathway’s contribution to error correction in cells, however, was unknown. Here, we identify a Stu2 mutant that abolishes its kinetochore function and show that it causes error correction defects in vivo. We also show that this intrinsic tension-sensing pathway functions in concert with the Aurora B-mediated pathway. Together, our work indicates that cells employ at least two pathways to ensure biorientation and the accuracy of chromosome segregation.

scholarly journals PP2A-B56 opposes Mps1 phosphorylation of Knl1 and thereby promotes spindle assembly checkpoint silencing

2014 ◽  
Vol 206 (7) ◽  
pp. 833-842 ◽  
Author(s):  
Antonio Espert ◽  
Pelin Uluocak ◽  
Ricardo Nunes Bastos ◽  
Davinderpreet Mangat ◽  
Philipp Graab ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Mammalian Cells ◽  
Feedback Loop ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Eukaryotic Cells ◽  
Aurora B ◽  
Safeguard Mechanism

The spindle assembly checkpoint (SAC) monitors correct attachment of chromosomes to microtubules, an important safeguard mechanism ensuring faithful chromosome segregation in eukaryotic cells. How the SAC signal is turned off once all the chromosomes have successfully attached to the spindle remains an unresolved question. Mps1 phosphorylation of Knl1 results in recruitment of the SAC proteins Bub1, Bub3, and BubR1 to the kinetochore and production of the wait-anaphase signal. SAC silencing is therefore expected to involve a phosphatase opposing Mps1. Here we demonstrate in vivo and in vitro that BubR1-associated PP2A-B56 is a key phosphatase for the removal of the Mps1-mediated Knl1 phosphorylations necessary for Bub1/BubR1 recruitment in mammalian cells. SAC silencing is thus promoted by a negative feedback loop involving the Mps1-dependent recruitment of a phosphatase opposing Mps1. Our findings extend the previously reported role for BubR1-associated PP2A-B56 in opposing Aurora B and suggest that BubR1-bound PP2A-B56 integrates kinetochore surveillance and silencing of the SAC.

scholarly journals CSC-1

2003 ◽  
Vol 161 (2) ◽  
pp. 229-236 ◽  
Author(s):  
Alper Romano ◽  
Annika Guse ◽  
Ivica Krascenicova ◽  
Heinke Schnabel ◽  
Ralf Schnabel ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Genetic Analysis ◽  
Chromosome Segregation ◽  
Kinase Activity ◽  
Aurora B ◽  
Aurora B Kinase ◽  
C Elegans ◽  
The Individual

The Aurora B kinase complex is a critical regulator of chromosome segregation and cytokinesis. In Caenorhabditis elegans, AIR-2 (Aurora B) function requires ICP-1 (Incenp) and BIR-1 (Survivin). In various systems, Aurora B binds to orthologues of these proteins. Through genetic analysis, we have identified a new subunit of the Aurora B kinase complex, CSC-1. C. elegans embryos depleted of CSC-1, AIR-2, ICP-1, or BIR-1 have identical phenotypes. CSC-1, BIR-1, and ICP-1 are interdependent for their localization, and all are required for AIR-2 localization. In vitro, CSC-1 binds directly to BIR-1. The CSC-1/BIR-1 complex, but not the individual subunits, associates with ICP-1. CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo. ICP-1 dramatically stimulates AIR-2 kinase activity. This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase.

scholarly journals RMD-1, a novel microtubule-associated protein, functions in chromosome segregation in Caenorhabditis elegans

2007 ◽  
Vol 179 (6) ◽  
pp. 1149-1162 ◽  
Author(s):  
Kumiko Oishi ◽  
Hideyuki Okano ◽  
Hitoshi Sawa
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Growth Defect ◽  
Aurora B ◽  
C Elegans ◽  
Spindle Poles ◽  
Protein Functions ◽  
Microtubule Growth ◽  
Mild Defect

For proper chromosome segregation, the sister kinetochores must attach to microtubules extending from the opposite spindle poles. Any errors in microtubule attachment can induce aneuploidy. In this study, we identify a novel conserved Caenorhabditis elegans microtubule-associated protein, regulator of microtubule dynamics 1 (RMD-1), that localizes to spindle microtubules and spindle poles. Depletion of RMD-1 induces severe defects in chromosome segregation, probably through merotelic attachments between microtubules and chromosomes. Although rmd-1 embryos also have a mild defect in microtubule growth, we find that mutants of the microtubule growth regulator XMAP215/ZYG-9 show much weaker segregation defects. This suggests that the microtubule growth defect in rmd-1 embryos does not cause abnormal chromosome segregation. We also see that RMD-1 interacts with aurora B in vitro. Our results suggest that RMD-1 functions in chromosome segregation in C. elegans embryos, possibly through the aurora B–mediated pathway. Human homologues of RMD-1 could also bind microtubules, which would suggest a function for these proteins in chromosome segregation during mitosis in other organisms as well.

scholarly journals SKAP interacts with Aurora B to guide end-on capture of spindle microtubules via phase separation

2021 ◽  
Author(s):  
Manjuan Zhang ◽  
Fengrui Yang ◽  
Wenwen Wang ◽  
Xiwei Wang ◽  
Dongmei Wang ◽  
...  
Keyword(s):  
Phase Separation ◽  
Chromosome Segregation ◽  
Aurora B ◽  
Spindle Microtubule ◽  
Dynamic Interactions ◽  
Chromosome Alignment ◽  
Spindle Microtubules ◽  
And Behavior

Abstract Chromosome segregation in mitosis is orchestrated by the dynamic interactions between the kinetochore and spindle microtubules. Our recent studies show that mitotic motor CENP-E cooperates with SKAP and forms a link between kinetochore core MIS13 complex and spindle microtubule plus-ends to achieve accurate chromosome alignment in mitosis. However, it remains elusive how SKAP regulates kinetochore attachment from lateral association to end-on attachment during metaphase alignment. Here, we identify a novel interaction between Aurora B and SKAP that orchestrates accurate interaction between the kinetochore and dynamic spindle microtubules. Interestingly, SKAP spontaneously phase-separates in vitro via weak, multivalent interactions into droplets with fast internal dynamics. SKAP and Aurora B form heterogeneous coacervates in vitro, which recapitulate the dynamics and behavior of SKAP comets in vivo. Importantly, SKAP interaction with Aurora B via phase separation is essential for accurate chromosome segregation and alignment. Based on those findings, we reason that SKAP–Aurora B interaction via phase separation constitutes a dynamic pool of Aurora B activity during the lateral to end-on conversion of kinetochore–microtubule attachments to achieve faithful cell division.

scholarly journals Aurora B switches relative strength between kinetochore–microtubule attachment modes to promote error correction

2018 ◽  
Author(s):  
Harinath Doodhi ◽  
Taciana Kasciukovic ◽  
Lesley Clayton ◽  
Tomoyuki U. Tanaka
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Relative Strength ◽  
Lateral Side ◽  
Aurora B ◽  
Spindle Poles ◽  
Microtubule Attachment ◽  
Attachment Strength ◽  
Dam1 Complex

AbstractFor proper chromosome segregation, sister kinetochores must interact with microtubules from opposite spindle poles; this is called bi-orientation. To establish bi-orientation prior to chromosome segregation, any aberrant kinetochore–microtubule interaction must be resolved (error correction) by Aurora B kinase that phosphorylates outer kinetochore components. Aurora B differentially regulates kinetochore attachment to the microtubule plus end and its lateral side (end-on and lateral attachment, respectively). However, it is still not fully understood how kinetochore–microtubule interactions are exchanged during error correction. Here we reconstituted the kinetochore–microtubule interface of budding yeast in vitro by attaching the Ndc80 complexes (Ndc80C) to nanobeads. These Ndc80C–nanobeads recapitulated in vitro the lateral and end-on attachments of authentic kinetochores, on dynamic microtubules loaded with the Dam1 complex. This in vitro assay enabled the direct comparison of lateral and end-on attachment strength and showed that Dam1 phosphorylation by Aurora B makes the end-on attachment weaker than the lateral attachment. We suggest that the Dam1 phosphorylation weakens interaction with the Ndc80 complex, disrupts the end-on attachment and promotes the exchange to a new lateral attachment, leading to error correction. Our study reveals a fundamental mechanism of error correction for establishment of bi-orientation.

scholarly journals Bod1, a novel kinetochore protein required for chromosome biorientation

2007 ◽  
Vol 179 (2) ◽  
pp. 187-197 ◽  
Author(s):  
Iain M. Porter ◽  
Sarah E. McClelland ◽  
Guennadi A. Khoudoli ◽  
Christopher J. Hunter ◽  
Jens S. Andersen ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Hela Cells ◽  
Aurora B ◽  
Macromolecular Complex ◽  
Mitotic Spindles ◽  
Kinetochore Protein ◽  
Spindle Poles ◽  
Interfering Rna ◽  
Rna Depletion

We have combined the proteomic analysis of Xenopus laevis in vitro–assembled chromosomes with RNA interference and live cell imaging in HeLa cells to identify novel factors required for proper chromosome segregation. The first of these is Bod1, a protein conserved throughout metazoans that associates with a large macromolecular complex and localizes with kinetochores and spindle poles during mitosis. Small interfering RNA depletion of Bod1 in HeLa cells produces elongated mitotic spindles with severe biorientation defects. Bod1-depleted cells form syntelic attachments that can oscillate and generate enough force to separate sister kinetochores, suggesting that microtubule–kinetochore interactions were intact. Releasing Bod1-depleted cells from a monastrol block increases the frequency of syntelic attachments and the number of cells displaying biorientation defects. Bod1 depletion does not affect the activity or localization of Aurora B but does cause mislocalization of the microtubule depolymerase mitotic centromere- associated kinesin and prevents its efficient phosphorylation by Aurora B. Therefore, Bod1 is a novel kinetochore protein that is required for the detection or resolution of syntelic attachments in mitotic spindles.

scholarly journals Tension promotes kinetochore–microtubule release by Aurora B kinase

2021 ◽  
Vol 220 (6) ◽  
Author(s):  
Geng-Yuan Chen ◽  
Fioranna Renda ◽  
Huaiying Zhang ◽  
Alper Gokden ◽  
Daniel Z. Wu ◽  
...  
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Input Signal ◽  
Kinase Activity ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Catch Bond ◽  
Spindle Poles ◽  
Low Tension

To ensure accurate chromosome segregation, interactions between kinetochores and microtubules are regulated by a combination of mechanics and biochemistry. Tension provides a signal to discriminate attachment errors from bi-oriented kinetochores with sisters correctly attached to opposite spindle poles. Biochemically, Aurora B kinase phosphorylates kinetochores to destabilize interactions with microtubules. To link mechanics and biochemistry, current models regard tension as an input signal to locally regulate Aurora B activity. Here, we show that the outcome of kinetochore phosphorylation depends on tension. Using optogenetics to manipulate Aurora B at individual kinetochores, we find that kinase activity promotes microtubule release when tension is high. Conversely, when tension is low, Aurora B activity promotes depolymerization of kinetochore–microtubules while maintaining attachment. Thus, phosphorylation converts a catch-bond, in which tension stabilizes attachments, to a slip-bond, which releases microtubules under tension. We propose that tension is a signal inducing distinct error-correction pathways, with release or depolymerization being advantageous for typical errors characterized by high or low tension, respectively.

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