scholarly journals Delineating the contribution of Spc105-bound PP1 to spindle checkpoint silencing and kinetochore microtubule attachment regulation

2019 ◽  
Vol 218 (12) ◽  
pp. 3926-3942 ◽  
Author(s):  
Babhrubahan Roy ◽  
Vikash Verma ◽  
Janice Sim ◽  
Adrienne Fontan ◽  
Ajit P. Joglekar
Keyword(s):  
Cell Division ◽  
Error Correction ◽  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Spindle Checkpoint ◽  
Spindle Assembly ◽  
Protein Phosphatase 1 ◽  
Microtubule Attachment ◽  
Error Correction Mechanism

Accurate chromosome segregation during cell division requires the spindle assembly checkpoint (SAC), which detects unattached kinetochores, and an error correction mechanism that destabilizes incorrect kinetochore–microtubule attachments. While the SAC and error correction are both regulated by protein phosphatase 1 (PP1), which silences the SAC and stabilizes kinetochore–microtubule attachments, how these distinct PP1 functions are coordinated remains unclear. Here, we investigate the contribution of PP1, docked on its conserved kinetochore receptor Spc105/Knl1, to SAC silencing and attachment regulation. We find that Spc105-bound PP1 is critical for SAC silencing but dispensable for error correction; in fact, reduced PP1 docking on Spc105 improved chromosome segregation and viability of mutant/stressed states. We additionally show that artificially recruiting PP1 to Spc105/Knl1 before, but not after, chromosome biorientation interfered with error correction. These observations lead us to propose that recruitment of PP1 to Spc105/Knl1 is carefully regulated to ensure that chromosome biorientation precedes SAC silencing, thereby ensuring accurate chromosome segregation.

scholarly journals Minimization of a harmful cross-talk between mitotic checkpoint silencing and error correction

2018 ◽  
Author(s):  
Babhrubahan Roy ◽  
Vikash Verma ◽  
Janice Sim ◽  
Adrienne Fontan ◽  
Ajit P. Joglekar
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Cross Talk ◽  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Mitotic Checkpoint ◽  
Spindle Pole ◽  
Protein Phosphatase 1 ◽  
Spindle Poles ◽  
Combined Action

AbstractAccurate chromosome segregation during cell division requires that the pair of sister kinetochores on each chromosome attach to microtubules originating from opposite spindle poles. This is ensured by the combined action of the Spindle Assembly Checkpoint (SAC), which detects unattached kinetochores, and an error correction mechanism that destabilizes incorrect attachment of both sister kinetochores to the same spindle pole. These processes are downregulated by Protein Phosphatase 1 (PP1), which both silences the SAC and stabilizes kinetochore-microtubule attachments. We find that this dual PP1 role can be problematic: if PP1 is recruited to the kinetochore for SAC silencing prior to chromosome biorientation, it interferes with error correction. We show that to mitigate this cross-talk, the yeast kinetochore uses independent PP1 sources to stabilize correct attachments and to silence the SAC, and also delays the recruitment of PP1 for SAC silencing. Consequently, chromosome biorientation precedes SAC silencing ensuring accurate chromosome segregation.

Interplay between mitotic kinesins and the Aurora kinase–PP1 (protein phosphatase 1) axis

2013 ◽  
Vol 41 (6) ◽  
pp. 1761-1765 ◽  
Author(s):  
John C. Meadows
Keyword(s):  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Spindle Checkpoint ◽  
Aurora Kinase ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Spatial Gradient ◽  
Cell Cycle Regulators ◽  
Aurora B Kinase ◽  
Surveillance Mechanism

Correct transmission of genetic information from mother to daughter cells is necessary for development and survival. Accurate segregation is achieved by bipolar attachment of sister kinetochores in each chromatid pair to spindle microtubules emanating from opposite spindle poles, a process known as chromosome bi-orientation. Achieving this requires dynamic interplay between kinetochore proteins, kinesin motor proteins and cell cycle regulators. Chromosome bi-orientation is monitored by a surveillance mechanism known as the SAC (spindle assembly checkpoint). The Aurora B kinase, which is bound to the inner centromere during early mitosis, plays a central role in both chromosome bi-orientation and the spindle checkpoint. The application of tension across centromeres establishes a spatial gradient of high phosphorylation activity at the inner centromere and low phosphorylation activity at the outer kinetochore. This gradient is further refined by the association of PP1 (protein phosphatase 1) to the outer kinetochore, which stabilizes kinetochore–microtubule interactions and silences the spindle checkpoint by dephosphorylating Aurora B kinase targets when chromosome bi-orientation is achieved. In the present review, I discuss emerging evidence that bidirectional cross-talk between mitotic kinesins and the Aurora kinase–PP1 axis is crucial for co-ordinating chromosome bi-orientation and spindle checkpoint signalling in eukaryotes.

scholarly journals The Opposing Functions of Protein Kinases and Phosphatases in Chromosome Bipolar Attachment

2019 ◽  
Vol 20 (24) ◽  
pp. 6182 ◽  
Author(s):  
Delaney Sherwin ◽  
Yanchang Wang
Keyword(s):  
Cell Division ◽  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Model Organism ◽  
Eukaryotic Cells ◽  
Genome Integrity ◽  
Chromosome Missegregation ◽  
Spindle Poles ◽  
Mitosis And Meiosis

Accurate chromosome segregation during cell division is essential to maintain genome integrity in all eukaryotic cells, and chromosome missegregation leads to aneuploidy and therefore represents a hallmark of many cancers. Accurate segregation requires sister kinetochores to attach to microtubules emanating from opposite spindle poles, known as bipolar attachment or biorientation. Recent studies have uncovered several mechanisms critical to chromosome bipolar attachment. First, a mechanism exists to ensure that the conformation of sister centromeres is biased toward bipolar attachment. Second, the phosphorylation of some kinetochore proteins destabilizes kinetochore attachment to facilitate error correction, but a protein phosphatase reverses this phosphorylation. Moreover, the activity of the spindle assembly checkpoint is regulated by kinases and phosphatases at the kinetochore, and this checkpoint prevents anaphase entry in response to faulty kinetochore attachment. The fine-tuned kinase/phosphatase balance at kinetochores is crucial for faithful chromosome segregation during both mitosis and meiosis. Here, we discuss the function and regulation of protein phosphatases in the establishment of chromosome bipolar attachment with a focus on the model organism budding yeast.

scholarly journals Interactions between N-Terminal Modules in MPS1 Enable Spindle Checkpoint Silencing

2018 ◽  
Author(s):  
Spyridon T. Pachis ◽  
Yoshitaka Hiruma ◽  
Anastassis Perrakis ◽  
Geert J.P.L. Kops
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Intramolecular Interactions ◽  
Mitotic Progression ◽  
Microtubule Attachment ◽  
Anaphase Onset ◽  
Regulatory Input ◽  
Tpr Domain

ABSTRACTFaithful chromosome segregation relies on the ability of the spindle assembly checkpoint (SAC) to delay anaphase onset until all chromosomes are attached to the mitotic spindle via their kinetochores. MPS1 kinase is recruited to unattached kinetochores to initiate SAC signaling, and is removed from kinetochores once stable microtubule attachments have been formed to allow normal mitotic progression. Here we show that a helical fragment within the kinetochore-targeting NTE module of MPS1 is required for interactions with kinetochores, and also forms intramolecular interactions with its adjacent TPR domain. Bypassing this NTE-TPR interaction results in high MPS1 levels at kinetochores due to loss of regulatory input into MPS1 localization, ineffecient MPS1 delocalization from kinetochores upon microtubule attachment, and SAC silencing defects. These results show that SAC responsiveness to attachments relies on regulated intramolecular interactions in MPS1 and highlight the sensitivity of mitosis to perturbations in the dynamics of the MSP1-NDC80-C interactions.

scholarly journals Spindle assembly checkpoint satisfaction occurs through end-on but not lateral kinetochore-microtubule interactions under tension

2017 ◽  
Author(s):  
Jonathan Kuhn ◽  
Sophie Dumont
Keyword(s):  
Real Time ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Microtubule Attachment ◽  
Normal Mitosis

AbstractTo ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) prevents anaphase until all kinetochores attach to the spindle. What signals the SAC monitors remains unclear. We do not know the contributions of different microtubule attachment features, or tension from biorientation, to SAC satisfaction in normal mitosis - or how these possible cues change during attachment. Here, we quantify concurrent Mad1 intensity, reporting on SAC silencing, and real-time attachment geometry, occupancy, and tension at individual mammalian kinetochores. We show that Mad1 loss from the kinetochore occurs in switch-like events with robust kinetics, and that metaphase-like tension across sister kinetochores is established just before Mad1 loss events at the first sister. We demonstrate that CenpE-mediated lateral attachment of the second sister can persistently generate this metaphase-like tension prior to biorientation, likely stabilizing sister end-on attachment, yet cannot induce Mad1 loss from that kinetochore. Instead, Mad1 loss begins after several end-on microtubules attach. Thus, end-on attachment provides geometry-specific molecular cues, or force on specific kinetochore linkages, that other attachment geometries cannot provide.SummaryThe spindle assembly checkpoint (SAC) delays anaphase until kinetochores are properly attached to the spindle. The authors demonstrate that the SAC monitors geometry-specific molecular cues, or force on specific kinetochore linkages, that “end-on” but not “lateral” attachments generating persistent tension can provide.

scholarly journals Dissecting the role of MPS1 in chromosome biorientation and the spindle checkpoint through the small molecule inhibitor reversine

2010 ◽  
Vol 190 (1) ◽  
pp. 73-87 ◽  
Author(s):  
Stefano Santaguida ◽  
Anthony Tighe ◽  
Anna Morena D'Alise ◽  
Stephen S. Taylor ◽  
Andrea Musacchio
Keyword(s):  
Error Correction ◽  
Small Molecule ◽  
Spindle Assembly Checkpoint ◽  
Spindle Checkpoint ◽  
Spindle Assembly ◽  
Dependent Manner ◽  
Crucial Component ◽  
Molecule Inhibitor ◽  
The Relationship

The catalytic activity of the MPS1 kinase is crucial for the spindle assembly checkpoint and for chromosome biorientation on the mitotic spindle. We report that the small molecule reversine is a potent mitotic inhibitor of MPS1. Reversine inhibits the spindle assembly checkpoint in a dose-dependent manner. Its addition to mitotic HeLa cells causes the ejection of Mad1 and the ROD–ZWILCH–ZW10 complex, both of which are important for the spindle checkpoint, from unattached kinetochores. By using reversine, we also demonstrate that MPS1 is required for the correction of improper chromosome–microtubule attachments. We provide evidence that MPS1 acts downstream from the AURORA B kinase, another crucial component of the error correction pathway. Our experiments describe a very useful tool to interfere with MPS1 activity in human cells. They also shed light on the relationship between the error correction pathway and the spindle checkpoint and suggest that these processes are coregulated and are likely to share at least a subset of their catalytic machinery.

scholarly journals Knl1 participates in spindle assembly checkpoint signaling in maize

2021 ◽  
Vol 118 (20) ◽  
pp. e2022357118
Author(s):  
Handong Su ◽  
Yang Liu ◽  
Chunhui Wang ◽  
Yalin Liu ◽  
Chao Feng ◽  
...  
Keyword(s):  
Cell Division ◽  
Evolutionary History ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Helical Conformation ◽  
Evolutionary Patterns ◽  
Checkpoint Signaling ◽  
Microtubule Attachment ◽  
Tpr Domain

The Knl1-Mis12-Ndc80 (KMN) network is an essential component of the kinetochore–microtubule attachment interface, which is required for genomic stability in eukaryotes. However, little is known about plant Knl1 proteins because of their complex evolutionary history. Here, we cloned the Knl1 homolog from maize (Zea mays) and confirmed it as a constitutive central kinetochore component. Functional assays demonstrated their conserved role in chromosomal congression and segregation during nuclear division, thus causing defective cell division during kernel development when Knl1 transcript was depleted. A 145 aa region in the middle of maize Knl1, that did not involve the MELT repeats, was associated with the interaction of spindle assembly checkpoint (SAC) components Bub1/Mad3 family proteins 1 and 2 (Bmf1/2) but not with the Bmf3 protein. They may form a helical conformation with a hydrophobic interface with the TPR domain of Bmf1/2, which is similar to that of vertebrates. However, this region detected in monocots shows extensive divergence in eudicots, suggesting that distinct modes of the SAC to kinetochore connection are present within plant lineages. These findings elucidate the conserved role of the KMN network in cell division and a striking dynamic of evolutionary patterns in the SAC signaling and kinetochore network.

scholarly journals Protein Phosphatase 1 inactivates Mps1 to ensure efficient Spindle Assembly Checkpoint silencing

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Margarida Moura ◽  
Mariana Osswald ◽  
Nelson Leça ◽  
João Barbosa ◽  
António J Pereira ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Exit ◽  
Protein Phosphatase 1 ◽  
Anaphase Onset ◽  
Phosphorylation Cascade ◽  
Spindle Microtubules ◽  
Early Mitosis

Faithfull genome partitioning during cell division relies on the Spindle Assembly Checkpoint (SAC), a conserved signaling pathway that delays anaphase onset until all chromosomes are attached to spindle microtubules. Mps1 kinase is an upstream SAC regulator that promotes the assembly of an anaphase inhibitor through a sequential multi-target phosphorylation cascade. Thus, the SAC is highly responsive to Mps1, whose activity peaks in early mitosis as a result of its T-loop autophosphorylation. However, the mechanism controlling Mps1 inactivation once kinetochores attach to microtubules and the SAC is satisfied remains unknown. Here we show in vitro and in Drosophila that Protein Phosphatase 1 (PP1) inactivates Mps1 by dephosphorylating its T-loop. PP1-mediated dephosphorylation of Mps1 occurs at kinetochores and in the cytosol, and inactivation of both pools of Mps1 during metaphase is essential to ensure prompt and efficient SAC silencing. Overall, our findings uncover a mechanism of SAC inactivation required for timely mitotic exit.

scholarly journals Phospho-regulation of the Shugoshin - Condensin interaction at the centromere in budding yeast

2019 ◽  
Author(s):  
Galal Yahya Metwaly ◽  
Yehui Wu ◽  
Karolina Peplowska ◽  
Jennifer Röhrl ◽  
Young-Min Soh ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Budding Yeast ◽  
Spindle Assembly ◽  
Mass Spectrometry Analysis ◽  
Spectrometry Analysis ◽  
Spindle Poles ◽  
Condensin Complex ◽  
Centromeric Protein

AbstractCorrect bioriented attachment of sister chromatids to mitotic spindle is essential for chromosome segregation. The conserved protein shugoshin (Sgo1) contributes in budding yeast to biorientation by recruiting the protein phosphatase PP2A-Rts1 and the condensin complex to centromeres. Using peptide prints, we identified a Serine-Rich Motif (SRM) of Sgo1 that mediates the interaction with condensin and is essential for centromeric condensin recruitment and the establishment of biorientation. We show that the interaction is regulated via phosphorylation within the SRM and we determined the phospho-sites using mass spectrometry. Analysis of the phosphomimicking and phosphoresistant mutants revealed that SRM phosphorylation disrupts the shugoshin – condensin interaction. We present an evidence that Mps1, a central kinase in the spindle assembly checkpoint, directly phosphorylates Sgo1 within the SRM to regulate the interaction with condensin and thereby condensin localization to centromeres. Our findings identify novel mechanisms that control shugoshin activity at the centromere in budding yeast.Author summaryProper chromosome segregation in eukaryotes is ensured through correct attachment of the spindle microtubules to the centromeric chromosomal regions. The attachment is mediated via the multimolecular proteinaceous complex called kinetochore and precisely regulated. This enables the establishment of so called bioirentation, when each sister chromatid is attached to microtubules emanating from opposite spindle poles. Shugoshin (Sgo1) is a conserved centromeric protein that facilitates biorientation through its interactions with the protein phosphatase PP2A/Rts1, chromosome passanger complex and centromeric condensin. Here, we identified a serin-rich motif that is required for the interaction of shugoshin with the condensin complex. We show that loss of this region impairs condensin enrichment at the centromere, chromosome biorientation, segregation as well as the function of the chromosome passanger complex in the error correction. Moreover, the interaction is phosphoregulated, as phosphorylation of the serin-rich motif on Sgo1 disrupts its interaction with condensin. Finally, we show that the conserved spindle assembly checkpoint kinase Mps1 is responsible for this phosphorylation. Our findings uncover novel regulatory mechanisms that facilitate proper chromosome segregation.

scholarly journals Spindle assembly checkpoint satisfaction occurs via end-on but not lateral attachments under tension

2017 ◽  
Vol 216 (6) ◽  
pp. 1533-1542 ◽  
Author(s):  
Jonathan Kuhn ◽  
Sophie Dumont
Keyword(s):  
Real Time ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Microtubule Attachment

To ensure accurate chromosome segregation, the spindle assembly checkpoint (SAC) prevents anaphase until all kinetochores attach to the spindle. What signals the SAC monitors remains unclear. We do not know the contributions of different microtubule attachment features or tension from biorientation to SAC satisfaction nor how these possible cues change during attachment. In this study, we quantify concurrent Mad1 intensity and report on SAC silencing, real-time attachment geometry, occupancy, and tension at individual mammalian kinetochores. We show that Mad1 loss from the kinetochore is switch-like with robust kinetics and that tension across sister kinetochores is established just before Mad1 loss events at the first sister. We demonstrate that CenpE-mediated lateral attachment of the second sister can persistently generate this metaphase-like tension before biorientation, likely stabilizing sister end-on attachment, yet cannot induce Mad1 loss from that kinetochore. Instead, Mad1 loss begins after several end-on microtubules attach. Thus, end-on attachment provides geometry-specific molecular cues or force on specific kinetochore linkages that other attachment geometries cannot provide.

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