scholarly journals Aurora B-dependent Ndc80 Degradation Regulates Kinetochore Composition in Meiosis

2019 ◽  
Author(s):  
Jingxun Chen ◽  
Andrew Liao ◽  
Emily N Powers ◽  
Hanna Liao ◽  
Lori A Kohlstaedt ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Ubiquitin Ligase ◽  
Meiotic Prophase ◽  
Aurora B ◽  
Phosphorylation Sites ◽  
Independent Manner ◽  
N Terminus ◽  
Spindle Microtubules ◽  
Necessary And Sufficient ◽  
Single Subunit

ABSTRACTThe kinetochore complex is a conserved machinery that connects chromosomes to spindle microtubules. During meiosis, the kinetochore is restructured to accommodate a specialized chromosome segregation pattern. In budding yeast, meiotic kinetochore remodeling is mediated by the temporal changes in the abundance of a single subunit called Ndc80. We have previously described the regulatory events that control the timely synthesis of Ndc80. Here, we report that Ndc80 turnover is also tightly regulated in meiosis: Ndc80 degradation is active in meiotic prophase, but not in metaphase I. Ndc80 degradation depends on the ubiquitin ligase APCAma1 and is mediated by the proteasome. Importantly, Aurora B-dependent Ndc80 phosphorylation, a mark that has been previously implicated in correcting erroneous microtubule–kinetochore attachments, is essential for Ndc80 degradation in a microtubule-independent manner. The N-terminus of Ndc80, including a 27-residue sequence and Aurora B phosphorylation sites, is both necessary and sufficient for kinetochore protein degradation. Finally, defects in Ndc80 turnover predispose meiotic cells to chromosome mis-segregation. Our study elucidates the mechanism by which meiotic cells modulate their kinetochore composition through regulated Ndc80 degradation, and demonstrates that Aurora B-dependent regulation of kinetochores extends beyond altering microtubule attachments.

scholarly journals Differential requirement for Bub1 and Bub3 in regulation of meiotic versus mitotic chromosome segregation

2020 ◽  
Vol 219 (4) ◽  
Author(s):  
Gisela Cairo ◽  
Anne M. MacKenzie ◽  
Soni Lacefield
Keyword(s):  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Mitotic Chromosome ◽  
Budding Yeast ◽  
Meiotic Chromosome ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Chromosome Missegregation ◽  
Anaphase Onset ◽  
Spindle Microtubules

Accurate chromosome segregation depends on the proper attachment of kinetochores to spindle microtubules before anaphase onset. The Ipl1/Aurora B kinase corrects improper attachments by phosphorylating kinetochore components and so releasing aberrant kinetochore–microtubule interactions. The localization of Ipl1 to kinetochores in budding yeast depends upon multiple pathways, including the Bub1–Bub3 pathway. We show here that in meiosis, Bub3 is crucial for correction of attachment errors. Depletion of Bub3 results in reduced levels of kinetochore-localized Ipl1 and concomitant massive chromosome missegregation caused by incorrect chromosome–spindle attachments. Depletion of Bub3 also results in shorter metaphase I and metaphase II due to premature localization of protein phosphatase 1 (PP1) to kinetochores, which antagonizes Ipl1-mediated phosphorylation. We propose a new role for the Bub1–Bub3 pathway in maintaining the balance between kinetochore localization of Ipl1 and PP1, a balance that is essential for accurate meiotic chromosome segregation and timely anaphase onset.

scholarly journals NF-κB activation is a turn on for vaccinia virus phosphoprotein A49 to turn off NF-κB activation

2019 ◽  
Vol 116 (12) ◽  
pp. 5699-5704 ◽  
Author(s):  
Sarah Neidel ◽  
Hongwei Ren ◽  
Alice A. Torres ◽  
Geoffrey L. Smith
Keyword(s):  
Vaccinia Virus ◽  
Ubiquitin Ligase ◽  
Molecular Mimicry ◽  
E3 Ubiquitin Ligase ◽  
Virus Protein ◽  
Biological Regulation ◽  
Turn On ◽  
N Terminus ◽  
Iκbα Phosphorylation ◽  
Necessary And Sufficient

Vaccinia virus protein A49 inhibits NF-κB activation by molecular mimicry and has a motif near the N terminus that is conserved in IκBα, β-catenin, HIV Vpu, and some other proteins. This motif contains two serines, and for IκBα and β-catenin, phosphorylation of these serines enables recognition by the E3 ubiquitin ligase β-TrCP. Binding of IκBα and β-catenin by β-TrCP causes their ubiquitylation and thereafter proteasome-mediated degradation. In contrast, HIV Vpu and VACV A49 are not degraded. This paper shows that A49 is phosphorylated at serine 7 but not serine 12 and that this is necessary and sufficient for binding β-TrCP and antagonism of NF-κB. Phosphorylation of A49 S7 occurs when NF-κB signaling is activated by addition of IL-1β or overexpression of TRAF6 or IKKβ, the kinase needed for IκBα phosphorylation. Thus, A49 shows beautiful biological regulation, for it becomes an NF-κB antagonist upon activation of NF-κB signaling. The virulence of viruses expressing mutant A49 proteins or lacking A49 (vΔA49) was tested. vΔA49 was attenuated compared with WT, but viruses expressing A49 that cannot bind β-TrCP or bind β-TrCP constitutively had intermediate virulence. So A49 promotes virulence by inhibiting NF-κB activation and by another mechanism independent of S7 phosphorylation and NF-κB antagonism. Last, a virus lacking A49 was more immunogenic than the WT virus.

scholarly journals Phosphorylation of CENP-C by Aurora B facilitates kinetochore attachment error correction in mitosis

2017 ◽  
Vol 114 (50) ◽  
pp. E10667-E10676 ◽  
Author(s):  
Xing Zhou ◽  
Fan Zheng ◽  
Chengliang Wang ◽  
Minhao Wu ◽  
Xiaozhen Zhang ◽  
...  
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Mitotic Chromosome ◽  
Regulatory Mechanism ◽  
Dynamic Interaction ◽  
Aurora B ◽  
Kinetochore Assembly ◽  
Important Pathway ◽  
Spindle Microtubules

Kinetochores are superprotein complexes that orchestrate chromosome segregation via a dynamic interaction with spindle microtubules. A physical connection between CENP-C and the Mis12–Ndc80–Knl1 (KMN) protein network is an important pathway that is used to assemble kinetochores on CENP-A nucleosomes. Multiple outer kinetochore components are phosphorylated by Aurora B kinase to activate the spindle assembly checkpoint (SAC) and to ensure accurate chromosome segregation. However, it is unknown whether Aurora B can phosphorylate inner kinetochore components to facilitate proper mitotic chromosome segregation. Here, we reported the structure of the fission yeast Schizosaccharomyces pombe Mis12–Nnf1 complex and showed that N-terminal residues 26–50 in Cnp3 (the CENP-C homolog of S. pombe) are responsible for interacting with the Mis12 complex. Interestingly, Thr28 of Cnp3 is a substrate of Ark1 (the Aurora B homolog of S. pombe), and phosphorylation impairs the interaction between the Cnp3 and Mis12 complex. The expression of a phosphorylation-mimicking Cnp3 mutant results in defective chromosome segregation due to improper kinetochore assembly. These results establish a previously uncharacterized regulatory mechanism involved in CENP-C–Mis12-facilitated kinetochore attachment error correction to ensure accurate chromosome segregation during mitosis.

scholarly journals Aurora B Kinase Exists in a Complex with Survivin and INCENP and Its Kinase Activity Is Stimulated by Survivin Binding and Phosphorylation

2002 ◽  
Vol 13 (9) ◽  
pp. 3064-3077 ◽  
Author(s):  
Margaret A. Bolton ◽  
Weijie Lan ◽  
Shannon E. Powers ◽  
Mark L. McCleland ◽  
Jian Kuang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromosome Segregation ◽  
Kinase Activity ◽  
Genetic Interactions ◽  
Aurora B ◽  
Hydrodynamic Properties ◽  
Aurora B Kinase ◽  
Survivin Gene ◽  
Spindle Microtubules ◽  
Cycle Dependent

Aurora B regulates chromosome segregation and cytokinesis and is the first protein to be implicated as a regulator of bipolar attachment of spindle microtubules to kinetochores. Evidence from several systems suggests that Aurora B is physically associated with inner centromere protein (INCENP) in mitosis and has genetic interactions with Survivin. It is unclear whether the Aurora B and INCENP interaction is cell cycle regulated and if Survivin physically interacts in this complex. In this study, we cloned theXenopus Survivin gene, examined its association with Aurora B and INCENP, and determined the effect of its binding on Aurora B kinase activity. We demonstrate that in the Xenopusearly embryo, all of the detectable Survivin is in a complex with both Aurora B and INCENP throughout the cell cycle. Survivin and Aurora B bind different domains on INCENP. Aurora B activity is stimulated >10-fold in mitotic extracts; this activation is phosphatase sensitive, and the binding of Survivin is required for full Aurora B activity. We also find the hydrodynamic properties of the Aurora B/Survivin/INCENP complex are cell cycle regulated. Our data indicate that Aurora B kinase activity is regulated by both Survivin binding and cell cycle-dependent phosphorylation.

scholarly journals Distinct Mechanisms Control the Stability of the Related S-Phase Cyclins Clb5 and Clb6

2006 ◽  
Vol 26 (6) ◽  
pp. 2456-2466 ◽  
Author(s):  
Leisa P. Jackson ◽  
Steven I. Reed ◽  
Steven B. Haase
Keyword(s):  
Ubiquitin Ligase ◽  
S Phase ◽  
Phosphorylation Sites ◽  
Anaphase Promoting Complex ◽  
Functional Differences ◽  
Ubiquitin Ligase Complex ◽  
N Terminus ◽  
Phase Progression ◽  
The Stability ◽  
Related Proteins

ABSTRACT The yeast S-phase cyclins Clb5 and Clb6 are closely related proteins that are synthesized late in G1. Although often grouped together with respect to function, Clb5 and Clb6 exhibit differences in their ability to promote S-phase progression. DNA replication is significantly slowed in clb5Δ mutants but not in clb6Δ mutants. We have examined the basis for the differential functions of Clb5 and Clb6 and determined that unlike Clb5, which is stable until mitosis, Clb6 is degraded rapidly at the G1/S border. N-terminal deletions of CLB6 were hyperstabilized, suggesting that the sequences responsible for directing the destruction of Clb6 reside in the N terminus. Clb6 lacks the destruction box motif responsible for the anaphase promoting complex-mediated destruction of Clb5 but contains putative Cdc4 degron motifs in the N terminus. Clb6 was hyperstabilized in cdc34-3 and cdc4-3 mutants at restrictive temperatures and when S/T-P phosphorylation sites in the N terminus were mutated to nonphosphorylatable residues. Efficient degradation of Clb6 requires the activities of both Cdc28 and Pho85. Finally, hyperstabilized Clb6 expressed from the CLB6 promoter rescued the slow S-phase defect exhibited by clb5Δ cells. Taken together, these findings suggest that the SCFCdc4 ubiquitin ligase complex regulates Clb6 turnover and that the functional differences exhibited by Clb5 and Clb6 arise from the distinct mechanisms controlling their stability.

scholarly journals How cyclin A destruction escapes the spindle assembly checkpoint

2010 ◽  
Vol 190 (4) ◽  
pp. 501-509 ◽  
Author(s):  
Barbara Di Fiore ◽  
Jonathon Pines
Keyword(s):  
Ubiquitin Ligase ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Cyclin A ◽  
Cyclin Dependent Kinase ◽  
Anaphase Promoting Complex ◽  
N Terminus ◽  
Specific Proteins ◽  
Necessary And Sufficient

The anaphase-promoting complex/cyclosome (APC/C) is the ubiquitin ligase essential to mitosis, which ensures that specific proteins are degraded at specific times to control the order of mitotic events. The APC/C coactivator, Cdc20, is targeted by the spindle assembly checkpoint (SAC) to restrict APC/C activity until metaphase, yet early substrates, such as cyclin A, are degraded in the presence of the active checkpoint. Cdc20 and the cyclin-dependent kinase cofactor, Cks, are required for cyclin A destruction, but how they enable checkpoint-resistant destruction has not been elucidated. In this study, we answer this problem: we show that the N terminus of cyclin A binds directly to Cdc20 and with sufficient affinity that it can outcompete the SAC proteins. Subsequently, the Cks protein is necessary and sufficient to promote cyclin A degradation in the presence of an active checkpoint by binding cyclin A–Cdc20 to the APC/C.

scholarly journals Kinetochores respond to subtle changes in the stability of microtubule attachments

2021 ◽  
Author(s):  
Jessica D. Warren ◽  
Sarah Y. Valles ◽  
Duane A. Compton
Keyword(s):  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Protein Localization ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Regulatory Enzymes ◽  
Summary Statement ◽  
Spindle Microtubules ◽  
The Stability ◽  
Induced Changes

AbstractProper attachment of spindle microtubules to kinetochores is necessary to satisfy the spindle assembly checkpoint and ensure faithful chromosome segregation. Microtubules detach from kinetochores to correct improperly oriented attachments, and overall kinetochore-microtubule (k-MT) attachment stability is determined in response to regulatory enzymes and the activities of kinetochore-associated microtubule stabilizing and destabilizing proteins. However, it is unknown whether regulatory enzyme activity or kinetochore-associated protein localization respond to subtle changes in k-MT attachment stability. To test for this feedback response, we monitored Aurora B kinase activity and the localization of select kinetochore proteins in metaphase cells following treatments that subtly stabilize or destabilize k-MT attachments using low dose Taxol or UMK57 (an MCAK agonist), respectively. Increasing k-MT stability induced changes in the abundance of some kinetochore proteins. In contrast, reducing k-MT stability induced both increases in Aurora B kinase signaling and changes in the abundance of some kinetochore proteins. Thus, kinetochores dynamically respond to changes in the stability of their attached microtubules. This feedback control contributes to tuning k-MT attachment stability required for efficient error correction to facilitate faithful chromosome segregation.Summary StatementLive cell imaging demonstrates that kinetochore signaling responds to feedback from attached microtubules to tune their stability to ensure faithful chromosome segregation during cell division.

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 A stochastic model of kinetochore–microtubule attachment accurately describes fission yeast chromosome segregation

2012 ◽  
Vol 196 (6) ◽  
pp. 757-774 ◽  
Author(s):  
Guillaume Gay ◽  
Thibault Courtheoux ◽  
Céline Reyes ◽  
Sylvie Tournier ◽  
Yannick Gachet
Keyword(s):  
Fission Yeast ◽  
Chromosome Segregation ◽  
Aurora B ◽  
Segregation Behavior ◽  
Microtubule Attachment ◽  
Anaphase Onset ◽  
Sister Chromatids ◽  
Yeast Chromosome ◽  
Spindle Microtubules ◽  
Early Mitosis

In fission yeast, erroneous attachments of spindle microtubules to kinetochores are frequent in early mitosis. Most are corrected before anaphase onset by a mechanism involving the protein kinase Aurora B, which destabilizes kinetochore microtubules (ktMTs) in the absence of tension between sister chromatids. In this paper, we describe a minimal mathematical model of fission yeast chromosome segregation based on the stochastic attachment and detachment of ktMTs. The model accurately reproduces the timing of correct chromosome biorientation and segregation seen in fission yeast. Prevention of attachment defects requires both appropriate kinetochore orientation and an Aurora B–like activity. The model also reproduces abnormal chromosome segregation behavior (caused by, for example, inhibition of Aurora B). It predicts that, in metaphase, merotelic attachment is prevented by a kinetochore orientation effect and corrected by an Aurora B–like activity, whereas in anaphase, it is corrected through unbalanced forces applied to the kinetochore. These unbalanced forces are sufficient to prevent aneuploidy.

scholarly journals Regulated targeting of protein phosphatase 1 to the outer kinetochore by KNL1 opposes Aurora B kinase

2010 ◽  
Vol 188 (6) ◽  
pp. 809-820 ◽  
Author(s):  
Dan Liu ◽  
Mathijs Vleugel ◽  
Chelsea B. Backer ◽  
Tetsuya Hori ◽  
Tatsuo Fukagawa ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Genomic Stability ◽  
Feedback Mechanism ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Conserved Motif ◽  
Spindle Microtubules ◽  
Positive Feedback Mechanism

Regulated interactions between kinetochores and spindle microtubules are essential to maintain genomic stability during chromosome segregation. The Aurora B kinase phosphorylates kinetochore substrates to destabilize kinetochore–microtubule interactions and eliminate incorrect attachments. These substrates must be dephosphorylated to stabilize correct attachments, but how opposing kinase and phosphatase activities are coordinated at the kinetochore is unknown. Here, we demonstrate that a conserved motif in the kinetochore protein KNL1 directly interacts with and targets protein phosphatase 1 (PP1) to the outer kinetochore. PP1 recruitment by KNL1 is required to dephosphorylate Aurora B substrates at kinetochores and stabilize microtubule attachments. PP1 levels at kinetochores are regulated and inversely proportional to local Aurora B activity. Indeed, we demonstrate that phosphorylation of KNL1 by Aurora B disrupts the KNL1–PP1 interaction. In total, our results support a positive feedback mechanism by which Aurora B activity at kinetochores not only targets substrates directly, but also prevents localization of the opposing phosphatase.

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