scholarly journals Higher eukaryote-specific APC/C composition is a determinant of spindle assembly checkpoint importance

2017 ◽  
Author(s):  
Thomas Wild ◽  
Magda Budzowska ◽  
Gopal Karemore ◽  
Chunaram Choudhary
Keyword(s):  
Ubiquitin Ligase ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Cyclin B1 ◽  
Anaphase Promoting Complex ◽  
Mitotic Progression ◽  
Proper Timing ◽  
Dependent Inhibition ◽  
Cellular Fate

AbstractThe multisubunit ubiquitin ligase APC/C (anaphase promoting complex/cyclosome) is essential for mitosis by promoting timely degradation of cyclin B1. Proper timing of APC/C activation is regulated by the spindle assembly checkpoint (SAC), which is initiated by the kinase MPS1 and implemented by MAD2-dependent inhibition of the APC/C. Here we analysed the contribution of the higher eukaryote-specific APC/C subunits APC7 and APC16 to APC/C composition, function and regulation. APC16 is required for APC7 assembly into the APC/C, while APC16 assembles independently of APC7. ΔAPC7 and ΔAPC16 cells display no major defects in mitotic progression, cyclin B1 degradation or SAC response. Strikingly, however, deletion of either APC7 or APC16 is sufficient to provide synthetic viability to MAD2 deletion. ΔAPC7ΔMAD2 cells display an accelerated mitosis and require SAC-independent MPS1 function for maintaining their genome stability. Overall, these results show how human APC/C composition critically influences the cellular fate upon loss of SAC activity.

scholarly journals Cyclin B1 scaffolds MAD1 at the corona to activate the spindle assembly checkpoint

2019 ◽  
Author(s):  
Lindsey A Allan ◽  
Magda Reis ◽  
Yahui Liu ◽  
Pim Huis in ’t Veld ◽  
Geert JPL Kops ◽  
...  
Keyword(s):  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Point Mutations ◽  
Spindle Assembly ◽  
Cyclin B1 ◽  
Cyclin B ◽  
Mitotic Progression ◽  
Mitotic Kinase ◽  
Binding Interface

ABSTRACTThe Cyclin B:CDK1 kinase complex is the master regulator of mitosis that phosphorylates hundreds of proteins to coordinate mitotic progression. We show here that, in addition to these kinase functions, Cyclin B also scaffolds a localised signalling pathway to help preserve genome stability. Cyclin B1 localises to an expanded region of the outer kinetochore, known as the corona, where it scaffolds the spindle assembly checkpoint (SAC) machinery by binding directly to MAD1. In vitro reconstitutions map the key binding interface to a few acidic residues in the N-terminus of MAD1, and point mutations in this region remove corona MAD1 and weaken the SAC. Therefore, Cyclin B1 is the long-sought-after scaffold that links MAD1 to the corona and this specific pool of MAD1 is needed to generate a robust SAC response. Robustness, in this context, arises because Cyclin B1-MAD1 localisation becomes MPS1-independent after the corona has been established. We demonstrate that this allows corona-MAD1 to persist at kinetochores when MPS1 activity falls, ensuring that it can still be phosphorylated on a key C-terminal catalytic site by MPS1. Therefore, this study explains how corona MAD1 generates a robust SAC signal and why stripping of this pool by dynein is essential for SAC silencing. It also reveals that the key mitotic kinase, Cyclin B1-Cdk1, scaffolds the pathway that inhibits its own degradation.

scholarly journals The ubiquitin ligase CRL2ZYG11 targets cyclin B1 for degradation in a conserved pathway that facilitates mitotic slippage

2016 ◽  
Vol 215 (2) ◽  
pp. 151-166 ◽  
Author(s):  
Riju S. Balachandran ◽  
Cassandra S. Heighington ◽  
Natalia G. Starostina ◽  
James W. Anderson ◽  
David L. Owen ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Spindle Assembly Checkpoint ◽  
Cyclin B1 ◽  
Human Cells ◽  
Anaphase Promoting Complex ◽  
Mitotic Progression ◽  
Animal Cells ◽  
C Elegans ◽  
Chemotherapy Drugs ◽  
Mitotic Slippage

The anaphase-promoting complex/cyclosome (APC/C) ubiquitin ligase is known to target the degradation of cyclin B1, which is crucial for mitotic progression in animal cells. In this study, we show that the ubiquitin ligase CRL2ZYG-11 redundantly targets the degradation of cyclin B1 in Caenorhabditis elegans and human cells. In C. elegans, both CRL2ZYG-11 and APC/C are required for proper progression through meiotic divisions. In human cells, inactivation of CRL2ZYG11A/B has minimal effects on mitotic progression when APC/C is active. However, when APC/C is inactivated or cyclin B1 is overexpressed, CRL2ZYG11A/B-mediated degradation of cyclin B1 is required for normal progression through metaphase. Mitotic cells arrested by the spindle assembly checkpoint, which inactivates APC/C, often exit mitosis in a process termed “mitotic slippage,” which generates tetraploid cells and limits the effectiveness of antimitotic chemotherapy drugs. We show that ZYG11A/B subunit knockdown, or broad cullin–RING ubiquitin ligase inactivation with the small molecule MLN4924, inhibits mitotic slippage in human cells, suggesting the potential for antimitotic combination therapy.

scholarly journals Uncoupling Anaphase-Promoting Complex/Cyclosome Activity from Spindle Assembly Checkpoint Control by Deregulating Polo-Like Kinase 1

2005 ◽  
Vol 25 (5) ◽  
pp. 2031-2044 ◽  
Author(s):  
Barbara C. M. van de Weerdt ◽  
Marcel A. T. M. van Vugt ◽  
Catherine Lindon ◽  
Jos J. W. Kauw ◽  
Marieke J. Rozendaal ◽  
...  
Keyword(s):  
Double Mutant ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Catastrophe ◽  
Anaphase Promoting Complex ◽  
Checkpoint Control ◽  
Mitotic Progression ◽  
Specific Antibodies ◽  
Mitotic Entry

ABSTRACT Polo-like kinase 1 (Plk1) plays a role in numerous events in mitosis, but how the multiple functions of Plk1 are separated is poorly understood. We studied regulation of Plk1 through two putative phosphorylation residues, Ser-137 and Thr-210. Using phospho-specific antibodies, we found that Thr-210 phosphorylation precedes Ser-137 phosphorylation in vivo, the latter occurring specifically in late mitosis. We show that expression of two activating mutants of these residues, S137D and T210D, results in distinct mitotic phenotypes. Whereas expression of both phospho-mimicking mutants as well as of the double mutant leads to accelerated mitotic entry, further progression through mitosis is dramatically different: the T210D mutant causes a spindle assembly checkpoint-dependent delay, whereas the expression of the S137D mutant or the double mutant results in untimely activation of the anaphase-promoting complex/cyclosome (APC/C) and frequent mitotic catastrophe. Using nonphosphorylatable Plk1-S137A and Plk1-T210A mutants, we show that both sites contribute to proper mitotic progression. Based on these observations, we propose that Plk1 function is altered at different stages of mitosis through consecutive posttranslational events, e.g., at Ser-137 and Thr-210. Furthermore, our data show that uncontrolled Plk1 activation can uncouple APC/C activity from spindle assembly checkpoint control.

scholarly journals The HECT E3 ligase Smurf2 is required for Mad2-dependent spindle assembly checkpoint

2008 ◽  
Vol 183 (2) ◽  
pp. 267-277 ◽  
Author(s):  
Evan C. Osmundson ◽  
Dipankar Ray ◽  
Finola E. Moore ◽  
Qingshen Gao ◽  
Gerald H. Thomsen ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Spindle Assembly Checkpoint ◽  
Spindle Checkpoint ◽  
E3 Ligase ◽  
Spindle Assembly ◽  
Cyclin B ◽  
Carboxyl Terminus ◽  
Anaphase Promoting Complex ◽  
Mitotic Spindles ◽  
Anaphase Onset

Activation of the anaphase-promoting complex/cyclosome (APC/C) by Cdc20 is critical for the metaphase–anaphase transition. APC/C-Cdc20 is required for polyubiquitination and degradation of securin and cyclin B at anaphase onset. The spindle assembly checkpoint delays APC/C-Cdc20 activation until all kinetochores attach to mitotic spindles. In this study, we demonstrate that a HECT (homologous to the E6-AP carboxyl terminus) ubiquitin ligase, Smurf2, is required for the spindle checkpoint. Smurf2 localizes to the centrosome, mitotic midbody, and centromeres. Smurf2 depletion or the expression of a catalytically inactive Smurf2 results in misaligned and lagging chromosomes, premature anaphase onset, and defective cytokinesis. Smurf2 inactivation prevents nocodazole-treated cells from accumulating cyclin B and securin and prometaphase arrest. The silencing of Cdc20 in Smurf2-depleted cells restores mitotic accumulation of cyclin B and securin. Smurf2 depletion results in enhanced polyubiquitination and degradation of Mad2, a critical checkpoint effector. Mad2 is mislocalized in Smurf2-depleted cells, suggesting that Smurf2 regulates the localization and stability of Mad2. These data indicate that Smurf2 is a novel mitotic regulator.

scholarly journals Inhibition of the anaphase-promoting complex by the Xnf7 ubiquitin ligase

2005 ◽  
Vol 169 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Jessica B. Casaletto ◽  
Leta K. Nutt ◽  
Qiju Wu ◽  
Jonathan D. Moore ◽  
Laurence D. Etkin ◽  
...  
Keyword(s):  
Ubiquitin Ligase ◽  
Spindle Assembly Checkpoint ◽  
Cyclin B1 ◽  
Specific Protein ◽  
Anaphase Promoting Complex ◽  
Protein Substrates ◽  
Ubiquitin Ligase Activity ◽  
Egg Extracts ◽  
Core Components ◽  
Cytostatic Factor

Degradation of specific protein substrates by the anaphase-promoting complex/cyclosome (APC) is critical for mitotic exit. We have identified the protein Xenopus nuclear factor 7 (Xnf7) as a novel APC inhibitor able to regulate the timing of exit from mitosis. Immunodepletion of Xnf7 from Xenopus laevis egg extracts accelerated the degradation of APC substrates cyclin B1, cyclin B2, and securin upon release from cytostatic factor arrest, whereas excess Xnf7 inhibited APC activity. Interestingly, Xnf7 exhibited intrinsic ubiquitin ligase activity, and this activity was required for APC inhibition. Unlike other reported APC inhibitors, Xnf7 did not associate with Cdc20, but rather bound directly to core subunits of the APC. Furthermore, Xnf7 was required for spindle assembly checkpoint function in egg extracts. These data suggest that Xnf7 is an APC inhibitor able to link spindle status to the APC through direct association with APC core components.

scholarly journals Slip slidin’ away of mitosis with CRL2Zyg11

2016 ◽  
Vol 215 (2) ◽  
pp. 143-145 ◽  
Author(s):  
Michael Brandeis
Keyword(s):  
Spindle Assembly Checkpoint ◽  
E3 Ligase ◽  
Spindle Assembly ◽  
Cyclin B1 ◽  
Anaphase Promoting Complex ◽  
Cell Biol ◽  
Mitotic Slippage ◽  
Mitotic Cells

The spindle assembly checkpoint arrests mitotic cells by preventing degradation of cyclin B1 by the anaphase-promoting complex/cyclosome, but some cells evade this checkpoint and slip out of mitosis. Balachandran et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201601083) show that the E3 ligase CRL2ZYG11 degrades cyclin B1, allowing mitotic slippage.

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 Coupling of Cdc20 inhibition and activation by BubR1

2020 ◽  
Author(s):  
Jamin Hein ◽  
Dimitriya H Garvanska ◽  
Isha Nasa ◽  
Arminja Kettenbach ◽  
Jakob Nilsson
Keyword(s):  
Ubiquitin Ligase ◽  
Cross Talk ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Cyclin B1 ◽  
Mitotic Checkpoint ◽  
Anaphase Onset ◽  
Mitotic Checkpoint Complex

Tight regulation of the APC/C-Cdc20 ubiquitin ligase that targets Cyclin B1 for degradation is important for mitotic fidelity. The spindle assembly checkpoint (SAC) inhibits Cdc20 through the mitotic checkpoint complex (MCC). In addition, phosphorylation of Cdc20 by Cyclin B1-Cdk1 independently inhibits APC/C-Cdc20 activation. This creates a conundrum for how Cdc20 gets activated prior to Cyclin B1 degradation. Here we show that the MCC component BubR1 harbours both Cdc20 inhibition and activation activities, allowing for cross-talk between the two Cdc20 inhibition pathways. Specifically BubR1 acts as a substrate specifier for PP2A-B56 to enable efficient Cdc20 dephosphorylation in the MCC. A mutant Cdc20 mimicking the dephosphorylated state escapes a mitotic checkpoint arrest arguing that restricting Cdc20 dephosphorylation to the MCC is important. Collectively our work reveals how Cdc20 can be dephosphorylated in the presence of Cyclin B1-Cdk1 activity without causing premature anaphase onset.

scholarly journals p31comet acts to ensure timely spindle checkpoint silencing subsequent to kinetochore attachment

2011 ◽  
Vol 22 (22) ◽  
pp. 4236-4246 ◽  
Author(s):  
Robert S. Hagan ◽  
Michael S. Manak ◽  
Håkon Kirkeby Buch ◽  
Michelle G. Meier ◽  
Patrick Meraldi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Exit ◽  
Cyclin B ◽  
Anaphase Promoting Complex ◽  
Mitotic Progression ◽  
Microtubule Attachment ◽  
And Function ◽  
High Cyclin

The spindle assembly checkpoint links the onset of anaphase to completion of chromosome-microtubule attachment and is mediated by the binding of Mad and Bub proteins to kinetochores of unattached or maloriented chromosomes. Mad2 and BubR1 traffic between kinetochores and the cytosol, thereby transmitting a “wait anaphase” signal to the anaphase-promoting complex. It is generally assumed that this signal dissipates automatically upon kinetochore-microtubule binding, but it has been shown that under conditions of nocodazole-induced arrest p31comet, a Mad2-binding protein, is required for mitotic progression. In this article we investigate the localization and function of p31comet during normal, unperturbed mitosis in human and marsupial cells. We find that, like Mad2, p31comet traffics on and off kinetochores and is also present in the cytosol. Cells depleted of p31comet arrest in metaphase with mature bipolar kinetochore-microtubule attachments, a satisfied checkpoint, and high cyclin B levels. Thus p31comet is required for timely mitotic exit. We propose that p31comet is an essential component of the machinery that silences the checkpoint during each cell cycle.

scholarly journals Recent Progress on the Localization of the Spindle Assembly Checkpoint Machinery to Kinetochores

Cells ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 278 ◽  
Author(s):  
Zhen Dou ◽  
Diogjena Prifti ◽  
Ping Gui ◽  
Xing Liu ◽  
Sabine Elowe ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Genome Stability ◽  
Cell Cycle Progression ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Progression ◽  
Cycle Progression ◽  
Daughter Cells ◽  
Microtubule Attachment ◽  
Surveillance Mechanism

Faithful chromosome segregation during mitosis is crucial for maintaining genome stability. The spindle assembly checkpoint (SAC) is a surveillance mechanism that ensures accurate mitotic progression. Defective SAC signaling leads to premature sister chromatid separation and aneuploid daughter cells. Mechanistically, the SAC couples the kinetochore microtubule attachment status to the cell cycle progression machinery. In the presence of abnormal kinetochore microtubule attachments, the SAC prevents the metaphase-to-anaphase transition through a complex kinase-phosphatase signaling cascade which results in the correct balance of SAC components recruited to the kinetochore. The correct kinetochore localization of SAC proteins is a prerequisite for robust SAC signaling and, hence, accurate chromosome segregation. Here, we review recent progresses on the kinetochore recruitment of core SAC factors.

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