scholarly journals Mitotic phosphorylation of tumor suppressor DAB2IP maintains spindle assembly checkpoint and chromosomal stability through activating PLK1-Mps1 signal pathway and stabilizing mitotic checkpoint complex

Oncogene ◽  
2021 ◽  
Author(s):  
Lan Yu ◽  
Yue Lang ◽  
Ching-Cheng Hsu ◽  
Wei-Min Chen ◽  
Jui-Chung Chiang ◽  
...  
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Checkpoint ◽  
Anaphase Promoting Complex ◽  
Independent Manner ◽  
Chromosome Separation ◽  
Surveillance Mechanism ◽  
Mitotic Phosphorylation ◽  
Mitotic Checkpoint Complex ◽  
Mitotic Regulation

AbstractChromosomal instability (CIN) is a driving force for cancer development. The most common causes of CIN include the dysregulation of the spindle assembly checkpoint (SAC), which is a surveillance mechanism that prevents premature chromosome separation during mitosis by targeting anaphase-promoting complex/cyclosome (APC/C). DAB2IP is frequently silenced in advanced prostate cancer (PCa) and is associated with aggressive phenotypes of PCa. Our previous study showed that DAB2IP activates PLK1 and functions in mitotic regulation. Here, we report the novel mitotic phosphorylation of DAB2IP by Cdks, which mediates DAB2IP’s interaction with PLK1 and the activation of the PLK1-Mps1 pathway. DAB2IP interacts with Cdc20 in a phosphorylation-independent manner. However, the phosphorylation of DAB2IP inhibits the ubiquitylation of Cdc20 in response to SAC, and blocks the premature release of the APC/C-MCC. The PLK1-Mps1 pathway plays an important role in mitotic checkpoint complex (MCC) assembly. It is likely that DAB2IP acts as a scaffold to aid PLK1-Mps1 in targeting Cdc20. Depletion or loss of the Cdks-mediated phosphorylation of DAB2IP destabilizes the MCC, impairs the SAC, and increases chromosome missegregation and subsequent CIN, thus contributing to tumorigenesis. Collectively, these results demonstrate the mechanism of DAB2IP in SAC regulation and provide a rationale for targeting the SAC to cause lethal CIN against DAB2IP-deficient aggressive PCa, which exhibits a weak SAC.

scholarly journals Spindle assembly checkpoint: the third decade

2011 ◽  
Vol 366 (1584) ◽  
pp. 3595-3604 ◽  
Author(s):  
Andrea Musacchio
Keyword(s):  
Cell Cycle Progression ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Checkpoint ◽  
Anaphase Promoting Complex ◽  
Checkpoint Control ◽  
Checkpoint Response ◽  
The Third ◽  
Binding Interface ◽  
Mitotic Checkpoint Complex

The spindle assembly checkpoint controls cell cycle progression during mitosis, synchronizing it with the attachment of chromosomes to spindle microtubules. After the discovery of the mitotic arrest deficient ( MAD ) and budding uninhibited by benzymidazole ( BUB ) genes as crucial checkpoint components in 1991, the second decade of checkpoint studies (2001–2010) witnessed crucial advances in the elucidation of the mechanism through which the checkpoint effector, the mitotic checkpoint complex, targets the anaphase-promoting complex (APC/C) to prevent progression into anaphase. Concomitantly, the discovery that the Ndc80 complex and other components of the microtubule-binding interface of kinetochores are essential for the checkpoint response finally asserted that kinetochores are crucial for the checkpoint response. Nevertheless, the relationship between kinetochores and checkpoint control remains poorly understood. Crucial advances in this area in the third decade of checkpoint studies (2011–2020) are likely to be brought about by the characterization of the mechanism of kinetochore recruitment, activation and inactivation of checkpoint proteins, which remains elusive for the majority of checkpoint components. Here, we take a molecular view on the main challenges hampering this task.

scholarly journals Mechanism of APC/CCDC20 activation by mitotic phosphorylation

2016 ◽  
Vol 113 (19) ◽  
pp. E2570-E2578 ◽  
Author(s):  
Renping Qiao ◽  
Florian Weissmann ◽  
Masaya Yamaguchi ◽  
Nicholas G. Brown ◽  
Ryan VanderLinden ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Checkpoint ◽  
Anaphase Promoting Complex ◽  
Loop Region ◽  
Evolutionarily Conserved ◽  
Terminal Loop ◽  
Different Types ◽  
Mitotic Phosphorylation ◽  
Mitotic Checkpoint Complex

Chromosome segregation and mitotic exit are initiated by the 1.2-MDa ubiquitin ligase APC/C (anaphase-promoting complex/cyclosome) and its coactivator CDC20 (cell division cycle 20). To avoid chromosome missegregation, APC/CCDC20 activation is tightly controlled. CDC20 only associates with APC/C in mitosis when APC/C has become phosphorylated and is further inhibited by a mitotic checkpoint complex until all chromosomes are bioriented on the spindle. APC/C contains 14 different types of subunits, most of which are phosphorylated in mitosis on multiple sites. However, it is unknown which of these phospho-sites enable APC/CCDC20 activation and by which mechanism. Here we have identified 68 evolutionarily conserved mitotic phospho-sites on human APC/C bound to CDC20 and have used the biGBac technique to generate 47 APC/C mutants in which either all 68 sites or subsets of them were replaced by nonphosphorylatable or phospho-mimicking residues. The characterization of these complexes in substrate ubiquitination and degradation assays indicates that phosphorylation of an N-terminal loop region in APC1 is sufficient for binding and activation of APC/C by CDC20. Deletion of the N-terminal APC1 loop enables APC/CCDC20 activation in the absence of mitotic phosphorylation or phospho-mimicking mutations. These results indicate that binding of CDC20 to APC/C is normally prevented by an autoinhibitory loop in APC1 and that its mitotic phosphorylation relieves this inhibition. The predicted location of the N-terminal APC1 loop implies that this loop controls interactions between the N-terminal domain of CDC20 and APC1 and APC8. These results reveal how APC/C phosphorylation enables CDC20 to bind and activate the APC/C in mitosis.

scholarly journals Intermediates in the assembly of mitotic checkpoint complexes and their role in the regulation of the anaphase-promoting complex

2016 ◽  
Vol 113 (4) ◽  
pp. 966-971 ◽  
Author(s):  
Sharon Kaisari ◽  
Danielle Sitry-Shevah ◽  
Shirly Miniowitz-Shemtov ◽  
Avram Hershko
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Spindle ◽  
Spindle Assembly Checkpoint ◽  
Mitotic Checkpoint ◽  
Anaphase Promoting Complex ◽  
Checkpoint Proteins ◽  
Sister Chromatids ◽  
Unknown Species ◽  
Mitotic Checkpoint Complex

The mitotic (or spindle assembly) checkpoint system prevents premature separation of sister chromatids in mitosis and thus ensures the fidelity of chromosome segregation. Kinetochores that are not attached properly to the mitotic spindle produce an inhibitory signal that prevents progression into anaphase. The checkpoint system acts on the Anaphase-Promoting Complex/Cyclosome (APC/C) ubiquitin ligase, which targets for degradation inhibitors of anaphase initiation. APC/C is inhibited by the Mitotic Checkpoint Complex (MCC), which assembles when the checkpoint is activated. MCC is composed of the checkpoint proteins BubR1, Bub3, and Mad2, associated with the APC/C coactivator Cdc20. The intermediary processes in the assembly of MCC are not sufficiently understood. It is also not clear whether or not some subcomplexes of MCC inhibit the APC/C and whether Mad2 is required only for MCC assembly and not for its action on the APC/C. We used purified subcomplexes of mitotic checkpoint proteins to examine these problems. Our results do not support a model in which Mad2 catalytically generates a Mad2-free APC/C inhibitor. We also found that the release of Mad2 from MCC caused a marked (although not complete) decrease in inhibitory action, suggesting a role of Mad2 in MCC for APC/C inhibition. A previously unknown species of MCC, which consists of Mad2, BubR1, and two molecules of Cdc20, contributes to the inhibition of APC/C by the mitotic checkpoint system.

scholarly journals EFFECTORS OF THE SPINDLE ASSEMBLY CHECKPOINT BUT NOT THE MITOTIC EXIT NETWORK ARE CONFINED WITHIN THE NUCLEUS OF SACCHAROMYCES CEREVISIAE

2018 ◽  
Author(s):  
Lydia R Heasley ◽  
Jennifer G DeLuca ◽  
Steven M Markus
Keyword(s):  
Nuclear Envelope ◽  
Mammalian Cells ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Checkpoint ◽  
Mitotic Exit ◽  
Cell Cycle Checkpoints ◽  
Anaphase Promoting Complex ◽  
Mitotic Exit Network ◽  
And Function

The Spindle Assembly Checkpoint (SAC) prevents erroneous chromosome segregation by delaying mitotic progression when chromosomes are incorrectly attached to the mitotic spindle. This delay is mediated by Mitotic Checkpoint Complexes (MCCs), which assemble at unattached kinetochores and repress the activity of the Anaphase Promoting Complex/Cyclosome (APC/C). The cellular localizations of MCCs are likely critical for proper SAC function, yet remain poorly defined. We recently demonstrated that in mammalian cells, in which the nuclear envelope disassembles during mitosis, MCCs diffuse throughout the spindle region and cytoplasm. Here, we employed binucleate yeast zygotes to examine the localization dynamics of SAC effectors required for MCC assembly and function in budding yeast, in which the nuclear envelope remains intact throughout mitosis. Our findings indicate that in yeast MCCs are confined to the nuclear compartment and excluded from the cytoplasm during mitosis. In contrast, we find that effectors of the Mitotic Exit Network (MEN) - a pathway that initiates disassembly of the anaphase spindle only when it is properly oriented - are in fact freely exchanged between multiple nuclei within a shared cytoplasm. Our study provides insight into how cell cycle checkpoints have evolved to function in diverse cellular contexts.

scholarly journals Recruitment of Cdc20 to the Kinetochore Requires BubR1 but Not Mad2 in Drosophila melanogaster

2010 ◽  
Vol 30 (13) ◽  
pp. 3384-3395 ◽  
Author(s):  
Deyu Li ◽  
Gary Morley ◽  
Michael Whitaker ◽  
Jun-Yong Huang
Keyword(s):  
Drosophila Melanogaster ◽  
Rna Interference ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Cyclin B ◽  
Stable Complex ◽  
S2 Cells ◽  
Anaphase Promoting Complex ◽  
Surveillance Mechanism ◽  
Initial Binding

ABSTRACT To prevent aneuploidy, cells require a mitotic surveillance mechanism, the spindle assembly checkpoint (SAC). The SAC prevents metaphase/anaphase transition by blocking the ubiquitylation and destruction of cyclin B and securin via the Cdc20-activated anaphase-promoting complex or cyclosome (APC/C)-mediated proteolysis pathway. This checkpoint involves the kinetochore proteins Mad2, BubR1, and Cdc20. Mad2 and BubR1 are inhibitors of the APC/C, but Cdc20 is an activator. Exactly how the SAC regulates Cdc20 via unattached kinetochores remains unclear; in vertebrates, most current models suggest that kinetochore-bound Mad2 is required for initial binding to Cdc20 to form a stable complex that includes BubR1. Here, we show that the Mad2 kinetochore dimerization recruitment mechanism is conserved and that the recruitment of Cdc20 to kinetochores in Drosophila requires BubR1 but not Mad2. BubR1 and Mad2 can bind to Cdc20 independently, and the interactions are enhanced after cells are arrested at mitosis by the depletion of Cdc27 using RNA interference (RNAi) in S2 cells or by MG132 treatment in syncytial embryos. These findings offer an explanation of why BubR1 is more important than Mad2 for SAC function in flies. These findings could lead to a better understanding of vertebrate SAC mechanisms.

scholarly journals BubR1 recruitment to the kinetochore via Bub1 enhances Spindle Assembly Checkpoint signaling

2021 ◽  
Author(s):  
Anand Banerjee ◽  
Chu Chen ◽  
Lauren Humphrey ◽  
John J. Tyson ◽  
Ajit Joglekar
Keyword(s):  
Mathematical Modeling ◽  
Dose Response ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Checkpoint ◽  
Local Concentration ◽  
Checkpoint Signaling ◽  
Response Characteristics ◽  
Anaphase Onset ◽  
Mitotic Checkpoint Complex

During mitosis, unattached kinetochores in a dividing cell generate the anaphase-inhibitory Mitotic Checkpoint Complex (MCC) to activate the Spindle Assembly Checkpoint (SAC) and delay anaphase onset. To generate MCC, these kinetochores recruit MCC constituent proteins including the protein BubR1. The increased local concentration of BubR1 resulting from this recruitment should enhance MCC generation, but prior studies found this not to be the case. We analyzed the contribution of two BubR1 recruitment pathways to MCC generation in human kinetochores. For these analyses, we isolated a subset of the MCC generation reactions to the cytosol using ectopic SAC activation systems. These analyses and mathematical modeling show that BubR1 binding to the SAC protein Bub1, but not to the 'KI' motifs in the kinetochore protein Knl1, significantly enhances the rate of Bub1-mediated MCC generation in the kinetochore. Our work also suggests that Bub1-BubR1 stoichiometry will strongly influence the dose-response characteristics of SAC signaling.

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.

The Mad2-Binding Protein p31comet as a potential target for human cancer therapy

2021 ◽  
Vol 21 ◽  
Author(s):  
Ana C. Henriques ◽  
Patrícia M. A. Silva ◽  
Bruno Sarmento ◽  
Hassan Bousbaa
Keyword(s):  
Cancer Therapy ◽  
Spindle Assembly Checkpoint ◽  
Human Cancer ◽  
Binding Protein ◽  
Mitotic Checkpoint ◽  
Mitotic Exit ◽  
Mitotic Progression ◽  
Spindle Microtubules ◽  
Surveillance Mechanism ◽  
Mitotic Checkpoint Complex

: The spindle assembly checkpoint (SAC) is a surveillance mechanism that prevents mitotic exit at the metaphase-to-anaphase transition until all chromosomes have established correct bipolar attachment to spindle microtubules. Activation of SAC relies on the assembly of the mitotic checkpoint complex (MCC), which requires conformational change from inactive open Mad2 (O-Mad2) to the active closed Mad2 (C-Mad2) at unattached kinetochores. The Mad2-binding protein p31comet plays a key role in controlling timely mitotic exit by promoting SAC silencing, through preventing Mad2 activation and promoting MCC disassembly. Besides, increasing evidences highlight the p31comet potential as target for cancer therapy. Here, we provide an updated overview of the functional significance of p31comet in mitotic progression, and discuss the potential of deregulated expression of p31comet in cancer and in therapeutic strategies.

scholarly journals Explaining the oligomerization properties of the spindle assembly checkpoint protein Mad2

2005 ◽  
Vol 360 (1455) ◽  
pp. 637-648 ◽  
Author(s):  
Anna DeAntoni ◽  
Valeria Sala ◽  
Andrea Musacchio
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Mitotic Checkpoint ◽  
Checkpoint Activation ◽  
Anaphase Onset ◽  
Open Conformation ◽  
Chromosome Attachment ◽  
A Subunit ◽  
Mitotic Checkpoint Complex ◽  
Spindle Assembly Checkpoint Protein

Mad2 is an essential component of the spindle assembly checkpoint (SAC), a molecular device designed to coordinate anaphase onset with the completion of chromosome attachment to the spindle. Capture of chromosome by microtubules occur on protein scaffolds known as kinetochores. The SAC proteins are recruited to kinetochores in prometaphase where they generate a signal that halts anaphase until all sister chromatid pairs are bipolarly oriented. Mad2 is a subunit of the mitotic checkpoint complex, which is regarded as the effector of the spindle checkpoint. Its function is the sequestration of Cdc20, a protein required for progression into anaphase. The function of Mad2 in the checkpoint correlates with a dramatic conformational rearrangement of the Mad2 protein. Mad2 adopts a closed conformation (C-Mad2) when bound to Cdc20, and an open conformation (O-Mad2) when unbound to this ligand. Checkpoint activation promotes the conversion of O-Mad2 to Cdc20-bound C-Mad2. We show that this conversion requires a C-Mad2 template and we identify this in Mad1-bound Mad2. In our proposition, Mad1-bound C-Mad2 recruits O-Mad2 to kinetochores, stimulating Cdc20 capture, implying that O-Mad2 and C-Mad2 form dimers. We discuss Mad2 oligomerization and link our discoveries to previous observations related to Mad2 oligomerization.

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