scholarly journals A chemical tool box defines mitotic and interphase roles for Mps1 kinase

2010 ◽  
Vol 190 (1) ◽  
pp. 21-24 ◽  
Author(s):  
Weijie Lan ◽  
Don W. Cleveland
Keyword(s):  
Chromosome Segregation ◽  
Kinase Activity ◽  
Mitotic Checkpoint ◽  
Checkpoint Kinase ◽  
Checkpoint Proteins ◽  
Cell Biol ◽  
Chemical Inhibitors ◽  
Mitotic Inhibitors

In this issue, three groups (Hewitt et al. 2010. J. Cell Biol. doi:10.1083/jcb.201002133; Maciejowski et al. 2010. J. Cell Biol. doi:10.1083/jcb.201001050; Santaguida et al. 2010. J. Cell Biol. doi:10.1083/jcb.201001036) use chemical inhibitors to analyze the function of the mitotic checkpoint kinase Mps1. These studies demonstrate that Mps1 kinase activity ensures accurate chromosome segregation through its recruitment to kinetochores of mitotic checkpoint proteins, formation of interphase and mitotic inhibitors of Cdc20, and correction of faulty microtubule attachments.

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 Release of Mps1 from kinetochores is crucial for timely anaphase onset

2010 ◽  
Vol 191 (2) ◽  
pp. 281-290 ◽  
Author(s):  
Nannette Jelluma ◽  
Tobias B. Dansen ◽  
Tale Sliedrecht ◽  
Nicholas P. Kwiatkowski ◽  
Geert J.P.L. Kops
Keyword(s):  
Error Correction ◽  
Chromosome Segregation ◽  
Kinase Activity ◽  
Mitotic Checkpoint ◽  
Normal Chromosome ◽  
Half Time ◽  
Anaphase Onset ◽  
Chromosome Attachment

Mps1 kinase activity is required for proper chromosome segregation during mitosis through its involvements in microtubule–chromosome attachment error correction and the mitotic checkpoint. Mps1 dynamically exchanges on unattached kinetochores but is largely removed from kinetochores in metaphase. Here we show that Mps1 promotes its own turnover at kinetochores and that removal of Mps1 upon chromosome biorientation is a prerequisite for mitotic checkpoint silencing. Inhibition of Mps1 activity increases its half-time of recovery at unattached kinetochores and causes accumulation of Mps1 protein at these sites. Strikingly, preventing dissociation of active Mps1 from kinetochores delays anaphase onset despite normal chromosome attachment and alignment, and high interkinetochore tension. This delay is marked by continued recruitment of Mad1 and Mad2 to bioriented chromosomes and is attenuated by Mad2 depletion, indicating chronic engagement of the mitotic checkpoint in metaphase. We propose that release of Mps1 from kinetochores is essential for mitotic checkpoint silencing and a fast metaphase-to-anaphase transition.

scholarly journals Aberrant BUB1 Overexpression Promotes Mitotic Segregation Errors and Chromosomal Instability in Multiple Myeloma

Cancers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2206
Author(s):  
Yuto Fujibayashi ◽  
Reiko Isa ◽  
Daichi Nishiyama ◽  
Natsumi Sakamoto-Inada ◽  
Norichika Kawasumi ◽  
...  
Keyword(s):  
Multiple Myeloma ◽  
Disease Progression ◽  
Chromosome Segregation ◽  
Early Stage ◽  
Chromosome Instability ◽  
Underlying Mechanism ◽  
Mitotic Checkpoint ◽  
Checkpoint Proteins ◽  
Segmental Aneuploidy ◽  
Chromosomal Changes

Chromosome instability (CIN), the hallmarks of cancer, reflects ongoing chromosomal changes caused by chromosome segregation errors and results in whole chromosomal or segmental aneuploidy. In multiple myeloma (MM), CIN contributes to the acquisition of tumor heterogeneity, and thereby, to disease progression, drug resistance, and eventual treatment failure; however, the underlying mechanism of CIN in MM remains unclear. Faithful chromosomal segregation is tightly regulated by a series of mitotic checkpoint proteins, such as budding uninhibited by benzimidazoles 1 (BUB1). In this study, we found that BUB1 was overexpressed in patient-derived myeloma cells, and BUB1 expression was significantly higher in patients in an advanced stage compared to those in an early stage. This suggested the involvement of aberrant BUB1 overexpression in disease progression. In human myeloma-derived cell lines (HMCLs), BUB1 knockdown reduced the frequency of chromosome segregation errors in mitotic cells. In line with this, partial knockdown of BUB1 showed reduced variations in chromosome number compared to parent cells in HMCLs. Finally, BUB1 overexpression was found to promote the clonogenic potency of HMCLs. Collectively, these results suggested that enhanced BUB1 expression caused an increase in mitotic segregation errors and the resultant emergence of subclones with altered chromosome numbers and, thus, was involved in CIN in MM.

scholarly journals Yeast Fin1-PP1 dephosphorylates an Ipl1 substrate, Ndc80, to remove Bub1-Bub3 checkpoint proteins from the kinetochore during anaphase

PLoS Genetics ◽  
2021 ◽  
Vol 17 (5) ◽  
pp. e1009592
Author(s):  
Michael Bokros ◽  
Delaney Sherwin ◽  
Marie-Helene Kabbaj ◽  
Yanchang Wang
Keyword(s):  
Chromosome Segregation ◽  
Protein Phosphatase ◽  
Spindle Assembly Checkpoint ◽  
Kinase Activity ◽  
Protein Phosphatase 1 ◽  
Regulatory Subunit ◽  
Cyclin Dependent Kinase ◽  
Checkpoint Proteins ◽  
Anaphase Onset ◽  
Chromosome Attachment

The spindle assembly checkpoint (SAC) prevents anaphase onset in response to chromosome attachment defects, and SAC silencing is essential for anaphase onset. Following anaphase onset, activated Cdc14 phosphatase dephosphorylates the substrates of cyclin-dependent kinase to facilitate anaphase progression and mitotic exit. In budding yeast, Cdc14 dephosphorylates Fin1, a regulatory subunit of protein phosphatase 1 (PP1), to enable kinetochore localization of Fin1-PP1. We previously showed that kinetochore-localized Fin1-PP1 promotes the removal of the SAC protein Bub1 from the kinetochore during anaphase. We report here that Fin1-PP1 also promotes kinetochore removal of Bub3, the Bub1 partner, but has no effect on another SAC protein Mad1. Moreover, the kinetochore localization of Bub1-Bub3 during anaphase requires Aurora B/Ipl1 kinase activity. We further showed that Fin1-PP1 facilitates the dephosphorylation of kinetochore protein Ndc80, a known Ipl1 substrate. This dephosphorylation reduces kinetochore association of Bub1-Bub3 during anaphase. In addition, we found that untimely Ndc80 dephosphorylation causes viability loss in response to tensionless chromosome attachments. These results suggest that timely localization of Fin1-PP1 to the kinetochore controls the functional window of SAC and is therefore critical for faithful chromosome segregation.

scholarly journals Human Bubr1 Is a Mitotic Checkpoint Kinase That Monitors Cenp-E Functions at Kinetochores and Binds the Cyclosome/APC

1999 ◽  
Vol 146 (5) ◽  
pp. 941-954 ◽  
Author(s):  
G.K.T. Chan ◽  
S.A. Jablonski ◽  
V. Sudakin ◽  
J.C. Hittle ◽  
T.J. Yen
Keyword(s):  
Cell Cycle ◽  
Kinase Activity ◽  
Mitotic Checkpoint ◽  
Human Cells ◽  
Anaphase Promoting Complex ◽  
Mitotic Progression ◽  
Checkpoint Kinase ◽  
Microtubule Inhibitors ◽  
Interphase Cells ◽  
Combined Data

Human cells express two kinases that are related to the yeast mitotic checkpoint kinase BUB1. hBUB1 and hBUBR1 bind to kinetochores where they are postulated to be components of the mitotic checkpoint that monitors kinetochore activities to determine if chromosomes have achieved alignment at the spindle equator (Jablonski, S.A., G.K.T. Chan, C.A. Cooke, W.C. Earnshaw, and T.J. Yen. 1998. Chromosoma. 107:386–396). In support of this, hBUB1 and the homologous mouse BUB1 have been shown to be important for the mitotic checkpoint (Cahill, D.P., C. Lengauer, J. Yu, G.J. Riggins, J.K. Willson, S.D. Markowitz, K.W. Kinzler, and B. Vogelstein. 1998. Nature. 392:300–303; Taylor, S.S., and F. McKeon. 1997. Cell. 89:727–735). We now demonstrate that hBUBR1 is also an essential component of the mitotic checkpoint. hBUBR1 is required by cells that are exposed to microtubule inhibitors to arrest in mitosis. Additionally, hBUBR1 is essential for normal mitotic progression as it prevents cells from prematurely entering anaphase. We establish that one of hBUBR1's checkpoint functions is to monitor kinetochore activities that depend on the kinetochore motor CENP-E. hBUBR1 is expressed throughout the cell cycle, but its kinase activity is detected after cells have entered mitosis. hBUBR1 kinase activity was rapidly stimulated when the spindle was disrupted in mitotic cells. Finally, hBUBR1 was associated with the cyclosome/anaphase-promoting complex (APC) in mitotically arrested cells but not in interphase cells. The combined data indicate that hBUBR1 can potentially provide two checkpoint functions by monitoring CENP-E–dependent activities at the kinetochore and regulating cyclosome/APC activity.

scholarly journals ETAA1 ensures proper chromosome segregation: A matter of S phase or mitosis?

2019 ◽  
Vol 218 (12) ◽  
pp. 3883-3884
Author(s):  
Marina Alejandra González Besteiro ◽  
Vanesa Gottifredi
Keyword(s):  
Chromosome Segregation ◽  
S Phase ◽  
Chromosome Stability ◽  
Checkpoint Kinase ◽  
Cell Biol

ETAA1 activates the master checkpoint kinase ATR. Bass and Cortez (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201810058) recently reported an intra-mitotic function of ETAA1 that safeguards chromosome stability. In this issue, Achuthankutty et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201905064) describe a mechanism controlling the ATR-activating potential of ETAA1 in S phase to preserve chromosome stability.

scholarly journals The closed form of Mad2 is bound to Mad1 and Cdc20 at unattached kinetochores

2018 ◽  
Author(s):  
Gang Zhang ◽  
Jakob Nilsson
Keyword(s):  
Closed Form ◽  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Mitotic Checkpoint ◽  
Mutant Form ◽  
Wild Type ◽  
Checkpoint Proteins ◽  
Anaphase Onset ◽  
Mitotic Checkpoint Complex ◽  
Direct Readout

ABSTRACTThe spindle assembly checkpoint (SAC) ensures accurate chromosome segregation by delaying anaphase onset in response to unattached kinetochores. Anaphase is delayed by the generation of the mitotic checkpoint complex (MCC) composed of the checkpoint proteins Mad2 and BubR1/Bub3 bound to the protein Cdc20. Current models assume that MCC production is catalyzed at unattached kinetochores and that the Mad1/Mad2 complex is instrumental in the conversion of Mad2 from an open form (O-Mad2) to a closed form (C-Mad2) that can bind to Cdc20. Importantly the levels of Mad2 at kinetochores correlate with SAC activity but whether C-Mad2 at kinetochores exclusively represents its complex with Mad1 is not fully established. Here we use a recently established C-Mad2 specific monoclonal antibody to show that Cdc20 and C-Mad2 levels correlate at kinetochores and that depletion of Cdc20 reduces Mad2 but not Mad1 kinetochore levels. Importantly reintroducing wild type Cdc20 but not Cdc20 R132A, a mutant form that cannot bind Mad2, restores Mad2 levels. In agreement with this live cell imaging of fluorescent tagged Mad2 reveals that Cdc20 depletion strongly reduces Mad2 localization to kinetochores. These results support the presence of Mad2-Cdc20 complexes at kinetochores in agreement with current models of the SAC but also argue that Mad2 levels at kinetochores cannot be used as a direct readout of Mad1 levels.

Kinetochore Stretching-Mediated Rapid Silencing of Mitotic Checkpoint Required for Failsafe Chromosome Segregation

2019 ◽  
Author(s):  
Kazuhiko S.K. Uchida ◽  
Minji Jo ◽  
Kota Nagasaka ◽  
Motoko Takahashi ◽  
Norihisa Shindo ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Checkpoint

scholarly journals Aneuploid abortion correlates positively with MAD1 overexpression and miR-125b down-regulation

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Juan Zhao ◽  
Hui Li ◽  
Guangxin Chen ◽  
Lijun Du ◽  
Peiyan Xu ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Spindle Assembly Checkpoint ◽  
Mitotic Checkpoint ◽  
Early Embryo ◽  
Vital Role ◽  
Control Group ◽  
Embryo Abortion ◽  
Protein Levels ◽  
Mitotic Checkpoint Complex

Abstract Background Aneuploidy is the most frequent cause of early-embryo abortion. Any defect in chromosome segregation would fail to satisfy the spindle assembly checkpoint (SAC) during mitosis, halting metaphase and causing aneuploidy. The mitotic checkpoint complex (MCC), comprising MAD1, MAD2, Cdc20, BUBR1 and BUB3, plays a vital role in SAC activation. Studies have confirmed that overexpression of MAD2 and BUBR1 can facilitate correct chromosome segregation and embryo stability. Research also proves that miR-125b negatively regulates MAD1 expression by binding to its 3′UTR. However, miR-125b, Mad1 and Bub3 gene expression in aneuploid embryos of spontaneous abortion has not been reported to date. Methods In this study, embryonic villi from miscarried pregnancies were collected and divided into two groups (aneuploidy and euploidy) based on High-throughput ligation-dependent probe amplification (HLPA) and Fluorescence in situ hybridization (FISH) analyses. RNA levels of miR-125b, MAD1 and BUB3 were detected by Quantitative real-time PCR (qRT-PCR); protein levels of MAD1 and BUB3 were analysed by Western blotting. Results statistical analysis (p < 0.05) showed that miR-125b and BUB3 were significantly down-regulated in the aneuploidy group compared to the control group and that MAD1 was significantly up-regulated. Additionally, the MAD1 protein level was significantly higher in aneuploidy abortion villus, but BUB3 protein was only mildly increased. Correlation analysis revealed that expression of MAD1 correlated negatively with miR-125b. Conclusion These results suggest that aneuploid abortion correlates positively with MAD1 overexpression, which might be caused by insufficient levels of miR-125b. Taken together, our findings first confirmed the negative regulatory mode between MAD1 and miR-125b, providing a basis for further mechanism researches in aneuploid abortion.

scholarly journals Bub1 mediates cell death in response to chromosome missegregation and acts to suppress spontaneous tumorigenesis

2007 ◽  
Vol 179 (2) ◽  
pp. 255-267 ◽  
Author(s):  
Karthik Jeganathan ◽  
Liviu Malureanu ◽  
Darren J. Baker ◽  
Susan C. Abraham ◽  
Jan M. van Deursen
Keyword(s):  
Cell Death ◽  
Chromosome Segregation ◽  
Physiological Role ◽  
Mitotic Checkpoint ◽  
Critical Threshold ◽  
Wild Type ◽  
Checkpoint Protein ◽  
Chromosome Missegregation ◽  
Mitotic Checkpoint Protein

The physiological role of the mitotic checkpoint protein Bub1 is unknown. To study this role, we generated a series of mutant mice with a gradient of reduced Bub1 expression using wild-type, hypomorphic, and knockout alleles. Bub1 hypomorphic mice are viable, fertile, and overtly normal despite weakened mitotic checkpoint activity and high percentages of aneuploid cells. Bub1 haploinsufficient mice, which have a milder reduction in Bub1 protein than Bub1 hypomorphic mice, also exhibit reduced checkpoint activity and increased aneuploidy, but to a lesser extent. Although cells from Bub1 hypomorphic and haploinsufficient mice have similar rates of chromosome missegregation, cell death after an aberrant separation decreases dramatically with declining Bub1 levels. Importantly, Bub1 hypomorphic mice are highly susceptible to spontaneous tumors, whereas Bub1 haploinsufficient mice are not. These findings demonstrate that loss of Bub1 below a critical threshold drives spontaneous tumorigenesis and suggest that in addition to ensuring proper chromosome segregation, Bub1 is important for mediating cell death when chromosomes missegregate.

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