GO:0033597 mitotic checkpoint complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0033597 describes the mitotic checkpoint complex (MCC), a multiprotein inhibitor of the anaphase-promoting complex/cyclosome (APC/C) that prevents premature chromosome segregation.
• In mammalian cells the MCC is composed of MAD2, BUBR1, BUB3 and CDC20; in budding yeast it consists of Mad2p, Mad3p, Bub3p and Cdc20p.
• MCC assembly is driven by kinetochore catalysis and involves a conformational change in MAD2 and CDC20 incorporation.
• The MCC binds and inhibits APC/C, delaying anaphase until all chromosomes are properly attached to the spindle.
• Deregulation of MCC components is linked to aneuploidy and familial cancer predisposition.
• Studying the MCC requires integrated structural, biochemical and CRISPR-based approaches to dissect its assembly and function.
Description
The mitotic checkpoint complex (MCC) is a conserved multiprotein assembly that safeguards chromosome segregation by inhibiting the anaphase-promoting complex/cyclosome (APC/C) until all kinetochores are properly attached to the mitotic spindle. This checkpoint, also known as the spindle assembly checkpoint, prevents premature sister chromatid separation and ensures genomic stability. The MCC is therefore a central node in cell cycle control, and its dysfunction is associated with aneuploidy and cancer. Researchers study the MCC to understand how cells maintain chromosome number and to identify therapeutic targets in proliferative diseases.
mitotic checkpoint complex At A Glance
| GO ID | GO:0033597 |
|---|---|
| GO term | mitotic checkpoint complex |
| Ontology | cellular_component |
| Synonym | MCC |
| Major function | Inhibits APC/C to delay anaphase until chromosomes are properly attached |
| Composition (mammals) | MAD2, BUBR1, BUB3, CDC20 |
| Composition (budding yeast) | Mad2p, Mad3p, Bub3p, Cdc20p |
| Assembly trigger | Kinetochore catalysis and conformational change of MAD2 |
| Associated process | Spindle assembly checkpoint signalling |
What Is GO:0033597?
The mitotic checkpoint complex (MCC) is a cellular component defined by GO:0033597 as a multiprotein complex that functions as a mitotic checkpoint inhibitor of the anaphase-promoting complex/cyclosome (APC/C). In budding yeast, the MCC consists of Mad2p, Mad3p, Bub3p and Cdc20p, while in mammalian cells it is composed of MAD2, BUBR1, BUB3 and CDC20.
Why Is mitotic checkpoint complex Important in Cell Biology?
The MCC is essential for maintaining genomic integrity by preventing premature chromosome segregation. Its correct assembly and timely disassembly are critical for normal cell division, and defects in MCC components lead to aneuploidy, a hallmark of many cancers. Understanding MCC biology provides insights into cancer predisposition and potential therapeutic strategies targeting the spindle assembly checkpoint.
• Prevents aneuploidy by delaying anaphase until all kinetochores are attached.
• Directly inhibits APC/C, controlling the metaphase-to-anaphase transition.
• Mutations in MCC genes are linked to familial cancer syndromes.
• MCC dysfunction contributes to chromosomal instability in solid tumors.
• Serves as a target for chemotherapeutic agents that perturb mitosis.
• Its assembly is a model for studying conformational switches in signaling.
• MCC components are potential biomarkers for cancer prognosis.
• Understanding MCC regulation can inform strategies to overcome drug resistance.
• MCC is conserved from yeast to humans, enabling genetic studies.
• MCC research intersects with cell cycle, kinetochore and ubiquitin biology.
What Happens During mitotic checkpoint complex?
Activation at unattached kinetochores
In simple terms: When chromosomes are not properly attached to the spindle, the MCC is built at the kinetochore to pause cell division.
Unattached kinetochores catalyze the assembly of the MCC, which involves the recruitment of MAD2 and other components. Kinetochore-driven catalysis accelerates the formation of the MCC, ensuring a rapid response to attachment defects.
MCC assembly and conformational change
In simple terms: The MCC is put together through a shape change in MAD2 that allows it to bind CDC20.
MAD2 undergoes a conformational change from an open to a closed state, enabling it to bind CDC20 and incorporate into the MCC. CDC20 itself assists its catalytic incorporation into the complex, as shown by structural and biochemical studies.
Inhibition of APC/C
In simple terms: The finished MCC grabs onto APC/C and stops it from triggering chromosome separation.
The MCC binds to APC/C and inhibits its ubiquitin ligase activity, preventing the degradation of securin and cyclin B, which are required for anaphase onset. This inhibition is reversible and is relieved once all chromosomes are correctly attached.
Disassembly and checkpoint silencing
In simple terms: Once chromosomes are properly attached, the MCC falls apart so cell division can continue.
Checkpoint silencing involves the disassembly of the MCC and release of APC/C inhibition, allowing anaphase to proceed. The mechanisms of MCC disassembly are tightly regulated and involve additional factors that promote the transition to anaphase.
Key Genes Involved in GO:0033597 mitotic checkpoint complex
The following genes and proteins are core components or regulators of the mitotic checkpoint complex.
| Gene | Major Role | Research Relevance |
|---|---|---|
| MAD2 (MAD2L1) | Core MCC component; binds CDC20 and inhibits APC/C | Knockout causes premature anaphase and aneuploidy |
| BUBR1 (BUB1B) | Core MCC component; scaffolds MCC assembly | Mutations linked to mosaic variegated aneuploidy and cancer |
| BUB3 | Core MCC component; binds BubR1 and Mad2 | Required for checkpoint function and kinetochore localization |
| CDC20 | Core MCC component; activates APC/C but is inhibited in MCC | Overexpression associated with cancer |
| MAD1 (MAD1L1) | Required for MAD2 recruitment to kinetochores | Knockout abolishes checkpoint |
| MAD3 (yeast) | Yeast ortholog of BUBR1 | Model for MCC assembly studies |
| BUB1 | Kinetochore kinase that recruits checkpoint proteins | Regulates MCC assembly and chromosome alignment |
| MPS1 (TTK) | Kinetochore kinase essential for checkpoint signaling | Inhibitors used to probe MCC dynamics |
| RNF8 | E3 ubiquitin ligase that scaffolds MAD2 in glioma | Potential target in glioblastoma |
| CAMK2D | Scaffold for RNF8-MAD2 complex in glioma | Modulates mitotic checkpoint in cancer |
| APC/C | Ubiquitin ligase inhibited by MCC | Central to mitotic progression |
| SWR1 | Chromatin remodeling complex preventing mitotic slippage | Links chromatin to checkpoint arrest |
| Cdc20p (yeast) | Yeast CDC20 ortholog | Genetic studies of MCC |
| Mad2p (yeast) | Yeast MAD2 ortholog | Model for conformational switch |
| Bub3p (yeast) | Yeast BUB3 ortholog | Conserved checkpoint component |
| Mad3p (yeast) | Yeast BUBR1 ortholog | Scaffold for MCC in yeast |
How Is mitotic checkpoint complex Regulated?
The MCC is regulated by kinetochore-associated kinases such as MPS1 and BUB1, which control the recruitment and activation of checkpoint proteins. Additionally, the SWR1 chromatin remodeling complex has been shown to prevent mitotic slippage during spindle position checkpoint arrest, linking chromatin state to checkpoint regulation. In glioma, the CAMK2D-RNF8-MAD2 axis modulates mitotic checkpoint activity, highlighting tissue-specific regulatory mechanisms.
mitotic checkpoint complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| BUBR1 | Mosaic variegated aneuploidy, cancer predisposition | Knock-in of patient mutations in cell lines |
| MAD2 | Aneuploidy, tumorigenesis | Knockout in cancer cell lines |
| CDC20 | Various cancers, overexpression | Overexpression in normal fibroblasts |
| RNF8 | Glioma progression | Knockout in glioma cell lines |
| CAMK2D | Glioma mitotic checkpoint | Point mutation to disrupt scaffold function |
Cancer and aneuploidy
Defects in MCC components lead to chromosomal instability and aneuploidy, which are hallmarks of many cancers. Familial cancer syndromes have been linked to mutations in BUBR1 and other checkpoint genes, underscoring the importance of the MCC in tumor suppression.
Glioma
In glioma, the CAMK2D-RNF8-MAD2 complex regulates the mitotic checkpoint, and its disruption affects tumor cell proliferation. This suggests that MCC-associated proteins could be therapeutic targets in glioblastoma.
Developmental disorders
Mutations in BUBR1 cause mosaic variegated aneuploidy, a rare developmental disorder characterized by chromosomal instability. This highlights the non-cancer consequences of MCC dysfunction.
From mitotic checkpoint complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of MAD2 cause premature anaphase? | MAD2 knockout cell line |
| How does BUBR1 mutation affect checkpoint? | BUBR1 point-mutation knock-in |
| Can CDC20 overexpression drive aneuploidy? | CDC20 overexpression model |
| Where does MAD2 localize during mitosis? | Tagged knock-in of MAD2 with fluorescent protein |
| What is the role of RNF8 in glioma checkpoint? | RNF8 knockout in glioma cells |
| How does SWR1 prevent mitotic slippage? | SWR1 knockout yeast or human cells |
How to Study the mitotic checkpoint complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging | Dynamics of MCC components at kinetochores | Visualizing checkpoint activation |
| Co-immunoprecipitation | Protein-protein interactions within MCC | Mapping complex composition |
| Mass spectrometry | Identification of MCC-associated proteins | Discovery of novel regulators |
| Cryo-EM | High-resolution structure of MCC | Understanding conformational changes |
| CRISPR knockout screens | Gene essentiality for checkpoint function | Identifying MCC regulators |
| RNA-seq | Transcriptional changes upon MCC disruption | Assessing downstream effects |
| Flow cytometry | Cell cycle profiles and aneuploidy | Quantifying chromosomal instability |
Live-cell imaging
Live-cell imaging of fluorescently tagged MCC components allows real-time visualization of complex assembly and disassembly at kinetochores. This method is essential for understanding the dynamics of checkpoint signaling.
Proteomics and interactomics
Affinity purification coupled with mass spectrometry can identify MCC components and their interactors, revealing the composition and regulation of the complex. This approach has been used to map the MCC-APC/C interaction.
Structural biology
Cryo-electron microscopy and X-ray crystallography provide high-resolution structures of the MCC and its subcomplexes, elucidating the conformational changes required for assembly.
Functional genomics
CRISPR-based knockout screens and RNAi can systematically test the requirement of individual genes for MCC function and checkpoint arrest. Such screens have identified novel regulators of the spindle assembly checkpoint.
How CRISPR Can Be Used to Study GO:0033597 mitotic checkpoint complex
Knockout
CRISPR knockout of core MCC genes such as MAD2 or BUBR1 results in checkpoint bypass and premature anaphase, providing direct evidence for their essential roles. These models are valuable for studying aneuploidy and cancer progression.
Point Mutation
Introducing patient-derived point mutations in BUBR1 or MAD2 via CRISPR can recapitulate disease-associated phenotypes and reveal structure-function relationships. Such models help dissect the molecular basis of checkpoint defects.
Knock-in
Tagged knock-in of MCC components with fluorescent or affinity tags enables live-cell imaging and proteomic studies without altering endogenous expression levels. This approach preserves physiological regulation.
Overexpression
Overexpression of CDC20 or other MCC components can drive aneuploidy and tumorigenesis, modeling the effects of gene amplification in cancer. These models are useful for testing therapeutic interventions.
How EDITGENE Supports mitotic checkpoint complex Research
Researchers studying mitotic checkpoint complex-related genes often need to determine whether a candidate gene is causally involved in checkpoint control or aneuploidy. EDITGENE provides comprehensive CRISPR-based services to create precise cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for mitotic checkpoint complex research.
Frequently Asked Questions About mitotic checkpoint complex
What is the mitotic checkpoint complex?
The mitotic checkpoint complex (MCC) is a multiprotein assembly that inhibits the anaphase-promoting complex/cyclosome (APC/C) to prevent premature chromosome segregation until all chromosomes are properly attached to the spindle.
What genes are involved in the mitotic checkpoint complex?
Core genes include MAD2, BUBR1, BUB3 and CDC20 in mammals, and their orthologs Mad2p, Mad3p, Bub3p and Cdc20p in budding yeast.
What is the function of GO:0033597?
GO:0033597 describes the cellular component known as the mitotic checkpoint complex, which functions as a mitotic checkpoint inhibitor of APC/C.
How is the mitotic checkpoint complex assembled?
Assembly is triggered at unattached kinetochores and involves a conformational change in MAD2 that allows it to bind CDC20, with CDC20 assisting its own incorporation.
What happens when the mitotic checkpoint complex is defective?
Defects lead to premature anaphase, aneuploidy and chromosomal instability, which are associated with cancer and developmental disorders.
Which diseases are linked to the mitotic checkpoint complex?
Mutations in MCC components are linked to familial cancer syndromes, mosaic variegated aneuploidy and glioma.
How can I study the mitotic checkpoint complex in the lab?
Common methods include live-cell imaging of tagged proteins, co-immunoprecipitation, mass spectrometry, cryo-EM and CRISPR-based knockout screens.
What CRISPR models are available for MCC research?
Knockout, point mutation, knock-in and overexpression models can be generated for MCC genes to study their roles in checkpoint control and disease.
Is the mitotic checkpoint complex conserved across species?
Yes, the MCC is conserved from yeast to humans, with analogous components performing similar functions.
What is the relationship between the MCC and APC/C?
The MCC binds and inhibits APC/C, preventing the ubiquitination and degradation of securin and cyclin B, thereby delaying anaphase.
Conclusion
The mitotic checkpoint complex (GO:0033597) is a critical regulator of chromosome segregation, ensuring genomic stability by inhibiting APC/C until all chromosomes are properly attached. Its dysfunction is implicated in aneuploidy and cancer, making it a focal point for both basic and translational research. Advanced CRISPR models and integrated methodologies will continue to unravel the complexities of MCC assembly and regulation.
References
- 1. Chuah YH et al.. 2023. CAMK2D serves as a molecular scaffold for RNF8-MAD2 complex to induce mitotic checkpoint in glioma.. Cell Death Differ 30(8):1973-1987 PMID: 37468549
- 2. Villarroya-Beltri C et al.. 2022. Mitotic Checkpoint Imbalances in Familial Cancer.. Cancer Res 82(19):3432-3434 PMID: 36193651
- 3. McAinsh AD et al.. 2023. Principles and dynamics of spindle assembly checkpoint signalling.. Nat Rev Mol Cell Biol 24(8):543-559 PMID: 36964313
- 4. Caydasi AK et al.. 2023. SWR1 chromatin remodeling complex prevents mitotic slippage during spindle position checkpoint arrest.. Mol Biol Cell 34(2):ar11 PMID: 36542480
- 5. Sitry-Shevah D et al.. 2024. The Mitotic Checkpoint Complex controls the association of Cdc20 regulatory protein with the ubiquitin ligase APC/C in mitosis.. Proc Natl Acad Sci U S A 121(37):e2413089121 PMID: 39231204
- 6. Sethi S et al.. 2025. Interplay of kinetochores and catalysts drives rapid assembly of the mitotic checkpoint complex.. Nat Commun 16(1):4823 PMID: 40410156
- 7. Piano V et al.. 2021. CDC20 assists its catalytic incorporation in the mitotic checkpoint complex.. Science 371(6524):67-71 PMID: 33384373
- 8. Nagaoka SI et al.. 2012. Human aneuploidy: mechanisms and new insights into an age-old problem.. Nat Rev Genet 13(7):493-504 PMID: 22705668
