GO:0140499 negative regulation of mitotic spindle assembly checkpoint signaling: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0140499 describes any process that stops, prevents, or reduces the frequency, rate or extent of negative regulation of mitotic spindle assembly checkpoint signaling.
• The mitotic spindle assembly checkpoint (SAC) ensures accurate chromosome segregation by delaying anaphase until all chromosomes are properly attached to the spindle [1,8].
• Negative regulators of SAC signaling include proteins such as Smurf2, GSK3, HORMAD1, PKMYT1, and importin beta, which modulate checkpoint strength and timing [1,2,3,5,7].
• Dysregulation of SAC negative regulation contributes to chromosomal instability, tumorigenesis, and sensitivity to mitotic kinase inhibitors [1,3,7].
• Key experimental approaches to study this process include live-cell imaging, RNA interference, CRISPR knockout, and phospho-proteomics [2,3,7].
• Understanding GO:0140499 is critical for developing cancer therapeutics that target mitotic checkpoints and for interpreting resistance mechanisms [1,3,4].
Description
The mitotic spindle assembly checkpoint (SAC) is a surveillance mechanism that ensures chromosomes are correctly attached to the mitotic spindle before anaphase onset [1,8]. Negative regulation of SAC signaling, captured by the Gene Ontology term GO:0140499, refers to processes that attenuate or terminate checkpoint activity, allowing timely mitotic progression. This regulation is essential for maintaining genomic stability, as excessive or prolonged checkpoint activation can lead to mitotic slippage, aneuploidy, or cell death [1,4]. Researchers study GO:0140499 to understand how cells balance fidelity and speed during mitosis, and how perturbations contribute to diseases such as cancer [1,3]. Key negative regulators include E3 ubiquitin ligases like Smurf2, kinases such as GSK3 and PKMYT1, and nuclear transport factors like importin beta [1,2,5,7]. These proteins modulate checkpoint protein stability, localization, and activity, thereby influencing cell fate [1,2,5]. This article synthesizes current knowledge on the mechanisms, genes, and experimental models relevant to GO:0140499, providing a resource for biomedical researchers.
negative regulation of mitotic spindle assembly checkpoint signaling At A Glance
| GO ID | GO:0140499 |
|---|---|
| GO term | negative regulation of mitotic spindle assembly checkpoint signaling |
| Ontology | biological_process |
| Synonym | none |
| Major function | Attenuation or termination of the mitotic spindle assembly checkpoint to allow mitotic progression |
| Key regulators | Smurf2, GSK3, HORMAD1, PKMYT1, importin beta, APC/C |
| Associated diseases | Cancer, chromosomal instability, tumorigenesis |
| Research methods | CRISPR knockout, RNAi, live-cell imaging, phospho-proteomics |
What Is GO:0140499?
GO:0140499 is defined as any process that stops, prevents, or reduces the frequency, rate or extent of negative regulation of mitotic spindle assembly checkpoint signaling. In simpler terms, it encompasses the molecular events that dampen the SAC, ensuring that the checkpoint is silenced once chromosomes are properly aligned, thereby permitting anaphase onset and mitotic exit [1,8].
Why Is negative regulation of mitotic spindle assembly checkpoint signaling Important in Cell Biology?
GO:0140499 is crucial because the precise timing of SAC silencing determines whether cells divide accurately or become aneuploid. Negative regulation of SAC signaling ensures that the checkpoint is not overly active, which could cause mitotic arrest and cell death, or too weak, leading to chromosomal missegregation [1,4]. Understanding this process provides insights into cancer biology, as many tumors exhibit altered SAC regulation and sensitivity to mitotic inhibitors [1,3,7].
• Prevents prolonged mitotic arrest that could trigger apoptosis or senescence [1,4].
• Ensures timely anaphase onset and faithful chromosome segregation [1,8].
• Dysregulation leads to chromosomal instability, a hallmark of cancer [1,3].
• Modulates sensitivity to mitotic kinase inhibitors like PKMYT1 inhibitors [3,7].
• Involved in tissue-specific tumorigenesis, e.g., HORMAD1 expression in cancers.
• Provides targets for cancer therapy, such as GSK3 and Smurf2 [1,2].
• Impacts cell cycle checkpoints and DNA damage responses [4,6].
• Relevant to understanding aneuploidy and tumor evolution [1,3].
• Guides development of CRISPR-based models for drug discovery [2,3,7].
• Links mitotic regulation to endocytic and signaling pathways.
What Happens During negative regulation of mitotic spindle assembly checkpoint signaling?
Initiation of SAC Silencing
In simple terms: Once chromosomes are properly attached, the checkpoint needs to be turned off.
SAC silencing begins when all kinetochores achieve proper microtubule attachment, leading to the removal of checkpoint proteins from kinetochores [1,8]. This process is actively promoted by negative regulators that counteract SAC components, such as Mad2 and BubR1. For example, Smurf2, an E3 ubiquitin ligase, targets SAC proteins for degradation, thereby reducing checkpoint signaling.
Ubiquitin-Mediated Degradation of SAC Components
In simple terms: Tagging checkpoint proteins for destruction helps shut down the checkpoint.
Smurf2 ubiquitinates and promotes the degradation of SAC proteins, including Mad2, contributing to checkpoint inactivation. Similarly, the anaphase-promoting complex/cyclosome (APC/C) targets securin and cyclin B for degradation, but its role in SAC negative regulation is indirect. GSK3 also modulates SAC protein stability, as its inhibition affects checkpoint response.
Phosphorylation-Dependent Regulation
In simple terms: Adding phosphate groups can weaken checkpoint signals.
GSK3 phosphorylates components of the SAC, influencing checkpoint strength and duration. PKMYT1, a kinase involved in mitotic timing, also affects chromosome segregation fidelity, and its loss perturbs SAC negative regulation. HORMAD1 expression perturbs mitotic arrest, suggesting it modulates SAC signaling through phosphorylation or protein interactions.
Nuclear Transport and Localization
In simple terms: Moving proteins in and out of the nucleus can control the checkpoint.
Importin beta regulates the nuclear localization of SAC proteins, and its dysfunction affects checkpoint silencing. Negative regulation of endocytic adaptor Dab2 in mitosis also impacts SAC signaling, linking membrane trafficking to checkpoint control.
Temporal Control and G1 Arrest
In simple terms: The time taken to silence the checkpoint can signal danger.
Prolonged SAC activation can lead to G1 arrest after mitosis, acting as a danger signal. Negative regulation ensures that SAC is silenced within a physiological timeframe, preventing unnecessary G1 arrest and promoting cell cycle progression.
Key Genes Involved in GO:0140499 negative regulation of mitotic spindle assembly checkpoint signaling
The following genes and proteins are key players in the negative regulation of mitotic spindle assembly checkpoint signaling, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SMURF2 | E3 ubiquitin ligase that targets SAC proteins for degradation | Regulates SAC strength and tumorigenesis |
| GSK3A/GSK3B | Kinase that phosphorylates SAC components | Modulates checkpoint response and mitotic timing |
| HORMAD1 | Meiosis-specific protein aberrantly expressed in tumors | Perturbs mitotic arrest and sensitizes to mitotic inhibitors |
| PKMYT1 | Kinase that regulates CDK1 activity and mitotic timing | Important for chromosome segregation fidelity |
| KPNB1 (Importin beta) | Nuclear transport receptor | Regulates SAC protein localization |
| DAB2 | Endocytic adaptor | Negatively regulated in mitosis, affects SAC |
| APC/C | E3 ubiquitin ligase complex | Controls mitotic transitions and SAC silencing |
| MAD2 | SAC component | Target of negative regulation |
| BUBR1 | SAC component | Modulated by negative regulators |
| CDC20 | APC/C coactivator | Involved in SAC silencing |
| CDK1 | Mitotic kinase | Regulated by PKMYT1 and GSK3 [2,7] |
| CCNB1 | Cyclin B | Degraded by APC/C to exit mitosis |
| PTTG1 | Securin | Degraded by APC/C |
| PLK1 | Polo-like kinase | Regulates SAC and mitotic progression |
| AURKA | Aurora kinase A | Involved in spindle assembly and SAC |
| AURKB | Aurora kinase B | Regulates chromosome segregation and SAC |
| MAD1 | SAC component | Part of checkpoint complex |
How Is negative regulation of mitotic spindle assembly checkpoint signaling Regulated?
The negative regulation of SAC signaling is itself regulated by various upstream pathways. For instance, GSK3 activity is modulated by cellular signals, and its inhibition alters SAC response. HORMAD1 expression is tumor-specific and perturbs mitotic arrest, indicating that its regulation is context-dependent. Additionally, importin beta levels and localization affect SAC protein transport. The APC/C, activated by CDC20, is a key regulator of mitotic exit and indirectly influences SAC silencing. Temporal control mechanisms, such as those involving PKMYT1, ensure that SAC is silenced at the right time.
negative regulation of mitotic spindle assembly checkpoint signaling and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SMURF2 | Cancer, chromosomal instability | CRISPR knockout in cancer cell lines |
| HORMAD1 | Tumorigenesis, mitotic inhibitor sensitivity | Overexpression in cancer cells |
| PKMYT1 | Cancer, chromosome segregation errors | Point mutation knock-in in cell lines |
| GSK3B | Cancer, mitotic checkpoint defects | Knockout or inhibitor treatment |
| KPNB1 | Nuclear transport disorders, cancer | Knockdown or knockout |
Cancer and Chromosomal Instability
Dysregulation of SAC negative regulation leads to chromosomal instability (CIN), a hallmark of cancer. Smurf2 downregulation or loss of function results in SAC hyperactivation or impaired silencing, contributing to tumorigenesis. HORMAD1 expression in tumors perturbs mitotic arrest and drives sensitivity to mitotic kinase inhibitors, suggesting its role as a therapeutic target. PKMYT1 is also implicated in cancer, as its inhibition affects chromosome segregation and may synergize with other mitotic drugs.
Therapeutic Targeting of Mitotic Checkpoints
Inhibitors of mitotic kinases, such as PKMYT1 and GSK3, are being explored as cancer therapeutics [2,7]. Understanding negative regulation of SAC signaling helps predict resistance and identify biomarkers. For example, HORMAD1 expression may serve as a biomarker for sensitivity to mitotic kinase inhibitors.
Other Proliferative Disorders
Altered SAC negative regulation may contribute to other diseases characterized by abnormal cell proliferation, such as certain developmental disorders, though direct evidence is limited. The role of importin beta in nuclear transport and SAC regulation suggests potential links to diseases with nuclear envelope defects.
From negative regulation of mitotic spindle assembly checkpoint signaling-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does Smurf2 regulate SAC protein stability? | SMURF2 knockout cell line |
| How does GSK3 inhibition affect SAC? | GSK3 point mutation or knockout |
| Does HORMAD1 expression perturb mitotic arrest? | HORMAD1 overexpression |
| What is the role of PKMYT1 in chromosome segregation? | PKMYT1 knockout or point mutation |
| How does importin beta regulate SAC protein localization? | KPNB1 knockdown or knockout |
| Does Dab2 negative regulation affect SAC? | DAB2 knockout or tagged knock-in |
How to Study the negative regulation of mitotic spindle assembly checkpoint signaling Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging | Dynamics of SAC proteins and mitotic timing | Assessing checkpoint silencing [1,4] |
| CRISPR knockout | Loss-of-function effects on SAC | Identifying negative regulators [2,7] |
| Phospho-proteomics | Phosphorylation of SAC components | Mapping kinase substrates [2,7] |
| RNAi knockdown | Gene silencing effects | Validating candidate genes [1,3] |
| Overexpression | Gain-of-function effects | Studying HORMAD1 |
| Flow cytometry | Cell cycle profiles | Measuring mitotic arrest |
| Immunofluorescence | Kinetochore localization of SAC proteins | Visualizing checkpoint components [1,5] |
| Western blot | Protein stability and degradation | Assessing ubiquitination |
Live-Cell Imaging
Live-cell imaging of fluorescently tagged SAC proteins (e.g., Mad2, BubR1) allows real-time monitoring of checkpoint dynamics and silencing [1,3]. This method is essential for assessing the timing and extent of negative regulation.
CRISPR-Based Genetic Screens
Genome-wide CRISPR knockout screens can identify novel negative regulators of SAC signaling [2,7]. For example, screens in cancer cell lines treated with mitotic inhibitors can reveal genes whose loss alters checkpoint response.
Phospho-Proteomics
Mass spectrometry-based phospho-proteomics identifies phosphorylation events on SAC components mediated by kinases like GSK3 and PKMYT1 [2,7]. This helps map signaling pathways that negatively regulate the checkpoint.
RNA Interference and Overexpression
RNAi knockdown or overexpression of candidate genes (e.g., SMURF2, HORMAD1) followed by mitotic assays (e.g., mitotic index, chromosome segregation) can validate their roles in SAC negative regulation [1,3].
How CRISPR Can Be Used to Study GO:0140499 negative regulation of mitotic spindle assembly checkpoint signaling
Knockout
CRISPR knockout of negative regulators such as SMURF2 or GSK3 can reveal their essential roles in SAC silencing and mitotic progression [1,2]. Knockout cell lines are valuable for drug sensitivity studies.
Point Mutation
Introducing point mutations in kinase domains (e.g., GSK3, PKMYT1) can dissect phosphorylation-dependent regulation of SAC [2,7]. This allows precise interrogation of specific residues.
Knock-in
Knock-in of tagged versions (e.g., GFP, HA) of SAC proteins enables live-cell imaging and proteomic analysis [1,5]. Tagged knock-ins preserve endogenous regulation.
Overexpression
Overexpression of HORMAD1 or other negative regulators can mimic tumor-specific expression and assess effects on mitotic arrest and drug sensitivity. This is useful for modeling cancer phenotypes.
How EDITGENE Supports negative regulation of mitotic spindle assembly checkpoint signaling Research
Researchers studying negative regulation of mitotic spindle assembly checkpoint signaling-related genes often need to determine whether a candidate gene is causally involved in checkpoint control, and how its perturbation affects mitotic fidelity and drug response. EDITGENE provides comprehensive CRISPR-based services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for negative regulation of mitotic spindle assembly checkpoint signaling research.
Frequently Asked Questions About negative regulation of mitotic spindle assembly checkpoint signaling
What is GO:0140499?
GO:0140499 is a Gene Ontology term for negative regulation of mitotic spindle assembly checkpoint signaling, describing processes that attenuate or terminate the SAC to allow mitotic progression.
What genes are involved in negative regulation of the spindle assembly checkpoint?
Key genes include SMURF2, GSK3A/B, HORMAD1, PKMYT1, KPNB1, and DAB2, among others [1,2,3,5,6,7].
How does Smurf2 regulate the spindle assembly checkpoint?
Smurf2 is an E3 ubiquitin ligase that targets SAC proteins like Mad2 for degradation, thereby reducing checkpoint signaling.
What is the role of GSK3 in the mitotic checkpoint?
GSK3 phosphorylates SAC components and modulates checkpoint strength and duration.
How does HORMAD1 affect mitotic arrest?
HORMAD1 expression perturbs mitotic arrest and drives sensitivity to mitotic kinase inhibitors, likely by interfering with SAC signaling.
What experimental models are used to study SAC negative regulation?
Common models include CRISPR knockout cell lines, point mutation knock-ins, overexpression systems, and live-cell imaging [1,2,3,7].
Why is negative regulation of the SAC important in cancer?
Dysregulation leads to chromosomal instability and tumorigenesis, and affects sensitivity to mitotic inhibitors [1,3,7].
What methods can identify new SAC negative regulators?
Genome-wide CRISPR screens, phospho-proteomics, and RNAi are effective approaches [2,3,7].
How does PKMYT1 influence chromosome segregation?
PKMYT1 regulates CDK1 activity and mitotic timing, and its loss affects chromosome segregation fidelity.
Can EDITGENE help create custom CRISPR models for SAC research?
Yes, EDITGENE offers knockout, point mutation, knock-in, overexpression, and library screening services tailored to SAC research [1,2,3,7].
Conclusion
GO:0140499, negative regulation of mitotic spindle assembly checkpoint signaling, is a critical process that ensures timely mitotic progression and genomic stability. Key regulators such as Smurf2, GSK3, HORMAD1, and PKMYT1 modulate checkpoint strength and are implicated in cancer and chromosomal instability [1,2,3,7]. Understanding these mechanisms offers opportunities for therapeutic intervention and biomarker discovery. Advanced CRISPR models and screening technologies from EDITGENE can accelerate research in this field, enabling precise dissection of SAC negative regulation and its role in disease.
References
- 1. Osmundson EC et al.. 2009. Smurf2 as a novel mitotic regulator: From the spindle assembly checkpoint to tumorigenesis.. Cell Div 4:14 PMID: 19583833
- 2. Rashid MS et al.. 2018. Analysis of the role of GSK3 in the mitotic checkpoint.. Sci Rep 8(1):14259 PMID: 30250048
- 3. Walker C et al.. 2026. Tumour specific HORMAD1 expression perturbs mitotic arrest and drives sensitivity to mitotic kinase inhibitors.. Nat Commun 17(1) PMID: 41813673
- 4. Fulcher LJ et al.. 2026. Time as a danger signal promoting G1 arrest after mitosis.. Trends Cell Biol 36(2):142-153 PMID: 40628545
- 5. Harel A et al.. 2004. Importin beta: conducting a much larger cellular symphony.. Mol Cell 16(3):319-30 PMID: 15525506
- 6. Chetrit D et al.. 2011. Negative regulation of the endocytic adaptor disabled-2 (Dab2) in mitosis.. J Biol Chem 286(7):5392-403 PMID: 21097498
- 7. Belbelazi A et al.. 2026. PKMYT1 has an important role in the timing and fidelity of chromosome segregation.. EMBO Rep 27(13):3564-3584 PMID: 42243523
- 8. Fang G et al.. 1999. Control of mitotic transitions by the anaphase-promoting complex.. Philos Trans R Soc Lond B Biol Sci 354(1389):1583-90 PMID: 10582244
