GO:0170027 SKA complex: Components, Assembly and Research Methods, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0170027 defines the SKA complex, an outer kinetochore assembly containing SKA1, SKA2 and SKA3 that attaches microtubule ends to chromosomes during mitosis.
• The SKA complex interacts with the Ndc80 complex to form a load-bearing kinetochore-microtubule attachment that resists tension.
• SKA complex recruitment to kinetochores is regulated by phosphorylation and phosphatases, including PP2A and PP1.
• The SKA complex promotes Aurora B activity to ensure chromosome biorientation and timely metaphase-anaphase transition.
• Overexpression of SKA complex subunits is associated with poor prognosis in gliomas, linking the complex to cancer biology.
• SKA complex components are conserved in metazoans and are required for meiotic maturation in mouse oocytes.
Description
The SKA complex (GO:0170027) is a conserved outer kinetochore assembly that mediates the attachment of spindle microtubule ends to chromosomes during mitosis. It is composed of three subunits in humans: SKA1, SKA2 and SKA3. The complex is essential for chromosome segregation, as it couples dynamic microtubule plus-ends to the kinetochore and ensures proper force transmission. Researchers study the SKA complex to understand the molecular basis of chromosome biorientation, the spindle assembly checkpoint, and how errors in these processes contribute to aneuploidy and cancer. The SKA complex also functions in meiosis, as shown by its localization and requirement during mouse oocyte maturation. Its recruitment and activity are tightly regulated by kinases and phosphatases, making it a hub for cell cycle control.
SKA complex At A Glance
| GO ID | GO:0170027 |
|---|---|
| GO term | SKA complex |
| Ontology | cellular_component |
| Synonym | SKA1 complex |
| Definition | An outer kinetochore complex involved in the attachment of microtubule ends to the chromosomes during mitosis. In humans, it contains the subunits SKA1, SKA2 and SKA3. |
| Major function | Attachment of microtubule ends to chromosomes during mitosis; load-bearing kinetochore-microtubule coupling. |
| Subunits | SKA1, SKA2, SKA3. |
| Conservation | Present in metazoans; studied in human cells, mouse oocytes and C. elegans. |
| Regulation | Recruitment and activity regulated by Aurora B, PP2A and PP1. |
What Is GO:0170027?
According to the Gene Ontology, GO:0170027 (SKA complex) is an outer kinetochore complex involved in the attachment of microtubule ends to the chromosomes during mitosis. In humans, it contains the subunits SKA1, SKA2 and SKA3. The synonym SKA1 complex is also used. This definition places the SKA complex at the kinetochore-microtubule interface, where it contributes to the mechanical coupling required for chromosome movement.
Why Is SKA complex Important in Cell Biology?
The SKA complex is important because it provides the essential mechanical link between spindle microtubules and kinetochores, enabling accurate chromosome segregation. Without proper SKA function, cells fail to biorient chromosomes, leading to mitotic delays, aneuploidy and potential cell death. Its role in recruiting protein phosphatase 1 to kinetochores further connects it to the metaphase-anaphase transition and checkpoint silencing. Clinically, SKA complex overexpression is associated with poor prognosis in gliomas, highlighting its relevance to cancer. Thus, the SKA complex is a key node for understanding both basic chromosome segregation and disease-associated mitotic defects.
• Essential for chromosome biorientation and accurate mitosis.
• Forms a load-bearing assembly with the Ndc80 complex to strengthen kinetochore-microtubule attachments.
• Recruits protein phosphatase 1 to kinetochores to drive the metaphase-anaphase transition.
• Promotes Aurora B activity to ensure error correction and biorientation.
• Regulated by centrosomal PP2A in C. elegans, linking centrosome signaling to kinetochore recruitment.
• Required for mouse oocyte meiotic maturation, indicating roles beyond mitosis.
• Overexpression is associated with poor prognosis in gliomas.
• Serves as a target for studying aneuploidy and chromosomal instability in cancer.
• Provides a model for phosphatase-regulated kinetochore assembly.
• Conserved subunits make it tractable for genetic studies across model organisms.
SKA complex: Biological Process, Structure and Molecular Mechanism
Kinetochore recruitment and assembly
In simple terms: The SKA complex is delivered to the kinetochore at the right time in mitosis.
The SKA complex localizes to outer kinetochores during mitosis and is recruited in a phosphorylation-dependent manner. Phosphatase-regulated recruitment has been demonstrated, with PP2A and PP1 controlling the timing and stability of SKA at kinetochores. In C. elegans, centrosomal PP2A regulates kinetochore recruitment of the Ska complex, showing conservation of regulatory logic. This recruitment is essential for the complex to engage microtubules and perform its functions.
Load-bearing attachment to microtubules
In simple terms: The SKA complex grips microtubule ends and connects them to chromosomes so they can be pulled apart.
The human Ska complex interacts directly with the Ndc80 complex to form a load-bearing assembly that strengthens kinetochore-microtubule attachments. This interaction allows the kinetochore to withstand the forces generated by spindle microtubules during chromosome alignment and segregation. The SKA complex is therefore a core component of the outer kinetochore mechanical interface.
Chromosome biorientation and Aurora B
In simple terms: The SKA complex helps ensure that each chromosome is attached correctly before separation.
The Ska complex promotes Aurora B activity to ensure chromosome biorientation. Aurora B is a key kinase that corrects erroneous kinetochore-microtubule attachments, and SKA-dependent regulation of Aurora B is required for timely biorientation. Loss of SKA function leads to biorientation defects and mitotic progression delays.
Metaphase-anaphase transition and PP1 recruitment
In simple terms: The SKA complex helps trigger the switch from alignment to separation by bringing a phosphatase to kinetochores.
The human SKA complex drives the metaphase-anaphase cell cycle transition by recruiting protein phosphatase 1 to kinetochores. This recruitment is required for checkpoint silencing and timely anaphase onset. Thus, the SKA complex couples mechanical attachment to cell cycle progression.
Meiotic roles
In simple terms: The SKA complex also works during the special cell division that makes eggs.
Localization and function of the Ska complex during mouse oocyte meiotic maturation have been demonstrated, indicating roles in meiosis in addition to mitosis. This expands the biological importance of the complex beyond mitotic cells.
Key Genes Involved in GO:0170027 SKA complex
The SKA complex is composed of three core subunits, SKA1, SKA2 and SKA3, which are the primary genes studied in this context.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SKA1 | Core subunit of the SKA complex; required for kinetochore-microtubule attachment | Knockout causes mitotic defects; overexpression linked to glioma prognosis |
| SKA2 | Core subunit of the SKA complex; interacts with SKA1 and SKA3 | Essential for complex assembly and load-bearing function |
| SKA3 | Core subunit of the SKA complex; required for recruitment and stability | Target for studying kinetochore recruitment and cancer |
| NDC80 | Interacts with SKA complex to form load-bearing attachment | Studied for kinetochore-microtubule coupling |
| NUF2 | Component of Ndc80 complex; interacts with SKA | Model for outer kinetochore assembly |
| SPC24 | Component of Ndc80 complex; interacts with SKA | Model for outer kinetochore assembly |
| SPC25 | Component of Ndc80 complex; interacts with SKA | Model for outer kinetochore assembly |
| AURKB | Kinase promoted by SKA complex for biorientation | Target for studying error correction |
| PPP1CA | Phosphatase recruited by SKA complex to kinetochores | Model for metaphase-anaphase transition |
| PPP2CA | Phosphatase regulating SKA recruitment | Model for phosphatase-regulated recruitment |
| BUB1 | Spindle checkpoint kinase; functional interplay with SKA | Studied in checkpoint signaling |
| PLK1 | Mitotic kinase; regulates kinetochore assembly including SKA | Target for mitotic regulation studies |
| CDK1 | Cyclin-dependent kinase; controls mitotic progression | Model for cell cycle regulation |
| MAD1L1 | Spindle assembly checkpoint component | Studied with SKA in checkpoint control |
| MAD2L1 | Spindle assembly checkpoint component | Studied with SKA in checkpoint control |
| BUB3 | Spindle checkpoint component | Studied with SKA in checkpoint control |
| CDC20 | Activator of anaphase-promoting complex | Model for metaphase-anaphase transition |
| KNL1 | Outer kinetochore scaffold | Studied for kinetochore assembly |
How Is SKA complex Regulated?
SKA complex function is regulated by phosphorylation and dephosphorylation events. Phosphatase-regulated recruitment of the Ska complex to kinetochores has been demonstrated, with PP2A and PP1 controlling its localization and activity. In C. elegans, centrosomal PP2A regulates kinetochore recruitment of the Ska complex, indicating a conserved role for phosphatases in this process. Aurora B activity is promoted by the Ska complex, creating a feedback loop that ensures biorientation. Additionally, the human SKA complex recruits protein phosphatase 1 to kinetochores to drive the metaphase-anaphase transition. These regulatory mechanisms ensure that SKA complex function is tightly coupled to the cell cycle and to the mechanical state of kinetochore-microtubule attachments.
SKA complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SKA1 | Glioma prognosis; chromosomal instability | Overexpression in glioma cell lines; knockout in cancer cells |
| SKA2 | Mitotic defects; potential cancer relevance | Knockout in HeLa or RPE1 cells |
| SKA3 | Glioma prognosis; kinetochore dysfunction | Knockout and rescue in cancer cell lines |
| AURKB | Biorientation defects; cancer | Point mutation of Aurora B in SKA-dependent assays |
| PPP1CA | Metaphase-anaphase transition defects | Knockout or point mutation in human cells |
SKA complex in cancer
Overexpression of SKA complex subunits is associated with poor prognosis in gliomas. This suggests that dysregulated SKA function may contribute to chromosomal instability and tumor progression. Because the SKA complex is essential for accurate chromosome segregation, its overexpression could promote aneuploidy, a hallmark of cancer.
SKA complex and aneuploidy
Defects in SKA complex function lead to chromosome biorientation errors and mitotic delays, which can result in aneuploidy. Aneuploidy is a common feature of many cancers and developmental disorders. Studying SKA complex regulation provides insight into how aneuploidy arises.
SKA complex in meiosis and reproductive biology
The Ska complex localizes and functions during mouse oocyte meiotic maturation, suggesting that its dysfunction could affect fertility. Meiotic errors are a major cause of miscarriage and developmental disorders. Thus, SKA complex components are relevant to reproductive biology.
From SKA complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the role of SKA1 in mitosis? | SKA1 knockout cell line (e.g., HeLa) |
| How does SKA2 phosphorylation affect kinetochore recruitment? | Point mutation of SKA2 at phosphosites |
| Does SKA3 overexpression promote aneuploidy? | SKA3 overexpression in cancer cells |
| How does SKA complex interact with Ndc80? | Knock-in of tagged SKA1 for proteomics |
| What is the meiotic function of SKA? | Mouse oocyte knockout or knockdown |
| How is SKA recruitment regulated by PP2A? | C. elegans mutants or human cell PP2A knockout |
How to Study the SKA complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Live-cell imaging | Kinetochore recruitment and chromosome segregation dynamics | Tracking SKA-GFP in mitotic cells |
| Immunofluorescence | SKA localization at kinetochores | Assessing recruitment defects |
| Mass spectrometry | Protein interactions of SKA complex | Identifying Ndc80 complex binding |
| CRISPR knockout | Requirement for SKA subunits | Mitotic progression assays |
| Phosphoproteomics | Phosphorylation sites on SKA subunits | Mapping regulatory sites |
| In vitro reconstitution | Load-bearing capacity of kinetochore complexes | Measuring mechanical strength |
| Mouse oocyte maturation assay | Meiotic function of SKA | Studying meiosis-specific roles |
| C. elegans genetics | Conservation of SKA regulation | Testing PP2A-dependent recruitment |
Imaging-based assays
Live-cell imaging of fluorescently tagged SKA subunits and kinetochore markers allows tracking of recruitment dynamics and chromosome segregation errors. Immunofluorescence can quantify SKA localization at kinetochores and its dependence on regulators.
Proteomics and interaction studies
Affinity purification coupled to mass spectrometry can identify SKA complex interactors, such as Ndc80 complex components. Phosphoproteomics can reveal regulatory phosphorylation sites on SKA subunits.
Genetic perturbation
RNAi, CRISPR knockout and rescue experiments are used to test the requirement for SKA subunits in mitosis and meiosis. Point mutations can dissect phospho-regulation.
Biochemical reconstitution
In vitro reconstitution of kinetochore complexes can measure load-bearing capacity and microtubule binding. Such assays help define the mechanical role of the SKA complex.
How CRISPR Can Be Used to Study GO:0170027 SKA complex
Knockout
CRISPR knockout of SKA1, SKA2 or SKA3 in human cell lines can abolish SKA complex function, leading to chromosome biorientation defects and mitotic delays. Such models are useful for testing rescue constructs and for identifying synthetic lethal interactions.
Point Mutation
Point mutations can be introduced into SKA subunits to test the role of specific phosphorylation sites in kinetochore recruitment and function. For example, phospho-deficient or phospho-mimetic mutants can reveal how phosphatases regulate SKA localization.
Knock-in
Knock-in of epitope tags or fluorescent proteins at endogenous SKA loci allows real-time imaging and proteomic analysis of the complex. Tagged knock-in models preserve endogenous regulation and can be used to study dynamic interactions.
Overexpression
Overexpression of SKA subunits, particularly SKA1 and SKA3, has been linked to poor prognosis in gliomas. Overexpression models can be used to study how excess SKA complex contributes to aneuploidy and cancer progression.
How EDITGENE Supports SKA complex Research
Researchers studying SKA complex-related genes often need to determine whether a candidate gene is causally involved in kinetochore function, chromosome segregation or cancer progression. EDITGENE provides a comprehensive suite of CRISPR-based services to enable such studies with precision and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for SKA complex research.
Frequently Asked Questions About SKA complex
What is the SKA complex?
The SKA complex is an outer kinetochore complex that attaches microtubule ends to chromosomes during mitosis, composed of SKA1, SKA2 and SKA3.
What genes are involved in the SKA complex?
The core genes are SKA1, SKA2 and SKA3, which encode the three subunits of the complex.
What is the function of GO:0170027?
GO:0170027 describes the SKA complex, which functions in kinetochore-microtubule attachment and chromosome segregation.
How is the SKA complex regulated?
It is regulated by phosphorylation and phosphatases such as PP2A and PP1, which control its recruitment and activity.
What diseases are associated with SKA complex?
Overexpression of SKA complex subunits is associated with poor prognosis in gliomas, and defects can lead to aneuploidy.
What is the role of SKA1 in mitosis?
SKA1 is a core subunit required for kinetochore-microtubule attachment and chromosome biorientation.
How does the SKA complex interact with Ndc80?
The SKA complex binds the Ndc80 complex to form a load-bearing assembly that strengthens kinetochore-microtubule attachments.
Is the SKA complex involved in meiosis?
Yes, the Ska complex localizes and functions during mouse oocyte meiotic maturation.
What research methods are used to study the SKA complex?
Common methods include live-cell imaging, immunofluorescence, proteomics, CRISPR knockout and in vitro reconstitution.
What model systems are available for SKA complex research?
Human cell lines, mouse oocytes and C. elegans are established models for studying SKA complex function.
Conclusion
The SKA complex (GO:0170027) is a critical outer kinetochore assembly that ensures accurate chromosome segregation by linking microtubules to chromosomes and regulating key mitotic transitions. Its subunits SKA1, SKA2 and SKA3 are conserved and tightly regulated by kinases and phosphatases. Dysregulation of the SKA complex is linked to cancer and aneuploidy, making it a compelling target for both basic and translational research. Continued investigation using CRISPR models and advanced imaging will further illuminate its mechanistic roles and therapeutic potential.
References
- 1. Yu S. 2021. Overexpression of SKA Complex Is Associated With Poor Prognosis in Gliomas.. Front Neurol 12:755681 PMID: 35095717
- 2. Helgeson LA et al.. 2018. Human Ska complex and Ndc80 complex interact to form a load-bearing assembly that strengthens kinetochore-microtubule attachments.. Proc Natl Acad Sci U S A 115(11):2740-2745 PMID: 29487209
- 3. Zhang Q et al.. 2018. Multitasking Ska in Chromosome Segregation: Its Distinct Pools Might Specify Various Functions.. Bioessays 40(3) PMID: 29359816
- 4. Zhang QH et al.. 2012. Localization and function of the Ska complex during mouse oocyte meiotic maturation.. Cell Cycle 11(5):909-16 PMID: 22336914
- 5. Redli PM et al.. 2016. The Ska complex promotes Aurora B activity to ensure chromosome biorientation.. J Cell Biol 215(1):77-93 PMID: 27697923
- 6. Sivakumar S et al.. 2017. Phosphatase-regulated recruitment of the spindle- and kinetochore-associated (Ska) complex to kinetochores.. Biol Open 6(11):1672-1679 PMID: 28982702
- 7. Lange KI et al.. 2019. Kinetochore Recruitment of the Spindle and Kinetochore-Associated (Ska) Complex Is Regulated by Centrosomal PP2A in Caenorhabditis elegans.. Genetics 212(2):509-522 PMID: 31018924
- 8. Sivakumar S et al.. 2016. The human SKA complex drives the metaphase-anaphase cell cycle transition by recruiting protein phosphatase 1 to kinetochores.. Elife 5 PMID: 26981768
