GO:0005958 DNA-dependent protein kinase-DNA ligase 4 complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0005958 describes the DNA-dependent protein kinase-DNA ligase 4 complex, a large cellular component required for repair of DNA double-strand breaks and, in mammals, V(D)J recombination.
• The complex contains the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), the DNA end-binding heterodimer Ku70/Ku80, XRCC4 or a homolog, and DNA ligase IV.
• DNA-PKcs phosphorylates DNA ligase IV and regulates its stability, linking kinase activity to ligation capacity.
• DNA-PK and XRCC4-DNA ligase IV are mobilized in cells after DNA double-strand breaks, supporting dynamic assembly at damage sites.
• DNA-PK-dependent phosphorylation of Ku70/80 is not required for non-homologous end joining, indicating that not every phosphorylation event in the complex is essential for repair.
• The complex is relevant to cancer biology, hypoxia adaptation, viral replication, and chromosome end protection.
Description
The DNA-dependent protein kinase-DNA ligase 4 complex (GO:0005958) is a large protein assembly that carries out repair of DNA double-strand breaks and, in mammals, V(D)J recombination. It is defined as a cellular component containing the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), the DNA end-binding heterodimer Ku, the nuclear phosphoprotein XRCC4 or a homolog thereof, and DNA ligase IV. Because double-strand breaks are among the most toxic DNA lesions, the composition and regulation of this complex are central to genome stability research. The complex is not a static entity; DNA-PK and XRCC4-DNA ligase IV are mobilized in the cell in response to DNA double-strand breaks, allowing assembly and action at damage sites. DNA-PKcs also phosphorylates DNA ligase IV and regulates its stability, directly connecting kinase signaling to the ligation step of repair. In addition to its canonical role in non-homologous end joining, the complex participates in specialized contexts such as chromosome end protection, where RAP1-mediated inhibition of DNA-PK helps safeguard chromosome ends. It also contributes to cellular adaptation to hypoxia through a DNA-dependent stress response involving DNA-PK, and DNA-PK-related pathways intersect with viral replication programs. For researchers, GO:0005958 provides a precise annotation target for studying how cells detect, tether, and ligate broken DNA ends, and for dissecting how mutations or pharmacological inhibition of its components affect genome integrity, immune receptor diversity, and disease.
DNA-dependent protein kinase-DNA ligase 4 complex At A Glance
| GO ID | GO:0005958 |
|---|---|
| GO term | DNA-dependent protein kinase-DNA ligase 4 complex |
| Ontology | cellular_component |
| Synonym | (none) |
| Major function | Repair of DNA double-strand breaks and, in mammals, V(D)J recombination |
| Key components | DNA-PKcs, Ku heterodimer, XRCC4 or homolog, DNA ligase IV |
| Dynamic behavior | DNA-PK and XRCC4-DNA ligase IV are mobilized in response to DNA double-strand breaks |
| Regulatory feature | DNA-PKcs phosphorylates DNA ligase IV and regulates its stability |
| Related biology | Chromosome end protection, hypoxia stress response, viral replication |
What Is GO:0005958?
GO:0005958 is a cellular component term describing a large protein complex involved in the repair of DNA double-strand breaks and, in mammals, V(D)J recombination events. According to the QuickGO definition, it consists of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), the DNA end-binding heterodimer Ku, the nuclear phosphoprotein XRCC4 or a homolog thereof, and DNA ligase IV. In practice, this means the term captures the assembled machinery that brings together DNA end recognition, kinase signaling, and ligation activity at sites of DNA damage.
Why Is DNA-dependent protein kinase-DNA ligase 4 complex Important in Cell Biology?
GO:0005958 is important because it defines the core non-homologous end joining machinery that cells use to survive DNA double-strand breaks, and because its components are directly linked to immune diversity through V(D)J recombination. The complex is dynamically mobilized to damage sites, and its kinase subunit regulates the stability of DNA ligase IV, making it a focal point for understanding how repair is coordinated. Beyond canonical repair, the complex participates in chromosome end protection and cellular stress responses, which broadens its relevance to cancer, hypoxia, and host-pathogen interactions.
• Defines the core protein assembly for non-homologous end joining of DNA double-strand breaks.
• Required for V(D)J recombination in mammals, linking the complex to adaptive immune receptor diversity.
• DNA-PKcs phosphorylates DNA ligase IV and regulates its stability, connecting kinase signaling to ligation.
• DNA-PK and XRCC4-DNA ligase IV are mobilized in cells after DNA double-strand breaks.
• Ku70/80 phosphorylation by DNA-PK is not required for non-homologous end joining, revealing separable regulatory layers.
• RAP1-mediated inhibition of DNA-PK contributes to chromosome end protection.
• A DNA-dependent stress response involving DNA-PK occurs in hypoxic cells and supports adaptation to hypoxia.
• The ATR pathway is activated by herpes simplex virus 1 and required for efficient viral replication, highlighting DNA damage response intersections.
• Normal V(D)J recombination is observed in cells from patients with Nijmegen breakage syndrome, helping distinguish complex-specific defects.
• The complex is a target for experimental perturbation by knockout, point mutation, knock-in, and overexpression models.
What Happens During DNA-dependent protein kinase-DNA ligase 4 complex?
DNA end recognition and complex recruitment
In simple terms: The complex first finds and holds the broken DNA ends.
The DNA-dependent protein kinase-DNA ligase 4 complex is involved in repair of DNA double-strand breaks and, in mammals, V(D)J recombination events. The Ku heterodimer provides DNA end-binding activity within the complex, while DNA-PKcs, XRCC4 or a homolog, and DNA ligase IV complete the assembly. DNA-PK and XRCC4-DNA ligase IV are mobilized in the cell in response to DNA double-strand breaks, indicating that recruitment to damage sites is a regulated step.
Kinase signaling and ligase regulation
In simple terms: A kinase in the complex tags the ligase to control its stability.
DNA-PKcs phosphorylates DNA ligase IV and regulates its stability, linking kinase activity to the ligation step. DNA-PK-dependent phosphorylation of Ku70/80 is not required for non-homologous end joining, showing that some phosphorylation events in the complex are dispensable for repair. This separation suggests that the complex integrates multiple regulatory inputs rather than relying on a single phosphorylation event.
End joining and ligation
In simple terms: The complex seals the broken DNA ends back together.
The complex is defined by its role in the repair of DNA double-strand breaks and, in mammals, V(D)J recombination events. Nonhomologous DNA end-joining is a major pathway for repair of DNA double-strand breaks, and the DNA-dependent protein kinase-DNA ligase 4 complex is a central component of this pathway. The presence of DNA ligase IV within the complex provides the catalytic ligation activity needed to restore DNA continuity.
Chromosome end protection and stress contexts
In simple terms: The complex is also controlled at chromosome ends and under stress.
Chromosome end protection can occur by RAP1-mediated inhibition of DNA-PK, showing that the complex is actively restrained at natural chromosome ends. A DNA-dependent stress response involving DNA-PK occurs in hypoxic cells and contributes to cellular adaptation to hypoxia. The ATR protein kinase pathway is activated by herpes simplex virus 1 and required for efficient viral replication, indicating that DNA damage response signaling intersects with viral infection.
Key Genes Involved in GO:0005958 DNA-dependent protein kinase-DNA ligase 4 complex
The following genes and proteins represent the core and associated factors of the DNA-dependent protein kinase-DNA ligase 4 complex (GO:0005958).
| Gene | Major Role | Research Relevance |
|---|---|---|
| PRKDC | Encodes DNA-PKcs, the catalytic subunit of the complex | Central kinase for complex assembly and ligase regulation |
| XRCC6 | Encodes Ku70, part of the DNA end-binding heterodimer | DNA end recognition within the complex |
| XRCC5 | Encodes Ku80, part of the DNA end-binding heterodimer | DNA end recognition and phosphorylation target |
| XRCC4 | Encodes XRCC4, a core component of the complex | Scaffold for ligation and complex mobilization |
| LIG4 | Encodes DNA ligase IV, the ligation component | Phosphorylated and stabilized by DNA-PKcs |
| NBN | Encodes nibrin, related to Nijmegen breakage syndrome | Used to distinguish complex-specific defects from other repair disorders |
| RAP1 | Mediates inhibition of DNA-PK at chromosome ends | Chromosome end protection studies |
| ATM | DNA damage response kinase intersecting with repair pathways | Context for ATR/ATM-related viral replication studies |
| ATR | Protein kinase pathway activated by herpes simplex virus 1 | Viral replication and DNA damage response research |
| HIF1A | Hypoxia-related transcription factor context for DNA-PK stress response | Hypoxia adaptation studies |
| TP53 | Frequently studied in genome stability contexts | Downstream of double-strand break repair |
| MRE11 | Homologous recombination and damage sensing factor | Pathway comparison with non-homologous end joining |
| RAD50 | Damage sensing and repair factor | Pathway comparison with non-homologous end joining |
| CHEK1 | Checkpoint kinase downstream of ATR signaling | Viral replication and checkpoint studies |
| CHEK2 | Checkpoint kinase in DNA damage response | DNA damage signaling research |
| POLQ | Alternative end joining factor | Comparison with canonical non-homologous end joining |
| PARP1 | DNA damage sensor and repair factor | Context for repair pathway crosstalk |
How Is DNA-dependent protein kinase-DNA ligase 4 complex Regulated?
The DNA-dependent protein kinase-DNA ligase 4 complex is regulated at multiple levels. DNA-PKcs phosphorylates DNA ligase IV and regulates its stability, directly controlling the abundance and function of a core ligation component. DNA-PK and XRCC4-DNA ligase IV are mobilized in the cell in response to DNA double-strand breaks, indicating damage-dependent redistribution of complex components. DNA-PK-dependent phosphorylation of Ku70/80 is not required for non-homologous end joining, showing that some post-translational modifications within the complex are not essential for repair. Chromosome end protection can be achieved by RAP1-mediated inhibition of DNA-PK, providing a mechanism to prevent inappropriate repair at natural chromosome ends. In hypoxic cells, a DNA-dependent stress response involving DNA-PK contributes to cellular adaptation to hypoxia, linking complex activity to environmental stress. Viral infection can also intersect with DNA damage response pathways, as the ATR protein kinase pathway is activated by herpes simplex virus 1 and required for efficient viral replication.
DNA-dependent protein kinase-DNA ligase 4 complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PRKDC | DNA repair deficiency and genome instability | Knockout cell model |
| LIG4 | Defective ligation and repair | Point mutation knock-in |
| XRCC4 | Impaired non-homologous end joining | Knockout and rescue |
| NBN | Nijmegen breakage syndrome-related V(D)J recombination | Patient-derived cell comparison |
| RAP1 | Chromosome end protection | Overexpression and inhibition studies |
Cancer and genome instability
Defects in the DNA-dependent protein kinase-DNA ligase 4 complex can compromise repair of DNA double-strand breaks, a hallmark of genome instability relevant to cancer. Because the complex is required for non-homologous end joining, its components are studied as determinants of sensitivity to DNA-damaging agents. DNA-PKcs regulation of DNA ligase IV stability further links complex function to cellular responses that influence tumor cell survival.
Hypoxia and cellular stress
A DNA-dependent stress response involving DNA-PK occurs in hypoxic cells and contributes to cellular adaptation to hypoxia. This places the complex in the context of tumor microenvironment stress and broader cellular adaptation programs.
Immune diversity and V(D)J recombination
The complex is involved in V(D)J recombination events in mammals, which are essential for generating diverse immune receptors. Normal V(D)J recombination in cells from patients with Nijmegen breakage syndrome helps distinguish complex-specific requirements from other repair disorders.
Viral infection and host response
The ATR protein kinase pathway is activated by herpes simplex virus 1 and required for efficient viral replication, showing that DNA damage response signaling intersects with viral infection. This context is relevant for understanding how host repair machinery, including DNA-PK-related complexes, may influence viral replication.
From DNA-dependent protein kinase-DNA ligase 4 complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is PRKDC required for complex assembly? | PRKDC knockout cell line |
| Does DNA-PKcs phosphorylation of DNA ligase IV affect stability? | LIG4 point mutation knock-in |
| Can XRCC4 homologs substitute in the complex? | XRCC4 knock-in with tagged allele |
| Does overexpression of DNA-PKcs alter repair efficiency? | PRKDC overexpression cell model |
| How does loss of Ku80 phosphorylation affect end joining? | XRCC5 point mutation knock-in |
| Can RAP1 inhibition of DNA-PK be modeled? | RAP1 overexpression model |
How to Study the DNA-dependent protein kinase-DNA ligase 4 complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Co-immunoprecipitation | Protein-protein association in the complex | Confirm DNA-PKcs, Ku, XRCC4, and DNA ligase IV interaction |
| Western blot | Protein levels and stability | Assess DNA ligase IV stability after DNA-PKcs perturbation |
| Phospho-specific immunoblot | Phosphorylation status | Measure Ku70/80 phosphorylation by DNA-PK |
| Immunofluorescence | Subcellular localization and mobilization | Track DNA-PK and XRCC4-DNA ligase IV after damage |
| Proteomics | Complex composition and interactors | Define assembly state of GO:0005958 components |
| Hypoxia cell culture | Stress response activation | Study DNA-PK-dependent adaptation to hypoxia |
| Viral infection assay | Viral replication efficiency | Test ATR pathway requirement during herpes simplex virus 1 infection |
| V(D)J recombination reporter | Recombination activity | Evaluate complex function in immune receptor assembly |
Proteomic analysis of complex composition
Because GO:0005958 is defined by a specific set of proteins including DNA-PKcs, Ku, XRCC4 or a homolog, and DNA ligase IV, proteomic methods can be used to confirm component association and stoichiometry. Mobilization of DNA-PK and XRCC4-DNA ligase IV after DNA double-strand breaks can be monitored by comparing treated and untreated cells.
Phosphorylation and stability assays
DNA-PKcs phosphorylates DNA ligase IV and regulates its stability, so phospho-specific assays and stability measurements are appropriate for studying complex regulation. DNA-PK-dependent phosphorylation of Ku70/80 can also be assessed, though it is not required for non-homologous end joining.
Damage response imaging
Recruitment of complex components to DNA double-strand breaks can be visualized by imaging approaches that track DNA-PK and XRCC4-DNA ligase IV mobilization. Chromosome end protection studies can examine RAP1-mediated inhibition of DNA-PK at telomeric or end regions.
Stress and infection models
Hypoxic cell culture can be used to study the DNA-dependent stress response involving DNA-PK. Viral infection models, such as herpes simplex virus 1, can be combined with DNA damage response readouts because the ATR pathway is activated and required for efficient viral replication.
How CRISPR Can Be Used to Study GO:0005958 DNA-dependent protein kinase-DNA ligase 4 complex
Knockout
CRISPR knockout of PRKDC, XRCC6, XRCC5, XRCC4, or LIG4 can be used to test which components are required for the DNA-dependent protein kinase-DNA ligase 4 complex to support repair of DNA double-strand breaks and V(D)J recombination. Knockout models also help determine whether loss of a component affects DNA ligase IV stability.
Point Mutation
Point mutation knock-in can be used to separate phosphorylation-dependent from phosphorylation-independent functions, because DNA-PK-dependent phosphorylation of Ku70/80 is not required for non-homologous end joining. Such models can also test specific residues in DNA ligase IV that are targeted by DNA-PKcs.
Knock-in
Tagged knock-in of XRCC4, LIG4, or PRKDC allows tracking of complex assembly and mobilization after DNA double-strand breaks. Knock-in of homologs can test whether XRCC4 homologs can substitute within the complex as defined by GO:0005958.
Overexpression
Overexpression of DNA-PKcs, Ku subunits, XRCC4, or DNA ligase IV can be used to study whether increased component dosage alters repair efficiency or chromosome end protection. Overexpression of RAP1 can model inhibition of DNA-PK at chromosome ends.
How EDITGENE Supports DNA-dependent protein kinase-DNA ligase 4 complex Research
Researchers studying DNA-dependent protein kinase-DNA ligase 4 complex-related genes often need to determine whether a candidate gene is causally involved in DNA double-strand break repair, V(D)J recombination, or stress adaptation, and which protein domains or phosphorylation sites mediate its function.
Contact EDITGENE today to design your custom CRISPR model for DNA-dependent protein kinase-DNA ligase 4 complex research.
Frequently Asked Questions About DNA-dependent protein kinase-DNA ligase 4 complex
What is GO:0005958?
GO:0005958 is the DNA-dependent protein kinase-DNA ligase 4 complex, a cellular component involved in repair of DNA double-strand breaks and, in mammals, V(D)J recombination events.
What genes are involved in the DNA-dependent protein kinase-DNA ligase 4 complex?
The complex includes DNA-PKcs, the Ku heterodimer, XRCC4 or a homolog, and DNA ligase IV, corresponding to genes such as PRKDC, XRCC6, XRCC5, XRCC4, and LIG4.
What does the DNA-dependent protein kinase-DNA ligase 4 complex do?
It repairs DNA double-strand breaks and participates in V(D)J recombination in mammals.
How is DNA ligase IV regulated in this complex?
DNA-PKcs phosphorylates DNA ligase IV and regulates its stability.
Is Ku70/80 phosphorylation required for non-homologous end joining?
No, DNA-PK-dependent phosphorylation of Ku70/80 is not required for non-homologous end joining.
How is the complex mobilized after DNA damage?
DNA-PK and XRCC4-DNA ligase IV are mobilized in the cell in response to DNA double-strand breaks.
How is DNA-PK controlled at chromosome ends?
Chromosome end protection can occur by RAP1-mediated inhibition of DNA-PK.
Does DNA-PK respond to hypoxia?
Yes, a DNA-dependent stress response involving DNA-PK occurs in hypoxic cells and contributes to cellular adaptation to hypoxia.
How can I study GO:0005958 in the lab?
Common approaches include knockout, point mutation, knock-in, overexpression, proteomics, imaging, and CRISPR library screening.
What diseases are linked to this complex?
The complex is linked to genome instability and cancer biology, hypoxia adaptation, V(D)J recombination disorders, and viral infection contexts.
Conclusion
GO:0005958 defines the DNA-dependent protein kinase-DNA ligase 4 complex, a central cellular component for repairing DNA double-strand breaks and for V(D)J recombination in mammals. Its core components, DNA-PKcs, Ku, XRCC4 or a homolog, and DNA ligase IV, are dynamically mobilized after damage, and DNA-PKcs regulates DNA ligase IV stability. The complex also intersects with chromosome end protection, hypoxia adaptation, and viral replication, making it a broad research target. Experimental dissection of this complex benefits from knockout, point mutation, knock-in, and overexpression models, combined with proteomic, imaging, and screening approaches.
References
- 1. Eickhoff P et al.. 2025. Chromosome end protection by RAP1-mediated inhibition of DNA-PK.. Nature 642(8069):1090-1096 PMID: 40240611
- 2. Drouet J et al.. 2005. DNA-dependent protein kinase and XRCC4-DNA ligase IV mobilization in the cell in response to DNA double strand breaks.. J Biol Chem 280(8):7060-9 PMID: 15520013
- 3. Wang YG et al.. 2004. Phosphorylation and regulation of DNA ligase IV stability by DNA-dependent protein kinase.. J Biol Chem 279(36):37282-90 PMID: 15194694
- 4. Pannunzio NR et al.. 2018. Nonhomologous DNA end-joining for repair of DNA double-strand breaks.. J Biol Chem 293(27):10512-10523 PMID: 29247009
- 5. Douglas P et al.. 2005. DNA-PK-dependent phosphorylation of Ku70/80 is not required for non-homologous end joining.. DNA Repair (Amst) 4(9):1006-18 PMID: 15941674
- 6. Bouquet F et al.. 2011. A DNA-dependent stress response involving DNA-PK occurs in hypoxic cells and contributes to cellular adaptation to hypoxia.. J Cell Sci 124(Pt 11):1943-51 PMID: 21576354
- 7. Harfst E et al.. 2000. Normal V(D)J recombination in cells from patients with Nijmegen breakage syndrome.. Mol Immunol 37(15):915-29 PMID: 11282395
- 8. Edwards TG et al.. 2018. The ATM and Rad3-Related (ATR) Protein Kinase Pathway Is Activated by Herpes Simplex Virus 1 and Required for Efficient Viral Replication.. J Virol 92(6) PMID: 29263259
