GO:0070421 DNA ligase III-XRCC1 complex: Components, Assembly and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0070421 describes the DNA ligase III-XRCC1 complex, a cellular component required for base excision repair (BER).
• The complex contains DNA ligase III (LIG3) and XRCC1, and seals DNA nicks after gap filling during BER.
• It is especially important for repairing single-strand breaks and clustered DNA damage, where 8-oxoguanine can retard its activity.
• Oxidants and environmental toxicants can compromise DNA ligation during BER, making this complex a target in exposure research.
• The complex also functions in nucleosome disruption to promote efficient BER in chromatin.
• Studying GO:0070421 helps explain cancer, neurodegeneration, and aging phenotypes linked to defective single-strand break repair.
Description
The DNA ligase III-XRCC1 complex (GO:0070421) is a cellular component that contains DNA ligase III and XRCC1 and is involved in base excision repair. Base excision repair (BER) is the main pathway that removes small base lesions and repairs single-strand breaks, and the final ligation step is often carried out by this complex. Because BER is essential for genome maintenance, the DNA ligase III-XRCC1 complex is a central node in the cellular response to endogenous and exogenous DNA damage. Researchers study GO:0070421 to understand how cells preserve genomic integrity, how repair fails in disease, and how environmental exposures alter DNA repair capacity. The complex is also relevant to chromatin biology because it can disrupt nucleosomes to access damage sites. This article summarizes the definition, composition, mechanism, disease links, and experimental models for GO:0070421, based on QuickGO annotation and verified PubMed literature.
DNA ligase III-XRCC1 complex At A Glance
| GO ID | GO:0070421 |
|---|---|
| GO term | DNA ligase III-XRCC1 complex |
| Ontology | cellular_component |
| Synonym | None listed in QuickGO |
| Major function | Base excision repair; sealing DNA nicks after gap filling |
| Key components | DNA ligase III (LIG3) and XRCC1 |
| Related processes | Single-strand break repair; BER of oxidized bases |
| Disease relevance | Defective BER is linked to cancer, neurodegeneration, and aging |
| Research methods | KO, point mutation, knock-in, overexpression, and BER assays |
What Is GO:0070421?
GO:0070421 is a Gene Ontology cellular component term defined as a protein complex that contains DNA ligase III and XRCC1, and is involved in base excision repair. In practice, this means the term describes the physical assembly of LIG3 and XRCC1 that carries out the nick-sealing step of BER and contributes to single-strand break repair.
Why Is DNA ligase III-XRCC1 complex Important in Cell Biology?
The DNA ligase III-XRCC1 complex is important because it performs the final ligation step of base excision repair, without which cells accumulate DNA breaks and mutations. This complex is particularly relevant for repairing single-strand breaks and clustered damage, where its activity can be modulated by oxidized bases such as 8-oxoguanine. Environmental toxicants and oxidants can compromise DNA ligation during BER, making this complex a key factor in exposure-related genome instability. Because BER defects are associated with cancer, neurodegeneration, and aging, understanding GO:0070421 supports both mechanistic biology and translational research.
• Seals DNA nicks during base excision repair, a core genome maintenance pathway.
• Required for efficient repair of single-strand breaks and clustered DNA damage.
• Its activity can be retarded by 8-oxoguanine within clustered damage sites.
• Compromised by oxidants and environmental toxicants, linking exposure to genome instability.
• Participates in nucleosome disruption to facilitate BER in chromatin.
• Relevant to cancer biology because unrepaired DNA breaks drive mutations.
• Relevant to neurodegeneration because neurons are sensitive to DNA damage.
• A target for experimental models using KO, point mutation, and knock-in approaches.
• Helps interpret BER defects in patient-derived cells and toxicology studies.
• Provides a defined GO entity for annotating cellular component in repair research.
What Happens During DNA ligase III-XRCC1 complex?
Recognition and assembly at damage sites
In simple terms: The complex forms at sites of DNA damage to prepare for repair.
The DNA ligase III-XRCC1 complex is involved in base excision repair, where it assembles with other BER factors to process damaged bases and single-strand breaks. XRCC1 serves as a scaffold that helps recruit and coordinate the complex at repair sites. This assembly is essential for efficient repair of abasic sites and oxidized bases.
Gap filling and nick sealing
In simple terms: After the damaged base is removed, the complex seals the remaining DNA nick.
During BER, DNA polymerase fills the gap and the DNA ligase III-XRCC1 complex seals the nick to restore an intact DNA strand. This ligation step is critical because unrepaired nicks can lead to strand breaks and genomic instability. The complex works with other BER proteins to ensure substrate-product channeling during repair.
Nucleosome disruption for efficient repair
In simple terms: The complex can help open chromatin so repair enzymes can reach DNA damage.
Nucleosome disruption by DNA ligase III-XRCC1 promotes efficient base excision repair, indicating that the complex contributes to chromatin accessibility during repair. This activity helps explain how BER proceeds in the context of packaged DNA.
Impact of clustered damage and oxidized bases
In simple terms: Certain types of damage can slow down the complex.
8-OxoG retards the activity of the ligase III/XRCC1 complex during the repair of a single-strand break when present within a clustered DNA damage site. Oxidant and environmental toxicant-induced effects can also compromise DNA ligation during base excision DNA repair. These findings highlight how damage context and exposure influence the complex's function.
Key Genes Involved in GO:0070421 DNA ligase III-XRCC1 complex
The DNA ligase III-XRCC1 complex is defined by two core proteins, but its function intersects with many BER and single-strand break repair factors.
| Gene | Major Role | Research Relevance |
|---|---|---|
| LIG3 | DNA ligase III catalytic subunit that seals nicks in BER | Core component of GO:0070421; KO and point mutation models |
| XRCC1 | Scaffold protein that coordinates BER and recruits LIG3 | Core component; essential for complex assembly and function |
| POLB | DNA polymerase beta fills gaps during BER | Functional partner; substrate-product channeling with LIG3-XRCC1 |
| OGG1 | Removes oxidized bases such as 8-oxoguanine | Upstream of the complex in BER of oxidized damage |
| APEX1 | Processes abasic sites during BER | Works upstream of ligation; relevant to abasic site repair |
| PARP1 | Detects single-strand breaks and recruits repair factors | Related to single-strand break repair pathways |
| LIG4 | DNA ligase IV involved in non-homologous end joining | Contrast for ligation fidelity studies; not part of GO:0070421 |
| XRCC4 | Partner of DNA ligase IV in NHEJ | Contrast for ligation fidelity; not part of GO:0070421 |
| FEN1 | Processes flap structures in BER | Related BER factor; context for ligation step |
| PCNA | Coordinates DNA repair and replication | Potential regulator of BER progression |
| RPA | Binds single-stranded DNA during repair | Supports repair intermediate handling |
| ATM | DNA damage response kinase | Signaling context for repair pathway choice |
| TP53 | Tumor suppressor involved in DNA damage response | Disease relevance for BER defects |
| BRCA1 | DNA repair and genome stability | Pathway context for single-strand break repair |
| BRCA2 | Homologous recombination repair | Contrast with BER ligation |
| MUTYH | Removes adenine opposite 8-oxoguanine | Upstream of BER ligation |
| NEIL1 | Initiates BER of oxidized bases | Upstream of the complex |
| NTHL1 | Initiates BER of oxidized pyrimidines | Upstream of the complex |
How Is DNA ligase III-XRCC1 complex Regulated?
The DNA ligase III-XRCC1 complex is regulated by its interaction with other BER proteins and by the chemical context of DNA damage. For example, substrate-product channeling with Pol β influences the efficiency of gap filling and ligation during BER opposite oxidized 5-methylcytosine modifications. Oxidant and environmental toxicant exposure can compromise DNA ligation, indicating that cellular redox status and toxicant exposure modulate complex activity. The presence of 8-oxoguanine within clustered damage sites can retard the complex, showing that damage structure regulates its function. Nucleosome disruption by the complex also reflects regulation by chromatin context.
DNA ligase III-XRCC1 complex and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| LIG3 | Cancer; genome instability | LIG3 knockout and point mutation cell lines |
| XRCC1 | Cancer; neurodegeneration | XRCC1 knockout and knock-in models |
| POLB | Cancer; BER deficiency | POLB knockout with BER assays |
| OGG1 | Oxidative damage-related diseases | OGG1 knockout with clustered damage assays |
| APEX1 | Cancer; neurodegeneration | APEX1 knockout and overexpression models |
Cancer and genome instability
Defective base excision repair and single-strand break repair can lead to mutations and genome instability, which are hallmarks of cancer. The DNA ligase III-XRCC1 complex is central to the ligation step of BER, so its dysfunction may contribute to cancer predisposition or progression. Studying GO:0070421 helps clarify how repair defects drive mutagenesis.
Neurodegeneration and aging
Neurons are particularly sensitive to DNA damage, and impaired BER has been linked to neurodegeneration and aging. The DNA ligase III-XRCC1 complex is required for efficient repair of single-strand breaks, and its compromise by oxidized bases or toxicants may exacerbate neuronal vulnerability. This makes the complex relevant to age-related neurological decline.
Environmental exposure and toxicology
Oxidant and environmental toxicant-induced effects compromise DNA ligation during base excision DNA repair, implicating the DNA ligase III-XRCC1 complex in exposure-related health effects. These findings support the use of the complex as a biomarker or target in toxicology research.
From DNA ligase III-XRCC1 complex-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of LIG3 affect BER efficiency? | LIG3 knockout cell line |
| Does XRCC1 mutation alter complex assembly? | XRCC1 point mutation knock-in |
| How does tagged LIG3 localize to damage sites? | Tagged knock-in of LIG3 |
| Does overexpression of XRCC1 enhance repair? | XRCC1 overexpression cell line |
| How do oxidants affect ligation? | Wild-type and mutant cells treated with oxidants |
| Does 8-oxoguanine retard complex activity? | Clustered damage substrates in cell extracts |
How to Study the DNA ligase III-XRCC1 complex Process
| Method | What It Measures | Typical Application |
|---|---|---|
| In vitro BER assay | Ligation efficiency | Testing substrates with clustered damage |
| Co-IP/MS | Protein interactions | Mapping complex composition |
| CRISPR KO | Loss-of-function phenotypes | LIG3 or XRCC1 knockout |
| CRISPR knock-in | Tagged or mutant protein function | Localization and assembly studies |
| Comet assay | DNA strand breaks | Measuring repair capacity |
| Immunofluorescence | Repair foci formation | Visualizing complex recruitment |
| Toxicant exposure assays | Ligation compromise | Environmental toxicology |
| Substrate-product channeling | BER intermediate handling | Pol β and LIG3 coordination |
BER activity assays
In vitro BER assays using defined DNA substrates can measure the ligation step carried out by the DNA ligase III-XRCC1 complex. These assays help quantify how clustered damage or oxidized bases affect repair.
Co-immunoprecipitation and proteomics
Co-immunoprecipitation and mass spectrometry can identify proteins associated with the DNA ligase III-XRCC1 complex and map its interactions. Such approaches reveal how the complex assembles with other BER factors.
CRISPR knockout and knock-in models
CRISPR knockout of LIG3 or XRCC1 and knock-in of tagged or mutant versions allow functional dissection of the complex in cells. These models are essential for linking genotype to repair phenotypes.
Imaging of repair foci
Fluorescence imaging of repair proteins can visualize recruitment of the DNA ligase III-XRCC1 complex to damage sites. This helps study spatial and temporal dynamics of BER.
How CRISPR Can Be Used to Study GO:0070421 DNA ligase III-XRCC1 complex
Knockout
CRISPR knockout of LIG3 or XRCC1 can disrupt the DNA ligase III-XRCC1 complex and reveal its requirement for base excision repair. These models are useful for measuring sensitivity to DNA-damaging agents.
Point Mutation
Point mutations in LIG3 or XRCC1 can be introduced to test specific residues required for complex assembly or catalysis. Such models help separate ligation activity from scaffolding functions.
Knock-in
Knock-in of tagged LIG3 or XRCC1 allows tracking of the complex in live cells and mapping its recruitment to damage sites. This approach supports dynamic studies of BER.
Overexpression
Overexpression of XRCC1 or LIG3 can test whether increased complex levels enhance repair capacity or alter damage sensitivity. These models are useful for gain-of-function studies.
How EDITGENE Supports DNA ligase III-XRCC1 complex Research
Researchers studying DNA ligase III-XRCC1 complex-related genes often need to determine whether a candidate gene is causally involved in base excision repair, single-strand break repair, or disease phenotypes. EDITGENE provides CRISPR-based cell models and screening services to enable these studies.
Contact EDITGENE today to design your custom CRISPR model for DNA ligase III-XRCC1 complex research.
Frequently Asked Questions About DNA ligase III-XRCC1 complex
What is GO:0070421?
GO:0070421 is the Gene Ontology cellular component term for the DNA ligase III-XRCC1 complex, a protein complex involved in base excision repair.
What genes are involved in the DNA ligase III-XRCC1 complex?
The core genes are LIG3 (DNA ligase III) and XRCC1, with functional interactions with BER factors such as POLB.
What does the DNA ligase III-XRCC1 complex do?
It seals DNA nicks during base excision repair and contributes to single-strand break repair.
Where does the DNA ligase III-XRCC1 complex act?
It acts at sites of DNA damage in the nucleus, including single-strand breaks and base lesions.
How is the DNA ligase III-XRCC1 complex regulated?
Its activity is influenced by other BER proteins, chromatin context, and damage structure such as clustered lesions.
What diseases are linked to the DNA ligase III-XRCC1 complex?
Defects in BER and single-strand break repair are linked to cancer, neurodegeneration, and aging.
How can I study the DNA ligase III-XRCC1 complex?
CRISPR knockout, point mutation, knock-in, overexpression, and BER assays are common approaches.
Does 8-oxoguanine affect the DNA ligase III-XRCC1 complex?
Yes, 8-oxoguanine can retard the activity of the ligase III/XRCC1 complex during repair of a single-strand break within clustered damage.
Can environmental toxicants affect this complex?
Oxidant and environmental toxicant-induced effects can compromise DNA ligation during base excision repair.
What experimental models are available for GO:0070421?
Knockout, point mutation, knock-in, and overexpression cell models are available, along with CRISPR screening.
Conclusion
The DNA ligase III-XRCC1 complex (GO:0070421) is a defined cellular component that carries out the ligation step of base excision repair and supports single-strand break repair. Its activity is sensitive to damage context, including clustered lesions and oxidized bases, and can be compromised by environmental toxicants. Studying this complex with CRISPR models and BER assays provides mechanistic insight into genome maintenance and disease. EDITGENE offers comprehensive services to accelerate research on GO:0070421 and related pathways.
References
- 1. Odell ID et al.. 2011. Nucleosome disruption by DNA ligase III-XRCC1 promotes efficient base excision repair.. Mol Cell Biol 31(22):4623-32 PMID: 21930793
- 2. Wang Y et al.. 2007. Human DNA ligase IV and the ligase IV/XRCC4 complex: analysis of nick ligation fidelity.. Biochemistry 46(17):4962-76 PMID: 17407264
- 3. Dianov GL et al.. 2003. Repair of abasic sites in DNA.. Mutat Res 531(1-2):157-63 PMID: 14637252
- 4. Lomax ME et al.. 2004. 8-OxoG retards the activity of the ligase III/XRCC1 complex during the repair of a single-strand break, when present within a clustered DNA damage site.. DNA Repair (Amst) 3(3):289-99 PMID: 15177044
- 5. Çağlayan M et al.. 2015. Oxidant and environmental toxicant-induced effects compromise DNA ligation during base excision DNA repair.. DNA Repair (Amst) 35:85-9 PMID: 26466358
- 7. Çağlayan M et al.. 2015. Reprint of "Oxidant and environmental toxicant-induced effects compromise DNA ligation during base excision DNA repair".. DNA Repair (Amst) 36:86-90 PMID: 26596511
- 8. Çağlayan M. 2020. Pol β gap filling, DNA ligation and substrate-product channeling during base excision repair opposite oxidized 5-methylcytosine modifications.. DNA Repair (Amst) 95:102945 PMID: 32853828
