# LIG4

Source: https://onco.cc/targets/lig4/  
OnCo record `lig4` (Target). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

LIG4 (DNA ligase 4) is an enzyme. The public catalogues list it as a DNA repair gene, and the evidence so far is association rather than a proven role.

## Summary

DNA ligase involved in DNA non-homologous end joining (NHEJ); required for double-strand break (DSB) repair and V(D)J recombination. Catalyses the NHEJ ligation step of the broken DNA during DSB repair by resealing the DNA breaks after the gap filling is completed. Joins single-strand breaks in a double-stranded polydeoxynucleotide in an ATP-dependent reaction.

Open Targets scores its association with cancer at 0.54 (direct and indirect evidence; datatypes literature 0.88, animal model 0.51, genetic association 0.44, genetic literature 0.76).

## Fields

- Kind: Target
- Last checked: 2026-09-23
- Also known as: DNA ligase 4
- Tags: cancer-genes-wave
- Symbol: LIG4
- Class: enzyme
- Biology: DNA ligase involved in DNA non-homologous end joining (NHEJ); required for double-strand break (DSB) repair and V(D)J recombination. Catalyses the NHEJ ligation step of the broken DNA during DSB repair by resealing the DNA breaks after the gap filling is completed. Joins single-strand breaks in a double-stranded polydeoxynucleotide in an ATP-dependent reaction. LIG4 is mechanistically flexible: it can ligate nicks as well as compatible DNA overhangs alone, while in the presence of XRCC4, it can ligate ends with 2-nucleotides (nt) microhomology and 1-nt gaps. Forms a subcomplex with XRCC4; the LIG4-XRCC4 subcomplex is responsible for the NHEJ ligation step and XRCC4 enhances the joining activity of LIG4. Binding of the LIG4-XRCC4 complex to DNA ends is dependent on the assembly of the DNA-dependent protein kinase complex DNA-PK to these DNA ends. Location: Nucleus (UniProt). Locus 13q33.3 (HGNC).

## Notes

- Written by scripts/fetch-cancer-genes.ts from CIViC, Open Targets, IntOGen, HGNC and UniProt; the function text is UniProt's, condensed and in UK spelling. Roles: UniProt keyword "DNA repair". Evidence tier "association-only" is the strongest of those signals.
- Prevalence not recorded: none of the sources gives a positivity rate.

## Sources

- HGNC HGNC:6601: https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:6601
- UniProt P49917: https://www.uniprot.org/uniprotkb/P49917/entry
- NCBI Gene 3981: https://www.ncbi.nlm.nih.gov/gene/3981
- Ensembl ENSG00000174405: https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000174405

## Connected records

- collections: [Open Targets Platform](https://onco.cc/collections/open-targets/)
- pathways: [Double-strand break repair: HR versus end joining](https://onco.cc/pathways/homologous-recombination-repair/)

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JSON: https://onco.cc/api/v1/entities/lig4.json