Ku70:Ku80 complex

GO:0043564 · Other · Multiprotein complex · Proposed

Heterodimeric protein complex composed of a 70 kDa and a 80 kDa subunit, binds DNA through a channel formed by the heterodimer. Functions in DNA double stranded break repair, chromosome maintenance, transcription regulation, V(D)J recombination, and activation of DNA-PK. [GO:0043564]

Synonyms: Ku70:Ku80 heterodimer

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
Ku70 subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	70 kDa Ku-family DNA-end-binding constituent of the Ku70:Ku80 heterodimer. `GO:0043564` GO:0043564 defines the Ku70:Ku80 complex as a heterodimeric complex composed of a 70 kDa and an 80 kDa subunit. `PMID:8890183` Boulton and Jackson 1996 characterized the Saccharomyces cerevisiae Ku70 homologue.
Ku80 subunit	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	80 kDa Ku-family DNA-end-binding constituent of the Ku70:Ku80 heterodimer. `GO:0043564` GO:0043564 defines the Ku70:Ku80 complex as a heterodimeric complex composed of a 70 kDa and an 80 kDa subunit. `DOI:10.1093/nar/24.23.4639` Boulton and Jackson 1996 identified a Saccharomyces cerevisiae Ku80 homologue. `DOI:10.1074/jbc.271.44.27765` Feldmann et al. 1996 identified Hdf2 as a second subunit of the Saccharomyces cerevisiae Ku homologue.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast has a two-subunit Ku homologue whose Hdf2/Ku80 constituent was characterized as the second subunit of the complex. [DOI:10.1074/jbc.271.44.27765]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Reference budding-yeast system in which Hdf2/Ku80 evidence resolved a two-subunit Ku homologue. [DOI:10.1074/jbc.271.44.27765]

Functions

DNA end binding GO:0045027 — The Ku70:Ku80 heterodimer binds DNA through a channel formed by its two subunits, including at DNA ends.
- GO:0043564 GO:0043564 defines the Ku70:Ku80 complex as binding DNA through the heterodimer channel.
- GO:0045027 GO:0045027 is the Gene Ontology molecular-function term for DNA end binding.
- DOI:10.1038/nrm1367 Downs and Jackson 2004 reviewed Ku as a Ku70-Ku80 heterodimer that binds DNA ends.
double-strand break repair via nonhomologous end joining GO:0006303 — The Ku70:Ku80 complex participates in nonhomologous-end-joining repair of DNA double-strand breaks.
- GO:0043564 GO:0043564 defines the Ku70:Ku80 complex as functioning in DNA double-strand-break repair.
- GO:0006303 GO:0006303 is the Gene Ontology biological-process term for double-strand break repair via nonhomologous end joining.
- DOI:10.1093/nar/24.23.4639 Boulton and Jackson 1996 connected the Saccharomyces cerevisiae Ku80 homologue to DNA double-strand-break rejoining.
- DOI:10.1038/nrm1367 Downs and Jackson 2004 reviewed Ku-mediated nonhomologous end joining.

Mechanism graphs

Ku70:Ku80 binds DNA ends for end joining (FUNCTION)

The Ku70 and Ku80 subunits form a heterodimeric complex that binds DNA and participates in nonhomologous-end-joining repair.

Subject	Predicate	Object	Evidence
Ku70 subunit	contributes to	Ku70:Ku80 complex	`GO:0043564` GO:0043564 defines the complex as a heterodimer that includes a 70 kDa subunit. `PMID:8890183` Boulton and Jackson 1996 studied Saccharomyces cerevisiae Ku70.
Ku80 subunit	contributes to	Ku70:Ku80 complex	`GO:0043564` GO:0043564 defines the complex as a heterodimer that includes an 80 kDa subunit. `DOI:10.1093/nar/24.23.4639` Boulton and Jackson 1996 studied the Saccharomyces cerevisiae Ku80 homologue.
Ku70:Ku80 complex	binds	DNA end	`GO:0043564` GO:0043564 defines the complex as binding DNA through a heterodimer channel. `GO:0045027` GO:0045027 is the molecular-function term for DNA end binding. `DOI:10.1038/nrm1367` Downs and Jackson 2004 reviewed Ku binding to DNA ends and facilitating nonhomologous end joining.
Ku70:Ku80 complex	enables	DNA end binding	`GO:0043564` GO:0043564 defines the complex as a DNA-binding heterodimer. `GO:0045027` GO:0045027 is the molecular-function term for DNA end binding. `DOI:10.1038/nrm1367` Downs and Jackson 2004 reviewed Ku binding to DNA ends and facilitating nonhomologous end joining.
Ku70:Ku80 complex	supports	double-strand break repair via nonhomologous end joining	`GO:0043564` GO:0043564 defines the complex as functioning in DNA double-strand-break repair. `GO:0006303` GO:0006303 is the biological-process term for double-strand break repair via nonhomologous end joining. `DOI:10.1038/nrm1367` Downs and Jackson 2004 reviewed Ku binding to DNA ends and facilitating nonhomologous end joining.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral family groundings for the Ku70 and Ku80 constituents of the Ku70:Ku80 complex. GO:0043564 exactly identifies the heterodimeric Ku70:Ku80 complex and its 70 kDa and 80 kDa constituents, but exact source-neutral InterPro, Pfam, NCBIfam or UniProtKB family boundaries for the two Ku-family subunit classes need narrower follow-up curation.

Evidence

GO:0043564 Gene Ontology cellular-component term for the Ku70:Ku80 complex.
GO:0140513 Gene Ontology cellular-component parent term for nuclear protein-containing complexes.
GO:0045027 Gene Ontology molecular-function term for DNA end binding.
GO:0006303 Gene Ontology biological-process term for double-strand break repair via nonhomologous end joining.
PMID:12518983 PubMed identifier for Koike 2002, the Journal of Radiation Research review on Ku70 and Ku80 dimerization, translocation and localization.
DOI:10.1269/jrr.43.223 DOI for Koike 2002, verified through PubMed.
PMID:15122350 PubMed identifier for Downs and Jackson 2004, the Nature Reviews Molecular Cell Biology review on Ku and DNA ends.
DOI:10.1038/nrm1367 DOI for Downs and Jackson 2004, verified through PubMed.
PMID:8890183 PubMed identifier for Boulton and Jackson 1996, the EMBO Journal paper on Saccharomyces cerevisiae Ku70.
PMID:8972848 PubMed identifier for Boulton and Jackson 1996, the Nucleic Acids Research paper on the Saccharomyces cerevisiae Ku80 homologue.
DOI:10.1093/nar/24.23.4639 DOI for Boulton and Jackson 1996 on the Saccharomyces cerevisiae Ku80 homologue, verified through PubMed and PMC.
PMID:8910371 PubMed identifier for Feldmann et al. 1996, the Journal of Biological Chemistry paper on HDF2 as the second subunit of the Saccharomyces cerevisiae Ku homologue.
DOI:10.1074/jbc.271.44.27765 DOI for Feldmann et al. 1996, verified through PubMed.

Curation history

2026-09-27T10:19:40Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-27T10:20:49Z codex · EXPANDED_RECORD — Added GO Ku70:Ku80 synonymy, nuclear protein-containing-complex parentage, two reviewed-label-only Ku constituent rows, budding-yeast scope, DNA-end-binding and nonhomologous-end-joining functions, GO/PubMed/DOI evidence, a nonmechanistic function graph, and a Ku subunit-grounding TODO.
2026-09-27T10:21:34Z codex · TIGHTEN_EVIDENCE — Added Downs and Jackson 2004 as review evidence for Ku DNA-end binding and NHEJ, and narrowed the budding-yeast canonical example to the HDF2/Ku80 two-subunit-complex evidence.

Source: data/structures/other/ku70_ku80_complex.yaml