Ku70 (IPR006165)

Short name: Ku70

Overlapping homologous superfamilies

Family relationships



Ku70 (also known as XRCC6) is a eukaryotic protein that is involved in the repair of DNA double-strand breaks by non-homologous end-joining [PMID: 11839498, PMID: 10377944]. Ku is a heterodimer of approximately 70kDa and 80kDa subunits [PMID: 11493912]. Both these subunits have strong sequence similarity and it has been suggested that they may have evolved by gene duplication from a homodimeric ancestor in eukaryotes [PMID: 11839498]. Homologues of the eukaryotic DNA-end-binding protein Ku were identified in several bacterial and one archaeal genome using iterative database searches; these prokaryotic Ku members are homodimers that have been predicted to be involved in the DNA repair system, which is mechanistically similar to eukaryotic non-homologous end joining [PMID: 11483577, PMID: 11445083] though they are not members of this family. Recent findings have implicated yeast Ku in telomeric structure maintenance in addition to non-homologous end-joining. Some of the phenotypes of Ku-knockout mice may indicate a similar role for Ku at mammalian telomeres [PMID: 11516951].

Evolutionary notes: With the current available phyletic information it is difficult to determine the correct evolutionary trajectory of the Ku domain. It is possible that the core Ku domain was present in bacteria and archaea even before the presence of the eukaryotes. Eukaryotes might have vertically inherited the Ku core protein from a common ancestor shared with a certain archaeal lineage, or through horizontal transfer from bacteria. Alternatively, the core Ku domain could have evolved in the eukaryotic lineage and then horizontally transferred to the prokaryotes. Sequencing of additional archaeal genomes and those of early-branching eukaryotes may help resolve the evolutionary history of the Ku domain.

Structure notes: The eukaryotic Ku heterodimer is comprised of an alpha/beta N-terminal, a central beta-barrel domain and a helical C-terminal arm [PMID: 11493912]. Structural analysis of the Ku70/80 heterodimer bound to DNA indicates that subunit contacts lead to the formation of a highly charged channel through which the DNA passes without making any contacts with the DNA bases [PMID: 11493912].

GO terms

Biological Process

GO:0006303 double-strand break repair via nonhomologous end joining
GO:0000723 telomere maintenance

Molecular Function

GO:0003677 DNA binding
GO:0003684 damaged DNA binding
GO:0042162 telomeric DNA binding

Cellular Component

GO:0043564 Ku70:Ku80 complex
GO:0005634 nucleus

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.