The p70/p80 autoantigen is a nuclear complex consisting of two subunits with molecular masses of approximately 70 and 80 kDa. The complex functions as a single-stranded DNA-dependent ATP-dependent helicase. The complex may be involved in the repair of nonhomologous DNA ends such as that required for double-strand break repair, transposition, and V(D)J recombination. High levels of autoantibodies to p70 and p80 have been found in some patients with systemic lupus erythematosus. [provided by RefSeq].

Ku70 heterodimerises with Ku80 to form the ATP-dependent DNA helicase II, a single stranded helicase that binds preferentially to fork-like ends of double-stranded DNA in a cell cycle-dependent manner. The heterodimer plays a role in non-homologous end-joining (NHEJ) required for double-strand break repair and V(D)J recombination. It acts as the regulatory subunit of the DNA-dependent protein kinase complex DNA-PK by increasing the affinity of the catalytic subunit (PRKDC) for DNA. The Ku70/80 heterodimer is also required for osteocalcin gene expression.