DNA Ligase IV

Human DNA Ligase IV/XRCC4 participates in the repair of double-strand breaks in DNA via a direct non-homologous end-joining (NHEJ) pathway. The repair involves the concerted action of several proteins, including heterodimeric Ku70/Ku80, DNA-dependent protein kinase, other accessory factors, and DNA ligase IV/XRCC4, which carries out the actual ligation reaction. DNA Ligase IV/XRCC4 exists as a tetramer containing two copies of each polypeptide with a molecular weight of approximately 300 kDa. The tetramer functions together with Ku protein, DNA-dependent protein kinase catalytic subunit, and other repair factors in a cell-free end-joining assay.