DNA-dependent protein kinase catalytic subunit, also known as DNA-PKcs, is an enzyme that plays a crucial role in repairing DNA double-strand breaks and has a number of other DNA housekeeping functions.[5] In humans it is encoded by the gene designated as PRKDC or XRCC7.[6] DNA-PKcs belongs to the phosphatidylinositol 3-kinase-related kinase protein family. The DNA-Pkcs protein is a serine/threonine protein kinase consisting of a single polypeptide chain of 4,128 amino acids.[7][8]