In NHEJ, the DSB is sensed by the lupus Ku autoantigen protein p80 (Ku80)–lupus Ku autoantigen protein p70 (Ku70) heterodimer, which recruits and assembles the DNA–PK complex, which, in turn, processes the DNA ends and increases the recruitment of ligase IV/X‐ray repair complementing defective repair in Chinese hamster cells 4 (XRCC4), which carries out the rejoining reaction 74. This evidence concerns the gene XRCC4 and systemic lupus erythematosus.