DNA double strand break repair and V(D)J recombination protein XRCC4,DNA repair protein XRCC4,SSMED,X ray repair complementing defective repair in Chinese hamster cells 4,X ray repair cross complementing 4,X ray repair cross complementing protein 4,X-ray repair cross-complementing protein 4,XRCC 4,XRCC4,XRCC4