properties.Promotes processing of hairpin DNA structures in V(D)J recombination by activation of the hairpin endonuclease artemis(DCLRE1C).The assembly of the DNA-PK complex at DNA ends is also required for the NHEJ ligation step.Required to protect and align broken ends of DNA.May also act as a scaffold protein to aid the localization of DNA repair proteins to the site of damage.Found at the ends of chromosomes,suggesting a further role in the maintenance of telomeric stability and the prevention of chromosomal end fusion.Also involved in modulation of transcription.Recognizes the substrate consensus sequence[ST]-Q.Phosphorylates'Ser-139' of histone variant H2AX/H2AFX,thereby regulating DNA damage response mechanism.Phosphorylates DCLRE1C,c-Abl/ABL1,histone H1,HSPCA,c-jun/JUN,p53/TP53, PARP1, POU2F1, DHX9, SRF, XRCC1, XRCC1, XRCC4, XRCC5, XRCC6, WRN, MYC and RFA2.Can phosphorylate C1D not only in the presence of linear DNA but also in the presence of supercoiled DNA.Ability to phosphorylate p53/TP53 in the presence of supercoiled DNA is dependent on C1D.