 Ku70/80 then sequesters one DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to the DNA ends to enable the binding of Artemis protein to one end of each DNA-PKcs.One end of the DNA-PKcs joins to stabilize the proximity of the DSB and allow very short regions of DNA complementarity to hybridize.DNA-PKcs then phosphorylates Artemis at a serine/threonine to activate its exonuclease activity and cleave nucleotides at the single strand tails that are not hybridized in a 5’ to 3’ direction.