 In the case of the XRCC4 protein, the consensus sequence surrounding lysine 210 is IKQE.Chinese hamster ovary cells, CHO, that express the mutated form of XRCC4 at K210 cannot be modified with SUMO, fail recruitment to the nucleus and instead accumulate in the cytoplasm.Furthermore, these cells are radiation sensitive and do not successfully complete V(D)J recombination.