Next, to ask if Cdk2 phosphorylated Nbs1 in the Mre11 complex with the same dependence on Ser432, we performed labeling in extracts of NBS-T cells—transformed fibroblasts derived from a patient with NBS, which do not express full-length Nbs1—or the same cells expressing full-length Nbs1 after transient transfection. Here, CDK2 is linked to Nijmegen breakage syndrome.