p30 interacts in vivo with Nbs1 and Rad50 but not with MRE11 proteins. 293T cells were transfected for 48 hours with p30-HA and the Nbs1-myc (A), MRE11-myc (B), or Rad50-flag (C) expression vectors. Immunoprecipitation of cell extracts was performed with the indicated antibodies, followed by Western blot analysis of the corresponding proteins. (D) p30 affects the interaction of the MRN complex components in vivo. 293T cells were transfected with either Nbs1-myc or Nbs-1-myc and p30-HA–expressing vectors and irradiated 48 hours after transfection. Nbs1-myc was immunoprecipitated with an anti-myc antibody, followed by Western blot analysis with an anti-MRE11 antibody. (E) Rescue of the HR DNA repair by ectopic expression of MRN complex components. HeLa cells were transfected with the HR assay vectors (DR-GFP and pSceI) and either with p30 alone or with p30 and Nbs1 or p30 and Rad50 expression vectors together. After 48 hours of transfection, the percentage of GFP⁺ cells was measured by FACS and is represented by the histograms of 3 independent experiments.