p30 disrupts the formation of the MRN complex on DSB DNA foci. HeLa cells nontransfected or transfected with GFP-p30 (green) were γ-irradiated (10 Gy) and incubated at 37°C. Seven hours later, cells were fixed and stained with antibodies (red) directed against p-H2AX (A), MRE11 (B), Rad50 endogenous proteins (C), or expressed Nbs1-myc tagged protein (D). Cells expressing GFP-p30 have diffused MRN complex proteins compared with nontransfected cells. (E) Relative expression of MRE11, Nbs1, and Rad50 was not affected by the expression of p30. HeLa cells were infected with mock or p30-myc–expressing lentivirus. The titer of the virus was calculated to have 100% of cells infected, and Western blot analysis was performed on the cell extracts using antibodies directed against p-H2AX, MRE11, and Rad50 endogenous proteins or expressed Nbs1-myc.