Figure 4.

Cell cycle dependent colocalization of BRCA1 with the MRE11–RAD50–NBS1 complex after ionizing radiation. (A–C,M–O) Asynchronous MCF7 cells were fixed and stained with (A–C) anti-RAD50 and anti-BRCA1 or (M–O) anti-MRE11 and anti-BRCA1 antibodies. Asynchronous (D–F,P–R), G₀/G₁ arrested (G–I,S–U), or S-phase synchronized (J–L,V–X) MCF7 cells were exposed to 12 Gy of γ-irradiation then incubated for 5 hr prior to fixation and immunostaining. Appropriate FITC or Cy3-conjugated secondary antibodies were used for indirect visualization of the epitopes. Confocal images were captured on a Bio-Rad confocal microscope at 1260× magnification.