Figure 2.

Protein interactions with the DSB-flanking chromatin. (A) Exponentially growing U2OS cells were sensitized with BrdU and microirradiated. 1 h later, the cells were fixed and stained with the indicated antibodies. Insets show higher magnifications of the microirradiated fields. (B) Accumulation of checkpoint mediators at the sites of DNA damage can occur throughout interphase. U2OS cells stably expressing GFP-tagged Mdc1 were treated as in A. After fixation, the cells were immunostained for cyclin A and the p32 subunit of RPA to indicate the cell cycle position (schematically illustrated in the right panel). Bars, 10 μm.