BRCA1/BARD1 downregulation prevents recruitment of these proteins along with Rad51 to chromatin following MMS treatment.

A) HeLa cells were treated for 6 hrs with IR (10 Gy) or 200 µM MMS (with or without pretreatment with MG132). Chromatin from control or treated cells was prepared as described in material and methods and proteins were detected by western blotting. Histones were stained with coomassie blue to ensure equal loading. B) HeLa cells were treated as in panel A and harvested for immunostaining (left panel). Cells with more than 10 foci were counted and the data are presented as percentage of cells with foci under each condition (right panel). The values represent the average ± SD of three independent experiments. C) HeLa cells were treated as in A except that a permeabilization step was added before fixation and immunostaining (left panel). Cells with more than 10 foci were counted and the data are presented as percentage of cells with foci under each condition (right panel). The values represent the average ± SD of three independent experiments.