Fig 4.

RNF4 is required for the recruitment of BRCA1 to DSBs. (A) U2OS cells were transfected with control or RNF4-specific siRNAs and subsequently treated with IR. Cells were allowed to recover for 2 h and recruitment of BRCA1 to γH2AX-labeled repair foci was analyzed by immunofluorescence microscopy. Bar = 5 μm. (B) Quantitative analysis of BRCA1 recruitment to γH2AX-labeled repair foci in cells transfected with control or RNF4-specific siRNAs. Analyses were performed 0.5, 1.0, and 2.0 h after treatment with IR. Results are representative of three independent experiments. Error bars equal standard deviations. (C) Quantitative analysis of BRCA1 recruitment to γH2AX-labeled repair foci in cells cotransfected with RNF4-specific siRNA and RNAi-resistant RNF4-GFP cDNA. Analysis was performed 0.5 h after treatment with IR. (D) Model for hybrid SUMO-ubiquitin chain-dependent recruitment of RAP80 and the BRCA1-A complex to DSBs.