RA3331 FA-P cell line is null for SLX4. (A) Indirect immunofluorescence with an antibody against ERCC1 in U2OS cells transfected with a combination of 3 siRNAs against SLX4 or against Luciferase (Luc) as a control. The U2OS cells were pre-extracted with Triton-X100 before fixation. Nuclei were stained with 4,6-diamidino-2-phenylindole (DAPI). (B) Efficiency of SLX4 knockdown. The bar graph represents the decrease in relative SLX4 mRNA in U2OS cell line transfected with Luc or SLX4 siRNA. The error bars represent SD in triplicate experiments. (C) Indirect immunofluorescence with an antibody against ERCC1 in BJ/hTERT, RA3083/hTERT, and RA3331/E6E7/hTERT cell lines. The cell lines were prepared as in panel A. (D) Indirect immunofluorescence staining of RA3331/E6E7/hTERT expressing indicated SLX4 mutants using anti-HA and anti-ERCC1 antibodies. Nuclei were stained with DAPI. The cell lines were prepared as in panel A.