RECQ1 preferentially binds to FRA16D after treatment with aphidicolin. A. Genomic organization of the FRA16D region. Primer set used for qPCR analyses of the FRA16D locus is indicated. B. Quantification of cross-linked FRA16D chromatin immunoprecipitated from HeLa cells untreated or treated with aphidicolin (0.5 μM) for 24 h using a specific RECQ1 antibody or rabbit IgG. Fold enrichment of FRA16D containing sequences in RECQ1 ChIP was determined by normalizing enrichment obtained with IgG and is shown for both untreated and APH-treated cells. Relative occupancy of RECQ1 at FRA16D versus a non-fragile negative control site GAPDH shows preferential recruitment of RECQ1 to fragile site locus in aphidicolin treated cells. Results are expressed as means ± SEM for at least three independent experiments. C. A representative gel of the amplified DNA immunoprecipitated with indicated antibodies. Input represents 1% of the cross-linked chromatin used for ChIP. D. qPCR analyses of RECQ1, ORC2 or γH2AX -binding in ChIP experiments to DNA sequence containing β-actin in HeLa cells. E. A representative gel of the amplified β-actin sequence immunoprecipitated with indicated antibodies. Input represents 1% of the cross-linked chromatin used for ChIP. APH, aphidicolin.