FIGURE 5.

DNA damage contributes to PNC disassembly. HeLa cells were treated with the maximum tolerated concentrations of two catalytic topo II inhibitors, merbarone (464 μm) and ICRF-193 (100 μm) (A), and with the maximum tolerated concentrations of DNA intercalators, chloroquine (100 μm) and ethidium bromide (EtBr, 10 μm) for 20 h (B). PNC prevalence was then determined (n = 3, error bars =±S.D.). C, siRNA was utilized to knock down the expression of topo I in PC-3M cells (band intensities listed below the immunoblot represent the average from three independent experiments), and after 3 days the PNC prevalence was determined for mock-transfected cells, cells transfected with a negative control oligonucleotide (Cnt oligo), and cells transfected with topo I siRNA (n = 3, error bars =±S.D.).