Fig. 4.

Vpr expression induces Topo1-mediated DDR and DSB. a, b Involvement of Topo1 in Vpr-induced DDR. Flow cytometry analysis was performed in Mit-23 cells transfected with indicated siRNAs to measure the Vpr-induced phosphorylation of H2AX. Representative scatter plots of γH2AX are shown in (a). Green colored plots were gated as γH2AX positive cells. Mean percentages of γH2AX positive cells are shown in (b). Error bars indicate ± SEM. Data obtained from more than three independent experiments. *P < 0.01. c, d Effects of Topo1 siRNA on Vpr-induced cell-cycle abnormality. DNA contents were measured in Mit-23 cells transfected with indicated siRNAs by flow cytometry. Representative histograms of DNA contents (c) and average of ratios of G₂ to G₁ cells (d) are shown. **P < 0.05. e, f Involvement of Topo1 on Vpr-induced DSB. Neutral comet assay was performed in Mit-23 cells transfected with indicated siRNAs to quantitate the amounts of DSB. Representative images of each comet (e) and average of Olive-tail moment (f) are shown