RNF4 expression required for DNA damage–induced relocalization of Tax. (A) RNF4-depleted cells (RNF4) or control cells (control) were transfected with S-TaxGFP. At 48 hours after transfection, the cells were either left untreated (−IR) or irradiated with 10 Gy (+IR) before recovery for 30 minutes. Cells were then fixed, counterstained with 4′,6-diamidino-2-phenylindole/TO-PRO (blue), and Tax (green) was visualized using confocal microscopy. Shown is the overlay image. (B) RNF4-depleted cells were cotransfected with S-TaxGFP (green) and RNF4-mCherry (red). Cells were fixed and analyzed by confocal microscopy. Shown are the individual and overlay (Merged) images. (C) Quantitation of Tax redistribution after IR. The graph represents the relative cellular distribution of Tax within the control cells or the RNF4-depleted cells before and after ionizing radiation.