Ionizing radiation induces cytoplasmic accumulation of Tax. (A) HEK 293T cells were transfected to express Tax-GFP (green). Shown is a representative of Tax expression in cells at 40 hours after transfection before exposure (−IR) and at 10 minutes and 4 hours after exposure to 10 Gy of ionizing radiation (post-IR). The nuclei were counterstained with 4′,6-diamidino-2-phenylindole/TO-PRO and the images merged. (B) Tax-expressing HEK 293T cells were exposed to optimal doses of either UV or IR. The nuclei were counterstained with 4′,6-diamidino-2-phenylindole/TO-PRO and the images merged. (C) The HTLV-1–infected T-cell line C8166 was grown to the log phase, plated onto polylysine-coated slides, and prepared for immunofluorescence confocal microscopy. Endogenous Tax (red) was visualized by indirect immunofluorescence confocal microscopy before exposure to IR (−IR) and at 30 minutes and 60 minutes after exposure to 10 Gy (post-IR). At the 60-minute time point, cells were costained for ubiquitin (green).