Vpr associates with TAK1. (A) HEK293T cells (4 × 106) were co-transfected with Myc-TAK1 and Flag-Vpr. Co-immunoprecipitation was performed with indicated antibodies. Samples from both cell lysates and immunoprecipitates were subjected to Western blotting and probed with rabbit anti-TAK1 and mouse anti-Flag antibodies. (B) Vpr associates with endogenous TAK1. Lysates of Flag-Vpr-expressing HEK293T cells (4 × 106) were immunoprecipitated with control mouse IgG and mouse anti-TAK1 (left) or anti-Flag (right) antibodies. Samples from both cell lysates and immunoprecipitates were subjected to Western blotting. (C) Vpr co-localizes at least in part with TAK1. HeLa cells (0.1 × 106) were transfected with Flag-Vpr and/or Myc-TAK1 plasmid DNA. Indirect IFA was used to localize Vpr (with rabbit anti-Flag antibody and FITC-conjugated goat anti mouse secondary antibody) and TAK1 (with mouse anti-Myc antibody and TRITC-conjugated goat anti mouse secondary antibody). Nuclei were visualized with DAPI staining. Representative images are shown.