Quantitation of RNF4-induced Tax cellular redistribution. (A) HEK 293T cells were transiently transfected to express TaxGFP and at 48 hours after transfection, Tax localization was classified into 3 groups (cytoplasmic, mixed, and TSS). Shown are representative examples of each expression phenotype. (B) Quantitation of Tax distribution. Shown is the relative distribution of Tax-GFP localization alone, after coexpression of Tax-GFP and RNF4-mCherry (+ RNF4), and after coexpression of Tax-GFP and RNF4-mCherry RM (+ RNF4 RM). (C) The effect of RNF4 overexpression on the basal activity of the HTLV-1–LTR and the NF-κB–responsive promoter was assessed. Results are reported as the relative activity of the reporter alone and in the presence of RNF4 as determined by the luciferase enzyme assay. Also analyzed was the effect of RNF4 expression on Tax transcriptional activation of the HTLV-1–LTR (D) and the NF-κB–responsive promoter (E). Results are reported as the fold activation by Tax over basal transcription. (F) The impact of RNF4 expression on the activation of both HTLV-1–LTR and NF-κB–responsive promoters in HUT102 cells by endogenous Tax. Error bars indicate the SD of experiments performed in triplicate.