Nuclear translocation of STAT-GFP constructs. The S9-13 and R15-3 cell lines were transfected with IRF9, Stat1, or Stat2 GFP fusion constructs (-) and (+) IFN-α (1,000 IU/ml) and their nuclear translocation was observed under a confocal microscope. The images are represented as the superimposition of Green Fluorescent Protein (green), To-Pro3 633 (far red), and the differential interference contrast images (DIC) (gray scale). Fluorescence green and red microscopic picture of the same area were taken and superimposed using Abode Photoshop. Left panel shows high resolution picture showing that the IRF9-GFP fusion protein translocates to the nucleus of both S9-13 and R15-3 cells in an IFN-α independent manner. Middle panel shows s tat1-GFP fusion protein efficiently localized to the nucleus of S9-13 cells within 30 minutes after IFN-α treatment. Stat1-GFP was unable to localize to the nucleus in R15-3 cells. Right panel shows stat2-GFP efficiently localized to the nucleus of S9-13 cells within 30 minutes after IFN-α treatment. Stat2-GFP was unable to localize to the nucleus in R15-3 cells.