Fig. 4. wtSTAT1 rescues STAT1(L407A)-deficient nuclear accumulation. (A) HT1080 cells expressing wtSTAT1–GFP (a and b) or STAT1–GFP(L407A) (c and d) were untreated (a and c) or treated with IFN-γ for 30 min (b and d). Cells were fixed and STAT1–GFP cellular localization was examined by fluorescent microscopy. (B) The importin- α5 interaction assay was performed on whole-cell lysates from STAT1–GFP(L407A) expressing HT1080 cells either untreated (–) or treated with IFN-γ (+). Input is displayed in lanes 1 and 2. Cell lysates were incubated with GST (lanes 3 and 4) or GST–importin-α5 (lane 5 and 6) bound to glutathione beads. The interacting proteins were analyzed by western blot with anti-STAT1 phosphotyrosine antibody and the positions of endogenous wtSTAT1 and STAT1–GFP(L407A) are noted.