FIGURE 1.

A KPNA1 binding mutation in STAT1 blocks rapamycin-induced STAT1 nuclear import. A549 or COS7 cells expressing the recombinant ECFP-STAT1 trafficking mutants L407A, Y701F, or S727A were incubated without or with 50 ng/ml rapamycin (Rap) or 100 units/ml IFN-γ for 0 or 1 h. ECFP-STAT1 (cyan) was detected by direct fluorescence confocal microscopy. The slides were mounted with solution containing the nuclear marker DAPI (navy blue). Summarized data (mean nuclear to cytoplasmic pixel density ratio ± S.E., n = 3–5 cells/experiment) are shown below the images and are representative of three independent experiments. *, p < 0.05 versus control by Student's t test; ns, not statistically significant.