Fig. 4. Phosphorylation mimic at S189 and not T198 affects the localization of mSTI1-EGFP. (A) NIH3T3 fibroblasts were stably transfected with pB-mSTI1-EGFP or derivative plasmids pB-mSTI1(S189A)-EGFP, pB-mSTI1(T198A)-EGFP, pB-mSTI1(S189E)-EGFP and pB-mSTI1(T198E)-EGFP. Cells were fixed in 3.7% paraformaldehyde before mounting and visualization by confocal laser fluorescence microscopy. Scale bars, 10 µm. (B) Cells were transfected as above, and cells demonstrating cytoplasmic fluorescence or nuclear and cytoplasmic fluorescence were quantified. The error bars represent standard deviations.