Endogenous STAT1/STAT3 nuclear translocation upon simultaneous activation.

<p><b>A</b>. Fluorescence microscopy images of an isolated single cell clone expressing the endogenous STAT1 protein tagged with GFP at the C-terminus and the endogenous STAT3 protein tagged with RFP at the N-terminus (A549 lung carcinoma). The cells were imaged live before and after addition of 100 ng/mL IFN-γ and 100 ng/mL IL-6 using a 40x/1.3 oil objective. The scale bar is equal to 25 µm. <b>B</b>. The nuclear redistribution of both fusion proteins over time was quantified using translocation analysis in MetaMorph. Mean values ± SE, n = 50 are shown. Exponential fits gave the following decay time (±SD): τ_STAT1 = 7.6 ± 3.0 min, τ_STAT3 = 4.8 ± 2.5 min.