Dynamic analysis of STAT6 signalling in living cells

Abstract
Functional activity of N‐ and C‐terminal fluorescent fusion proteins between STAT6 and EGFP was demonstrated through IL‐4‐dependent transcriptional activation and nuclear translocation. The N‐terminal (EGFP–STAT6) fusion protein appeared to be more active than the C‐terminal fusion. In HEK‐293 cells both fusion proteins formed fluorescent nuclear foci following IL‐4 stimulation, but in HeLa cells nuclear accumulation was homogeneous. Stimulation of the NF‐κB pathway through TNFα treatment, or expression of p65–EGFP fusion protein, repressed both basal STAT6‐dependent transcriptional activity and the extent of activation in response to IL‐4. This indicates a novel mechanism of inhibition of STAT6 signalling by NF‐κB activation.