Fig. 3

Cellular localization and binding of phospho-Stat3 to DNA in SKN-SH wild-type (W) and SKN-SH/Dox6 doxorubicin-resistant (R) human neuroblastoma cells. (A) Confocal microphotographs showing differences in expression of phospho-Stat3 between W and R cell lines. Note increased nuclear localization of phospho-Stat3 in R cells when compared to W cells. Cells were plated on a sterile slide, cultured for 2 days, and stained with anti-phospho-Stat3 and FITC-conjugated secondary antibody, as described in “Methods.” (B) DNA mobility gel shift analysis of phospho-Stat3 binding to sis-inducible element (SIE). Nuclear proteins were extracted and incubated with radiolabeled DNA. Protein-DNA complexes (SIE) and free SIE were separated on 5% SDS-PAGE and autoradiographs prepared.