Nar binds to SH2 domain, decreases STAT3 dimerization and inhibits STAT3 translocation into the nucleus
(A) The predicted binding complex structure of Nar in the SH2 domain of STAT3, where Nar interacts with the SH2 domain via four pronounced hydrogen bonds (red lines). (B) MCF-7 cells were treated with different concentrations of Nar for 24 h, separated using native PAGE, and STAT3 analyzed by western blot. (C) 293T cells were transfected with STAT3-luc, and then treated with Nar and stattic in the presence of 50 ng/mL IL-6 for 24 h. (D) Immunofluorescence staining for STAT3, p-STAT3, and the nucleus (DAPI, blue) after Nar treatment (100 nM, 24 h) in MCF-7 cells. (E) After treatment with Nar, the nuclear and cytoplasmic proteins were extracted to determine the levels of STAT3 and p-STAT3. (F) After treatment with Nar, STAT3 downstream target proteins (i.e., c-Myc, cyclin D1, surviving, and p53) were analyzed by western blot. Data are shown as mean ± SD. ∗∗p < 0.01, ∗∗∗p < 0.01, ###p < 0.001.