TRAF6 interacts with STAT3 and mediates the ubiquitination of STAT3.

<p>(A) TRAF6 interacts with STAT3 in mammalian cells. Myc-TRAF6 and Flag-STAT3 were co-transfected into HEK293 cells. After 24 h, the cell lysates were immunoprecipitated with anti-Flag antibody and subjected to Western blot with the anti-Flag or anti-Myc antibodies. (B) The cell lysates of HEK293 cells were immunoprecipitated with anti-TRAF6 antibody and subjected to Western blot with the anti-TRAF6 or anti-STAT3 antibodies. (C) Myc-TRAF6 was transfected into HEK293 cells in a dose-dependent manner. After 24 h, the cell lysates were probed with anti-Myc, anti-STAT3 and anti-GAPDH antibodies. (D, E and F) TRAF6 mediates the ubiquitination of STAT3. HA-Ub(WT) (D), HA-Ub(K63R) (E) or HA-Ub(K48R) (F) and Flag-STAT3 were co-expressed in HEK293 cells with Myc-TRAF6 or empty vectors. The cell lysates and immunoprecipitates were resolved by SDS-PAGE and immunoblotted with anti-HA or anti-Flag antibodies. The data are representative of at least three independent experiments.