Coexpression of Bmx induces activation of Stat3. (A) COS cells were transfected with Stat3 expression vector together with Syk, Fyn, c-Src, Bmx-HA, or Jak2-HA expression vectors. Lysates were analyzed in the mobility shift assay using ³³P-labeled SIE oligonucleotide. Lysates expressing Stat3 and Bmx-HA or Jak2-HA were supershifted using anti-Stat3 antibody. (B) The same lysates were electrophoresed in 7.5% SDS-PAGE and Western immunoblotted with anti-phosphotyrosine antibody or anti-Stat3 antibody. The autophosphorylated c-Src, Fyn, and Syk polypeptides are indicated by asterisks. (C) The Bmx-HA and Jak-HA containing lysates were also immunoblotted using anti-HA antibody.