Bmx does not phosphorylate endogenous Jak kinases. (A) 293T cells were transfected with Bmx-HA expression vector or left without transfection. Jak1 was immunoprecipitated from cell lysates using anti-Jak1 antibody and the immunoprecipitates were electrophoresed in 6% SDS-PAGE followed by Western immunoblotting using anti-Jak1 or anti-phosphotyrosine antibodies. The Ig heavy chains are indicated by an asterisk. (B) Total cell lysates were electrophoresed in 6% SDS-PAGE followed by Western immunoblotting with anti-phosphotyrosine antibodies.