FES is phosphorylated in cells that harbor KIT^D816V. Immunoprecipitations (IPs) were carried out on soluble cell lysates (SCLs) of serum-starved cells. SCLs were also directly probed with anti-FES to show equivalent quantity of proteins in all lysates. (A) IPs were done on SCLs of TF-1 cells with anti-FES antibody or with an isotype-matched irrelevant antibody (IP control), followed by Western blotting (WB) with an antiphosphotyrosine antibody (anti-PY) or anti-FES antibody. (B) IPs were done on SCLs from TF-1 cells with anti-PY antibody, followed by WB with anti-FES antibody. (C) Lysates from TF-1 KIT^D816V cells treated with siRNA were immunoprecipitated using anti-PY antibody, followed by WB with anti-FES antibody. KIT and FES protein expression were also controlled in the cell lysates. (D) IPs on lysates from mouse (P815 and D816VKIT BMMCs) or human (HMC-1) mastocytomas with anti-PY antibody or with an isotype-matched irrelevant antibody, followed by WB with anti-FES antibody. P-FES indicates phosphorylated FES protein. The data presented in each panel are representative of 1 out of at least 3 independent experiments.