Fes is activated by EPO stimulation and constitutively associates with Stat1 and Stat3.

(A) Phosphorylation of Fes by EPO stimulation in UT-7/EPO (left panel) or UT-7/EPO/GEY4F cells (right panel). EPO-starved cells were stimulated with EPO (10 U/mL) or G-CSF (200 ng/mL) for 7 minutes, and the cell lysates were prepared for immunoprecipitation with anti-Fes antibody. Western blotting analysis was performed by using antiphosphotyrosine (PY-20) or anti-Fes antibody. (B) Complex formation of Fes, Stat1, and Stat3. EPO-starved cells were stimulated with EPO (10 U/mL) for 7 minutes, and the cell lysates were prepared for immunoprecipitation with anti-Fes. Western blotting analysis was performed by using antibodies against Stat1, Stat3, or Fes.