The Epo receptor is not detected in anti-GAB1 immunoprecipitates. Anti-GAB1 and anti-EpoR immunoprecipitates were prepared from UT-7 cells stimulated for 10 minutes with 10 U/mL Epo or from control cells. These immunoprecipitates were analyzed by Western blot using antiphosphotyrosine (anti-PY) antibodies.