(A, B, and C) Crkl immunoprecipitates from thrombopoietin-treated UT7/TPO cells contain a tyrosine-phosphorylated 95- to 100-kD protein that is also recognized by a STAT5 MoAb. UT7/TPO cells were lysed at the indicated times by the addition of an equal amount of a buffer containing 2% Triton X-100 before and after exposure to thrombopoietin (100 ng/mL). Tyrosine-phosphorylated proteins (A), STAT5 (B), and Crkl (C) in the Crkl immunoprecipitates were detected as described in Fig 1.