SOCS3 differentially affects growth signals from JAK2 V617F. Ba/F3 cells expressing EPOR with either JAK2WT or JAK2 V617F and SOCS3 regulated by tetracycline removal (-) were incubated in cytokine-free medium for 4 hours, stimulated with EPO (100 U/mL) for 10 minutes, washed and incubated for 120 minutes in cytokine-free medium. Lysates were immunoprecipitated (IP) with JAK2 antibody and blotted with phosphotyrosine antibody (top panel). The blot was stripped and reprobed with JAK2 antibody (middle panel). SOCS3 expression was determined by probing of corresponding whole-cell lysates (WCLs) with FLAG antibody (bottom panel).