Deficient Stat5 activation of Kit^YY567/569FF is partially reconstituted by Kit-induced transactivation of IL-7R. (A) Stat5 activation by Kit^YY567/569FF is partially reconstituted in the presence of IL-7R. Stat5 was immunoprecipitated from unstimulated (lanes 1,3) or KL-stimulated (lanes 2,4) 293T cells coexpressing Kit^YY567/569FF and Jak3 in the presence (lanes 1,2) and absence (lanes 3,4) of IL-7R and analyzed for tyrosine phosphorylation (top panel) and Stat5 protein (bottom panel). (B) Total tyrosine phosphorylation and activation of Erk1/2 induced by Kit^YY567/569FF are independent of IL-7R. Lysates were separated on SDS/PAGE and were analyzed for levels of total tyrosine phosphorylation, Kit, γc, IL-7Rα protein, phosphorylation of Erk1/2, and Erk2 protein. (C) Quantification of 4 independent experiments analyzing Kit^YY567/569FF-induced phosphorylation of Stat5 (left) and Erk1/2 (right graph) in presence (+) or absence (−) of γc and IL-7Rα. Data are displayed and statistically analyzed as in Figure 4C.