JAK3 mutants transform Ba/F3 and MOHITO cells to cytokine-independent growth. (A) Schematic representation of JAK3 protein and its main domains; the four-point-one, Ezrin, Radixin, Moesin (FERM) domain; the Src homology-2 (SH2) domain; and the pseudokinase and kinase domains. Mutations studied in this work are shown. (B-C) The proliferation curve of Ba/F3 (B) or MOHITO (C) cells expressing various JAK3 mutants, JAK3 wild-type, or empty vector, in the absence of cytokines. Mutations that did not stimulate proliferation more than wild-type JAK3 were considered nontransforming mutants and are indicated with asterisk (*).