Y114A in Jak2V617F inhibits Myc and Pim expression regulated by Jak2V617F. Protein expression was determined in cellular lysates by immunoblotting as indicated. (A) Parental BaF3.EpoR cells and cells infected to express Jak2 or various mutants were growth factor deprived. The phosphorylation of STAT5 on its activation site and the expression of Pim1, Pim2, and c-Myc was detected. (B) HEL cells were treated for 48 hours with the indicated amount of Jak inhibitor I and cellular proteins detected. (C) Untreated BaF3 cells with doxycycline-inducible constitutively active STAT5 were used and compared with cells treated with 1 μg/mL doxycycline (Dox) or cells maintained in interleukin-3 (IL-3)–containing medium. Cellular expression of Pim1, Pim2, and c-Myc was detected. (D) HEL cells were treated for 48 hours with the indicated amount of N-acetylcysteine (NAC) and cellular proteins detected. *Significant differences (P ≤ .05) were observed between treated and control cells.