Figure 7.

IR3-deletion results in increased basal Jak2 activity and lack of cytokine-inducible signaling. (A) Schematic presentation of Jak2 constructs. (B) Expression plasmids for Jak2-HA, JH2Δ-HA, and 761Δ-HA were transfected into 293T cells, and cell lysates were immunoprecipitated using anti-HA antibody. Aliquots of the immunoprecipitates were separated in 7.5% SDS-PAGE and analyzed in anti-phosphotyrosine (top) and anti-HA immunoblots (middle). Aliquots of cell lysates were separated in 7.5% SDS-PAGE and analyzed in anti-HA immunoblot (bottom). (C) γ2A cells were transfected with Stat1-dependent luciferase reporter vector, pRLTK control vector, and Jak2, JH2Δ-Jak2, AflIIΔ-Jak2, or 761Δ-Jak2 constructs or with empty vector as a control. Five hours after transfection, the cells were changed into serum-free medium and starved for 15 h. The cells were stimulated with IFN-γ (1000 U/ml) for 5 h or left unstimulated. Luciferase activity was measured as described in MATERIALS AND METHODS. Shown is the mean from three independent experiments and the SEs of the mean.