Tec is involved in the cytokine-driven activation of c-fos proto-oncogene. (A) BA/F3-hGMRαβ cells (1 × 10⁷) were transfected with the pfos/luc reporter plasmid (2 μg) together with 5 μg each of the pSRα (Vector), pSRα-Syk (Syk), pSRα-Lyn (Lyn), pSRα-Jak2 (Jak), or pSRα-Tec (Tec). After 5 hours of incubation in cytokine-free medium, the cells were further cultured for 5 hours without (no factor) or with 5 ng/mL of human GM-CSF (+GM-CSF) or 25 U/mL of mouse IL-3 (+IL-3). Luciferase activity was assayed in each fraction and calculated as relative light units (RLU)/min/μg of protein. The mean value plus SD of the luciferase activities in triplicate samples from each fraction is shown as arbitrary units. (B) BA/F3-hGMRαβ cells were transfected with pSRα-Syk, pSRα-Lyn, pSRα-Jak2, or pSRα-Tec, and cultured for 24 hours in the presence of IL-3. Total cell lysates (10 μg/lane) were prepared from each set (+) and untransfected BA/F3-hGMRαβ cells (−), and were immunoblotted with the antibodies against the corresponding kinases.