Figure 1.

Suppression of IL-4-induced activation of a Stat6-responsive reporter gene by SOCS-1 and SOCS-3, but not SOCS-2, in transient transfection. A, M12 cells were transfected with increasing amounts of SOCS expression vector, 5 μg of p(Iε-IL4RE)₄-Luc reporter and 1 μg of pSV40-βgal by DEAE-dextran and electroporation. Total amount of transfected DNA was kept constant at 12 μg by addition of salmon testes DNA. One-half of each transfection was treated with IL-4 and, 24 h after transfection, cells were harvested and luciferase activity was determined. B, 293T cells were transfected with increasing amounts of SOCS expression vector, 5 μg of p(Iε-IL4RE)₄-Luc reporter, 1 μg of pSV40-βgal, and 0.5 μg HuStat6 expression vector by calcium phosphate precipitation. Total amount of DNA was kept constant at 10.5 μg by addition of salmon testes DNA. IL-4 was added to the media 24 h after transfection, and, 48 h after transfection, cells were harvested and luciferase activity was determined. Luciferase values are adjusted for transfection efficiency by standardizing with the β-galactosidase activity of each sample. The results shown are averages of three independent transfections: SOCS-1 (top panels), SOCS-2 (middle panels), and SOCS-3 (bottom panels).