FIG. 4.
Transactivation properties of the W37 and K70 mutant forms of Stat5a and Stat5b. (A) Mutations of W37 alone and of both W37 and K70 in Stat5a and Stat5b significantly reduce their transactivation functions. 293T cells were transfected with IL-2Rβ, γc, Jak3, and wild-type or mutant Stat5a and Stat5b proteins as well as with 1 μg of a PRRIII-luciferase reporter construct and 0.5 ng of a control luciferase plasmid, pRL-TKLuciferase. Twenty-four hours after transfection, cells were split into two groups, and one-half was stimulated with 2 nM IL-2 for 11 to 14 h. The relative luciferase activity is the activity of the reporter plasmid after normalization for the activity of the control reporter plasmid. (B) Experiments were performed as for panel A, but both Stat5a and Stat5b expression plasmids were simultaneously expressed. WT, wild type.