FIG. 10.

K88R mutant prevents WT PITX2a synergism with Pit-1. (A) CHO cells were transfected by electroporation with the prolactin-luciferase reporter alone or with 5 μg of PITX2a and/or K88R in the presence and absence of Pit-1 (10 μg), as indicated. (B) LS8 cells were transfected by lipofection with PITX2a (0.5 or 1 μg, as indicated) and Pit-1 (0.5 μg) alone or in combination with 0.5 μg of K88E, K88R, or T68P, as indicated. The activity is shown as the mean activation (fold) relative to results for reporter alone, ± standard errors of the means, from four separate experiments. (C) CHO cells were cotransfected by electroporation with the prolactin-luciferase reporter, Pit-1 (10 μg), PITX2a (5 μg), and the indicated amounts (μg) of additional PITX2a or K88R. Cotransfection of increasing amounts of K88R with 5 μg of WT PITX2a shows a significant decrease in activation relative to that seen with 5 μg of WT PITX2a alone (*, P < 0.03; **, P < 0.002; ***, P < 0.001). The data represent results from four separate experiments and represent the mean activations (fold) ± standard errors of the means.