Fig. 3.

Effects of the overexpression of the p72 mutants on ZAP's activity. The plasmid expressing the indicated Flag-tagged p72 proteins or Flag-tagged p68 was cotransfected with the pMLV-luc reporter into 293TRex-ZAP cells. Immediately after transfection, tetracycline was added to induce ZAP expression. Forty-eight hours after transfection, the cells were lysed. An aliquot of the lysate was analyzed for the luciferase activities, and another aliquot was analyzed for the expression of the p72 proteins or p68 by Western blotting. Fold inhibition was calculated as the luciferase activity in the mock-treated cells divided by the luciferase activity in the tetracycline-treated cells. (Upper) Relative fold inhibition was calculated as the fold inhibition in the presence of empty vector divided by the fold inhibition in the presence of the p68 or p72 proteins. The relative fold inhibition data are means + SE of three independent experiments, and the Western blotting result (Lower) is representative of three independent experiments. The asterisks denote to P < 0.05. F.I., fold inhibition; EV, empty vector; 72N, N-terminal domain of p72; 72C, C-terminal domain of p72; p72KR, p72-K142R mutant.