FIGURE 3.
A short segment of p38β is sufficient to render p38α spontaneously active in HEK293 cells. Cell lysates were prepared and analyzed by Western blot with the indicated antibodies 48 h post-transfection. A, transfections with 1.5 μg of each p38 expression plasmid with or without 0.5 μg of a plasmid containing MKK6EE. 30 μg of protein from each sample were prepared 48 h post-transfection, separated by SDS-PAGE, blotted, and probed with the indicated antibodies. B, cells were transfected as in A. 48 h post-transfection cells were irradiated by UV (120 J\m2) or not and lysed 1 h later. p38 proteins were immunoprecipitated with α-HA antibodies and subjected to an immune complex kinase assay with ATF2. Samples were separated by SDS-PAGE, exposed to film, and probed with an α-HA antibody. C, increasing amounts (1, 2, and 4 μg of DNA) of each p38 were transfected into HEK293 cells. Proteins were analyzed as in A. D, transfections were preformed as in A.