FIGURE 4.

Inhibition of endogenous ERK1/2 by dominant-negative mutants or PD98059 increases the nuclear localization of CIITA. COS7 cells were transfected with either wild-type XpCIITA (A-D) or the S288A/S293A double serine mutant (E-H) and co-transfected with ERK1/2 or dominant-negative ERK1/2 or treated with PD98059 at the time of transfection. Immunofluorescence was performed 24 h post-transfection using anti-Xp to detect the subcellular localization of CIITA. Samples were compared with the relatively even nuclear-cytoplasmic distribution of wild-type CIITA (A). DAPI, 4′,6-diamidino-2-phenylindole.