E47, PU.1 and IRF-4 synergistically activate CIITA-PIII in HeLa cells in a site-dependent manner. (A) Schematic representation of all CIITA-PIII reporter constructs tested. E-boxes and Site-C are indicated, and the mutated Ets-box of Site-C is depicted by an X. (B) The different mutant CIITA-PIII reporter constructs depicted panel A were cotransfected with expression plasmids coding for E47fd, PU.1, and IRF-4 or IRF-8 into HeLa cells as indicated. Cotransfections of PIIIs with expression plasmids coding for either E47fd, PU.1, IRF-4, or IRF-8 are indicated in lanes 15 to 18. Fold induction is indicated as “fold ind.” on top of panel B. HeLa cells were harvested after 48 and analyzed for luciferase activity. Luciferase activity values were normalized with Renilla luciferase activity values, and relative luciferase activities are indicated as mean SD of n = 4.