ASK1 is a CDC25A-interacting protein. (A) Yeast two-hybrid screening for CDC25A-interacting proteins. AD, activation domain; BD, binding domain; UAS, upstream activation sequence; minimum, TATA box minimum promoter; X, protein encoded in the library. (B) Complex formation of CDC25A and ASK1 in transfected COS cells. COS-7 cells were transfected with pcDNA3 expression vectors encoding the proteins shown in the panel. At 48 h posttransfection, extracts were prepared and analyzed by Western blotting (WB) with antibodies as shown (left panels). To detect complexes, extracts were immunoprecipitated (IP) with anti-CDC25A monoclonal antibody, followed by Western blotting with anti-HA monoclonal antibody (right panel). The arrow indicates HA-tagged ASK1 detected in CDC25A immunoprecipitation. Ig, IgG heavy chain in immunoprecipitation cross-reacted with the secondary antibody. (C) CDC25A-ASK1 complex in untransfected ovarian carcinoma cells. Extracts of exponentially growing OVCAR-8 cells were immunoprecipitated with anti-ASK1 polyclonal antibody, anti-CDC25A monoclonal antibody, or control mouse IgG, followed by Western blotting with the anti-ASK1 antibody.