Complexes of NF-Yc with USF2 and USF1 in K562 cell lysates. (A) K562 cell lysate was immunoprecipitated by the antibody against either USF1 or USF2, and the resulting precipitates were probed with the antibodies against 3 subunits of NF-Y. No signals were detected with anti-NF-Ya or anti-NF-Yb. (B) K562 NE was incubated with sepharose bead-linked GST-NF-Ya, GST-NF-Yb, or GST-NF-Yc fusion protein individually. After extensive washing, the bound products were eluted and then probed by the antibody against either USF1 (top blot) or USF2 (bottom blot) in Western blotting.