TAT-NF-Ya, NF-Yb, NF-Yc, USF1 complex binds to a HOXB4 promoter. (A) Coomassie-stained purified GST-tagged NF-Y subunits and USF-1, after SDS-PAGE. (B) EMSA detection of specific binding of TAT-NF-Ya protein to the HOXB4 promoter. A total of 50 ng each of NF-Ya, NF-Yb, NF-Yc, and USF1 was incubated for 30 minutes at room temperature with or without 2.5 μg of rabbit polyclonal anti–NF-Ya antibody, incubated with a radiolabeled 99-bp HOXB4 core promoter probe for 30 minutes at 30°C, and then subjected to electrophoresis under nondenaturing conditions on 5% agarose gels. Bands representing protein complexes retarded by complexing with transcription factors and/or antibody were detected by autoradiography. NF-Ya antibody retards a specific band only in the presence of TAT-NF-Ya protein within the reaction mixture.