The effect of ATRA on the binding of transcription factors to the TF promoter. (A) Effect of ATRA on the binding of c-Fos/c-Jun, Rel/p65, and Sp1. Nuclear extracts were isolated from THP-1 cells treated with or without ATRA (1 × 10⁻⁵ mol/L) for 30 minutes before the addition of LPS (10 μg/mL) for 2 hours. EMSAs were performed using AP-1, κB, and Sp1 sites. The position of c-Fos/c-Jun,c-Rel/p65, and Sp1 is indicated. Similar results were observed in an independent experiment. (B) Antibody supershift analysis of the protein-DNA complex formed using nuclear extracts from ATRA- and LPS-treated cells. Antibodies to various NF-κB proteins and Sp1 were incubated with nuclear extracts before the addition of a radiolabeled TF κB site.