Identification of optimal DNA demethylating agents. (A) Chemical structures of procainamide, the three selected agents IM25, CI-4-1, and 4e and their structurally related analogues IM9, CI-5-1, and 4o. (B) Potencies of procainamide, IM25, IM9, C-4-1, CI-5-1, 4e, and 4o in attenuating EGFP expression in the two-component reporter system. The EGFP intensities in individual treatments are illustrated on the right. Columns, mean (n = 3); error bars, S.D.