DAF promoter fragment between nucleotides − 437 and − 277 harbors NO regulatory region. (A) Ishikawa cells were transiently transfected with DAF promoter-β- galactosidase reporter plasmid, treated with DTNO (1 mM) or spent DTNO (1 mM) or the substrate for NOS enzyme L-arginine (L-arg, 0.3 mM) or L-arginine combined with NOS inhibitor L-NAME (3 mM) for 24h and the β- galactosidase activity was measured. Vector control (V) devoid of DAF promoter was also used as negative control. All experiments were performed three times, and one set of data is presented. Error bars indicate S.E of triplicate samples (*, **, p < 0.001versus control; *** p < 0.05 versus L-arg). (B) Systematic representation and cloning strategy of DAF gene promoter into pβgalb reporter vector. (C) DAF promoter deletions were cloned into pβgalb reporter vector and transfected to Ishikawa cells. Cells were treated with DTNO (1mM) for 24 h, and β-galactosidase activity was measured. All experiments were performed three times, and one set of data is presented. Error bars indicate S.E of triplicate samples (*, p < 0.0002; **, p < 0.041; ***, p < 0.0027 versus control in each group).