FIGURE 2. Effect of the 11G-loop in the human sod2 promoter region on the constitutive transcription.

A, the putative structure of 11G unpaired loop in the human sod2 promoter (loop/WT) and strategies for interrupting loop formation or loop reconstitution using mutagenesis approaches. The 11G sequence was deleted (loop/Del); the loop was straightened out (loop/Str); mutated sequence was found in cancer cells (loop/Cancer); and an alternative loop was formed (loop/Alt). Site-directed mutagenesis is indicated by arrows. B, the luciferase reporter gene driven by the wild-type of promoter (P7) and loop-deficient mutant promoters. SmaI-PvuII sites were used to insert the mutant promoter fragment (-135 to -61) into the P7 promoter. C, the promoter reporter constructs (0.5 nM) were cotransfected with a β-galactosidase internal control (0.1 nM) into VA13 cells. The promoter activity was determined by β-galactosidase-normalized luciferase reporter responses. Significant differences (p < 0.01) in the promoter activity compared with the loop-deficient promoters and vector only control are indicated by stars.