Differential functional roles for two AP1 binding sites of S100A7.

(A) The DNA sequence of S100A7 promoter (GenBank accession number: AF050167) is shown and two putative AP-1 binding sites are framed by gray shadow. (B) The schematic presentation of the luciferase reporters driven by S100A7 promoter containing different mutated AP-1 binding sites is indicated. (C) The luciferase reporter assays were performed using aforementioned individual construct in the absence or presence of either c-Jun/c-Fos or c-Jun/Fra-1 heterodimeric AP-1 complexes. Both the basal activity (lane 1, open bar) and AP-1-activated promoter activities (lanes 2 and 3, open bars) are inhibited by AP1-1 site mutation, indicating the essential role of this AP-1 binding site. On the other hand, the S100A7 promoter containing mutated AP1-2 site can still be activated by heterodimeric c-Jun/c-Fos instead of c-Jun/Fra-1 (compare lanes 2–3 to lane 1, dashed bars). The result indicated that the functional role of AP1-2 site is less than AP1-1 site for c-Jun/c-Fos; however, the two putative AP-1 binding are both important for c-Jun/Fra-1 to activate S100A7 promoter. Surprisingly, c-Jun/Fra-1 can activate the S100A7 promoter containing two mutated AP-1 binding sites (compare lanes 2–3 to lane 1, light grey bars), indicating that the S100A7 promoter may be activated by heterodimeric c-Jun/Fra-1 AP-1 complex with some unexplored mechanism. These data (C) are the average of three experiments (mean ± SD; n = 3). All p values less than 0.05 were considered statistically significant.