Zta-induced activation of the MMP3 promoter requires three AP-1 elements.

<p>(<b>A</b>) The MMP3 promoter used in the reporter gene assay is illustrated schematically. Three AP-1 elements at −216, −172, and −89 of the promoter are indicated and labeled as A, B, and C, respectively. (<b>B</b>) The reporter plasmids driven by the wild-type (wt) MMP3 promoter or its AP-1-mutated derivatives (mA, mB, mC, mAB, mBC, mAC, and mABC) were transfected into HONE-tetonZ cells in the presence (black bars) or absence (white bars) of doxycycline induction. The promoter activity was examined by using a luciferase assay. Expression of Zta and β-actin was examined by an immunoblotting assay.