Regulation of the human MMP-1 gene promoter by relaxin without or with β-estradiol requires both the AP-1 and PEA-3 motifs. Cell lysates from cells transiently transfected with the wild type minimal −90/−67 bp segment of the MMP-1 promoter containing the AP-1 and the PEA-3 sites (WTcol-tkCAT, WT) or this promoter with a mutated AP-1 site (mAP-1col-tkCAT, mAP-1) or mutated PEA-3 sites (mPEA-3col-tkCAT, mPEA-3) (A) and cotransfected with pSV-β-gal vector were assayed as described in figure 2. (B) Histogram for mean (± SE) fold induction of CAT/β-gal for each of the treatments relative to controls was plotted for four experiments. (C) Relaxin dose-response experiments were performed by transfecting disc fibrocartilaginous cells with the WTcol-tkCAT promoter, exposing them to increasing concentrations of relaxin with or without β-estradiol and assaying as described above. (*p < 0.05, **p < 0.005, ***p < 0.0005).