Regulation of Human Interstitial Collagenase (Matrix Metalloproteinase‐1) Promoter Activity by Fibroblast Growth Factor

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Abstract
Basic fibroblast growth factor (bFGF) is a pleiotropic factor that is implicated in tissue remodeling. The growth factor is capable of up‐regulating the expression of the interstitial collagenase (matrix metalloproteinase‐1 or MMP‐1) gene. In this study, the full‐length human MMP‐1 promoter, spanning 4.3 kb, was sequenced and the regulatory control of its activity by bFGF was examined in NIH3T3 fibroblasts. Several regulatory sequences, including five activator protein‐1 (AP‐1), five activator protein‐2 (AP‐2), five glucocorticoid‐response elements and multiple ets/polyoma enhancer‐binding 3 elements, were identified. Deletion constructs were prepared and transiently transfected into fibroblast cultures incubated with and without bFGF. The results showed that bFGF enhanced the activity of the deletion promoter fragments and the full‐length MMP‐1 promoter by sixfold or more in the cell cultures. Stimulation of the MMP‐1 promoter activity by bFGF was reflected in substantial increase of the collagenase mRNA levels. A bFGF‐responsive element appeared to be the AP‐1 consensus sequence. Mutation of the first AP‐1 site resulted in major reduction of the basal level of the MMP‐1 promoter activity, supporting the notion that the AP‐1 consensus sequence is essential for the constitutive expression of the MMP‐1 gene. Furthermore, bFGF induction of the activity of the promoter constructs containing a mutant AP‐1 site was essentially absent, suggesting that the regulatory element is necessary for the induction of the promoter activity by the growth factor. Thus, bFGF up‐regulates MMP‐1 gene expression in NIH3T3 fibroblasts via induction of its promoter activity that is dependent on an AP‐1 consensus sequence.