Transforming growth factor beta inhibitory element in the rabbit matrix metalloproteinase-1 (collagenase-1) gene functions as a repressor of constitutive transcription

Transforming growth factor beta (TGF-beta) is a potent modulator of the ext racellular matrix, enhancing collagen synthesis and regulating expression o f several genes that encode the matrix metalloproteinases (MMPs), enzymes t hat degrade the extracellular matrix. In this study, we explored the mechan isms whereby TGF-beta inhibits expression of the MMP-1 (collagenase 1) gene . We used transient transfection and gel mobility shift assays to character ize a TGF beta inhibitory element (TIE) at -249 bp in the rabbit MMP-1 prom oter, which is also conserved at -246 bp in the human gene. This sequence s hares homology to a previously identified TIE in the rat stromelysin-1 (MMP -3) promoter, where it is located at -709 bp. Mutational analyses and trans ient transfections indicate that MMP-1 TIE functions both as a constitutive repressor of MMP-1 gene expression and, in the presence of TGF-beta, as an antagonist of transcriptional induction by phorbol esters. c-Fos binds to the TIE in the rabbit MMP-1 promoter, along with other nuclear proteins, ev en in the absence of treatment with TGF-beta. However, the pattern of prote ins binding to the TIE is altered in the presence of nuclear extracts from TGF-beta-treated cells, suggesting that TGF-beta leads to an alteration in protein/DNA interaction, with subsequent modulation of MMP-1 gene expressio n. We conclude that in the rabbit MMP-1 promoter, the TIE has dual function s as a repressor of basal transcription and as a mediator of the biologic e ffects of TGF-beta. Furthermore, these dual functions provide additional an d subtle mechanisms for regulating MMP-1 gene expression under a variety of biological and pathological conditions. (C) 2000 Elsevier Science B.V. All rights reserved.