Promoter elements in the transcriptional activation of the human stromelysin-1 gene by the inflammatory cytokine, interleukin 1

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Abstract
Stromelysin-1, a tissue-remodelling metalloproteinase synthesized by fibroblasts, has proteolytic activity against a variety of extracellular matrix components. Stromelysin-1 gene transcription is induced by the inflammatory cytokine interleukin (IL)-1. In fibroblasts transiently transfected with constructs containing 5′-deletion mutants of the human stromelysin-1 gene promoter, IL-1-induced transcriptional activity was abolished with the removal of region -102 to -54. This region includes an AP-1 binding site at positions -70 to -64. The AP-1 site alone increased the basal activity of and conferred minimal IL-1 inducibility onto the heterologous gene promoter of thymidine kinase. Interestingly, although the removal of the AP-1 site from the native promoter (-1303 to +4) affected the absolute levels of IL-1-induced and basal promoter activity, it did not alter their ratio, indicating the involvement of regions outside the AP-1 site in the IL-1 response. Of the stromelysin-1 5′ flanking sequence examined, only the region -274 to -54 could confer IL-1 inducibility to a heterologous promoter independently of the AP-1 site. This region also bound specific nuclear factors. Further analysis revealed that the region composed of -86 to -71 and -63 to -54 could independently respond to IL-1 and bind protein of whole cell extracts. Protein binding to this region and to the AP-1 site was modestly induced by IL-1 treatment. From these results we conclude that, in fibroblasts, the AP-1 site (-70 to -64) is not necessary for the IL-1 response; however, it probably interacts through protein associations with the responsive region immediately surrounding it in the absolute transcriptional activation of the human stromelysin-1 gene by IL-1.