Transcriptional inhibition of stromelysin by interferon-gamma in normal human fibroblasts is mediated by the AP-1 domain

The expression of the major matrix-degrading metalloproteinase, stromelysin (SL), is modulated by a variety of cytokines and growth factors. Interfero n-gamma (IFN-gamma) is a potent modulator of SL expression, either inhibiti ng or activating expression in a cell-specific manner. We have investigated the mechanisms involved in the regulation of SL gene expression in culture d human fibroblasts by IFN-gamma. Reverse transcription-polymerase chain re action (RT-PCR) assays confirmed the previously reported profound inhibitor y response of SL mRNA expression to IFN-gamma [Amaldi et al., 1989]. For ev aluation in transient gene expression assays, 1.2-kilobase (kb) pairs (-121 4 to +14 relative to the transcription start sire), and shorter, deletion m utant fragments of the SL promoter were cloned into appropriate chloramphen icol acetyltransferase transferase (CAT) expression vectors. The SL promote r along this region contains an active polyomavirus enhancer A-binding prot ein-3 (PEA-3) site at -216 and an activator protein-1 (AP-1) site at -70. T reatment of transfected neonatal foreskin fibroblasts with 300-500 U/ml IFN -gamma resulted in down-regulation of both basal and IL-l p-induced CAT gen e expression. IFN-gamma also decreased CAT expression when placed under the control of a synthetic multimeric AP-1 site construct. Gel-shift assay dat a indicate a decrease in specific binding to AP-1 oligonucleotide of nuclea r extract from IFN-gamma and PMA/IFN-gamma-treated cells. The suppression o f SL expression by IFN-gamma, in human fibroblasts therefore is mediated th rough the AP-I element, J. Cell. Biochem. 72:373-386, 1999. (C) 1999 Wiley- Liss, Inc.