Collagenase Gene Expression in Cutis Laxa Fibroblasts Is Upregulated by Transcriptional Activation of the Promoter Gene Through a 12-O-Tetradecanoyl-Phorbol-13-Acetate (TPA)-Responsive Element

Abstract

Our previous work demonstrated that collagenase mRNA levels are increased in fibroblasts derived from patients with cutis laxa (CL). To pursue the mechanism of the upregulation of collagenase expression, we investigated transcriptional levels of the collagenase gene in CL fibroblasts. Fibroblasts cultured from the skin of three congenital CL patients were studied. Northern blot hybridization revealed 2.8- to 7.3-fold increases in collagenase mRNA levels in CL fibroblasts compared with normal cells. Nuclear run-off experiments demonstrated that the transcription rate of the collagenase gene in nuclei isolated from the same cells was 5.1- to 10.2-fold higher in the CL fibroblasts than in the controls. Transient transfection of a normal collagenase promoter-CAT construct into the cells further showed significantly enhanced transcriptional activity in CL but not in normal fibroblasts. Experiments of transient transfection of deleted or small substituted collagenase promoter-CAT constructs indicated that collagenase transcription in CL fibroblasts was activated the TPA-responsive element site of the collagenase promoter gene. Although the levels of Jun and Fos gene expression did not differ from those observed in normal fibroblasts, AP-1-binding activity, as measured by the ability to bind to an oligonucleotide containing a TPA-responsive element, was significantly elevated in CL fibroblasts as compared with normal fibroblasts. These data suggest that collagenase expression is upregulated at the transcriptional level by endogenous activation of DNA binding of AP-1 in CL fibroblasts [corrected].