COLLAGENASE GENE-EXPRESSION IN CUTIS LAXA FIBROBLASTS IS UP-REGULATEDBY TRANSCRIPTIONAL ACTIVATION OF THE PROMOTER GENE THROUGH A 12-O-TETRADECANOYL-PHORBOL-13-ACETATE (TPA)-RESPONSIVE ELEMENT

Our previous work demonstrated that collagenase mRNA levels are increa sed in fibroblasts derived from patients with cutis laxa (CL), To purs ue the mechanism of the upregulation of collagenase expression, we inv estigated transcriptional levels of the collagenase gene in CL fibrobl asts. Fibroblasts cultured from the skin of three congenital CL patien ts 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 transc ription 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 c ontrols. Transient transfection of a normal collagenase promoter-CAT c onstruct into the cells further showed significantly enhanced transcri ptional activity in CL but not in normal fibroblasts. Experiments of t ransient transfection of deleted or small substituted collagenase prom oter-CAT constructs indicated that collagenase transcription in CL fib roblasts was activated through the TPA-responsive element site of the collagenase promoter gene. Although the levels of Jun and Fos gene exp ression did not differ from those observed in normal fibroblasts, alka line phosphatase-1-binding activity, as measured by the ability to bin d to an oligonucleotide containing a TPA-responsive element, was signi ficantly elevated in CL fibroblasts as compared with normal fibroblast s. These data suggest that collagenase expression is upregulated at th e transcriptional level by endogenous activation of DNA binding of AP- 1 in CL fibroblasts.