Peroxisome proliferator-activated receptor gamma-mediated transcriptional up-regulation of the hepatocyte growth factor gene promoter via a novel composite cis-acting element

Hepatocyte growth factor (HGF) is a pleotropic polypeptide that can functio n as a morphogen, motogen, mitogen, angiogen, carcinogen, and tumor suppres sor, depending on the target cell and tissue. Previous studies from our lab oratory using transgenic mice have shown that HGF gene expression is tightl y regulated at the transcriptional level and that the upstream regulatory e lements are crucial for the control of HGF gene transcription, In the prese nt study, we have identified and characterized one of these elements as a p eroxisome proliferator-activated receptor gamma (PPAR gamma)-responsive ele ment. This regulatory element was localized at -246 to -233 base pairs upst ream from the transcription start site of the HGF gene promoter having the sequence GGGCCAGGTGACCT. Gel mobility shift and supershift assays demonstra ted that this cis-acting element strongly binds to the PPAR gamma isoforms as well as to chicken ovalbumin upstream promoter-transcription factor, a m ember of the orphan nuclear receptor subfamily. Mutational analysis and gel mobility band shift assays indicated that the binding site is an inverted repeat of the AGGTCA motif with two spacers (inverted repeat 2 configuratio n) and that the two spacers are important for PPAR gamma binding. This bind ing site overlaps with functional binding sites for activating protein-2, n uclear factor 1, and upstream stimulatory factor, and together, they consti tute a multifunctional composite binding site through which these different transcription factors exert their regulatory effects on HGF promoter activ ity. Functional assays revealed that PPAR gamma, with its ligand, 15-deoxy- prostaglandin J2, strongly stimulates HGF promoter activity. On the other h and, nuclear factor 1, activating protein-2, and chicken ovalbumin upstream promoter-transcription factor transcription factors repress the stimulator y action of PPAR gamma by competing with PPAR gamma for their overlapping b inding sites. Furthermore, for the first time, our studies demonstrate that the PPAR gamma ligand, 15-deoxy-prostaglandin J2, induces endogenous HGF m RNA and protein expression in fibroblasts in culture.