Hepatocyte growth factor (HGF) is a pleotropic
polypeptide that can function as a morphogen, motogen,
mitogen,
angiogen,
carcinogen, and
tumor suppressor, depending on the target cell and tissue. Previous studies from our laboratory using transgenic mice have shown that HGF gene expression is tightly regulated at the transcriptional level and that the upstream regulatory elements are crucial for the control of HGF gene transcription. In the present study, we have identified and characterized one of these elements as a
peroxisome proliferator-activated receptor gamma (
PPARgamma)-responsive
element. This regulatory
element was localized at -246 to -233 base pairs upstream from the transcription start site of the HGF gene promoter having the sequence GGGCCAGGTGACCT. Gel mobility shift and supershift assays demonstrated that this cis-acting
element strongly binds to the
PPARgamma isoforms as well as to chicken
ovalbumin upstream promoter-
transcription factor, a member 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 configuration) and that the two spacers are important for
PPARgamma binding. This binding site overlaps with functional binding sites for activating protein-2,
nuclear factor 1, and upstream stimulatory factor, and together, they constitute a multifunctional composite binding site through which these different
transcription factors exert their regulatory effects on HGF promoter activity. Functional assays revealed that
PPARgamma, with its
ligand, 15-deoxy-prostaglandin J2, strongly stimulates HGF promoter activity. On the other hand,
nuclear factor 1, activating protein-2, and chicken
ovalbumin upstream promoter-
transcription factor transcription factors repress the stimulatory action of
PPARgamma by competing with
PPARgamma for their overlapping binding sites. Furthermore, for the first time, our studies demonstrate that the
PPARgamma ligand, 15-deoxy-prostaglandin J2, induces endogenous HGF
mRNA and
protein expression in fibroblasts in culture.