An AP-1 enhancer mediates TPA-induced transcriptional activation of the chicken insulin-like growth factor I gene.
As a step to elucidate a role of protein kinase C(PKC) pathways in the regulation of insulin-like growth factor I(IGF-I) gene, we sought to determine whether the IGF-I gene promoter of chicken can be a target of regulation by PKC. An initial gene transfer study showed that, in a human cell line HepG2, the IGF-I gene promoter directs accurate transcription of IGF-I-luciferase fusion gene and enhances luciferase activity. Treatment of transfected cells with 12-o-tetradecanoylphorbol 13-acetate(TPA) increased promoter activity of 2100 and 600bp 5'-flanking sequence 4.9- and 3.6-fold, respectively. Site-directed mutagenesis in the AP-1-like sequence located within the 600bp resulted in 91% loss of its TPA-induced promoter activity, and a gel mobility-shift analysis revealed that TPA-stimulation of HepG2 cells caused a dramatic increase in specific protein-binding to the AP-1-like sequence, suggesting that the sequence functions as an AP-1 enhancer. These observations support a direct role for PKC pathways in activating the IGF-I gene promoter in chicken.
Kajimoto
Y
Y
First Department of Medicine, Osaka University Medical School, Japan.
Kawamori
R
R
Umayahara
Y
Y
Iwama
N
N
Imano
E
E
Morishima
T
T
Yamasaki
Y
Y
Kamada
T
T
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002645:Chickens; D004268:DNA-Binding Proteins / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects*
D004268:DNA-Binding Proteins; D016755:Proto-Oncogene Proteins c-jun; D007334:Insulin-Like Growth Factor I; D013755:Tetradecanoylphorbol Acetate