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  • Title: An AP-1 enhancer mediates TPA-induced transcriptional activation of the chicken insulin-like growth factor I gene.
    Author: Kajimoto Y, Kawamori R, Umayahara Y, Iwama N, Imano E, Morishima T, Yamasaki Y, Kamada T.
    Journal: Biochem Biophys Res Commun; 1993 Feb 15; 190(3):767-73. PubMed ID: 8439327.
    Abstract:
    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.
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