Nakata K, Motomura M, Nakabayashi H, Ido A, Tamaoki T
Department of Medical Biochemistry, University of Calgary, Alberta, Canada.
J Biol Chem. 1992 Jan 15;267(2):1331-4.
Epidermal growth factor (EGF) and 12-O-tetradecanoylphorbol-13-acetate (TPA) synergistically suppress activities of the promoter and enhancer of the human alpha-fetoprotein (AFP) gene in HuH-7 human hepatoma cells as analyzed by transient transfection assays using the chloramphenicol acetyltransferase gene as a reporter. In contrast to the AFP gene, albumin promoter and enhancer activities were not affected by EGF and TPA. Unexpectedly, however, Northern blot analysis revealed that the albumin mRNA level as well as the AFP mRNA level were reduced by treatment with EGF and TPA. We propose that in HuH-7 cells, the AFP enhancer stimulates the albumin promoter as well as the AFP promoter; and consequently, inhibition of the AFP enhancer by EGF and TPA results in reduction of both AFP and albumin mRNA levels. The significance of the involvement of the AFP enhancer in albumin transcription is discussed in relation to the inverse pattern of expression of the AFP and albumin genes in neonatal growth.
通过使用氯霉素乙酰转移酶基因作为报告基因的瞬时转染分析，发现表皮生长因子（EGF）和12 - O - 十四烷酰佛波醇 - 13 - 乙酸酯（TPA）协同抑制HuH - 7人肝癌细胞中人甲胎蛋白（AFP）基因启动子和增强子的活性。与AFP基因不同，白蛋白启动子和增强子活性不受EGF和TPA的影响。然而，出乎意料的是，Northern印迹分析显示，用EGF和TPA处理后，白蛋白mRNA水平以及AFP mRNA水平均降低。我们提出，在HuH - 7细胞中，AFP增强子刺激白蛋白启动子以及AFP启动子；因此，EGF和TPA对AFP增强子的抑制导致AFP和白蛋白mRNA水平均降低。结合AFP和白蛋白基因在新生儿生长过程中的反向表达模式，讨论了AFP增强子参与白蛋白转录的意义。
