Spear B T, Ellis A W
Department of Microbiology & Immunology, University of Kentucky College of Medicine, Lexington 40536-0084, USA.
Somat Cell Mol Genet. 1995 Jan;21(1):19-31. doi: 10.1007/BF02255819.
Mouse F9 teratocarcinoma cells provide a system to study developmentally regulated alpha-fetoprotein (AFP) gene expression. AFP is not expressed in undifferentiated F9 cells but is induced when cells differentiate as cell aggregates in the presence of retinoic acid. Previous studies have led to the suggestion that undifferentiated F9 cells contain negative regulators of AFP expression. To test this, we have used transient heterokaryons to ask whether inactive AFP genes in undifferentiated F9 cells are responsive to positively acting trans-acting factors. Our results indicate that silent endogenous and transfected AFP genes are activated when undifferentiated F9 cells are fused to human hepatoma HepG2 cells. This suggests that the lack of AFP expression in undifferentiated F9 cells is due to the absence or insufficient level of positive-acting transcription factors, rather than the presence of dominant negative regulators. We also demonstrate that stably transfected AFP genes, although unmethylated, are properly regulated in F9 cells.
小鼠F9畸胎瘤细胞提供了一个研究发育调控的甲胎蛋白（AFP）基因表达的系统。AFP在未分化的F9细胞中不表达，但当细胞在视黄酸存在下作为细胞聚集体分化时会被诱导表达。先前的研究表明，未分化的F9细胞含有AFP表达的负调控因子。为了验证这一点，我们使用瞬时异核体来探究未分化F9细胞中无活性的AFP基因是否对正向作用的反式作用因子有反应。我们的结果表明，当未分化的F9细胞与人肝癌HepG2细胞融合时，沉默的内源性和转染的AFP基因会被激活。这表明未分化F9细胞中AFP表达的缺失是由于正向作用转录因子的缺失或水平不足，而不是由于显性负调控因子的存在。我们还证明，稳定转染的AFP基因尽管未甲基化，但在F9细胞中受到适当调控。
