Trepicchio W L, Dyer M A, Baron M H
Department of Cellular and Developmental Biology, Harvard University, Cambridge, Massachusetts 02138.
Mol Cell Biol. 1994 Jun;14(6):3763-71. doi: 10.1128/mcb.14.6.3763-3771.1994.
Members of the human beta-globin gene family are expressed at discrete stages of development and therefore provide an important model system for examining mechanisms of temporal gene regulation. We have previously shown that expression of the embryonic beta-like globin gene (epsilon) is mediated by a complex array of positive and negative upstream control elements. Correct developmental stage- and tissue-specific gene expression is conferred by synergistic interactions between a positive regulatory element (termed epsilon-PRE II) which is active only in embryonic erythroid cells and at least two other regulatory domains upstream of the epsilon-globin gene promoter. A nuclear factor highly enriched in cultured embryonic erythroid cells and in mouse embryonic yolk sac binds to a novel, evolutionarily conserved sequence within epsilon-PRE II. We show here that binding of this factor to the conserved element within epsilon-PRE II is critical for transcriptional activity. Point mutations that interfere with protein binding to epsilon-PRE II abolish transcriptional activation of the constitutive epsilon-globin promoter. Adult erythroid nuclei (from cultured cells or adult mouse liver) also contain a factor that binds to this region, but the complex formed migrates more rapidly during nondenaturing electrophoresis, suggesting either that distinct proteins bind to epsilon-PRE II or that a single protein is differentially modified in these cells in a way that modulates its activity. Several lines of evidence suggest that the binding factors in embryonic and adult erythroid cells are distinguished by posttranscriptional differences.
人类β-珠蛋白基因家族的成员在发育的不同阶段表达,因此为研究时间基因调控机制提供了一个重要的模型系统。我们之前已经表明,胚胎β样珠蛋白基因(ε)的表达是由一系列复杂的正负上游控制元件介导的。正确的发育阶段和组织特异性基因表达是由一个仅在胚胎红细胞中活跃的正调控元件(称为ε-PRE II)与ε-珠蛋白基因启动子上游至少两个其他调控域之间的协同相互作用赋予的。一种在培养的胚胎红细胞和小鼠胚胎卵黄囊中高度富集的核因子与ε-PRE II内一个新的、进化上保守的序列结合。我们在此表明,该因子与ε-PRE II内保守元件的结合对于转录活性至关重要。干扰蛋白质与ε-PRE II结合的点突变消除了组成型ε-珠蛋白启动子的转录激活。成年红细胞核(来自培养细胞或成年小鼠肝脏)也含有一种与该区域结合的因子,但在非变性电泳过程中形成的复合物迁移得更快,这表明要么是不同的蛋白质与ε-PRE II结合,要么是一种单一蛋白质在这些细胞中以调节其活性的方式发生了差异修饰。几条证据表明,胚胎和成年红细胞中的结合因子在转录后存在差异。