Harju Susanna, Navas Patrick A, Stamatoyannopoulos George, Peterson Kenneth R
Department of Biochemistry and Molecular Biology, MS 3030, University of Kansas Medical Center, Kansas City, 66160-7421, USA.
Mol Cell Biol. 2005 Oct;25(20):8765-78. doi: 10.1128/MCB.25.20.8765-8778.2005.
To test the role of gene order in globin gene expression, mutant human beta-globin locus yeast artificial chromosome constructs were used, each having one additional globin gene encoding a "marked" transcript (epsilon(m), gamma(m), or beta(m)) integrated at different locations within the locus. When a beta(m)-globin gene was placed between the locus control region (LCR) and the epsilon-globin gene, beta(m)-globin expression dominated primitive and definitive erythropoiesis; only beta(m)-globin mRNA was detected during the fetal and adult definitive stages of erythropoiesis. When an (A)gamma(m)-globin gene was placed at the same location, (A)gamma(m)-globin was expressed during embryonic erythropoiesis and the fetal liver stage of definitive erythropoiesis but was silenced during the adult stage. The downstream wild-type gamma-globin genes were not expressed. When an epsilon(m)-globin gene was placed between the delta- and beta-globin genes, it remained silent during embryonic erythropoiesis; only the LCR-proximal wild-type epsilon-globin gene was expressed. Placement of a beta(m)-globin gene upstream of the (G)gamma-globin gene resulted in expression of beta(m)-globin in embryonic cells and in a significant decrease in expression of the downstream wild-type beta-globin gene. These results indicate that distance from the LCR, an inherent property of spatial gene order, is a major determinant of temporal gene expression during development.
为了测试基因顺序在珠蛋白基因表达中的作用，研究人员使用了突变的人类β-珠蛋白基因座酵母人工染色体构建体，每个构建体都有一个额外的珠蛋白基因，该基因编码一个“标记”转录本（ε(m)、γ(m)或β(m)），整合在基因座内的不同位置。当一个β(m)-珠蛋白基因置于基因座控制区（LCR）和ε-珠蛋白基因之间时，β(m)-珠蛋白表达主导原始和确定性红细胞生成；在红细胞生成的胎儿期和成人期确定性阶段仅检测到β(m)-珠蛋白mRNA。当一个(A)γ(m)-珠蛋白基因置于相同位置时，(A)γ(m)-珠蛋白在胚胎期红细胞生成和确定性红细胞生成的胎儿肝脏阶段表达，但在成人期沉默。下游的野生型γ-珠蛋白基因未表达。当一个ε(m)-珠蛋白基因置于δ-珠蛋白基因和β-珠蛋白基因之间时，它在胚胎期红细胞生成过程中保持沉默；仅表达LCR近端的野生型ε-珠蛋白基因。将一个β(m)-珠蛋白基因置于(G)γ-珠蛋白基因上游导致β(m)-珠蛋白在胚胎细胞中表达，并使下游野生型β-珠蛋白基因的表达显著降低。这些结果表明，与LCR的距离，即空间基因顺序的固有属性，是发育过程中时间基因表达的主要决定因素。
