Shimotsuma Motoshi, Matsuzaki Hitomi, Tanabe Osamu, Campbell Andrew D, Engel James Douglas, Fukamizu Akiyoshi, Tanimoto Keiji
Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8577, Japan.
Mol Cell Biol. 2007 Aug;27(16):5664-72. doi: 10.1128/MCB.00602-07. Epub 2007 Jun 4.
Enhancer elements modulate promoter activity over vast chromosomal distances, and mechanisms that ensure restrictive interactions between promoters and enhancers are critical for proper control of gene expression. The human beta-globin locus control region (LCR) activates expression of five genes in erythroid cells, including the proximal embryonic epsilon- and the distal adult beta-globin genes. To test for possible distance sensitivity of the genes to the LCR, we extended the distance between the LCR and genes by 2.3 kbp within the context of a yeast artificial chromosome, followed by the generation of transgenic mice (TgM). In these TgM lines, epsilon-globin gene expression decreased by 90%, while the more distantly located gamma- or beta-globin genes were not affected. Remarkably, introduction of a consensus EKLF binding site into the epsilon-globin promoter rendered its expression distance insensitive; when tested in an EKLF-null genetic background, expression of the mutant epsilon-globin gene was severely compromised. Thus, the epsilon-globin gene differs in its distance sensitivity to the LCR from the other beta-like globin genes, which is, at least in part, determined by the transcription factor EKLF.
增强子元件可在巨大的染色体距离上调节启动子活性，确保启动子与增强子之间进行特异性相互作用的机制对于基因表达的正确调控至关重要。人类β-珠蛋白基因座控制区（LCR）可激活红系细胞中五个基因的表达，包括近端胚胎期的ε-珠蛋白基因和远端成年期的β-珠蛋白基因。为了测试这些基因对LCR可能的距离敏感性，我们在酵母人工染色体的背景下，将LCR与基因之间的距离延长了2.3kbp，随后生成了转基因小鼠（TgM）。在这些TgM品系中，ε-珠蛋白基因的表达下降了90%，而位置更远的γ-或β-珠蛋白基因则未受影响。值得注意的是，在ε-珠蛋白启动子中引入一个共有EKLF结合位点，使其表达对距离不敏感；在EKLF基因缺失的遗传背景下进行测试时，突变的ε-珠蛋白基因的表达严重受损。因此，ε-珠蛋白基因对LCR的距离敏感性与其他β样珠蛋白基因不同，这至少部分是由转录因子EKLF决定的。
