Leibiger B, Walther R, Leibiger I B
Institut für Biochemie, Klinikum, Ernst-Moritz-Arndt-Universität Greifswald, Germany.
Biol Chem Hoppe Seyler. 1994 Feb;375(2):93-8. doi: 10.1515/bchm3.1994.375.2.93.
Sequence analysis of the 5'flanking region of the beta-cell specific transcription unit of the rat glucokinase gene (r beta GK) revealed the presence of sequence motifs very similar to the IEB-(Far)-box and a CT-motif which play a crucial role in transcriptional control of insulin genes. 5'deletional analysis of the r beta GK proximal promoter element (localized between nucleotides -278 and -49) as well as site directed mutagenesis showed that both motifs are mutationally sensitive and contribute to transcriptional control in HIT M2.2.2 cells. The combination of the IEB-(Far)-like motif with the CT-box was unable to form a "mini-enhancer" similar to the Far-FLAT-element of the rat insulin I gene promoter but rather functions as a beta-cell specific control element in r beta GK expression. Electrophoretic mobility shift assays (EMSAs) and competition studies using oligonucleotides containing CT-motifs of rat insulin genes promoters, human insulin gene promoter, and rat amylin gene promoter showed similar binding patterns with nuclear extracts isolated from insulin-producing cell lines. These studies indicate that CT-motifs of rat glucokinase, insulin, and amylin gene promoters may bind similar--probably identical--nuclear factor(s) and may play a central role in the coordinated expression of these genes in insulin-producing cells.
对大鼠葡萄糖激酶基因（rβGK）β细胞特异性转录单元5'侧翼区域的序列分析显示，存在与胰岛素增强子结合蛋白（IEB）-（远侧）-盒以及CT基序非常相似的序列基序，这些基序在胰岛素基因的转录调控中起关键作用。对rβGK近端启动子元件（位于核苷酸-278至-49之间）进行的5'缺失分析以及定点诱变表明，这两个基序对突变敏感，并有助于HIT M2.2.2细胞中的转录调控。IEB-（远侧）样基序与CT盒的组合无法形成类似于大鼠胰岛素I基因启动子的Far-FLAT元件的“微型增强子”，而是作为rβGK表达中的β细胞特异性控制元件发挥作用。使用含有大鼠胰岛素基因启动子、人胰岛素基因启动子和大鼠胰淀素基因启动子CT基序的寡核苷酸进行的电泳迁移率变动分析（EMSA）和竞争研究表明，与从胰岛素产生细胞系中分离的核提取物具有相似的结合模式。这些研究表明，大鼠葡萄糖激酶、胰岛素和胰淀素基因启动子的CT基序可能结合相似的——可能相同的——核因子，并可能在胰岛素产生细胞中这些基因的协调表达中起核心作用。
