Shirai H, Kamimura M, Fujiwara H
Department of Integrated Biosciences Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan.
Insect Mol Biol. 2007 Apr;16(2):253-64. doi: 10.1111/j.1365-2583.2006.00722.x. Epub 2007 Feb 6.
Two ecdysone receptor (EcR) isoforms, EcR-A and EcR-B1, are expressed in a tissue- and stage-specific manner, although the details of their transcription mechanisms are unknown. We determined the transcription start sites of EcR-A and EcR-B1 isoforms of Bombyx mori and found that both core promoter regions consist of initiator (Inr) and downstream promoter elements (DPE) but not TATA boxes. Promoter truncation analysis performed using the luciferase reporter assays and BmN cells showed that, in both isoforms, the regions -296 to -74 for BmEcR-B1, -104 to -61 for BmEcR-A and downstream regions of +1 are essential for basal transcriptional activity. Mutation experiments revealed that both DPE and its 5'-flanking CGCGCG sequence are crucial but DPE of BmEcR-B1 is not important for BmEcR-A transcription. These results indicate that the basal promoter activities differ between the two BmEcR isoforms.
两种蜕皮激素受体（EcR）亚型，即EcR-A和EcR-B1，以组织和阶段特异性的方式表达，尽管它们转录机制的细节尚不清楚。我们确定了家蚕EcR-A和EcR-B1亚型的转录起始位点，发现两个核心启动子区域均由起始子（Inr）和下游启动子元件（DPE）组成，而不包含TATA框。使用荧光素酶报告基因检测和BmN细胞进行的启动子截短分析表明，在这两种亚型中，BmEcR-B1的-296至-74区域、BmEcR-A的-104至-61区域以及+1的下游区域对于基础转录活性至关重要。突变实验表明，DPE及其5'侧翼CGCGCG序列都很关键，但BmEcR-B1的DPE对BmEcR-A转录并不重要。这些结果表明，两种BmEcR亚型之间的基础启动子活性存在差异。
