Vascular Smooth Muscle-Specific Transcriptional Regulation of the Gene for Platelet-Derived growth Factorβ-Receptor.

血小板衍生生长因子(PDGF)及其受体在细胞生长发育过程中广泛表达于多种组织中。在成年期，血小板衍生生长因子β受体(PDGFβR)主要在动脉粥样硬化病变和血管壁损伤等病理条件下检测到。本研究的目的是阐明血管平滑肌细胞在病理条件下血小板衍生生长因子βR基因表达的潜在机制，并找出影响组织特异性基因转录的重要顺式元件。凝胶迁移率改变分析和超转移分析表明，位于-67(C67)的CCAAT基序主要与NF-YC相互作用，该元件驱动该基因的基本启动子活性。另一方面，在-150到-121之间的30个碱基区(R30)发现了另一个对基础转录至关重要的重要序列。为了验证R30是否真的调控PDGFR基因的组织特异性转录，比较了VSMC和肝癌细胞系(HTC)的电迁移率变化规律。我们得到的结果是，只有在HTC核提取液中才有的DNA-蛋白质复合体以组织特异性的方式抑制HTC中的启动子活性。此外，C67和R30的顺式元件诱骗实验也表明，这两个元件在血管内皮细胞中的βR基因表达中起着重要的功能作用。这些结果表明，C67和R30的相互作用或协同作用可以反式激活βR基因表达的基础活性，而后者主要控制组织特异性基因的表达。

Platelet-derived growth factor (PDGF) and its receptors are widely expressed in several tissues in the stage of cellular growth and development. In adulthood, PDGF β-receptor (PDGF βR) is mainly detected in pathological conditions such as atherosclerotic lesion and injured vascular wall. The purpose of the present study was to elucidate the underlying mechanism of PDGF βR gene expression under the pathologic conditions in vascular smooth muscle cells (VSMC), and to identify the important cis-elements responsible for the tissue-specific gene transcription. Gel mobility shift assay and supershift assay indicated that the CCAAT motif located at -67 (C67) was mainly interacted with NF-YC, and this element drove the basal promoter activity of the gene as a putative promoter. On the other hand, another important sequence essential for the basal transcription was found at a 30-bp region (R30) spanning -150 to -121. To test whether R30 actually regulates the tissue-specific transcription of PDGF βR gene, electromobility shift pattern was compared between VSMC and hepatoma cell line (HTC). We obtained the result that DNA-protein complex seen only in nuclear extracts from HTC suppressed the promoter activity in HTC in a tissue-specific manner. Furthermore, cis-element decoy transfection experiments for C67 and R30 also revealed that both elements were functionally important in mRNA expression of PDGF βR in VSMC.From these results, we concluded that the basal activity of PDGF βR gene expression was transactivated by the interaction or coordination of both C67 and R30, and the latter one mainly controlled the tissue-specific gene expression in VSMC.