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

血小板衍生生长因子（Platelet-derived growth factor， PDGF）及其受体广泛表达于细胞生长发育阶段的多种组织中。在成年期，PDGF β-受体（PDGF βR）主要在动脉粥样硬化病变和血管壁损伤等病理状态下检测到。本研究旨在阐明PDGF βR基因在血管平滑肌细胞（VSMC）病理条件下表达的潜在机制，并鉴定组织特异性基因转录的重要顺式元件。凝胶迁移迁移和超迁移实验表明，位于-67 （C67）的CCAAT基序主要与NF-YC相互作用，该元件作为假定的启动子驱动了该基因的基础启动子活性。另一方面，在横跨-150至-121的30-bp区域（R30）发现了另一个重要的基础转录必需序列。为了验证R30是否真的调控PDGF βR基因的组织特异性转录，我们比较了VSMC和肝癌细胞系（HTC）的电迁移模式。我们得到的结果是，仅在HTC的核提取物中看到的dna -蛋白复合物以组织特异性的方式抑制HTC的启动子活性。此外，C67和R30的顺式元件诱饵转染实验也显示，这两个元件在VSMC中PDGF βR的mRNA表达中具有重要功能。综上所述，我们认为PDGF βR基因表达的基础活性是通过C67和R30的相互作用或协同作用而被反激活的，而后者主要控制VSMC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.