Wobus Manja, Wandel Elke, Prohaska Sonja, Findeiss Sven, Tschöp Katrin, Aust Gabriela
Department of Surgery, Research Laboratories, University of Leipzig, Leipzig, Germany.
Gene. 2008 Apr 30;413(1-2):67-75. doi: 10.1016/j.gene.2008.01.021. Epub 2008 Feb 9.
The EGF-TM7 receptor CD97 shows different features of expression and function in muscle cells compared to hematopoetic and tumor cells. Since the molecular function and regulation of CD97 are poorly understood, this study aimed at defining its basal transcriptional regulation in smooth muscle cells (SMCs). The computational analysis of the CD97 5'-flanking region revealed that the TATA box-lacking promoter possesses several GC-rich regions as putative Sp1/Sp3 binding sites. Transfection studies with serially deleted promoter constructs demonstrated that the minimal promoter fragment resided in the -218/+45 region containing one out of five identified GC-boxes in the leiomyosarcoma cell line SK-LMS-1 and human bronchial smooth muscle cells (HbSMCs). Mutation of the most proximal GC-site in CD97 reporter gene constructs caused a significant decrease in promoter activity. Gel shift assays and chromatin immunoprecipitation revealed that Sp1 and Sp3 bound specifically to the most proximal GC-site. Furthermore, we showed that Sp1 and Sp3 over-expression activates CD97 promoter activity in HEK293 cells. Our data characterize for the first time the activity of the human CD97 promoter which is controlled by Sp1/Sp3 transcription factors in SMCs.
与造血细胞和肿瘤细胞相比，表皮生长因子跨膜7受体CD97在肌肉细胞中表现出不同的表达和功能特征。由于对CD97的分子功能和调控了解甚少，本研究旨在确定其在平滑肌细胞（SMC）中的基础转录调控。对CD97 5'侧翼区域的计算分析表明，缺乏TATA盒的启动子具有几个富含GC的区域，作为假定的Sp1/Sp3结合位点。对串联缺失启动子构建体的转染研究表明，最小启动子片段位于-218/+45区域，该区域在平滑肌肉瘤细胞系SK-LMS-1和人支气管平滑肌细胞（HbSMC）中包含五个已鉴定的GC盒中的一个。CD97报告基因构建体中最近端GC位点的突变导致启动子活性显著降低。凝胶迁移试验和染色质免疫沉淀显示，Sp1和Sp3特异性结合到最近端的GC位点。此外，我们表明，Sp1和Sp3的过表达激活了HEK293细胞中的CD97启动子活性。我们的数据首次表征了人CD97启动子的活性，该启动子在SMC中受Sp1/Sp3转录因子控制。
