Sepulveda A R, Huang S L, Lebovitz R M, Lieberman M W
Department of Pathology, Baylor College of Medicine, Houston, Texas 77030, USA.
J Biol Chem. 1997 May 2;272(18):11959-67. doi: 10.1074/jbc.272.18.11959.
The mouse gamma-glutamyl transpeptidase (GGT) gene encodes seven distinct mRNAs that are transcribed from seven separate promoters. Type II mRNA is the most abundant in kidney. We have developed a cell line with features of renal proximal tubular cells which expresses GGT mRNA types with a pattern similar to that of mouse kidney. Because a 346-bp sequence from the type II promoter directed the highest level of CAT activity in these cells, this region was used to drive the expression of a beta-galactosidase reporter gene in transgenic mice. Two transgenic mouse lines expressed beta-galactosidase limited to the renal proximal tubules. Site-directed deletions within this 346-bp promoter region demonstrated that cis-elements containing the consensus binding sites for AP2, a glucocorticoid response element (GRE)-like element, and the initiator region were required for transcriptional activity and were not additive. Purified AP2 bound and footprinted the AP2 consensus region, making it likely that transcription from the GGT type II promoter is regulated in part by AP2. These data suggest that transcription of the type II promoter requires multiple protein DNA interactions involving at least an AP2 element, and probably a GRE-like element and the initiator region.
小鼠γ-谷氨酰转肽酶（GGT）基因编码7种不同的mRNA，它们由7个独立的启动子转录而来。II型mRNA在肾脏中最为丰富。我们已经建立了一种具有肾近端小管细胞特征的细胞系，该细胞系表达的GGT mRNA类型与小鼠肾脏中的模式相似。由于来自II型启动子的346 bp序列在这些细胞中指导了最高水平的CAT活性，因此该区域被用于驱动β-半乳糖苷酶报告基因在转基因小鼠中的表达。两个转基因小鼠品系在肾近端小管中特异性表达β-半乳糖苷酶。在这个346 bp启动子区域内进行的定点缺失实验表明，含有AP2共有结合位点、糖皮质激素反应元件（GRE）样元件和起始区域的顺式元件对于转录活性是必需的，且它们之间不存在累加效应。纯化的AP2能够结合并覆盖AP2共有区域，这表明GGT II型启动子的转录部分受AP2调控。这些数据表明，II型启动子的转录需要多种蛋白质与DNA的相互作用，至少涉及一个AP2元件，可能还包括一个GRE样元件和起始区域。
