Jakowlew S B, Lechleider R, Geiser A G, Kim S J, Santa-Coloma T A, Cubert J, Sporn M B, Roberts A B
Laboratory of Chemoprevention, National Cancer Institute, Bethesda, Maryland 20892.
Mol Endocrinol. 1992 Aug;6(8):1285-98. doi: 10.1210/mend.6.8.1406706.
The promoter regions of the three mammalian transforming growth factor-beta genes (TGF-beta s 1, 2, and 3) have been recently cloned and characterized. The sequences show little similarity, suggesting different mechanisms of transcriptional control of these genes. To study differences in transcriptional regulation of mammalian and avian TGF-beta, we have cloned and sequenced the 5'-flanking region of chicken TGF-beta 3. Characterization of this region showed a TATA box and cAMP-responsive element (CRE) and AP-2 binding site consensus sequences starting at 12 and 28 base pairs, respectively, upstream from the TATA box. Moreover, four additional AP-2-like sites, 10 binding sites for the transcription factor Sp1, as well as two AP-1-like sites were also identified. Except for 32 base pairs of identity centered around the TATA box and CRE site and four other relatively small regions of identity, the chicken TGF-beta 3 promoter was found to be structurally very different from the human TGF-beta 3 promoter. Promoter fragments were cloned into a chloramphenicol acetyltransferase reporter plasmid to study functional activity. Basal transcriptional activity of the promoter was regulated in quail fibrosarcoma QM7 cells and in human adenocarcinoma A375 cells by multiple upstream elements including the TATA, CRE, and AP-2 sites. As in the human TGF-beta 3 promoter, the CRE site showed activation by forskolin, an effect which could be shown by expression of TGF-beta 3 mRNA in cultured chicken and quail cells as well. Our results indicate a complex pattern of transcriptional regulation of the chicken TGF-beta 3 gene and suggest that differences in the regulation of expression of the genes for mammalian and avian TGF-beta 3 may result in part from the unique structure of their 5'-flanking regions.
三种哺乳动物转化生长因子-β基因（TGF-β1、2和3）的启动子区域最近已被克隆并进行了特征分析。这些序列显示出很少的相似性，表明这些基因的转录调控机制不同。为了研究哺乳动物和禽类TGF-β转录调控的差异，我们克隆并测序了鸡TGF-β3的5'侧翼区域。对该区域的特征分析显示，在TATA框上游12和28个碱基对处分别有一个TATA框、一个cAMP反应元件（CRE）和AP-2结合位点共有序列。此外，还鉴定出另外四个AP-2样位点、十个转录因子Sp1结合位点以及两个AP-1样位点。除了围绕TATA框和CRE位点的32个碱基对的同一性以及其他四个相对较小的同一性区域外，发现鸡TGF-β3启动子在结构上与人TGF-β3启动子有很大不同。将启动子片段克隆到氯霉素乙酰转移酶报告质粒中以研究功能活性。启动子的基础转录活性在鹌鹑纤维肉瘤QM7细胞和人腺癌A375细胞中受到多个上游元件的调控，包括TATA、CRE和AP-2位点。与人TGF-β3启动子一样，CRE位点显示出被福斯可林激活，这一效应在培养的鸡和鹌鹑细胞中TGF-β3 mRNA的表达中也得到了证实。我们的结果表明鸡TGF-β3基因的转录调控模式复杂，并表明哺乳动物和禽类TGF-β3基因表达调控的差异可能部分源于其5'侧翼区域的独特结构。
