Hellqvist M, Mahlapuu M, Samuelsson L, Enerbäck S, Carlsson P
Department of Molecular Biology, The Lundberg Laboratory, Göteborg University, Medicinaregatan 9C, S-413 90 Göteborg, Sweden.
J Biol Chem. 1996 Feb 23;271(8):4482-90. doi: 10.1074/jbc.271.8.4482.
We describe the cDNA sequences for two human transcription factors, Forkhead RElated ACtivator (FREAC)-1 and -2, that belong to the forkhead family of eukaryotic DNA binding proteins. FREAC-1 and -2 are encoded by distinct genes, are almost identical within their DNA binding domains and in the COOH termini, but are otherwise divergent. Cotransfections with a reporter carrying FREAC binding sites showed that both proteins are transcriptional activators, and deletions located the activation domains to the COOH-terminal side of the forkhead domains. Expression of FREAC-1 and FREAC-2 is restricted to lung and placenta. We show that the promoters of genes for lung-specific proteins such as pulmonary surfactant proteins A, B, and C (SPA, SPB, and SPC) and the Clara cell 10-kDa protein (CC10) contain potential binding sites for FREAC-1 and FREAC-2. DNaseI footprinting verified that FREAC proteins bind to the predicted sites in the CC10 and SPB promoters. While an SPB promoter construct could be transactivated by both FREAC-1 and FREAC-2, CC10 was only activated by FREAC-1. Efficient activation of CC10 by FREAC-1 is shown to be specific for a lung cell line with Clara cell characteristics (H441) and to involve a region of the FREAC-1 protein unable to activate in other cell types.
我们描述了两种人类转录因子Forkhead相关激活因子（FREAC）-1和-2的cDNA序列，它们属于真核生物DNA结合蛋白的叉头家族。FREAC-1和-2由不同基因编码，在其DNA结合结构域和COOH末端几乎相同，但在其他方面有所不同。与携带FREAC结合位点的报告基因共转染表明，这两种蛋白都是转录激活因子，缺失分析将激活结构域定位到叉头结构域的COOH末端一侧。FREAC-1和FREAC-2的表达仅限于肺和胎盘。我们发现，肺特异性蛋白如肺表面活性物质蛋白A、B和C（SPA、SPB和SPC）以及克拉拉细胞10 kDa蛋白（CC10）的基因启动子含有FREAC-1和FREAC-2的潜在结合位点。DNaseI足迹分析证实FREAC蛋白与CC10和SPB启动子中的预测位点结合。虽然SPB启动子构建体可被FREAC-1和FREAC-2共同反式激活，但CC10仅被FREAC-1激活。FREAC-1对CC10的有效激活显示对具有克拉拉细胞特征的肺细胞系（H441）具有特异性，并且涉及FREAC-1蛋白中在其他细胞类型中无法激活的区域。
