Watanabe Minoru, Rebbert Martha L, Andreazzoli Massimiliano, Takahashi Nobuhiro, Toyama Reiko, Zimmerman Steven, Whitman Malcolm, Dawid Igor B
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, USA.
Dev Dyn. 2002 Dec;225(4):448-56. doi: 10.1002/dvdy.10176.
The Lim-1 gene encodes a LIM-homeodomain transcription factor that is highly conserved among vertebrates and is required for successful gastrulation and head formation. The expression of this gene in the mesoderm of the gastrula is known to require an activin/nodal signal. Earlier studies have shown that the Xenopus Lim-1 (Xlim-1) gene contains an activin response element (ARE) in its first intron, which cooperates with an activin-unresponsive upstream promoter in the regulation of the gene. Here, we show that the Xlim-1 ARE contains a cluster of FAST-1/FoxH1 and Smad4 recognition sites; such sites have been shown to mediate activin/nodal responses in other genes. By using reporter constructs with mutated FAST-1/FoxH1 sites and FAST-1/FoxH1 protein chimeras, we show that the regulation of Xlim-1 by activin depends on FAST-1/FoxH1 function. Comparative studies on the zebrafish lim1 gene indicate the presence of FoxH1 sites in the first intron of this gene and provide evidence for the requirement for FoxH1 function in its regulation. These results illuminate the conserved nature of the transcriptional regulation of the Lim-1 gene in different vertebrate animals.
Lim-1基因编码一种LIM-同源结构域转录因子，该因子在脊椎动物中高度保守，是原肠胚形成和头部形成成功所必需的。已知该基因在原肠胚中胚层的表达需要激活素/节点信号。早期研究表明，非洲爪蟾Lim-1（Xlim-1）基因在其第一个内含子中含有一个激活素反应元件（ARE），该元件在基因调控中与一个对激活素无反应的上游启动子协同作用。在这里，我们表明Xlim-1 ARE包含一组FAST-1/FoxH1和Smad4识别位点；这些位点已被证明在其他基因中介导激活素/节点反应。通过使用具有突变FAST-1/FoxH1位点的报告构建体和FAST-1/FoxH1蛋白嵌合体，我们表明激活素对Xlim-1的调控取决于FAST-1/FoxH1的功能。对斑马鱼lim1基因的比较研究表明该基因第一个内含子中存在FoxH1位点，并为其调控中对FoxH1功能的需求提供了证据。这些结果阐明了Lim-1基因在不同脊椎动物中转录调控的保守性质。
