Differential response to the Dpp morphogen

描述(申请人提供)：转化生长因子-β信号分子家族 通过最终引导多种细胞和发育过程 控制基因表达。它们通过Smad蛋白发出信号，Smad蛋白的功能是 转录因子。在某些情况下，转化生长因子-β作用集中。 梯度作为形态因子来决定不同的细胞命运。果蝇的DPP 在胚泡胚背向腹面梯度中的功能，以及 通过对下游靶基因的不同调控，决定不同的命运。 例如。种族，一个高层次的目标。仅限于最背面的细胞。 Pannier，一个中级目标。是在更广泛的领域中表达的，而 托洛德。低级目标在最广泛的域中表达。这些是如何做到的 靶基因解释DPP梯度？我们的结果表明，一个简单的 涉及对Smad梯度的线性响应的机制不适用，但是 相反，它涉及一种具有附加因素的组合机制。这样的一个 Brinker因子是一些DPP靶基因的抑制因子。 有趣的是，低水平的DPP抑制了Brinker的表达，将其限制在 腹侧区域。因此。民进党通过压制布林克间接采取行动，但也采取了行动 直接激活一些目标。是什么分子机制导致了 不同的靶基因解释DPP和Brinker输入？是监管部门 所有靶基因在这些位点上的序列是否相似？如果是这样，他们 将读取沿DV轴的每个核中的Smads和Brinker的水平 相应地做出回应。或者它们彼此不同，每个都有 Smad或Brinker位点，和/或其他因子结合位点？要解决这个问题 问题，我们将比较最小DPP响应元素 具有代表性的靶基因Race、Pannier和Tolloid。此外，我们还将 操纵元素，并使用Smad和/或测试合成促进剂 布林克网站。我们将解决Smads如何在竞争中脱颖而出的问题 Brinker，要么通过DNA结合的竞争，要么通过反压制 涉及蛋白质相互作用的机制。我们还将调查民进党如何 信号导致对Brinker的抑制，特别是SMADS如何与 推定的抑制者，施努里。我们将确定更多的辅助因素 通过遗传和分子筛选参与DPP靶基因的调控。我们的 具体目标集中在不同的靶基因启动子以及Brinker和 SMAD和其他辅助因子与它们交互以控制和微调它们的 转录反应。这些结果将增进我们对 形态发生功能的分子基础，这是发育生物学中的一个关键概念。

DESCRIPTION (provided by applicant): The TGF-beta family of signaling molecules directs a wide variety of cellular and developmental processes by ultimately controlling gene expression. They signal through Smad proteins that function as transcription factors. In some instances, TGF-betas act in concentration gradients as morphogens to determine different cell fates. Dpp in Drosophila functions in a dorsal-to-ventral gradient in the blastoderm embryo, and specifies different fates by differentially regulating downstream target genes. For example. Race, a high-level target. is restricted to the dorsal-most cells. pannier, an intermediate-level target. is expressed in a broader domain, while tolloid. a low-level target is expressed in the broadest domain. How do these target genes interpret the Dpp gradient? Our results indicate that a simple mechanism involving a linear response to the Smad gradient does not apply, but rather, a combinatorial mechanism with additional factors is involved. One such factor, Brinker, functions as a repressor of some Dpp target genes. Interestingly, low levels of Dpp repress brinker expression limiting it to the ventral region. Thus. Dpp acts indirectly by repressing brinker, but also acts directly to activate some targets. What is the molecular mechanism by which the different target genes interpret Dpp and Brinker inputs? Are the regulatory sequences of all target genes similar with respect to these sites? If so, they would read the level of Smads and Brinker in each nucleus along the DV axis and respond accordingly. Or are they different from one another, each having either Smad or Brinker sites, and/or other factor binding sites? To address this question, we will compare the minimal Dpp-response elements of the representative target genes Race, pannier, and tolloid. In addition, we will manipulate the elements, as well as test synthetic promoters with Smad and/or Brinker sites. We will address the question of how Smads might outcompete Brinker, either by competition for DNA binding or by an anti-repression mechanism involving protein interactions. We will also investigate how Dpp signaling leads to repression of brinker, particularly how Smads interact with the putative repressor, Schnurri. We will identify additional cofactors involved in Dpp target gene regulation by genetic and molecular screens. Our specific aims focus on the different target gene promoters and how Brinker and Smads, and other cofactors, interact with them to control and fine-tune their transcriptional responses. These results will enhance our knowledge of the molecular basis of morphogen function, a key concept in developmental biology.