Differential response to the Dpp morphogen

描述（由申请人提供）：信号分子的TGF-β家族 指导各种各样的细胞和发育过程， 控制基因表达。它们通过Smad蛋白发出信号， 转录因子在某些情况下，TGF-β在浓度 梯度作为形态发生剂以确定不同的细胞命运。果蝇中的DPP 在胚盘胚胎中以背腹梯度起作用，和 通过差异调节下游靶基因来指定不同的命运。 比如种族，高级目标。仅限于最背侧的细胞。 pannier一个中级目标在更广泛的领域中表达，而 tolloid在最宽的域中表示低级目标。这些怎么 靶基因解释Dpp梯度？我们的研究结果表明，一个简单的 涉及对Smad梯度的线性响应的机制不适用，但 而是涉及具有附加因素的组合机制。一个这样 Brinker因子作为一些Dpp靶基因的阻遏物发挥作用。 有趣的是，低水平的Dpp抑制brinker表达，将其限制在 腹侧区因此。民进党通过压制布林克间接行动， 直接激活某些目标。什么是分子机制， 不同的靶基因解释Dpp和Brinker输入？监管机构 序列的所有目标基因相似，就这些网站？如果是这样，他们 将读取沿着DV轴的每个核中Smads和Brinker的水平， 相应地回答。或者他们彼此不同，每个人都有一个 Smad或Brinker位点，和/或其他因子结合位点？为了解决这个 问题，我们将比较最小的Dpp响应元素的 代表性靶基因Race、pannier和tolloid。此外，我们将 操纵元件，以及用Smad和/或 Brinker网站。我们将讨论斯麦兹如何在竞争中胜出的问题 Brinker，通过竞争DNA结合或通过抗抑制 涉及蛋白质相互作用的机制。我们还将调查民进党如何 信号传导导致抑制布林克，特别是Smads如何与 假定的阻遏物Schnurri我们将确定额外的辅因子 通过遗传和分子筛选参与Dpp靶基因调控。我们 具体的目标集中在不同的靶基因启动子，以及Brinker和 Smads和其他辅助因子与它们相互作用，以控制和微调它们的功能。 转录反应。这些结果将提高我们对 形态发生功能的分子基础，发育生物学的一个关键概念。

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.