Molecular Genetics of Segment Identity

描述（由申请人提供）： Hox家族的转录调节因子是同源结构域蛋白，在动物发育和疾病的许多方面发挥重要作用。为了使这些蛋白质发挥其功能，它们需要在体内实现正确的功能特异性。使用果蝇，果蝇，作为模型系统，该项目建立在早期的工作，以更好地了解这些转录调节因子在体内的功能。在以前的工作中，获得的结果表明，Hox蛋白，与辅因子的外齿（Exd，Pbx在脊椎动物）和同胸（Hth; Meis在脊椎动物）的家庭，实现DNA结合特异性通过阅读序列依赖的DNA结构，使用残基在其同源结构域和附近的接头区域。第二组发现表明，一些Hox蛋白通过多个部分冗余的相互作用基序与这些辅因子相互作用。第三，获得的结果显示，果蝇中的一种Hox蛋白，超双胸（Ubx），通过改变可扩散的形态发生剂如Decapentaplegic（Dpp）的水平和迁移率来改变附肢形态，特别是附肢大小。Ubx通过转录调节两个基因来执行这些修改，这两个基因是发育中的附肢中的厚脉主基因（mtv）和dally。在这些结果的基础上，本项目的目的是1）扩展和推广Exd依赖的Hox特异性模型，2）确定存在于一些Hox蛋白中的多个Exd相互作用基序的作用，以及3）确定先前在Ubx控制附件形态中确定的靶标中哪些直接受Hox蛋白调节。所有这些目标的方法在很大程度上依赖于使用果蝇遗传工具和体外蛋白质-DNA相互作用测定的组合。还将采用X射线晶体学来确定一些Hox-Exd-DNA三元复合物的三维结构。 公共卫生相关性：虽然最初是在前-后模式的背景下分析的，但在动物发育中有大量的关键功能 从运动神经元特化到器官发生再到干细胞维持 现在被认为是由Hox基因控制的同样重要且研究充分的是Hox基因及其辅因子在人类出生缺陷（如肢体畸形）和某些癌症（如白血病）中的作用。因此，对这些转录因子如何调节其靶基因的机制理解将影响我们对发育和疾病生物学许多方面的理解。

DESCRIPTION (provided by applicant): The Hox family of transcriptional regulators are homeodomain proteins that play important roles in many aspects of animal development and disease. For these proteins to perform their functions, they need to achieve the correct functional specificities in vivo. Using the fruit fly, Drosophila melanogaster, as the model system, this project builds on earlier work to better understand how these transcriptional regulators function in vivo. In previous work, results were obtained suggesting that Hox proteins, in conjunction with cofactors of the Extradenticle (Exd, Pbx in vertebrates) and Homothorax (Hth; Meis in vertebrates) families, achieve DNA binding specificity by reading a sequence-dependent DNA structure using residues in their homeodomains and nearby linker regions. A second set of findings demonstrated that some Hox proteins interact with these cofactors via multiple, partially redundant interaction motifs. Third, results were obtained showing that one Hox protein in Drosophila, Ultrabithorax (Ubx), modifies appendage morphologies, in particular, appendage size, by altering the levels and mobilities of diffusible morphogens such as Decapentaplegic (Dpp). Ubx executes these modfications in part by transcriptionally regulating two genes, master of thickveins (mtv) and dally in the developing appendage. Building on these results, the aims of this project are to 1) extend and generalize the Exd-dependent Hox specificity model, 2) determine the role of multiple Exd interaction motifs that are present in some Hox proteins, and 3) determine which of the targets identified previously in the control of appendage morphology by Ubx are directly regulated by this Hox protein. The approaches for all of these aims rely heavily on using a combination of Drosophila genetic tools and in vitro protein-DNA interaction assays. X-ray crystallography, to determine the three dimensional structures of some Hox-Exd-DNA ternary complexes, will also be employed. Public Health Relevance: Although first analyzed in the context of anterior-posterior patterning, there are a wealth of critical functions in animal development from motor neuron specification to organogenesis to stem cell maintenance that are now appreciated to be controlled by Hox genes. Equally important and well studied are the roles that Hox genes and their cofactors play in human birth defects, such as limb malformations, and some cancers, such as leukemia. Thus, a mechanistic understanding of how these transcription factors regulate their target genes will impact our understanding of many aspects of developmental and disease biology.