REGULATED MRNA TRANSLATION IN DROSOPHILA BODY PATTERNING

描述(申请人提供)：对基因表达的适当控制是所有细胞形成和功能的基础。翻译层面的监管一度被认为是范围有限的，但在从最早的发展阶段到神经系统功能的广泛背景下，翻译监管已成为一项重要特征。最近的进展揭示了microRNAs的广泛表达，它控制着一种新的翻译控制形式，进一步扩大了其翻译受到调控的mRNAs的比例。 在果蝇中，翻译控制和mRNA定位协同作用于卵母细胞和胚胎中特定位置的体型决定因素的部署。其中一个决定因素是由Oskar基因编码的，它对卵母细胞后极的限制是必不可少的。用于实现这一分布的控制包括两种形式的翻译抑制(一种与microRNA依赖的抑制惊人地相似)，mRNA定位，以及两种或两种以上形式的翻译激活。一种与Oskar mRNA结合的蛋白质Bruno，介导一种形式的抑制和一种形式的激活。 我们的长期目标是了解这些机制中的每一个以及它们是如何协调的。近期的目标集中在Bruno，以及当它与Oskar mRNA3‘UTR的一个区域结合时，它如何发挥抑制作用，以及当它与3’UTR的另一个区域结合时，它如何发挥激活作用。Oskar mRNA的两个Bruno结合区的组织方式不同，其中一个区域的RNA可以抑制Bruno/蛋白质的相互作用(二聚化)，而另一个区域的RNA不能。我们推测，结合位点的差异改变了结合Bruno的构象，或限制了Bruno结合的方式。然后，结合的Bruno的不同构象将促进或允许Bruno/蛋白质相互作用的不同选择(Bruno/Cup用于抑制，Bru/？用于激活)，并因此指定抑制或激活。我们将测试这个最符合当前数据的模型，以及其他模型。我们还将测试Bruno依赖的激活涉及细胞质多腺化的模型。 许多疾病是由不适当的基因表达引起的。我们在布鲁诺等在人类中有近亲的基因上所做的工作，将促进对控制基因表达的基本机制的理解。

DESCRIPTION (provided by applicant): Proper control of gene expression underlies the formation and function of all cells. Regulation at the level of translation, once thought to be limited in its scope, has emerged as an important feature in a wide range of settings, from the earliest stages of development to the function of the nervous system. Recent advances that reveal the widespread expression of microRNAs, which control a novel form of translational control, further expand the fraction of mRNAs whose translation is regulated. In Drosophila, translational control and mRNA localization act coordinately in deployment of body patterning determinants at particular positions in the oocyte and embryo. One determinant is encoded by the oskar gene, and its restriction to the posterior pole of the oocyte is essential. The controls used to achieve that distribution include two forms of translational repression (one strikingly similar to microRNA-dependent repression), mRNA localization, and two or more forms of translational activation. A protein that binds to oskar mRNA, Bruno, mediates one form of repression as well as one form of activation. Our long term goal is to understand each of these mechanisms and how they are coordinated. The immediate goals focus on Bruno, and how it can function as a represser when bound to one region of the oskar mRNA 3' UTR, and as an activator when bound to another region of the 3' UTR. The two Bruno-binding regions of the oskar mRNA are organized differently, and the RNA of one region can inhibit a Bruno/protein interaction (dimerization) while the other cannot. We hypothesize that the differences in the binding sites alter the conformation of bound Bruno, or limit the manner in which Bruno can bind. The different conformations of bound Bruno would then promote or allow different options for Bruno/protein interactions (Bruno/Cup for repression, Bru/? for activation), and thus specify repression or activation. We will test this model, which best fits the current data, as well as other models. We will also test the model that Bruno dependent activation involves cytoplasmic polyadenylation. Many diseases result from inappropriate gene expression. Our work, on genes such as Bruno that have close relatives in humans, will advance understanding of the basic mechanisms that control gene expression.