The role of Orc6 in DNA replication and cytokinesis

抽象的。 起源识别复合体(ORC)，异构体六亚单位蛋白 复杂，对DNA复制是必不可少的。ORC的功能也超越了DNA 复制。我们发现ORC亚基中最小的一种--ORC6蛋白对 DNA结合和复制，与转录因子具有结构同源性 TFIIB提示它可能以复制前复合体的形成为靶点 DNA复制的起源。此外，我们还确定了C-的保守基序。 ORC6的末端，负责其与核心ORC复合体的相互作用。 该基序中的突变会影响六亚单位ORC的完整性 梅尔-戈林综合征(MGS)的发病机制。ORC6也有一个函数 胞质分裂。它通过其果核亚基直接与Septin复合体结合，刺激 果蝇间隔蛋白复合体的固有GTP酶活性及其对间隔蛋白的极大促进作用 形成细丝。我们建议的总体目标是描述这一机制的特点 以果蝇为模型研究ORC6在DNA复制和胞质分裂中的作用 系统。我们的实验旨在回答有关 ORC6的结构，其在复制中的功能及其在Septin聚合中的作用。 果蝇模型系统将被用来分析自然发生的影响 以及结构导向的人类ORC6在不同蛋白质功能中的靶向突变。 由于ORC在进化中是保守的，我们对其功能的了解 果蝇对我们理解ORC在其他物种中的功能将是有价值的 真核生物。更好地理解ORC在果蝇中的功能将提供 洞察兽人在哺乳动物中的行为，并提供线索说明其如何 管理不善会导致癌症。

Abstract. The Origin Recognition Complex (ORC), heteromeric six-subunit protein complex, is essential for DNA replication. ORC's functions also extend beyond DNA replication. We found that the smallest of ORC subunit, Orc6 protein, is important for DNA binding and replication and has a structural homology with transcription factor TFIIB suggesting that it may target the formation of pre-replicative complex to the origins of DNA replication. Furthermore, we identified conserved motif within the C- terminus of Orc6 which is responsible for its interaction with the core ORC complex. Mutations in this motif affect the integrity of six-subunit ORC contributing to the pathogenesis of Meier-Gorlin syndrome (MGS) in humans. Orc6 also has a function in cytokinesis. It binds directly to septin complex via its Pnut subunit, stimulates the intrinsic GTPase activity of the Drosophila septin complex and greatly facilitates septin filament formation. The overall goal of our proposal is to characterize the mechanism of Orc6 functions in DNA replication and cytokinesis using Drosophila as a model system. Our experiments are designed to answer important questions about the structure of Orc6, its functions in replication and its role in septin polymerization. Drosophila model systems will be used to analyze the effects of naturally occurring and structure-guided targeted mutations of human Orc6 in diverse protein functions. Because ORC is conserved in evolution, what we learn about its functions in Drosophila will be valuable to our understanding of ORC's functions in other eukaryotes. A better understanding of how ORC functions in Drosophila will provide insights into ORC's behavior in mammals and provide clues as to how its misregulation leads to cancer.