The role of Orc6 in DNA replication and cytokinesis

抽象的。 起源识别复合物 (ORC)，异聚六亚基蛋白 复杂，对于 DNA 复制至关重要。 ORC的功能也超越了DNA 复制。我们发现最小的 ORC 亚基 Orc6 蛋白对于 DNA结合和复制并与转录因子具有结构同源性 TFIIB 表明它可能以复制前复合物的形成为目标 DNA复制的起源。此外，我们还发现了 C- 内的保守基序 Orc6 的末端负责与核心 ORC 复合体相互作用。 该基序的突变会影响六亚基 ORC 的完整性，从而导致 人类迈尔戈林综合征（MGS）的发病机制。 Orc6还有一个功能 胞质分裂。它通过其 Pnut 亚基直接与 septin 复合物结合，刺激 果蝇 septin 复合物的内在 GTP 酶活性，极大地促进了 septin 细丝形成。我们提案的总体目标是描述该机制的特征 以果蝇为模型研究 Orc6 在 DNA 复制和胞质分裂中的功能 系统。我们的实验旨在回答有关 Orc6 的结构、其复制功能及其在 septin 聚合中的作用。 果蝇模型系统将用于分析自然发生的影响 以及人类 Orc6 在多种蛋白质功能中的结构引导靶向突变。 由于 ORC 在进化中是保守的，因此我们对它的功能的了解是 果蝇对于我们理解 ORC 在其他方面的功能非常有价值 真核生物。更好地了解 ORC 在果蝇中的功能将提供 深入了解 ORC 在哺乳动物中的行为，并提供其如何发挥作用的线索 调节不当会导致癌症。

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.