The role of Orc6 in DNA replication and cytokinesis.

抽象的。 起源识别复合物（ORC），一种异聚体六亚基蛋白 复杂，是DNA复制所必需的。ORC的功能也超越了DNA 复制的最小的ORC亚基，Orc 6蛋白，对DNA非常重要。 在所有真核生物中复制我们已经证明，在果蝇中，Orc 6有一个额外的 通过与septin复合物（高度保守的）相互作用在胞质分裂中发挥作用 聚合蛋白质组装，这对许多物种的胞质分裂至关重要， 被认为是细胞骨架的重要组成部分。在初步研究中， 解决了人类Orc 6的结构，并确定了其结构特征， 直接影响蛋白质在复制和胞质分裂中的功能。我们的特点 Orc 6不同结构域的突变导致Meier-Gorlin综合征（MGS）， 人类，一种常染色体隐性遗传疾病，特征为原始侏儒症， 发育异常我们发现，尽管不同的潜在分子 这些突变导致相似的表型，前RC缺陷， 形成和受损的DNA复制。因此，Orc 6的多种分子功能 可以实验性地解剖，以获得其离散的完整理解。 细胞中的角色。本提案的总体目标是界定不同的机制， Orc 6在DNA复制和胞质分裂中的功能 系统我们建立了一个基于Orc 6的人源化果蝇模型系统， 用于分析自然发生的和结构导向的靶向效应 人Orc 6蛋白功能的突变。对复制和 ORC在后生动物中的非复制功能是有限的，尽管几十年来， research.我们完成这个项目将有助于填补这一空白，在我们的理解， 在后生动物中多种多样的ORC功能，并提供线索，如何一个特定的突变 或错误调节会导致生长和发育缺陷。

Abstract. The Origin Recognition Complex (ORC), a heteromeric six-subunit protein complex, is essential for DNA replication. ORC's functions also extend beyond DNA replication. The smallest of ORC subunits, Orc6 protein, is important for DNA replication in all eukaryotes. We have shown that in Drosophila Orc6 has an additional role in cytokinesis through interaction with the septin complex, a highly conserved polymerizing protein assembly that is critical for cytokinesis in many species and is recognized as important component of the cytoskeleton. In preliminary studies we solved the structure of human Orc6 and identified its structural features that contribute directly to the functions of the protein in replication and cytokinesis. We characterized the mutations in different domains of Orc6 leading to Meier-Gorlin syndrome (MGS) in humans, an autosomal recessive disorder characterized by primordial dwarfism and developmental abnormalities. We showed that despite different underlying molecular mechanisms these mutations resulted in similar phenotypes, defects in pre-RC formation and impaired DNA replication. Thus, the diverse molecular functions of Orc6 can be experimentally dissected to obtain a complete understanding of its discrete roles in the cell. The overall goal of this proposal is to define the distinct mechanisms of Orc6 function in DNA replication and in cytokinesis using Drosophila as a model system. We established a humanized Orc6-based Drosophila model system which will be used to analyze the effects of naturally occurring and structure-guided targeted mutations of human Orc6 in protein functions. Regulatory insights into replicative and non-replicative functions of ORC in metazoans are limited, despite decades of research. Our completion of this project will help to fill this gap in our understanding of diverse ORC's functions in metazoans and provide clues as to how a specific mutation or mis-regulation would lead to growth and developmental defects.