The role of Orc6 in DNA replication and cytokinesis.

抽象的。 起源识别复合体(ORC)--一种异构体六亚单位蛋白质 复杂，对DNA复制是必不可少的。ORC的功能也超越了DNA 复制。ORC中最小的亚基ORC6蛋白对DNA很重要 在所有真核生物中复制。我们已经证明，在果蝇中，ORC6有一个额外的 通过与Septin复合体相互作用在细胞质分裂中的作用，Septin复合体是一种高度保守的 聚合蛋白质组件，对许多物种的胞质分裂是关键的，并且是 被认为是细胞骨架的重要组成部分。在初步研究中，我们 解决了人类ORC6的结构并确定了其结构特征 直接影响到蛋白质在复制和胞质分裂中的功能。我们描述了 导致Meier-Gorlin综合征(MGS)的ORC6不同结构域突变 人类是一种常染色体隐性遗传病，其特征是原始侏儒症和 发育异常。我们发现，尽管存在不同的潜在分子 这些突变导致前RC表型相似、缺陷的机制 形成和DNA复制受损。因此，ORC6的不同分子功能 可以通过实验解剖，以获得对其离散的完整理解 在细胞中扮演的角色。这项提案的总体目标是定义不同的机制 以果蝇为模型研究ORC6在DNA复制和胞质分裂中的作用 系统。我们建立了一个人性化的基于ORC6的果蝇模型系统，它将 用于分析自然发生的和结构引导的针对性的效果 人类ORC6蛋白功能突变。对可复制性和 ORC在后生动物中的非复制功能是有限的，尽管几十年来 研究。我们完成这个项目将有助于填补我们对 ORC在后生动物中的不同功能，并提供了关于特定突变如何 否则，不当的监管将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.