DNA replication and cytokinesis

描述（由申请人提供）：起源识别复合物（ORC），异聚六亚基蛋白复合物，是DNA复制所必需的。ORC的功能也超出了DNA复制。在我们的初步研究中，我们发现果蝇最小的ORC亚基Orc 6对DNA结合和DNA复制很重要，但也通过与Septin蛋白Pnut的相互作用在胞质分裂中起作用。基于这些观察，我们假设Orc 6是一种多功能蛋白。orc 6可能参与协调细胞分裂周期许多过程的信号通路，如染色体复制和胞质分裂。我们假设Orc 6与转录因子TFIIB具有结构同源性，对于将ORC靶向至果蝇细胞中的起源和形成复制前复合物是必需的。Orc 6在胞质分裂中的功能是通过调节septin复合物的活性来实现的。为了验证这些假设，我们计划在分子、细胞和遗传水平上分析Orc 6的功能和活性及其在细胞周期中的作用。具体而言，我们将1）确定Orc 6的三维结构; 2）确定Orc 6在DNA结合和DNA复制中的功能; 3）阐明Orc 6在调节septin复合物功能中的作用。由于ORC在进化中是保守的，我们在果蝇中对其功能的了解将对我们了解其他真核生物中ORC的功能有价值。更好地了解ORC在果蝇中的功能将有助于深入了解ORC在哺乳动物中的行为，并提供有关其失调如何导致癌症的线索。

DESCRIPTION (provided by applicant): The Origin Recognition Complex (ORC), heteromeric six-subunit protein complex, is essential for DNA replication. ORC's functions also extend beyond DNA replication. In our preliminary studies, we found that the Drosophila smallest ORC subunit, Orc6, is important for DNA binding and DNA replication but also has a function in cytokinesis through the interaction with septin protein Pnut. Based on these observations we hypothesize that Orc6 is a multifunctional protein. Orc6 might be involved in a signaling pathway that coordinates many processes of the cell division cycle, such as chromosome duplication and cytokinesis. We hypothesize that Orc6, which bears a structural homology with transcription factor, TFIIB, is essential for targeting of ORC to the origins in Drosophila cells and for the formation of pre- replicative complex. The function of Orc6 in cytokinesis is achieved through the regulation of septin complex activities. To test these hypotheses we plan to analyze at the molecular, cellular and genetic levels the functions and activities of Orc6 and its role in cell cycle. Specifically we will 1) determine the three-dimensional structure of Orc6; 2) detertmine functions of Orc6 in DNA binding and DNA replication; and 3) elucidate the role of Orc6 in regulation of septin complex 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.