Mechanisms of Mitotic Recombination

在此输入文本，它是应用程序的新摘要信息。本节必须是否 超过30行的文本。 有丝分裂交换是有害的，因为它会导致杂合性或染色体的丢失。 基因重排，两者都与癌症有关。有丝分裂交叉的危险是 在布卢姆综合征患者中很明显，布卢姆综合征是一种罕见的遗传性疾病，其特征是高度的 广泛的恶性肿瘤的发病率升高和早期发作。细胞的一个主要特征 从这些患者是升高的有丝分裂交叉之间的姐妹染色单体，同源 染色体和异源染色体。对编码RecQ解旋酶的BLM的研究 为细胞阻止有丝分裂交叉的机制提供了重要的见解。我们 通过利用果蝇的独特优势， 作为后生动物模型，用于BLM细胞功能的遗传和分子研究 解旋酶我们已经开发了一个详细的模型，果蝇DmBLM的功能，在双- 链断裂修复;我们现在将测试这个模型的预测，以及由 其他人，使用已建立的和新的分子遗传分析。这包括设计的新测定法， 用于培养的人类细胞。虽然双链断裂的修复可能导致交叉， 大多数自发的有丝分裂交换被认为是由复制叉的问题引起的， 包括从块到分叉的进展、断开的分叉和一些分叉收敛。基于我们 当DmBLM和三种结构特异性DNA中的任何一种都 由于DmBLM在复制叉中的作用，我们修改了模型来解释DmBLM在复制叉中的作用。 我们将使用创新的方法来测试这些模型的关键预测。我们还将联合收割机 在体内和体外研究中揭示了这三种内切核酸酶的功能（MUS 81-MMS 4， GEN和MUS 312-SLX 1），其中每一种都与Holliday交界处的消退有关 中间体的重要的是，我们发现，GEN，这似乎只发挥次要作用， 芽殖酵母，而分裂酵母中没有，在果蝇中有几个重要的功能。我们 因此，研究将导致更好地了解这种酶的细胞功能， 其他假定的消退酶。最后，我们将确定其他基因/蛋白质参与预防或 通过研究候选基因和物理相互作用促进有丝分裂的交换 实验我们所提出的研究结果将增强我们对机制的理解 有丝分裂的交叉是通过什么产生的，以及细胞如何利用肿瘤抑制蛋白 BLM和其他蛋白质，以防止有丝分裂交叉，以及如何假定霍利迪连接 解离酶的功能是促进交换。

Enter the text here that is the new abstract information for your application. This section must be no longer than 30 lines of text. Mitotic crossing over is detrimental because it can lead to loss of heterozygosity or chromosome rearrangement, both of which are associated with cancer. The dangers of mitotic crossing over are evident in persons with Bloom syndrome, a rare, hereditary disease characterized by a highly elevated incidence and early onset of a broad range of malignancies. A predominant feature of cells from these patients is elevated mitotic crossing over between sister chromatids, homologous chromosomes, and heterologous chromosomes. Studies of BLM, which encodes a RecQ helicase, are providing important insights into mechanisms cells use to prevent mitotic crossing over. We have made significant contributions to these insights by exploiting unique advantages of Drosophila as a model metazoan for genetic and molecular studies of the cellular functions of the BLM helicase. We have developed a detailed model for the function of Drosophila DmBLM in double- strand break repair; we will now test predictions of this model, as well as models proposed by others, using established and novel molecular genetic assays. This includes novel assays designed for use in cultured human cells. Although repair of double-strand breaks may lead to crossing over, most spontaneous mitotic crossovers are thought to arise from problems at the replication fork, including blocks to fork progression, broken forks, and some fork convergences. Based on our studies of lethal phenotypes that occur when both DmBLM and any of three structure-specific DNA endonuclease is absent, we have modified models to explain roles of DmBLM in replication fork repair; we will use innovative methods to test key predictions of these models. We will also combine in vivo and in vitro studies to uncover functions of these three endonucleases (MUS81-MMS4, GEN, and MUS312-SLX1), each of which has been implicated in resolution of Holliday junction intermediates. Importantly, we find that GEN, which appears to play only a secondary role in budding yeast and is absent from fission yeast, has several important functions in Drosophila. Our studies will therefore lead to a greater understanding of the cellular functions of this enzyme and the other putative resolvases. Finally, we will identify additional genes/proteins involved in preventing or promoting mitotic crossovers through studies of candidate genes and through physical interaction experiments. The results from our proposed studies will enhance our understanding of mechanisms through which mitotic crossovers are generated and how cells employ the tumor suppressor protein BLM and other proteins to prevent mitotic crossing over, and how putative Holliday junction resolvases function to promote crossing over.