Alu Elements and Human Genetic Instability

描述（由申请人提供）：重复元件占人类基因组的近50%。曾经是“垃圾DNA”的经典例子，Alu元件和长散布元件-1（L1）最近获得了更突出的地位，因为几项研究确定了它们参与细胞功能和基因重塑。这些目前活跃的人类移动的元素被公认为是遗传不稳定性和相关遗传疾病（包括癌症）的重要贡献者。目前的估计将0.5%的人类遗传性遗传疾病归因于移动的元件插入和/或随后的诱变重组的结果。由于人类基因组中的所有Alu拷贝都是用含有L1核酸内切酶识别位点的靶位点重复产生的，因此在这些元件附近存在大约200万个潜在的切割位点，这些位点可能有助于Alu/Alu介导的事件。尽管Alu元件对人类基因组有巨大的影响，但参与Alu/Alu重组过程的Alu元件的许多具体方面仍然未被探索。 我们的长期目标是了解为什么某些遗传基因座特别容易发生这种形式的重组，以及我们是否可以预测基因组中遗传不稳定的区域，以便充分评估Alu元素对人类健康的影响。本申请的目的是首先确定Alu元件中的哪些因素影响Alu/Alu重组率，其次，使用L1作为在正常和核苷酸切除修复（NER）缺陷遗传背景中引起双链断裂（DSB）的来源来测量Alu/Alu重组。本申请的中心假设是Alu元件的特定方面影响Alu/Alu重组的速率，并且L1内切核酸酶活性介导人类基因组中的Alu/Alu重组。提出这项研究的理由是，这一系列的实验将使我们更好地了解导致人类基因组中诱变重组的因素，特别是在重复序列中。我们的具体目标是：1.评估Alu元件的特定方面对非等位基因同源重组的贡献。我们将具体评估方向（正向重复序列、反向重复序列）、错配、A尾长度和这些重复元件之间的距离的重要性。2.确定L1内切酶活性在正常和NER缺陷遗传背景下Alu/Alu重组中的作用。 公共卫生相关性：目前活跃的人类移动的元素家族（1号线和Alu）被公认为是遗传不稳定性和相关遗传疾病（包括癌症）的重要贡献者。这一建议将使我们更好地了解人类基因组中诱变重组的因素，特别是在重复序列中。最终，我们的研究结果可以让我们找出一些规则，允许基于Alu/Alu重组潜力预测各种基因组区域的稳定性。

DESCRIPTION (provided by applicant): Repetitive elements constitute nearly 50% of the human genome. Once classic examples of ''junk DNA,'' Alu elements and Long Interspersed Element -1 (L1) recently gained a more prominent status as several studies established their involvement in cell functions and gene remodeling. These currently active human mobile elements are well established as significant contributors to genetic instability and associated genetic diseases, including cancer. Current estimates attribute 0.5% of human inherited genetic disorders as is having been the consequence of mobile element insertions and/or subsequent mutagenic recombination's. As all Alu copies in the human genome are generated with target site duplications that contain an L1 endonuclease recognition site, there are roughly two million potential cleavage sites adjacent to these elements that may help them contribute to Alu/Alu- mediated events. Despite the tremendous impact of Alu elements on the human genome, much of the specific aspects of the Alu elements involved in the process of Alu/Alu recombination remain unexplored. Our long-term goal is to understand why some genetic loci are particularly prone to this form of recombination and whether we can predict regions of genetic instability in the genome in order to fully assess the impact of Alu elements on human health. The objective of this application is first, to determine which factors in the Alu element influence Alu/Alu recombination rates and second, to measure Alu/Alu recombination using L1 as a source to cause double strand breaks (DSBs) both in a normal and nucleotide excision repair (NER) deficient genetic background. The central hypothesis of the application is that specific aspects of Alu elements influence in the rate of Alu/Alu recombination and that L1 endonuclease activity mediates Alu/Alu recombination in the human genome. The rationale for the proposed research is that, this series of experiments will provide us with a better understanding of the factors contributing to mutagenic recombination in the human genome, particularly among repetitive sequences. Our specific aims are: 1. To evaluate the contribution of specific aspects of the Alu elements to non-allelic homologous recombination. We will specifically evaluate the importance of orientation (direct repeats, inverted repeats), mismatch, A-tail length, and distance between these repetitive elements. 2. To determine the role of L1 endonuclease activity in Alu/Alu recombination in normal and NER deficient genetic backgrounds. PUBLIC HEALTH RELEVANCE: The currently active human mobile elements families (Line 1 and Alu) are well established as significant contributors to genetic instability and associated genetic diseases, including cancer. This proposal will provide us with a better understanding of the factors contributing to mutagenic recombination in the human genome, particularly among repetitive sequences. Ultimately, the results of our research could allow us to figure out a number of rules that allow predictions about the stability of various genomic regions based on Alu/Alu recombination potential.