Alu Elements and Human Genetic Instability

描述(申请人提供)：重复元件占人类基因组的近50%。Alu元素和长分布的Element-1(L1)曾经是“垃圾DNA”的经典例子，最近随着几项研究证实它们参与了细胞功能和基因重塑，它们获得了更突出的地位。这些目前活跃的人类活动元件被公认为是遗传不稳定和相关遗传病(包括癌症)的重要贡献者。目前的估计是0.5%的人类遗传性疾病是移动元件插入和/或随后的突变重组的结果。由于人类基因组中的所有Alu拷贝都是通过包含L1核酸内切酶识别位点的目标位点复制而产生的，因此大约有200万个潜在的切割位点与这些元件相邻，这可能有助于它们促成Alu/Alu介导的事件。尽管Alu元素对人类基因组有巨大的影响，但Alu/Alu重组过程中涉及的Alu元素的许多具体方面仍未被探索。我们的长期目标是了解为什么一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的遗传不稳定区域，以便充分评估Alu元素对人类健康的影响。这项应用的目的首先是确定Alu元件中哪些因素影响Alu/Alu重组率，其次是以L1为来源测量在正常和核苷酸切除修复(NER)缺陷的遗传背景下引起双链断裂(DSB)的Alu/Alu重组。该应用的中心假设是，Alu元素的特定方面影响Alu/Alu重组的速度，并且L1内切酶活性介导了人类基因组中的Alu/Alu重组。这项拟议研究的基本原理是，这一系列实验将使我们更好地了解导致人类基因组中突变重组的因素，特别是重复序列之间的突变重组。我们的具体目标是：1.评估Alu元素的特定方面对非等位同源重组的贡献。我们将具体评估方向(正向重复、反向重复)、不匹配、A-尾部长度以及这些重复元素之间的距离的重要性。2.探讨L1内切酶活性在正常和NER缺陷型遗传背景下Alu/Alu重组中的作用。 公共卫生相关性：目前活跃的人类活动元件家族(1号线和ALU)被公认为是遗传不稳定和包括癌症在内的相关遗传病的重要贡献者。这一建议将使我们更好地了解导致人类基因组突变重组的因素，特别是重复序列之间的突变重组。最终，我们的研究结果可以让我们找出一些规则，根据Alu/Alu重组潜力预测不同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.