Alu Elements and Human Genetic Instability

描述（由申请人提供）：重复元素构成了近50%的人类基因组。作为“垃圾DNA”的经典例子，Alu元件和长穿插元件-1 （L1）最近获得了更突出的地位，因为一些研究证实它们参与细胞功能和基因重塑。这些目前活跃的人类可移动元素已被确定为导致遗传不稳定和相关遗传疾病（包括癌症）的重要因素。目前估计有0.5%的人类遗传疾病是由移动元件插入和/或随后的致突变重组造成的。由于人类基因组中的所有Alu拷贝都是由含有L1内切酶识别位点的靶位点复制产生的，因此在这些元件附近大约有200万个潜在的切割位点，这些位点可能有助于它们参与Alu/Alu介导的事件。尽管Alu元件对人类基因组的影响巨大，但Alu/Alu重组过程中涉及的Alu元件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基因位点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，以便全面评估Alu元素对人类健康的影响。本应用程序的目的首先是确定Alu元素中的哪些因素影响Alu/Alu重组率，其次，在正常和核苷酸切除修复（NER）缺陷的遗传背景下，使用L1作为导致双链断裂（dsb）的来源来测量Alu/Alu重组。该应用程序的中心假设是Alu元件的特定方面影响Alu/Alu重组的速度，L1内切酶活性介导人类基因组中的Alu/Alu重组。提出这项研究的基本原理是，这一系列的实验将使我们更好地了解导致人类基因组突变重组的因素，特别是在重复序列中。我们的具体目标是：1。评价Alu元素特定方面对非等位基因同源重组的贡献。我们将特别评估方向（直接重复、反向重复）、不匹配、a尾长度以及这些重复元素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。

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.