Complex Genomic Rearrangements by BIR and mmBIR

肿瘤基因组和致病拷贝数变异中的染色体重排 往往非常复杂。有人认为，人类细胞中的这些重排是修复的结果 当DNA复制叉子停滞或崩溃时，参与其中的通路。假想的修复路径 涉及到断裂诱导的复制(经典的BIR)和容易出错的微同源介导的断裂- 诱导复制(MMBIR)机制。目前尚不清楚哪些情况会促使MMBIR进行修复 而不是(相对)保守的BIR途径，关于MMBIR如何 会产生复杂的重排。这项建议的目的是建立在我们之前研究BIR的基础上 酵母。我们将使用酵母模型系统的强大遗传工具来进一步比较和表征 这两条修复路径。在这项提案的第一个目标中，我们将描述促进 Mm BIR。我们将研究是否可以在“典型”细胞条件下发生MMBIR，以及是否可以 更频繁地在氧化应激条件下使用，众所周知，氧化应激可降低关键蛋白的水平 经典BIR所需的蛋白质。我们还将研究断头的处理是否会影响 MMBIR修复途径的参与。在第二个目标中，我们将描述模板选择在 MMBIR途径，以确定需要多少同源性以及MmBIR是否受物理约束 所涉及的模板之间的距离。这两个目标的实验都将检验关于 模型，并将帮助我们了解哪些情况和环境促进了MMBIR 肿瘤和新生血管中复杂的基因组重排。

Chromosomal rearrangements in tumor genomes and in disease-causing copy number variations (CNVs) are often highly complex. It has been suggested that these rearrangements in human cells result from repair pathways that are engaged when DNA replication forks stall or collapse. The repair pathways hypothesized to be involved are break-induced replication (classical BIR) and the error-prone microhomology-mediated break- induced replication (mmBIR) mechanism. It remains unclear what conditions prompt repair by mmBIR rather than the (relatively) conservative BIR pathway, and much remains to be understood about how mmBIR generates complex rearrangements. The aims of this proposal build on our previous work studying BIR in yeast. We will use the powerful genetic tools of the yeast model system to further compare and characterize these two repair pathways. In the first aim of this proposal, we will characterize conditions that promote mmBIR. We will study whether mmBIR can occur under “typical” cellular conditions, and whether it is employed more frequently under conditions of oxidative stress, which are known to lower the level of key proteins needed for classical BIR. We will also study whether processing of the broken end influences engagement of the mmBIR repair pathway. In the second aim, we will characterize template choice in the mmBIR pathway to determine how much homology is required and whether mmBIR is constrained by physical distances between templates involved. The experiments in both of these aims will test hypotheses about the models of mmBIR and will help us understand which situations and environments promote mmBIR-mediated complex genomic rearrangements in tumors and CNVs.