Role of DNA double-strand break repair in the prevention of rereplication-induced genome instability

 描述(申请人提供)：真核细胞中的DNA复制受到严格控制，因此基因组只复制一次，并且每个细胞周期只复制一次。由于复制许可机制受损导致DNA复制控制中断，导致DNA重新复制，这通常会导致基因组不稳定，从而导致肿瘤发生。为了支持这一点，许可因子CDT1的非调控过度表达与一大组肿瘤相关。此外，许多癌基因被发现在癌症发展的早期阶段诱导DNA重新复制。因此，DNA再复制是肿瘤发生的驱动力。DNA双链断裂(DSB)经常在再复制过程中形成，但修复再复制诱导的DSB以维持基因组完整性的机制仍不清楚。由于DNA再复制会产生额外的DNA片段副本，并产生多个DSB，因此相关的修复过程预计会比一般单一DSB的修复过程复杂得多。在这项研究中，我们将研究如何去除再复制的DNA的详细机制，以及如何使用我们新建立的基于绿色荧光蛋白的新型DSB修复底物修复再复制叉处产生的DSB。我们还将研究再复制将导致的基因组不稳定的后果，如染色体损伤和基因扩增。由于DNA再复制是肿瘤发生的一个重要方面，我们提出的研究将为肿瘤的发生和发展提供新的机制，也将为未来癌症诊断和治疗策略的制定提供帮助。

 DESCRIPTION (provided by applicant): DNA replication in eukaryotic cells is tightly controlled so that the genome is replicated once and only once per cell cycle. Disruption of DNA replication control due to impaired replication licensing mechanisms causes DNA rereplication, which often leads to genome instability, contributing to tumorigenesis. In support of this, deregulated overexpression of the licensing factor Cdt1 is associated with a large panel of tumors. Furthermore, a number of oncogenes are found to induce DNA rereplication at the early stage of cancer development. Thus, DNA rereplication is a driving force for tumorigenesis. DNA double-strand breaks (DSBs) are frequently formed during rereplication, but the mechanisms underlying the repair of rereplication-induced DSBs to maintain genome integrity are still elusive. Since DNA rereplication produces extra copies of DNA segments and generates multiple DSBs, the associated repair process is expected to be much more complex than that for a general single DSB. In this study, we will investigate the detailed mechanisms of how rereplicated DNA is removed, and how DSBs generated at rereplication forks are repaired by using our newly established novel EGFP-based DSB repair substrates. We will also study the consequences for genome instability that rereplication would cause, such as chromosomal lesions and gene amplification. Since DNA rereplication is an integral aspect of tumorigenesis, our proposed study will provide insights into new mechanisms associated with tumor initiation and development, and will also shed light on developing strategies for cancer diagnosis and treatment in the future.