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

 描述（由申请人提供）：真核细胞中的DNA复制受到严格控制，因此基因组在每个细胞周期复制一次且仅复制一次。由于复制许可机制受损而导致的DNA复制控制的破坏导致DNA再复制，这通常导致基因组不稳定，从而促进肿瘤发生。为了支持这一点，许可因子Cdt1的过度表达失调与大量肿瘤相关。此外，发现许多癌基因在癌症发展的早期阶段诱导DNA再复制。因此，DNA再复制是肿瘤发生的驱动力。 DNA双链断裂（DSB）是在复制过程中经常形成的，但修复复制诱导的DSB以维持基因组完整性的机制仍然是难以捉摸的。由于DNA再复制产生额外的DNA片段拷贝并产生多个DSB，因此相关的修复过程预计比一般的单个DSB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，以及如何通过使用我们新建立的新的基于EGFP的DSB修复底物修复在再复制叉产生的DSB。我们还将研究再复制可能导致的基因组不稳定性的后果，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组成部分，我们提出的研究将提供与肿瘤发生和发展相关的新机制的见解，也将为未来制定癌症诊断和治疗策略提供启示。

 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.