Rampias Theodoros, Klinakis Apostolos
Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
Methods Mol Biol. 2023;2684:133-144. doi: 10.1007/978-1-0716-3291-8_7.
Sister chromatid exchange (SCE) is the process of exchanging regions between two sister chromatids during DNA replication. Exchanges between replicated chromatids and their sisters can be visualized in cells when DNA synthesis in one chromatid is labelled by 5-bromo-2'-deoxyuridine (BrdU). Homologous recombination (HR) is considered as the principal mechanism responsible for the sister chromatid exchange (SCE) upon replication fork collapse, and therefore SCE frequency upon genotoxic conditions reflects the capacity of HR repair to respond to replication stress. During tumorigenesis, inactivating mutations or altered transcriptome can affect a plethora of epigenetic factors that participate in DNA repair processes, and there are an increasing number of reports which demonstrate a link between epigenetic deregulation in cancer and homologous recombination deficiency (HRD). Therefore, the SCE assay can provide valuable information regarding the HR functionality in tumors with epigenetic deficiencies. In this chapter, we provide a method to visualize SCEs. The technique outlined below is characterized by high sensitivity and specificity and has been successfully applied to human bladder cancer cell lines. In this context, this technique could be used to characterize the dynamics of HR repair in tumors with deregulated epigenome.
姐妹染色单体交换（SCE）是DNA复制过程中两条姐妹染色单体之间交换区域的过程。当一条染色单体中的DNA合成被5-溴-2'-脱氧尿苷（BrdU）标记时，复制后的染色单体与其姐妹染色单体之间的交换在细胞中可以可视化。同源重组（HR）被认为是复制叉崩溃时负责姐妹染色单体交换（SCE）的主要机制，因此在遗传毒性条件下的SCE频率反映了HR修复对复制应激的反应能力。在肿瘤发生过程中，失活突变或转录组改变会影响大量参与DNA修复过程的表观遗传因子，并且越来越多的报告表明癌症中的表观遗传失调与同源重组缺陷（HRD）之间存在联系。因此，SCE检测可以提供有关表观遗传缺陷肿瘤中HR功能的有价值信息。在本章中，我们提供了一种可视化SCE的方法。下面概述的技术具有高灵敏度和特异性的特点，并且已成功应用于人类膀胱癌细胞系。在这种情况下，该技术可用于表征表观基因组失调的肿瘤中HR修复的动态变化。
