The timely activation of homologous recombination is essential for the maintenance of genome stability, in which the RAD51 recombinase plays a central role. Biochemically, human RAD51 polymerises faster on single-stranded DNA (ssDNA) compared to double-stranded DNA (dsDNA), raising a key conceptual question: how does it discriminate between them? In this study, we tackled this problem by systematically assessing RAD51 binding kinetics on ssDNA and dsDNA differing in length and flexibility using surface plasmon resonance. By directly fitting a mechanistic model to our experimental data, we demonstrate that the RAD51 polymerisation rate positively correlates with the flexibility of DNA. Once the RAD51-DNA complex is formed, however, RAD51 remains stably bound independent of DNA flexibility, but rapidly dissociates from flexible DNA when RAD51 self-association is perturbed. This model presents a new general framework suggesting that the flexibility of DNA, which may increase locally as a result of DNA damage, plays an important role in rapidly recruiting repair factors that multimerise at sites of DNA damage.

中文翻译：

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DNA 的分子灵活性是 RAD51 募集的关键决定因素。

同源重组的及时激活对于维持基因组稳定性至关重要，其中 RAD51 重组酶起着核心作用。在生化方面，与双链 DNA (dsDNA) 相比，人类 RAD51 在单链 DNA (ssDNA) 上的聚合速度更快，这引发了一个关键的概念问题：它如何区分它们？在这项研究中，我们通过使用表面等离子共振系统地评估 RAD51 在长度和灵活性上不同的 ssDNA 和 dsDNA 上的结合动力学来解决这个问题。通过将机械模型直接拟合到我们的实验数据中，我们证明 RAD51 聚合速率与 DNA 的灵活性呈正相关。然而，一旦形成 RAD51-DNA 复合物，RAD51 就会保持稳定结合，不受 DNA 灵活性的影响，但当 RAD51 自关联受到干扰时，它会迅速与柔性 DNA 解离。该模型提出了一个新的总体框架，表明 DNA 的灵活性可能由于 DNA 损伤而局部增加，在快速招募在 DNA 损伤位点多聚化的修复因子中起重要作用。