Breast Cancer Type 1 Susceptibility Protein (BRCA1) is a tumor-suppressor protein that regulates various cellular pathways, including those that are essential for preserving genome stability. One essential mechanism involves a BRCA1-A complex that is recruited to double-strand breaks (DSBs) by RAP80 before initiating DNA damage repair (DDR). How RAP80 itself is recruited to DNA damage sites, however, is unclear. Here, we demonstrate an intrinsic correlation between a methyltransferase DOT1L-mediated RAP80 methylation and BRCA1-A complex chromatin recruitment that occurs during cancer cell radiotherapy resistance. Mechanistically, DOT1L is quickly recruited onto chromatin and methylates RAP80 at multiple lysines in response to DNA damage. Methylated RAP80 is then indispensable for binding to ubiquitinated H2A and subsequently triggering BRCA1-A complex recruitment onto DSBs. Importantly, DOT1L-catalyzed RAP80 methylation and recruitment of BRCA1 have clinical relevance, as inhibition of DOT1L or RAP80 methylation seems to enhance the radiosensitivity of cancer cells both in vivo and in vitro. These data reveal a crucial role for DOT1L in DDR through initiating recruitment of RAP80 and BRCA1 onto chromatin and underscore a therapeutic strategy based on targeting DOT1L to overcome tumor radiotherapy resistance.

中文翻译：

---

DOT1L 介导的 RAP80 甲基化促进 BRCA1 募集以引发 DNA 修复


乳腺癌 1 型易感蛋白 (BRCA1) 是一种肿瘤抑制蛋白，可调节多种细胞途径，包括那些对于保持基因组稳定性至关重要的途径。一个重要机制涉及 BRCA1-A 复合物，该复合物在启动 DNA 损伤修复 (DDR) 之前被 RAP80 募集至双链断裂 (DSB)。然而，RAP80 本身如何被招募到 DNA 损伤位点尚不清楚。在这里，我们证明了甲基转移酶 DOT1L 介导的 RAP80 甲基化与癌细胞放疗抵抗期间发生的 BRCA1-A 复杂染色质募集之间的内在相关性。从机制上讲，DOT1L 会快速招募到染色质上，并在多个赖氨酸上甲基化 RAP80，以应对 DNA 损伤。甲基化 RAP80 对于与泛素化 H2A 结合并随后触发 BRCA1-A 复合物招募至 DSB 是必不可少的。重要的是，DOT1L 催化的 RAP80 甲基化和 BRCA1 的募集具有临床相关性，因为抑制 DOT1L 或 RAP80 甲基化似乎可以增强体内和体外癌细胞的放射敏感性。这些数据揭示了 DOT1L 通过启动 RAP80 和 BRCA1 招募到染色质上而在 DDR 中发挥关键作用，并强调了基于靶向 DOT1L 来克服肿瘤放疗耐药性的治疗策略。