Dipartimento di Bioscienze, Università degli Studi di Milano, 20131 Milano, Italy.
Dipartimento di Bioscienze, Università degli Studi di Milano, 20131 Milano, Italy.
Cell Rep. 2023 Feb 28;42(2):112060. doi: 10.1016/j.celrep.2023.112060. Epub 2023 Feb 1.
The nucleolytic processing (resection) of a DNA double-strand break (DSB) is a critical step to repair the lesion by homologous recombination (HR). PARylation, which is the attachment of poly(ADP-ribose) (PAR) units to specific targets by PAR polymerases (PARPs), regulates many steps of HR, including resection. Here, we show that preventing PARylation of the oncosuppressor BRCA1 induces hyper-resection of DSBs through BRCA2 and the EXO1 nuclease. Upon expression of the unPARylatable variant of BRCA1, we observe a reduced 53BP1-RIF1 barrier for resection accompanied by an increase in the recruitment of the RAD51 recombinase. Similar results are observed when cells are treated with the clinically approved PARP inhibitor olaparib. We propose that PARylation of BRCA1 is important to limit the formation of excessively extended DNA filaments, thereby reducing illegitimate chromosome rearrangements. Our results shed light on molecular aspects of HR and on the mechanisms of PARP inhibitor treatment.
DNA 双链断裂 (DSB) 的核酶加工 (切除) 是通过同源重组 (HR) 修复损伤的关键步骤。聚 ADP 核糖化 (PARylation) 是指 PAR 聚合酶 (PARPs) 将聚 (ADP-核糖) (PAR) 单位连接到特定靶标上，调节 HR 的许多步骤，包括切除。在这里，我们表明，通过 BRCA2 和 EXO1 核酸酶，抑制抑癌蛋白 BRCA1 的 PARylation 会诱导 DSB 的过度切除。当表达 BRCA1 的不可 PARylation 变体时，我们观察到 53BP1-RIF1 切除障碍减少，同时 RAD51 重组酶的募集增加。当细胞用临床批准的 PARP 抑制剂奥拉帕利处理时，也观察到类似的结果。我们提出 BRCA1 的 PARylation 对于限制过度延伸的 DNA 纤维的形成很重要，从而减少不合法的染色体重排。我们的研究结果揭示了 HR 的分子方面以及 PARP 抑制剂治疗的机制。
