Kolb Anna-Lena, Gunn Alasdair R, Lakin Nicholas D
Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK.
Nucleic Acids Res. 2017 Sep 29;45(17):10056-10067. doi: 10.1093/nar/gkx639.
ADP-ribosyltransferases promote repair of DNA single strand breaks and disruption of this pathway by Poly(ADP-ribose) polymerase (PARP) inhibitors (PARPi) is toxic to cells with defects in homologous recombination (HR). Here, we show that this relationship is conserved in the simple eukaryote Dictyostelium and exploit this organism to define mechanisms that drive resistance of the HR-deficient cells to PARPi. Dictyostelium cells disrupted in exonuclease I, a critical factor for HR, are sensitive to PARPi. Deletion of exo1 prevents the accumulation of Rad51 in chromatin induced by PARPi, resulting in DNA damage being channelled through repair by non-homologous end-joining (NHEJ). Inactivation of NHEJ supresses the sensitivity of exo1- cells to PARPi, indicating this pathway drives synthetic lethality and that in its absence alternative repair mechanisms promote cell survival. This resistance is independent of alternate-NHEJ and is instead achieved by re-activation of HR. Moreover, inhibitors of Mre11 restore sensitivity of dnapkcs-exo1- cells to PARPi, indicating redundancy between nucleases that initiate HR can drive PARPi resistance. These data inform on mechanism of PARPi resistance in HR-deficient cells and present Dictyostelium as a convenient genetic model to characterize these pathways.
ADP-核糖基转移酶促进DNA单链断裂的修复，而聚（ADP-核糖）聚合酶（PARP）抑制剂（PARPi）对这一途径的破坏对同源重组（HR）存在缺陷的细胞具有毒性。在此，我们表明这种关系在简单真核生物盘基网柄菌中是保守的，并利用这种生物体来确定驱动HR缺陷细胞对PARPi产生抗性的机制。在核酸外切酶I（HR的关键因子）中被破坏的盘基网柄菌细胞对PARPi敏感。exo1的缺失阻止了PARPi诱导的Rad51在染色质中的积累，导致DNA损伤通过非同源末端连接（NHEJ）进行修复。NHEJ的失活抑制了exo1 -细胞对PARPi的敏感性，表明该途径驱动合成致死性，并且在其不存在时，替代修复机制促进细胞存活。这种抗性独立于替代NHEJ，而是通过HR的重新激活来实现的。此外，Mre11抑制剂恢复了dnapkcs - exo1 -细胞对PARPi的敏感性，表明启动HR的核酸酶之间的冗余可以驱动PARPi抗性。这些数据揭示了HR缺陷细胞中PARPi抗性的机制，并将盘基网柄菌作为一种方便的遗传模型来表征这些途径。
