Department of Oncology, University of Alberta, Edmonton, Alberta T6G 2R3, Canada.
Nucleic Acids Res. 2024 Sep 9;52(16):9630-9653. doi: 10.1093/nar/gkae654.
DNA damage has been implicated in the stimulation of the type 1 interferon (T1IFN) response. Here, we show that downregulation of the DNA repair protein, polynucleotide kinase/phosphatase (PNKP), in a variety of cell lines causes robust phosphorylation of STAT1, upregulation of interferon-stimulated genes and persistent accumulation of cytosolic DNA, all of which are indicators for the activation of the T1IFN response. Furthermore, this did not require damage induction by ionizing radiation. Instead, our data revealed that production of reactive oxygen species (ROS) synergises with PNKP loss to potentiate the T1IFN response, and that loss of PNKP significantly compromises mitochondrial DNA (mtDNA) integrity. Depletion of mtDNA or treatment of PNKP-depleted cells with ROS scavengers abrogated the T1IFN response, implicating mtDNA as a significant source of the cytosolic DNA required to potentiate the T1IFN response. The STING signalling pathway is responsible for the observed increase in the pro-inflammatory gene signature in PNKP-depleted cells. While the response was dependent on ZBP1, cGAS only contributed to the response in some cell lines. Our data have implications for cancer therapy, since PNKP inhibitors would have the potential to stimulate the immune response, and also to the neurological disorders associated with PNKP mutation.
DNA 损伤已被牵连到 1 型干扰素（T1IFN）反应的刺激中。在这里，我们表明，在各种细胞系中下调 DNA 修复蛋白多核苷酸激酶/磷酸酶（PNKP）会导致 STAT1 的强烈磷酸化、干扰素刺激基因的上调和细胞质 DNA 的持续积累，所有这些都是 T1IFN 反应激活的指标。此外，这并不需要电离辐射引起的损伤。相反，我们的数据显示，活性氧（ROS）的产生与 PNKP 缺失协同作用，增强了 T1IFN 反应，而 PNKP 的缺失显著损害了线粒体 DNA（mtDNA）的完整性。mtDNA 的耗竭或用 ROS 清除剂处理 PNKP 耗竭的细胞会消除 T1IFN 反应，表明 mtDNA 是增强 T1IFN 反应所需的细胞质 DNA 的重要来源。STING 信号通路负责观察到的 PNKP 耗竭细胞中促炎基因特征的增加。虽然该反应依赖于 ZBP1，但 cGAS 仅在某些细胞系中对该反应有贡献。我们的数据对癌症治疗具有重要意义，因为 PNKP 抑制剂有可能刺激免疫反应，也与 PNKP 突变相关的神经紊乱有关。
