Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
Institute of Neuropathology, University of Freiburg, Freiburg, Germany.
J Cell Biol. 2020 Aug 3;219(8). doi: 10.1083/jcb.202002175.
DNA replication is highly regulated by the ubiquitin system, which plays key roles upon stress. The ubiquitin-like modifier ISG15 (interferon-stimulated gene 15) is induced by interferons, bacterial and viral infection, and DNA damage, but it is also constitutively expressed in many types of cancer, although its role in tumorigenesis is still largely elusive. Here, we show that ISG15 localizes at the replication forks, in complex with PCNA and the nascent DNA, where it regulates DNA synthesis. Indeed, high levels of ISG15, intrinsic or induced by interferon-β, accelerate DNA replication fork progression, resulting in extensive DNA damage and chromosomal aberrations. This effect is largely independent of ISG15 conjugation and relies on ISG15 functional interaction with the DNA helicase RECQ1, which promotes restart of stalled replication forks. Additionally, elevated ISG15 levels sensitize cells to cancer chemotherapeutic treatments. We propose that ISG15 up-regulation exposes cells to replication stress, impacting genome stability and response to genotoxic drugs.
DNA 复制受到泛素系统的高度调控，该系统在应激时发挥关键作用。泛素样修饰物 ISG15（干扰素刺激基因 15）可被干扰素、细菌和病毒感染以及 DNA 损伤诱导，但它也在许多类型的癌症中持续表达，尽管其在肿瘤发生中的作用仍很大程度上难以捉摸。在这里，我们表明 ISG15 定位于复制叉处，与 PCNA 和新生 DNA 形成复合物，从而调节 DNA 合成。事实上，高水平的 ISG15（由干扰素-β内在诱导或诱导）可加速 DNA 复制叉的进展，导致广泛的 DNA 损伤和染色体异常。这种效应在很大程度上独立于 ISG15 的缀合，依赖于 ISG15 与 DNA 解旋酶 RECQ1 的功能相互作用，从而促进停滞的复制叉重新启动。此外，ISG15 水平的升高使细胞对癌症化疗药物敏感。我们提出，ISG15 的上调使细胞暴露于复制应激之下，影响基因组稳定性和对遗传毒性药物的反应。
