The proliferation antigen Ki-67 has been widely used in clinical settings for cancer staging for many years, but investigations on its biological functions have lagged. Recently, Ki-67 has been shown to regulate both the composition of the chromosome periphery and chromosome behaviour in mitosis as well as to play a role in heterochromatin organisation and gene transcription. However, how the different roles for Ki-67 across the cell cycle are regulated and coordinated remain poorly understood. The progress towards understanding Ki-67 function have been limited by the tools available to deplete the protein, coupled to its abundance and fluctuation during the cell cycle. Here, we use a doxycycline-inducible E3 ligase together with an auxin-inducible degron tag to achieve a rapid, acute and homogeneous degradation of Ki-67 in HCT116 cells. This system, coupled with APEX2 proteomics and phospho-proteomics approaches, allows us to show that Ki-67 plays a role during DNA replication. In its absence, DNA replication is severely delayed, the replication machinery is unloaded, causing DNA damage that is not sensed by the canonical pathways and dependent on HUWE1 ligase. This leads to defects in replication and sister chromatids cohesion, but it also triggers an interferon response mediated by the cGAS/STING pathway in all the cell lines tested. We unveil a new function of Ki-67 in DNA replication and genome maintenance that is independent of its previously known role in mitosis and gene regulation.

中文翻译：

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Ki-67 在 DNA 复制过程中对于叉保护和基因组稳定性是必需的

增殖抗原Ki-67多年来已广泛应用于临床癌症分期，但对其生物学功能的研究却滞后。最近，Ki-67 已被证明可以调节染色体外围的组成和有丝分裂中的染色体行为，并在异染色质组织和基因转录中发挥作用。然而，人们对 Ki-67 在整个细胞周期中的不同作用如何调节和协调仍知之甚少。了解 Ki-67 功能的进展受到可用于消耗该蛋白质的工具的限制，再加上其在细胞周期中的丰度和波动。在这里，我们使用多西环素诱导型 E3 连接酶与生长素诱导型降解决定子标签一起在 HCT116 细胞中实现 Ki-67 的快速、急性和均匀降解。该系统与 APEX2 蛋白质组学和磷酸化蛋白质组学方法相结合，使我们能够证明 Ki-67 在 DNA 复制过程中发挥作用。如果没有它，DNA 复制会严重延迟，复制机制会被卸载，从而导致经典途径无法感知并依赖于 HUWE1 连接酶的 DNA 损伤。这会导致复制和姐妹染色单体凝聚力的缺陷，但它也会在所有测试的细胞系中触发由 cGAS/STING 途径介导的干扰素反应。我们揭示了 Ki-67 在 DNA 复制和基因组维护中的新功能，该功能独立于其先前已知的有丝分裂和基因调控作用。