Institute of Nuclear-Agricultural Sciences, Zhejiang University, Hangzhou, China.
Department of Cancer Genetics and Epigenetics, City of Hope National Medical Center and Beckman Research Institute, Duarte, CA, USA.
J Mol Cell Biol. 2018 Oct 1;10(5):460-474. doi: 10.1093/jmcb/mjy047.
Human flap endonuclease 1 (FEN1) is a structure-specific, multi-functional endonuclease essential for DNA replication and repair. We and others have shown that during DNA replication, FEN1 processes Okazaki fragments via its interaction with the proliferating cell nuclear antigen (PCNA). Alternatively, in response to DNA damage, FEN1 interacts with the PCNA-like Rad9-Rad1-Hus1 complex instead of PCNA to engage in DNA repair activities, such as homology-directed repair of stalled DNA replication forks. However, it is unclear how FEN1 is able to switch between these interactions and its roles in DNA replication and DNA repair. Here, we report that FEN1 undergoes SUMOylation by SUMO-1 in response to DNA replication fork-stalling agents, such as UV irradiation, hydroxyurea, and mitomycin C. This DNA damage-induced SUMO-1 modification promotes the interaction of FEN1 with the Rad9-Rad1-Hus1 complex. Furthermore, we found that FEN1 mutations that prevent its SUMO-1 modification also impair its ability to interact with HUS1 and to rescue stalled replication forks. These impairments lead to the accumulation of DNA damage and heightened sensitivity to fork-stalling agents. Altogether, our findings suggest an important role of the SUMO-1 modification of FEN1 in regulating its roles in DNA replication and repair.
人类的 flap endonuclease 1（FEN1）是一种结构特异性的多功能内切酶，对于 DNA 复制和修复至关重要。我们和其他人已经表明，在 DNA 复制过程中，FEN1 通过与增殖细胞核抗原（PCNA）的相互作用来处理 Okazaki 片段。或者，在响应 DNA 损伤时，FEN1 与 PCNA 样的 Rad9-Rad1-Hus1 复合物相互作用而不是与 PCNA 相互作用，以参与 DNA 修复活动，例如停滞的 DNA 复制叉的同源定向修复。然而，目前尚不清楚 FEN1 如何能够在这些相互作用之间切换以及在 DNA 复制和 DNA 修复中的作用。在这里，我们报告 FEN1 在 DNA 复制叉停滞剂（如紫外线照射、羟基脲和丝裂霉素 C）的作用下通过 SUMO-1 发生 SUMOylation。这种由 DNA 损伤诱导的 SUMO-1 修饰促进了 FEN1 与 Rad9-Rad1-Hus1 复合物的相互作用。此外，我们发现，阻止 FEN1 的 SUMO-1 修饰的突变也会损害其与 HUS1 的相互作用能力，并阻止停滞的复制叉。这些损伤导致 DNA 损伤的积累和对复制叉停滞剂的敏感性增加。总之，我们的研究结果表明，FEN1 的 SUMO-1 修饰在调节其在 DNA 复制和修复中的作用方面起着重要作用。
