使用咪唑霉素C（MMC）处理后激活 Fanconi 贫血（FA）途径，对于防止称为“辐射状”的染色体易位至关重要。当复制叉在 MMC 诱导的链间交联（ICL）处停滞时，FA 途径被激活以协调 ICL 解开和 DNA 断裂中介修复。然而，在 FA 缺陷细胞中，ICL 相关断裂如何以导致辐射状的方式解决尚不清楚。在这里，我们证明 MMC 诱导的辐射状依赖于 DNA 聚合酶θ（POLθ）介导的替代末端结合（A-EJ）。具体而言，我们展示了在 FANCD2-/- 细胞中观察到的辐射状依赖于 POLθ 和 DNA 连接酶III，并独立于经典的非同源末端结合。此外，使用 POLθ 抑制剂处理 FANCD2-/- 细胞可消除辐射状并导致积累与常染色体易损位点共定位的断裂。总体而言，这些观察结果将 A-EJ 牵涉到辐射状的形成中，并提供了针对 FA 途径缺陷癌症治疗的 POLθ 抑制剂的机制见解。

Activation of the Fanconi anemia (FA) pathway after treatment with mitomycin C (MMC) is essential for preventing chromosome translocations termed "radials." When replication forks stall at MMC-induced interstrand crosslinks (ICLs), the FA pathway is activated to orchestrate ICL unhooking and repair of the DNA break intermediates. However, in FA-deficient cells, how ICL-associated breaks are resolved in a manner that leads to radials is unclear. Here, we demonstrate that MMC-induced radials are dependent on DNA polymerase theta (POLθ)-mediated alternative end joining (A-EJ). Specifically, we show that radials observed in FANCD2-/- cells are dependent on POLθ and DNA ligase III and occur independently of classical non-homologous end joining. Furthermore, treatment of FANCD2-/- cells with POLθ inhibitors abolishes radials and leads to the accumulation of breaks co-localizing with common fragile sites. Uniformly, these observations implicate A-EJ in radial formation and provide mechanistic insights into the treatment of FA pathway-deficient cancers with POLθ inhibitors.Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.