Fanconi anemia-associated chromosomal radial formation is dependent on POLθ-mediated alternative end joining

  • Cell Rep. 2023 Apr 21;42(5):112428. doi: 10.1016/j.celrep.2023.112428.
Colette B Rogers  1 ,  Rachel E Kram  1 ,  Kevin Lin  2 ,  Chad L Myers  2 ,  Alexandra Sobeck  1 ,  Eric A Hendrickson  3 ,  Anja-Katrin Bielinsky  4
Affiliations
  • 1. Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA.
  • 2. Department of Computer Science and Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
  • 3. Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA. Electronic address: [email protected].
  • 4. Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA. Electronic address: [email protected].
PMID: 37086407 DOI: 10.1016/j.celrep.2023.112428
Abstract

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.

Keywords
CP: Molecular biology; FANCD2; Fanconi anemia; POLθ; RAD18; alternative end joining; common fragile sites; double-stranded break repair; radial chromosomes.
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