A nucleoskeleton network preserves genomic integrity by promoting NHEJ and restraining chromosome translocations.

Chromosomal translocation (CT) is characterized by incorrect ligation between chromosome fragments when multiple DNA double-strand breaks (DSBs) exist simultaneously. DNA repair, the three-dimensional structure of the nucleoskeleton, and the spatial and temporal movement of DSB ends contribute to CTs. Our earlier research showed that Intermediate Filament Family Orphan 1 (IFFO1) links the nucleoskeleton and non-homologous end joining (NHEJ) to prevent CTs. In this study, we identified the paralog IFFO2, which, together with IFFO1, forms a complex interaction network. We demonstrate that the C-terminus of these IFFOs binds to XRCC4 to facilitate its participation in the NHEJ process. In contrast, their N-termini oversee the building of the nucleoskeleton by connecting with each other and Lamin A/C. Interestingly, IFFO1 and IFFO2 show epistatic effects in suppressing CT by anchoring broken DNA ends and have non-epistatic roles in NHEJ-mediated DSB repair. Our results define an integrated nucleoskeleton composed of IFFO1-IFFO2-Lamin A/C, and reveal its dual functions in genome stability maintenance, the promotion of end-joining, and the suppression of CT.