Nuclear matrix protein involved in the immobilization of broken DNA ends and the suppression of chromosome translocation during DNA double-strand breaks (DSBs) (PubMed:31548606). Interacts with the nuclear lamina component LMNA, resulting in the formation of a nucleoskeleton that will relocalize to the DSB sites in a XRCC4-dependent manner and promote the immobilization of the broken ends, thereby preventing chromosome translocation (PubMed:31548606). Acts as a scaffold that allows the DNA repair protein XRCC4 and LMNA to assemble into a complex at the DSB sites (PubMed:31548606). Forms a heterotetramer with XRCC4 (By similarity). The interaction with XRCC4 is direct, involves LIG4-free XRCC4 and leads to relocalization of IFFO1 at the double-strand break (DSB) sites (By similarity). Interacts with LMNA; the interaction forms an interior nucleoskeleton and the recruitment to DNA double-strand breaks (By similarity). Mainly soluble, the remaining is localized in the nuclear matrix. Localized at double-strand break (DSB) sites near the lamina and nuclear matrix structures. Belongs to the intermediate filament family.