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 relocalizes to the DSB sites in a XRCC4-dependent manner and promotes 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 (PubMed:31548606). The interaction with XRCC4 is direct, involves LIG4-free XRCC4 and leads to relocalization of IFFO1 at the double-strand break (DSB) sites (PubMed:31548606). Interacts with LMNA; the interaction forms an interior nucleoskeleton and the recruitment to DNA double-strand breaks (PubMed:31548606). Mainly soluble, the remaining is localized in the nuclear matrix (PubMed:31548606). Localized at double-strand break (DSB) sites near the lamina and nuclear matrix structures (PubMed:31548606). Ubiquitously expressed. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the intermediate filament family.