Non-catalytic component of a structure-specific DNA repair endonuclease responsible for the 5'-incision during DNA repair. Responsible, in conjunction with SLX4, for the first step in the repair of interstrand cross-links (ICL). Participates in the processing of anaphase bridge-generating DNA structures, which consist in incompletely processed DNA lesions arising during S or G2 phase, and can result in cytokinesis failure. Also required for homology-directed repair (HDR) of DNA double-strand breaks, in conjunction with SLX4 (By similarity). Heterodimer composed of ERCC1 and ERRC4/XPF (By similarity). Interacts with USP4 (By similarity). Ubiquitinated with both 'Lys-48' and 'Lys-63' linkages. Deubiquitinated by USP45. Belongs to the ERCC1/RAD10/SWI10 family.