Claim: ERCC1–XPF, a structure-specific endonuclease, does not cut DNA that is exclusively single-stranded or double-stranded.
Evidence: The ERCC1–XPF complex is a structure-specific endonuclease. ERCC1-XPF does not cut DNA that is exclusively single-stranded or double-stranded, but it cleaves the DNA phosphodiester backbone specifically at junctions between double-stranded and single-stranded DNA.