Nucleotide excision repair (NER) is a major repair system for removing a variety of DNA lesions including UV-induced cyclobutane pyrimidine dimers and (6-4) photoproducts as well as chemically-induced bulky base adducts. Defects in the NER system give rise to xeroderma pigmentosum (XP), an autosomal recessive disease characterized by a predisposition to skin cancer and in some cases neurological abnormalities. The early process of human NER, from damage recognition to dual incision (removal of damage-containing oligonucleotides), is accomplished by six core NER factors, XPC-RAD23B, TFIIH, XPA, RPA, XPF-ERCC1 and XPG.

ERCC1 forms a stable complex with XPF and the heterodimer has an ability to make a nick on the DNA strand which makes the transition from duplex to single-stranded DNA in the 5' to 3' direction. In the NER process, ERCC1-XPF complex is responsible for 5'-incision at a dual incision step.