Other proteins, XPA (xeroderma pigmentosum complementation group A) and RPA (replication protein A), determine the site of cleavage and strand specificity and recruit XPG (xeroderma pigmentosum complementation group G, ERCC5 (excision repair cross-complementation group 5)), which incises DNA at the 3′ side of the damage, whereas incision on the other side is made by the ERCC1-XPF (excision repair cross-complementation group 1-xeroderma pigmentosum complementation group F) complex. This evidence concerns the gene ERCC1 and xeroderma pigmentosum.