Putative single-stranded DNA endonuclease involved in nucleotide excision repair (NER) of UV- and oxidative damaged DNA. May make the 3'-incision step in NER. Seems to play a role in senescence program. Binds 2 magnesium ions per subunit. They probably participate in the reaction catalyzed by the enzyme. May bind an additional third magnesium ion after substrate binding. Expressed in all tissues at low levels. Belongs to the XPG/RAD2 endonuclease family. XPG subfamily.