30 kb; 15 exons (from 61 to 1074 bp) and 14 introns (250 to 5763 bp)

xeroderma pigmentosum group G complementing factor; DNA-repair protein complementing XPG cells

The XPG protein has DNA endonuclease activity without preference for damaged DNA and is responsible for the 3 incision made during Nucleotide Excision Repair (NER). At the site of a lesion NER proteins create a DNA bubble structure over a length of approximately 25 nucleotides and the XPG protein incises the damaged DNA strand 0-2 nucleotides 3 to the ssDNA-dsDNA junction. In most studies the 3-incision made by the XPG protein appeared to be performed prior to and independently of the 5-incision by XPF-ERCC1. The XPG protein is required non-enzymatically for subsequent 5=D5incision by the XPF/ERCC1 heterodimer during the NER process. Patients belonging to the XP-G complementation group clinically exhibit heterogeneous symptoms, from mild to very severe, sometimes associated with CS. XP-G cells are almost completely repair-deficient and as UV-sensitive as XP-A cells. About half of the described XPG patients exhibit also CS symptoms. In that case, the XPG protein is also involved in the transcription-coupled repair of oxidative DNA lesions.

Extensive sequence similarities, in bipartite domain A and B, to products of RAD repair genes of two yeasts, Saccharomyces cerevisae RAD2 and Schizosaccharomyces pombe RAD13

5 XPG sequence alterations: 3 point mutations and two small deletions