Habraken Y, Sung P, Prakash L, Prakash S
Sealy Center for Molecular Science, UTMB, Galveston, TX 77555-1061.
Nucleic Acids Res. 1994 Aug 25;22(16):3312-6. doi: 10.1093/nar/22.16.3312.
Because of defective nucleotide excision repair of ultraviolet damaged DNA, xeroderma pigmentosum (XP) patients suffer from a high incidence of skin cancers. Cell fusion studies have identified seven XP complementation groups, A to G. Previous studies have implicated the products of these seven XP genes in the recognition of ultraviolet-induced DNA damage and in incision of the damage-containing DNA strand. Here, we express the XPG-encoded protein in Sf9 insect cells and purify it to homogeneity. We demonstrate that XPG is a single-strand specific DNA endonuclease, thus identifying the catalytic role of the protein in nucleotide excision repair. We suggest that XPG nuclease acts on the single-stranded region created as a result of the combined action of the XPB helicase and XPD helicase at the DNA damage site.
