Xeroderma Pigmentosum, Complementation Group A (XPA)

XPA encodes a zinc finger protein involved in DNA excision repair. The encoded protein is part of the NER (nucleotide excision repair) complext which is responsible for repair of UV radiation-induced photoproducts and DNA adducts induced by chemical carcinogens. The deduced 273-amino acid protein has a calculated molecular mass of 31 kD. The human protein is 95% similar to the mouse protein and contains several alpha-helices and a zinc-finger motif, consistent with a DNA-binding protein. Two mRNAs, 1.3-1.4 kb and 1.0-1.1 kb, were detected in normal human cells. Sequence analysis identified a truncated XPA protein that could be translated from an ATG present at position 176, which retained sufficient function to partially restore the DNA repair defect in XPA cells. A 1.0-1.1-kb mouse Xpa mRNA was also identified.