human xeroderma pigmentosum group A 25kbp, six exons, 2 polyadenylation signals

1377 b mRNA; suggestion of 1 major transcript; promoter G+C rich (73%); one CAAT box and no TATA box.

273 amino acids, 31 kDa. DNA excision repair protein. The functional domain for damaged DNA recognition contains a zinc-finger motif with 4 cysteine residues : Cys-X2-Cys-X17-Cys-X2-Cys motif and a glutamic acid cluster encoded by Exon 2. The nuclear localization signal is located in Exon 1.

ubiquitous

nuclear

Initiates DNA repair by binding to damaged sites with various affinities, depending upon the chemical structure of the lesion
Two proteins have been identified and implicated in (one of) the first steps of Nucleotide Excision Repair (NER), i.e. the recognition of lesions in the DNA: the XPA gene product and the XPC gene product. Cells from XPA patients are extremely sensitive to UV and have very low nucleotide excision repair activity. In vitro the XPA protein binds preferentially to damaged DNA compared to nondamaged DNA. The XPA protein binds to replication protein A (RPA) which enhances the affinity of XPA for damaged DNA and is essential for NER. The XPA protein has been shown to bind to ERCC1 and TFIIH. It is possible that the complex XPA/RPA may tell to the repair machinery which strand contained the damage and therefore should be eliminated.

Xpac (FlyBase ID) ; Xpa (MGI)

13 nucleotide substitutions and 5 small insertion/deletion in patients