Identification of four single nucleotide polymorphisms in DNA repair genes: XPA and XPB (ERCC3) in Polish population

A deficiency in DNA repair is associated with increased cancer risk. Inter-individual variations in DNA repair capacity observed in humans may result from genetic polymorphisms in DNA repair genes. In order to provide a basis for future functional and molecular epidemiology studies on cancer susceptibility, we screened 35 individuals for polymorphisms in coding regions of XPA and XPB genes involved in nucleotide excision repair (NER). Relevant cDNA sequences were amplified by PCR, sequenced with fluorescently labeled terminators and analyzed with automated sequencer. Two polymorphisms in XPB were found: AAA-->AGA (445A>G; GenBank M31899) causing K117R substitution and GGC-->TGC (1299G>T; GenBank M31899) causing G402C exchange. Also, two polymorphisms in XPB were detected: CGA-->CAA (709G>A; GenBank D14533) causing R228Q exchange, and A-->G (23A>G; GenBank D14533) substitution in the 5' non-coding region of the gene. The three aforementioned amino acid substitutions were uncommon in this population (1.4%). In contrast, the substitution located 4 nucleotides upstream of the ATG start codon of XPB was frequent (57%). To our best knowledge this is the first report of these sequence variants. The location of these polymorphisms in evolutionary conserved regions suggest that they may be of functional significance.