Introducing a novel allele for the polymorphism of variable number of tandem repeats in the promoter region of XRCC5.

Polymorphism of variable number of tandem repeats (VNTR) in the promoter region of X-ray repair cross-complementing 5 (XRCC5; MIM: 194364, rs6147172) has been reported. The main aim of the present study is to introduce a novel allele for the VNTR polymorphism in the promoter region of XRCC5. The participants of the present study were of 535 (140 males, 395 females), unrelated, adult, healthy Iranian blood donors (Caucasians/Muslims). Genotypes of XRCC5 VNTR were determined by a high resolution melting analysis, and confirmed by DNA sequencing. Based on the sequencing of new bands upper than the 2R allele band, a novel allele was introduced (named 3R allele). The promoter region of XRCC5 contains several copies of Sp1 recognition cis regulatory elements. The novel 3R allele is capable of expanding the number of cis regulatory elements to eight. The prevalence of the 0R, 1R, 2R and 3R alleles in our sample was 0.0645, 0.5439, 0.3794 and 0.0122, respectively. The study group was at the Hardy-Weinberg equilibrium for the genotypic frequencies (χ(2)=3.95, df=6, P=0.73). It is suggested that the prevalence of the novel allele (3R allele) among European populations may be higher than its prevalence among Iranians.