Rabbit Anti-Human XRCC6 monoclonal antibody, clone KN72-42

BACKGROUND: Nonhomologous end joining (NHEJ) is a pathway that repairs DNA double-strand breaks (DSBs) to maintain genomic stability in response to irradiation. The authors hypothesized that single nucleotide polymorphisms (SNPs) in NHEJ repair genes may affect clinical outcomes in patients with nonsmall cell lung cancer (NSCLC) who receive definitive radio(chemo)therapy. METHODS: The authors genotyped 5 potentially functional SNPs-x-ray repair complementing defective repair in Chinese hamster cells 4 (XRCC4) reference SNP (rs) number rs6869366 (-1394 guanine to thymine [-1394G -> T] change) and rs28360071 (intron 3, deletion/insertion), XRCC5 rs3835 (guanine to adenine [G -> A] change at nucleotide 2408), XRCC6 rs2267437 (-1310 cytosine to guanine [C -> G) change], and DNA ligase IV (LIG4) rs1805388 (threonine-to-isoleucine change at codon 9 [T9I])-and estimated their associations with severe radiation pneumonitis (RP) (grade >= 3) in 195 patients with NSCLC. RESULTS: A predictive role in radiation pneumonitis (RP) development was observed for the LIG4 SNP rs1805388 (adjusted hazard ratio, 2.08; 95% confidence interval, 1.04-4.12; P=.037 for the CT/TT genotype vs the CC genotype). In addition, men with the TT genotype of the XRCC4 rs6869366 SNP and women with AG + AA genotypes of the XRCC5 rs3835 SNP also were at increased risk of developing severe RP. CONCLUSIONS: The current results indicated that NHEJ genetic polymorphisms, particularly LIG4 rs1805388, may modulate the risk of RP in patients with NSCLC who receive definitive radio(chemo) therapy. Large studies will be needed to confirm these findings. Cancer 2012; 118: 528-35. (C) 2011 American Cancer Society.

DNA repair mechanisms maintain genomic integrity upon exposure to various types of DNA damage, which cause either single-or double-strand breaks in the DNA. Here, we propose a strategy for the functional study of single nucleotide polymorphisms (SNPs) in the human DNA repair genes XPD/ERCC2, RAD18, and KU70/XRCC6 and the checkpoint activation gene ATR that are essentially involved in the cell cycle and DNA damage repair. We analyzed the mutational effects of the DNA repair genes under DNA-damaging conditions, including ultraviolet irradiation and treatment with genotoxic reagents, using a Saccharomyces cerevisiae system to overcome the limitations of the human cell-based assay. We identified causal variants from selected SNPs in the present analyses. (i) R594C SNP in RAD3 (human XPD/ERCC2) caused severe reductions in the growth rate of mutant cells upon short-wavelength UV irradiation or chemical reagent treatment. (ii) The growth rates of the selected variants in RAD18, YKU70, and MEC1 were similar to those of wild-type cells on methyl methanesulfonate and hydroxyurea treated media. (iii) We also assessed the structural impact of the SNPs by analyzing differences in the structural conformation and calculating the root mean square deviation, which is a measure of the discordance of the Ca atoms between protein structures. Based on the above results, we propose that these analytical approaches serve as efficient methods for the identification of causal variants of human disease-causing genes and elucidation of yeast-cell based molecular mechanisms.