Folate modulates guanine-quadruplex frequency and DNA damage in Werner syndrome

Publication date: Available online 9 December 2017 Source:Mutation Research/Genetic Toxicology and Environmental Mutagenesis Author(s): Paniz Tavakoli Shirazi, Wayne Richard Leifert, Michael Felix Fenech, Maxime François Guanine-quadruplexes (G4) are stable tetra-stranded DNA structures that may cause DNA replication stress and inhibit gene expression. Defects in unwinding these structures by DNA helicases may result in telomere shortening and DNA damage. Furthermore, due to mutations in WRN helicase genes in Werner syndrome, G4 motifs are likely to be key elements in the expression of premature aging phenotypes. The methylation of DNA plays a significant role in the stability and occurrence of G4. Thus, G4 frequency and DNA methylation mechanisms may be affected by excesses or deficiencies in methyl donors such as folate. B-Lymphocytes from Werner patients (n = 5) and healthy individuals (n = 5) were cultured in RPMI medium under condition of folate deficiency (20 nM) or sufficiency (200 nM) for 14 days. Cells were fixed on microscope slides for immunofluorescent staining to measure G4 frequency and γH2AX (a marker of DNA strand breaks) intensity, using automated quantitative imaging fluorescent microscopy. There was a significant increase (p < 0.05) in G4 levels in Werner syndrome patients compared to healthy controls. Werner and control cells grown in 20 nM folate media also showed significant increases in G4 (p < 0.001) and γH2...
Source: Mutation Research Genetic Toxicology and Environmental Mutagenesis - Category: Genetics & Stem Cells Source Type: research