Low dose ionizing radiation strongly stimulates insertional mutagenesis in a γH2AX dependent manner

• DOI: 10.1371/journal.pgen.1008550
• Publication Date: 2020-01-16T18:25:51Z
• Authors: Alex N. Zelensky; Mascha Schoonakker; Inger Brandsma; Marcel Tijsterman; Dik C. van Gent; Jeroen Essers; Roland Kanaar
• Keywords: 0301 basic medicine; 0303 health sciences; EMC OR-01; Recombinational DNA Repair; DNA-Directed DNA Polymerase; QH426-470; Cell Line; 3. Good health; Histones; Mice; Mutagenesis, Insertional; 03 medical and health sciences; Radiation, Ionizing; Genetics; Animals; Humans; EMC MGC-01-12-03; DNA Breaks, Double-Stranded; Cells, Cultured; DNA Polymerase theta; Research Article

AbstractExtrachromosomal DNA can integrate into the genome with no sequence specificity producing an insertional mutation. This process, which is referred to as random integration (RI), requires a double stranded break (DSB) in the genome. Inducing DSBs by various means, including ionizing radiation, increases the frequency of integration. Here we report that non-lethal physiologically relevant doses of ionizing radiation (10-100 mGy), within the range produced by medical imaging equipment, stimulate RI of transfected and viral episomal DNA in human and mouse cells with an extremely high efficiency. Genetic analysis of stimulated RI (S-RI) revealed that it is distinct from the background RI, requires histone H2AX S139 phosphorylation (γH2AX) and is not reduced by DNA polymerase θ (Polq) inactivation. S-RI efficiency was unaffected by the main DSB repair pathway (homologous recombination and non-homologous end joining) disruptions, but double deficiency in MDC1 and 53BP1 phenocopies γH2AX inactivation. The robust responsiveness of S-RI to physiological amounts of DSBs has implications for radiation risk assessment and can be exploited for extremely sensitive, macroscopic and direct detection of DSB-induced mutations.