Marked contribution of alternative end-joining to chromosome-translocation-formation by stochastically induced DNA double-strand-breaks in G2-phase human cells

Publication date: Available online 4 July 2015 Source:Mutation Research/Genetic Toxicology and Environmental Mutagenesis Author(s): Aashish Soni , Maria Siemann , Gabriel E. Pantelias , George Iliakis Ionizing radiation (IR) induces double strand breaks (DSBs) in cellular DNA, which if not repaired correctly can cause chromosome translocations leading to cell death or cancer. Incorrect joining of DNA ends generating chromosome translocations can be catalyzed either by the dominant DNA-PKcs-dependent, classical non-homologous end-joining (c-NHEJ), or by an alternative end-joining (alt-EJ) process, functioning as backup to abrogated c-NHEJ, or homologous recombination repair. Alt-EJ operates with slower kinetics as compared to c-NHEJ and generates larger alterations at the junctions; it is also considered crucial to chromosome translocation-formation. A recent report posits that this view only holds for rodent cells and that in human cells c-NHEJ is the main mechanism of chromosome translocation formation. Since this report uses designer nucleases that induce DSBs with unique characteristics in specific genomic locations and PCR to detect translocations, we revisit the issue using stochastically distributed DSBs induced in the human genome by IR during the G2-phase of the cell cycle. For visualization and analysis of chromosome translocations, which manifest as chromatid translocations in cells irradiated in G2, we employ classical cytogenetics. In wild-type cells, we o...
Source: Mutation Research Genetic Toxicology and Environmental Mutagenesis - Category: Genetics & Stem Cells Source Type: research