Double-strand DNA breaks can be repaired by any of several alternative mechanisms that differ greatly in the nature of the final repaired products. We used a reporter construct, designated "Repair reporter 3" (Rr3), to measure the relative usage of these pathways in Drosophila germ cells. The method works by creating a double-strand break at a specific location such that expression of the red f...

Using the radiomimetic drug, bleomycin, we have determined the mutagenic potential of DNA strand breaks in the shuttle vector pZ189 in human fibroblasts. The bleomycin treatment conditions used produce strand breaks with 3'-phosphoglycolate termini as > 95% of the detectable dose-dependent lesions. Breaks with this end group represent 50% of the strand break damage produced by ionizing radiatio...

Introduction H istone deacetylase inhibitors (HDIs), as  radiation sensitizing agents, are considered as a novel class of anti-cancer factors, which are studied in various tumor cell-lines. Valproic acid (VPA) is an HDI, which is effectively used in the treatment of epilepsy, migraines, and some particular types of depression. In this study, we evaluated the effects of VPA and ionizing radiatio...

What is the Rad52 protein? The Saccharomyces cerevisiae Rad52 protein is a key player in DNA doublestrand break repair and homologous recombination. It forms a heptameric ring, catalyses DNA annealing and mediates Rad51-catalysed strand invasion. RAD52 is the defining member of an epistasis group of genes involved in repair of ionizing radiationinduced DNA double-strand breaks. Double-strand br...

The Mre11-Rad50 nuclease-ATPase is an evolutionarily conserved multifunctional DNA double-strand break (DSB) repair factor. Mre11-Rad50's mechanism in the processing, tethering, and signaling of DSBs is unclear, in part because we lack a structural framework for its interaction with DNA in different functional states. We determined the crystal structure of Thermotoga maritima Rad50(NBD) (nucleo...

The mobility (homing) of the yeast mitochondrial DNA group II intron al2 occurs via target DNA-primed reverse transcription at a double-strand break in the recipient DNA. Here, we show that the site-specific DNA endonuclease that makes the double-strand break is a ribonucleoprotein complex containing the al2-encoded reverse transcriptase protein and excised al2 RNA. Remarkably, the al2 RNA cata...