DNA double-strand break repair by homologous recombination

The induction of doublestrand breaks (DSBs) in DNA by exposure to DNA damaging agents, or as intermediates in normal cellular processes, constitutes a severe threat for the integrity of the genome. If not properly repaired, DSBs may result in chromosomal aberrations, which, in turn, can lead to cell death or to uncontrolled cell growth. To maintain the integrity of the genome, multiple pathways for the repair of DSBs have evolved during evolution: homologous recombination (HR), nonhomologous end joining (NHEJ) and singlestrand annealing (SSA). HR has the potential to lead to accurate repair of DSBs, whereas NHEJ and SSA are essentially mutagenic. In yeast, DSBs are primarily repaired via highfidelity repair of DSBs mediated by HR, whereas in higher eukaryotes, both HR and NHEJ are important. In this review, we focus on the functional conservation of HR from fungi to mammals and on the role of the individual proteins in this process.