Molecular mechanisms of DNA double-strand break repair

DNA double-strand breaks (DSBs) are major threats to the genomic integrity of cells. If not taken care of properly, they can cause chromosome fragment ation, loss and translocation, possibly resulting in carcinogenesis. Upon D SB formation, cell-cycle checkpoints are triggered and multiple DSB repair pathways can be activated. Recent research on the Nijmegen breakage syndrom e, which predisposes patients to cancer, suggests a direct link between act ivation of cell-cycle checkpoints and DSB repair. Furthermore, the biochemi cal activities of proteins involved in the two major DSB repair pathways, h omologous recombination and DNA end-joining, are now beginning to emerge. T his review discusses these new findings and their implications for the mech anisms of DSB repair.