Dynamics of DNA Double-strand Break Repair in Bacillus subtilis

Abstract

All organisms have developed a variety of DNA repair mechanisms to cope with DNA double strands breaks (DSBs). In replicating cells, homologous recombination (HR), which uses an intact homologous template to restore lost information at the break site, is the main pathway for error-free repair of one- or two-ended DSBs and for promoting the re-establishment of replication forks during vegetative growth. Genetic, cytological and biochemical approaches were used to analyse the requirements of exponentially growing Bacillus subtilis cells to survive broken ended and to visualize the choreography of DSB repair. The damage-induced multi-protein complex (recombinosome), organized into focal assemblies, has been confirmed by biochemical approaches. HR is coordinated with other essential processes, such as DNA replication, transcription and chromosomal segregation. When DSB recognition or end resection are severely impaired or when an intact homologous template is simply not available, the ends should be reconnected by template-independent mechanisms using minimal (single-strand annealing) or no-sequencehomology (non-homologous end joining). These effective repair mechanisms lead to loss of genetic information (if the DNA ends are altered before re-ligation), and to chromosomal rearrangements (if incorrect ends are rejoined)