Weller, G. R., Kysela, B., Roy, R., Tonkin, L., Scanlan, E., Della, M., Krogh Devine, S., Day, J. P., Wilkinson, A., d'Adda di Fagagna, F., Devine K., Bowater, R. P., Jeggo, P., Jackson, S. P. and Doherty, A. J. (2002) Identification of a DNA non-homologous end-joining complex in bacteria. Science 297:1686-1689.  

In eukaryotic cells, double-strand breaks (DSBs) in DNA are generally repaired either by the pathway of homologous recombination or via DNA non-homologous end joining (NHEJ). Both of these pathways have been highly conserved throughout eukaryotic evolution but no equivalent NHEJ system has been identified in the prokaryotic kingdom. The NHEJ pathway requires a DNA end-binding component called Ku. We have identified bacterial Ku homologs and show that these proteins retain the biochemical characteristics of the eukaryotic Ku heterodimer. Furthermore, we show that bacterial Ku specifically recruits DNA ligase to DNA ends and stimulates DNA ligation. Loss of these proteins leads to hypersensitivity to ionizing radiation in B. subtilis. These data provide evidence that many bacteria possess a DNA DSB repair apparatus that shares many features with the NHEJ system of eukarya and suggest that this DNA repair pathway arose before the divergence of the prokaryotic and eukaryotic lineages.