Recombination and replication in DNA repair of heavily irradiated Deinococcus radiodurans.

Deinococcus radiodurans' extreme resistance to ionizing radiation, desiccation, and DNA-damaging chemicals involves a robust DNA repair that reassembles its shattered genome. The repair process requires diploidy and commences with an extensive exonucleolytic erosion of DNA fragments. Liberated single-stranded overhangs prime strand elongation on overlapping fragments and the elongated complementary strands reestablish chromosomal contiguity by annealing. We explored the interdependence of the DNA recombination and replication processes in the reconstitution of the D. radiodurans genome disintegrated by ionizing radiation. The priming of extensive DNA repair synthesis involves RecA and RadA proteins. DNA polymerase III is essential for the initiation of repair synthesis, whereas efficient elongation requires DNA polymerases I and III. Inactivation of both polymerases leads to degradation of DNA fragments and rapid cell death. The present in vivo characterization of key recombination and replication processes dissects the mechanism of DNA repair in heavily irradiated D. radiodurans.