Recombination and Replication in DNA Repair of Heavily Irradiated Deinococcus radiodurans

Abstract

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.

Structure and Cellular Dynamics of Deinococcus radiodurans Single-stranded DNA (ssDNA)-binding Protein (SSB)-DNA Complexes

“…First, we have found that DrSSB accumulates in cells during the initial phase of genome reconstruction. It is possible that the increase in DrSSB levels is required to preserve newly generated ssDNA ends for their use as primers in ESDSA (13,46). DNA damage-dependent DrSSB accumulation was also corroborated in a recently published study (42).…”

Vieillissement : la chimie d’une horloge biologique flexible

“…Ce n'est pas surprenant : ce sont des protéines qui réparent l'ADN, et pas l'inverse. La démonstration en est apportée chez les bactéries [12,13] et chez les animaux [9] les plus résistants aux radiations : la réparation spectaculaire de l'ADN morcelé par des niveaux extrêmes de radiations ionisantes est due à la protection des protéines contre les dégâts oxydatifs radio-induits et non pas à l'évolution des systèmes nouveaux de réparation [13]. Il semble que les auteurs de cet effet protecteur soient de petites molécules qui neutralisent tous les ROS.…”

The Relationship Between Replication and Recombination

“…Beside manganese accumulation and specific protein protection, survival depends on the efficient and rapid reconstitution of a functional genome from numerous DNA fragments. Recombinational repair with extensive DNA synthesis is used (Slade et al, 2009). DNA repair is primed by recombination proteins RecA and RadA, while the elongation step is performed by Pol III and PolI.…”