engleski

Reconstitution of Deinococcus radiodurans Chromosomes Shattered by Radiation Involves DNA Replication and Recombination

Bacterium Deinococcus radiodurans is one of the most radiation resistant organisms known. It can sustain extreme levels of ionizing radiation that induce several hundred double-stranded DNA breaks in its genome. The key to its radioresistance seems to be a highly efficient DNA repair, however, the molecular mechanism of accurate joining of the broken chromosomes is not yet understood. We have studied the mechanism of reconstitution of D. radiodurans genome after an exposure to gamma radiation shattering the genome down to about 25 kb fragments. We found that the efficient and accurate repair of fragmented D. radiodurans genome involves coupled DNA replication and recombination processes. A massive DNA polymerase I - dependent synthesis correlates with repair of broken DNA and is presumably required for the extensive elongation of fragments' single-stranded ends facilitating their annealing. Conversion of the resulting long linear DNA intermediates to intact circular chromosomes requires RecA-dependent homologous recombination. The repaired density-labelled chromosomes appear as patchworks of old (synthesized before radiation) and new (synthesized after radiation) double-stranded DNA blocks.

Deinococcus radiodurans; radiation; DNA repair; DNA replication; recombination

nije evidentirano