Abstract
BackgroundThe ubiquitous Rad50 and Mre11 proteins play a key role in many processes involved in the maintenance of genome integrity in Bacteria and Eucarya, but their function in the Archaea is presently unknown. We showed previously that in most hyperthermophilic archaea, rad50-mre11 genes are linked to nurA encoding both a single-strand endonuclease and a 5' to 3' exonuclease, and herA, encoding a bipolar DNA helicase which suggests the involvement of the four proteins in common molecular pathway(s). Since genetic tools for hyperthermophilic archaea are just emerging, we utilized immuno-detection approaches to get the first in vivo data on the role(s) of these proteins in the hyperthermophilic crenarchaeon Sulfolobus acidocaldarius.ResultsWe first showed that S. acidocaldarius can repair DNA damage induced by high doses of gamma rays, and we performed a time course analysis of the total levels and sub-cellular partitioning of Rad50, Mre11, HerA and NurA along with the RadA recombinase in both control and irradiated cells. We found that during the exponential phase, all proteins are synthesized and display constant levels, but that all of them exhibit a different sub-cellular partitioning. Following gamma irradiation, both Mre11 and RadA are immediately recruited to DNA and remain DNA-bound in the course of DNA repair. Furthermore, we show by immuno-precipitation assays that Rad50, Mre11 and the HerA helicase interact altogether.ConclusionOur analyses strongly support that in Sulfolobus acidocaldarius, the Mre11 protein and the RadA recombinase might play an active role in the repair of DNA damage introduced by gamma rays and/or may act as DNA damage sensors. Moreover, our results demonstrate the functional interaction between Mre11, Rad50 and the HerA helicase and suggest that each protein play different roles when acting on its own or in association with its partners. This report provides the first in vivo evidence supporting the implication of the Mre11 protein in DNA repair processes in the Archaea and showing its interaction with both Rad50 and the HerA bipolar helicase. Further studies on the functional interactions between these proteins, the NurA nuclease and the RadA recombinase, will allow us to define their roles and mechanism of action.
Highlights
The ubiquitous Rad50 and Mre11 proteins play a key role in many processes involved in the maintenance of genome integrity in Bacteria and Eucarya, but their function in the Archaea is presently unknown
In Eucarya, Rad50 and Mre11 proteins are associated with a third eucaryal-specific partner, Xrs2 in yeast, Nbs1 in human, and play a key role in a surprising large range of pathways: the repair of double strand breaks (DSBs) by homologous recombination and, at least in Saccharomyces cerevisiae, non-homologous-end-joining, the repair of collapsed replication forks, DNA damage cell checkpoint, the maintenance of telomeres, and the generation as well as the resection of meiotic DSBs [7,8]
We found previously that in most hyperthermophilic archaea, rad50-mre11 genes are clustered with two unknown genes that we called nurA and herA and that the four genes are co-transcribed in the crenarchaeon Sulfolobus acidocaldarius [22,23]
Summary
The ubiquitous Rad and Mre proteins play a key role in many processes involved in the maintenance of genome integrity in Bacteria and Eucarya, but their function in the Archaea is presently unknown. The ability to signal and repair DNA damage is essential to any cell and requires many pathways Among these pathways, recombination processes constitute an important set of systems acting in the repair of DNA breaks and of stalled/collapsed replication forks [1,2,3]. In Eucarya, Rad and Mre proteins are associated with a third eucaryal-specific partner, Xrs in yeast, Nbs in human, and play a key role in a surprising large range of pathways: the repair of DSBs by homologous recombination and, at least in Saccharomyces cerevisiae, non-homologous-end-joining, the repair of collapsed replication forks, DNA damage cell checkpoint, the maintenance of telomeres, and the generation (except for Saccharomyces pombe) as well as the resection of meiotic DSBs [7,8]. The role of these proteins in vivo is presently unknown
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