Post-translational methylations of the archaeal Mre11:Rad50 complex throughout the DNA damage response.

The Mre11:Rad50 complex is central to DNA double strand break repair in the Archaea and Eukarya, and acts through mechanical and nuclease activities regulated by conformational changes induced by ATP binding and hydrolysis. Despite the widespread use of Mre11 and Rad50 from hyperthermophilic archaea for structural studies, little is known in the regulation of these proteins in the Archaea. Using purification and mass spectrometry approaches allowing nearly full sequence coverage of both proteins from the species Sulfolobus acidocaldarius, we show for the first time post-translational methylation of the archaeal Mre11:Rad50 complex.

The Mre11 protein interacts with both Rad50 and the HerA bipolar helicase and is recruited to DNA following gamma irradiation in the archaeon Sulfolobus acidocaldarius.

Background: 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. 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.

NurA, a novel 5'-3' nuclease gene linked to rad50 and mre11 homologs of thermophilic Archaea.

We isolated and characterized a new nuclease (NurA) exhibiting both single-stranded endonuclease activity and 5'-3' exonuclease activity on single-stranded and double-stranded DNA from the hyperthermophilic archaeon Sulfolobus acidocaldarius. Nuclease homologs are detected in all thermophilic archaea and, in most species, the nurA gene is organized in an operon-like structure with rad50 and mre11 archaeal homologs. This nuclease might thus act in concert with Rad50 and Mre11 proteins in archaeal recombination/repair.