The Deinococcus radiodurans RecN protein enhances the recombinase activity of RecA protein during homologous recombination in vitro

Unfaithful repair of DNA double strand breaks (DSBs) can lead to genomic instability, potentially increasing the risk of developing cancer in higher eukaryotic organisms as well as antibiotic resistance in bacteria. The homologous recombination pathway faithfully repairs DSBs in eukaryotic and bacterial systems. In bacteria, RecA is the central recombinase protein activated to search for homology within DNA regions to mediate DSB repair. Genetic studies suggest that RecN protein is also involved in the repair of DSBs. RecN is a member of the Structural Maintenance of Chromosomes family (SMCs) of proteins and we hypothesize that RecN is involved in maintaining damaged DNA molecules in close proximity by physically holding them together. We have previously demonstrated that the cohesin-like RecN protein is an ATPase and DNA binding protein that promotes intermolecular DNA interactions in-vitro. However, its role in DSB repair via the homologous recombination pathway is not well understood. The RecA-dependent DNA strand exchange assay was utilized to mimic homologous recombination in vitro. The presence of RecN (added at different stages of the DNA strand exchange reaction setup) stimulates the kinetics of intermediate molecule formation by RecA. Further biochemical studies suggest that RecN promotes the RecA-mediated DNA strand exchange reaction via protein-protein interactions that facilitates the RecA-dependent search for homology.