Mycobacterial RadA Functions in Cyclic Di-AMP Mediated Homologous Recombination in Addition to Supporting RecA...

Mycobacterium possesses unique DNA repair and recombination pathways that are absent in E. coli. The pathways are linked to mycobacterial virulence and survival within the host. Cyclic di-AMP, a secondary messenger present in Mycobacterium regulates DNA recombination, genome stability and SOS response. radA and disA exist in a conserved operon in several bacteria including Mycobacterium suggesting a role of RadA in cyclic di-AMP mediated DNA damage repair pathways. We show here that RadA is indeed involved in cyclic di-AMP mediated DSB repair pathways in Mycobacterium and has non-canonical function in DSB repair as well. Deletion of radA expectedly decreases HR efficiency but interestingly also results in illegitimate recombination outcome GC*. The illegitimate recombination GC* leads to increased stress induced mutagenesis giving rise to drug resistant mutants. We have also found that RadA influences NHEJ repair and in its absence the cells adopt alternative route of DNA repair. Our work shows active participation of RadA in several DNA repair and recombination pathways which could be targeted for potential therapeutics against Mycobacterium.