Functional analysis of PprI in the DNA damage response mechanism of Deinococcus radiodurans

Analysis of the genome sequences of Deinococcus spp. discovered the radiation/desiccation response (RDR) motif, existing upstream of the radiation-inducible genes (RDR regulons) such as pprA and recA genes. The RDR motif serves as an operator sequence in the unique DNA repair response system. Another regulatory protein DdrO binds RDR motif. Following DNA damage, the metalloprotease activity of PprI cleaves DdrO, resulting in induction of the RDR regulon. However, the detailed functional site of PprI protein in the DNA damage response mechanism is poorly understood. In an effort to gain an insight into the role of the PprI in DNA damage response mechanism in D. radiodurans, firstly, we generated a pprI-deleted mutant strain and pprI expression plasmid. Consequently, we successfully generated complete deletion strains for the D. radiodurans pprI genes. This deletion strain SXPI carrying pRAD1 exhibited extreme sensitivity to gamma-rays compare to the wild type strain carrying pRAD1. In the strain SXPI carrying pEXpprI, the survival rate following treatment with gamma rays was restored to the similar level of that in the wild type. This result suggests that D. radiodurans PprI is a key protein for the repair of damage induced by gamma rays as shown in the previous study