Functional Analysis Of PriA-like (dr2606) Gene In The Extremely Radioresistant Bacterium Deinococcus Radiodurans

Deinococcus radiodurans, the type species of the family Deinococcaceae, is one of the most radioresistant bacteria in the world. Replication fork progression can be blocked easily by DNA damage.Ionizing radiation kills cells by inducing forms of damage in DNA structures that lead to the formation of lethal chromosome aberrations. Damaged DNA repair and the subsequent restart of the stalled or collapsed replication forks are critical for cell survival. D. radiodurans has efficient DNA repair mechanisms and can mend hundreds of double-strand breaks (dsb) per chromosome without lethality or mutagenesis.However, cells also require methods to restart replication after fork stalling that do not rely on recombination, but instead restart replication downstream of the damage.The replication restart mechanism has not been reported in D. radiodurans.The PriA-dependent pathway is the major replication restart mechanism in bacteria.PriA completes the assembly of a new replisome at the stalled fork in E.coli together with other restart primosomal proteins, including PriB, DnaT, PriC, DnaB and DnaC. Comparative genomics have revealed that D. radiodurans encodes the priA gene,dr2606.But the homologues of priB,priC, dnaT and dnaC do not exist in this super bacterium.In order to understand the role of a priA-like gene (dr2606) in Deinococcus radiodurans, we get the Sequence alignment of dr2606 with its homologues in E. coli, and B. subtilis via bioinformatics.A dr2606 null mutant was constructed by replacing dr2606 open reading frame with a kanamycin-resistance gene. Successively, the dr2606 mutant showed a delayed growth and a dramatic decrease of cell viability. To test its role in DNA repair, dr2606 mutant was treated with UV and Mitomycin C (MMC). Unexpectedly, the DNA repair capability of D. radiodurans was not impaired by the inactivation of dr2606. However, the DNA transformation efficiency was largely compromised in the mutant. These data indicate the priA-like gene (dr2606) is dispensable for stalled DNA replication forks restart in D. radiodurans and origin-independent replication restart in D. radiodurans may be different from other bacteria.