The role of Deinococcus radiodurans RecFOR proteins in homologous recombination.
Deinococcus radiodurans exhibits extraordinary resistance to the lethal effect of DNA-damaging agents, a characteristic attributed to its highly proficient DNA repair capacity. Although the D. radiodurans genome is clearly devoid of recBC and addAB counterparts as RecA mediators, the genome possesses all genes associated with the RecFOR pathway. In an effort to gain insights into the role of D. radiodurans RecFOR proteins in homologous recombination, we generated recF, recO and recR disruptant strains and characterized the disruption effects. All the disruptant strains exhibited delayed growth relative to the wild-type, indicating that the RecF, RecO and RecR proteins play an important role in cell growth under normal growth conditions. A slight reduction in transformation efficiency was observed in the recF and recO disruptant strains compared to the wild-type strain. Interestingly, disruption of recR resulted in severe reduction of the transformation efficiency. On the other hand, the recF disruptant strain was the most sensitive phenotype to γ rays, UV irradiation and mitomycin C among the three disruptants. In the recF disruptant strain, the intracellular level of the LexA1 protein did not decrease following γ irradiation, suggesting that a large amount of the RecA protein remains inactive despite being induced. These results demonstrate that the RecF protein plays a crucial role in the homologous recombination repair process by facilitating RecA activation in D. radiodurans. Thus, the RecF and RecR proteins are involved in the RecA activation and the stability of incoming DNA, respectively, during RecA-mediated homologous recombination processes that initiated the ESDSA pathway in D. radiodurans. Possible mechanisms that involve the RecFOR complex in homologous intermolecular recombination and homologous recombination repair processes are also discussed.
Ion Beam Mutagenesis Research Group, Quantum Beam Science Directorate, Japan Atomic Energy Agency, Takasaki, Gunma, Japan. sato.katsuya@jaea.go.jp
Katsuya
K
Satoh
Masahiro
M
Kikuchi
Abu M
AM
Ishaque
Hirofumi
H
Ohba
Mitsugu
M
Yamada
Kouhei
K
Tejima
Takefumi
T
Onodera
Issay
I
Narumi
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D034301:Deinococcus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D005720:Gamma Rays; D059765:Homologous Recombination / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D042541:Intracellular Space / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D016685:Mitomycin / Q000494:pharmacology; D016296:Mutagenesis; D012697:Serine Endopeptidases / Q000378:metabolism; D014170:Transformation, Genetic / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D014466:Ultraviolet Rays; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D016685:Mitomycin; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein