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PprA : une protéine clé dans la radiorésistance chez Deinococcus radiodurans

Abstract : Deinococcus radiodurans, one of the most radioresistant organisms known to date is able to reconstruct an intact genome from hundreds of DNA fragments generated by γ-rays. More generally, this bacterium is also tolerant to other DNA-damaging agents. This exceptional ability to overcome effects of ionizing radiations is due to a combination of several well regulated mechanisms and factors acting together when cells are exposed the radiations. Among these factors, some specific proteins of the Deinococcaceae family which are induced after irradiation can be observed. The PprA protein is one of these specific proteins and has been shown to have an important role in radioresistance in D. radiodurans. This protein is one of the most induced after γ-rays treatment. None homologous protein have been identify for the PprA protein. Characteristics of the ΔpprA mutant were investigated in order to understand the involvement of PprA in radioresistance. This mutant is very sensitive to γ-rays and other DNA damaging agents as nalidixic acid or novobiocin. Phenotypic analyses of this mutant revealed that PprA protein seems to be implicated in chromosome segregation after irradiation when DNA is repaired in cells. Moreover, the PprA protein has been shown to interact in vivo with DNA gyrase after irradiation and to stimulate in vitro the decatenation activity of DNA gyrase, without affecting its DNA negative supercoiling activity. Phenotypes previously observed also suggest a potential interaction between the PprA protein and the protein SMC family which are SMC, SbcC and RecN in D. radiodurans. Surprisingly, we found that disrupting recN gene in a ΔpprA strain abolish the sensitivity to DNA damaging agents observed in a ΔpprA strain. These results suggest that the two genes, pprA and recN interact but the accurate link between the two proteins PprA and RecN remains to be highlighted.
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Alice Devigne. PprA : une protéine clé dans la radiorésistance chez Deinococcus radiodurans. Biologie moléculaire. Université Paris-Saclay, 2015. Français. ⟨NNT : 2015SACLS056⟩. ⟨tel-01968008⟩

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