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Limited concentration of RecA delays DNA double‐strand break repair in Deinococcus radiodurans R1
Author(s) -
Jolivet Edmond,
Lecointe François,
Coste Geneviève,
Satoh Katsuya,
Narumi Issay,
Bailone Adriana,
Sommer Suzanne
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2005.04946.x
Subject(s) - repressor lexa , deinococcus radiodurans , biology , sos response , dna repair , dna damage , microbiology and biotechnology , mutant , dna , deinococcus , gene , repressor , genetics , gene expression
Summary To evaluate the importance of RecA in DNA double‐strand break (DSB) repair, we examined the effect of low and high RecA concentrations such as 2500 and 100 000 molecules per cell expressed from the inducible P spac promoter in Deinococcus radiodurans in absence or in presence of IPTG respectively. We showed that at low concentration, RecA has a negligible effect on cell survival after γ‐irradiation when bacteria were immediately plated on TGY agar whereas it significantly decreased the survival to γ‐irradiation of Δ ddrA cells while overexpression of RecA can partially compensate the loss of DdrA protein. In contrast, when cells expressing limited concentration of RecA were allowed to recover in TGY2X liquid medium, they showed a delay in mending DSB, failed to reinitiate DNA replication and were committed to die during incubation. A deletion of irrE resulted in sensitivity to γ‐irradiation and mitomycin C treatment. Interestingly, constitutive high expression of RecA compensates partially the Δ irrE sensitization to mitomycin C. The cells with low RecA content also failed to cleave LexA after DNA damage. However, neither a deletion of the lexA gene nor the expression of a non‐cleavable LexA(Ind – ) mutant protein had an effect on survival or kinetics of DNA DSB repair compared with their lexA + counterparts in recA + as well as in bacteria expressing limiting concentration of RecA, suggesting an absence of relationship between the absence of LexA cleavage and the loss of viability or the delay in the kinetics of DSB repair. Thus, LexA protein seems to play no major role in the recovery processes after γ‐irradiation in D. radiodurans .