title: Additive effects of SbcCD and PolX deficiencies in the in vivo repair of DNA double-strand breaks in Deinococcus radiodurans.
abstract: Orthologs of proteins SbcD (Mre11) and SbcC (Rad50) exist in all kingdoms of life and are involved in a wide variety of DNA repair and maintenance functions, including homologous recombination and nonhomologous end joining. Here, we have inactivated the sbcC and/or sbcD genes of Deinococcus radiodurans, a highly radioresistant bacterium able to mend hundreds of radiation-induced DNA double-strand breaks (DSB). Mutants devoid of the SbcC and/or SbcD proteins displayed reduced survival and presented a delay in kinetics of DSB repair and cell division following gamma-irradiation. It has been recently reported that D. radiodurans DNA polymerase X (PolX) possesses a structure-modulated 3'-to-5' exonuclease activity reminiscent of specific nuclease activities displayed by the SbcCD complex from Escherichia coli. We constructed a double mutant devoid of SbcCD and PolX proteins. The double-mutant DeltasbcCD DeltapolX(Dr) (where Dr indicates D. radiodurans) bacteria are much more sensitive to gamma-irradiation than the single mutants, suggesting that the deinococcal SbcCD and PolX proteins may play important complementary roles in processing damaged DNA ends. We propose that they are part of a backup repair system acting to rescue cells containing DNA lesions that are excessively numerous or difficult to repair.
authors.affiliation: Institut de Génétique et Microbiologie, Bâtiment 409, Université Paris-Sud, F-91405 Orsay Cedex, France.
authors.forename: Esma
authors.initials: E
authors.lastname: Bentchikou
authors.forename: Pascale
authors.initials: P
authors.lastname: Servant
authors.forename: Geneviève
authors.initials: G
authors.lastname: Coste
authors.forename: Suzanne
authors.initials: S
authors.lastname: Sommer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D053903:DNA Breaks, Double-Stranded; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000172:deficiency / Q000235:genetics*; D034301:Deinococcus / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D003851:Deoxyribonucleases / Q000172:deficiency / Q000235:genetics*; D005720:Gamma Rays; D050296:Microbial Viability / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D016685:Mitomycin / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; C061563:SbcC protein, Bacteria; D016685:Mitomycin; C109534:DNA polymerase X; D004259:DNA-Directed DNA Polymerase; D003851:Deoxyribonucleases