engleski

Chromosome segregation and cell division defects in Escherichia coli after induction of double- strand DNA breaks

In Escherichia coli, double-strand DNA breaks (DSBs) are repaired by the RecBCD pathway of homologous recombination. In the initiation (presynaptic) stage of this process, the RecBCD enzyme resects double-strand DNA ends and loads RecA recombinase to the emerging single-strand DNA tails. RecA catalyzes the central reactions of homologous DNA pairing and strand exchange (synapsis), while RuvABC complex and RecG helicase process recombination intermediates (post- synapsis). In this work we have studied chromosome morphology and segregation after introduction of DSBs by I-SceI endonuclease in E. coli strains carrying mutations in presynaptic (recB, recO) and postsynaptic (ruvABC, recG) recombination functions. Induction of DSBs by I-SceI caused severe chromosome segregation defects and DNA-less cell formation in the ruvABC, recG, and ruvABC recG mutants. This phenotype was efficiently suppressed by the recB mutation, while the recO mutation had no suppressive effect. These findings indicate that attempted DSB repair via the RecBCD recombination pathway influences DNA distribution within the cell as well as its transmission upon cell division. We assume that the DNA strand exchange between sister chromosomes during homologous recombination causes a temporary delay in chromosome segregation and disruption of cell division. In the absence of the postsynaptic RuvABC and/or RecG functions, the RecBCD-mediated DSB repair leads to accumulation of recombination intermediates that interfere with chromosome partition and cell division.

recombination pathways ; DNA repair ; double-strand breaks ; RecBCD ; RuvABC ; RecG ; chromosome segregation defects

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