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Section: New Results

Quantitative genomic analysis of RecA protein binding during DNA double-strand break repair reveals RecBCD action in vivo

Participants : Charlotte Cockram, Milana Filatenkova, Vincent Danos [correspondant] , Meriem Karoui, Leach David.

Understanding molecular mechanisms in the context of living cells requires the development of new methods of in vivo biochemical analysis to complement established in vitro biochemistry. A critically important molecular mechanism is genetic recombination, required for the beneficial reassortment of genetic information and for DNA double-strand break repair (DSBR). Central to recombination is the RecA (Rad51) protein that assembles into a spiral filament on DNA and mediates genetic exchange. Here we developed a method that combines chromatin immunoprecipitation with next-generation sequencing (ChIP-Seq) and mathematical modeling to quantify RecA protein binding during the active repair of a single DSB in the chromosome of Escherichia coli. In  [29] we have used quantitative genomic analysis to infer the key in vivo molecular parameters governing RecA loading by the helicase/ nuclease RecBCD at recombination hot-spots, known as Chi. Our genomic analysis has also revealed that DSBR at the lacZ locus causes a second RecBCD-mediated DSBR event to occur in the ter- minus region of the chromosome, over 1 Mb away.