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Homologous Recombination by the RecBCD and RecF Pathways
Book chapter

Homologous Recombination by the RecBCD and RecF Pathways

Maria Spies and Stephen C Kowalczykowski
The Bacterial Chromosome, pp.389-403
ASM Press
10/31/2004
DOI: 10.1128/9781555817640.ch21

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Abstract

Interaction with χ affects the helicase activity of RecBCD enzyme. Recognition of χ causes the enzyme to pause briefly at χ and to resume translocation after the χ site, but at a rate that is reduced by approximately twofold. In response to χ the RecBCD enzyme accomplishes both tasks essential for initiation of homologous recombination: (i) it recesses the double‐strand break (DSB) to produce an ssDNA‐tailed duplex DNA with χ at its terminus, and (ii) it catalyzes formation of the RecA nucleoprotein filament on the ssDNA produced. Interestingly, the efficiency of conjugational and transductional recombination by the RecF pathway in the recBC sbcBC cells is similar to that of the RecBCD pathway in wild‐type cells, showing that the machinery of this pathway can be as productive as that of the RecBCD pathway. The loading of RecA protein is an essential aspect of recombination in the RecBCD pathway. On the other hand, recB recF double mutants are deficient in recombination between chromosomal direct repeats, suggesting that both RecBCD and RecF pathways play major roles in recombination. Homologous recombination can be initiated at either DSBs or single‐strand DNA gap (SSG) in duplex DNA. Two major pathways are responsible for homologous recombination in wild‐type E. coli: The RecBCD pathway is specific for the recombinational repair of DSBs, and in the wild‐type cells, the RecF pathway is primarily used for recombination that initiates at SSGs.
 double‐strand break homologous recombination RecA nucleoprotein filament RecBCD pathway RecF pathway

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