engleski

The recA730 dependent suppression of recombination deficiency in RecA loading mutants of Escherichia coli

Homologous recombination is an essential process required for double strand break repair. A central requirement for recombination is the formation of a RecA filament. Double strand breaks can be processed into RecA filament by the action of three enzymatic activities: helicase, 5'-3' exonuclease and RecA loading onto ssDNA. These activities are provided by the RecBCD enzyme in wild type cells or by the RecF pathway gene products in recBC sbcBC(D) cells. In the recBD1080A mutant (recB* mutant) the recombination machineries of RecBCD and RecF pathways are interchangeable and include RecB*CD enzyme (helicase), RecJ (5'-3' exonuclease) and RecFOR (RecA loading). The mutant RecA730 protein is able to produce a RecA filament without the help of RecFOR mediators since it more efficiently competes with SSB protein for ssDNA than normal RecA protein. It was previously shown that the recA730 mutation suppresses UV sensitivity in a uvrA recFOR genetic background. We tested whether the recA730 mutation can suppress recombination and DNA repair deficiency in a recB* mutant and its derivatives. We show that the recA730 mutation suppresses recombination deficiency in a recB* recFOR background where the defect is at the level of RecA loading, but not in the recB* recJ background where the defect is at the level of nuclease activity.

recombination ; RecA730 ; RecBCD ; RecFOR ; RecA loading

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