RECOMBINATIONAL DNA-REPAIR - THE RECF AND RECR PROTEINS LIMIT THE EXTENSION OF RECA FILAMENTS BEYOND SINGLE-STRAND DNA GAPS

In the presence of both the RecF and RecR proteins, RecA filament exte nsion from a single strand gap into adjoining duplex DNA is attenuated . RecR protein alone has no effect, and RecF protein alone has a reduc ed activity. The RecFR complexes bind randomly, primarily to the duple x regions of the DNA, and the extension of the RecA filament is halted at the first complex encountered. A very slow lengthening of RecA fil aments observed in the presence of RecFR is virtually eliminated when RecF is replaced with an RecF mutant protein that does not hydrolyze A TP. These observations are incorporated into an expanded model for the functions of RecF, RecO, and RecR proteins in the early stages of pos treplication DNA repair.