Reconsidering the Role of the RecF Protein in Repair of Post‐replication Gaps

Abstract

In Escherichia coli, the RecA protein is an important factor in homologous recombination and DNA repair. When a post‐replicative gap is formed, RecA is loaded onto the single strand (ss) DNA coated by SSB, a process facilitated by recombination mediator proteins (RMP), RecF, RecO, and RecR. Contrary to current models, RecF, RecO and, RecR do not form a complex. In vitro, RecR can interact with either RecO or RecF but they compete for RecR binding. In vivo, RecF and RecO have distinct locations within the cell. Only RecF colocalizes with the replisome after UV stress, suggesting that RecF and RecO have distinct functions. Moreover, in some conditions only RecF or RecOR appear to be required. The RecOR complex is believed to load RecA onto ssDNA. Nevertheless, the RecF’s role and the function of its ATPase activity remains enigmatic.Building evidence suggests that RecF may have an unanticipated function at the replication fork. Present understanding has been achieved by using a variety of techniques including biochemical assays, phenotypic characterization and single molecule imaging microscopy, all of which confirm and build upon the hypothesis that RecF has a unique and novel role independent of RecOR in gap repair. To further investigate this hypothesis, we use a combination of overexpression and deletion mutant experiments. We hope to further distinguish RecF’s role in gap formation by working with the RecA V79L mutant, which possesses an enhanced ability to bind and remove SSB from the ssDNA.