Mycobacteria encode three DNA double-strand break repair pathways: (i) RecA-dependent homologous recombination (HR), (ii) Ku-dependent nonhomologous end joining (NHEJ), and (iii) RecBCD-dependent single-strand annealing (SSA). Mycobacterial HR has two presynaptic pathway options that rely on the helicase-nuclease AdnAB and the strand annealing protein RecO, respectively. Ablation of adnAB or re...

Homologous, or general, recombination is a crucial biological process that involves the paring and transfer of strands between DNA molecules that share a region of significant sequence homology. After its discovery in 1946 by Lederberg and Tatum (48), homologous recombination in bacteria was associated with the sexual process of conjugation and was viewed as an evolutionary mechanism both for s...

During infection of homoimmune Escherichia coli lysogens ("repressed infections"), undamaged nonreplicating lambda phage DNA circles undergo very little recombination. Prior UV irradiation of phages dramatically elevates recombinant frequencies, even in bacteria deficient in UvrABC-mediated excision repair. We previously reported that 80-90% of this UvrABC-independent recombination required Mut...

RecBCD enzyme has multiple activities including helicase, exonuclease and endonuclease activities. Mutations in the genes recB or recC, encoding two subunits of the enzyme, reduce the frequency of many types of recombinational events. Mutations in recD, encoding the third subunit, do not reduce recombination even though most of the activities of the RecBCD enzyme are severely reduced. In this s...

The effect of mutations in known recombination genes (recA, recB, recC, recE, recF, recJ, recN, recO, recQ and ruv) on intramolecular recombination of plasmids was studied in recB recC sbcB and recB recC sbcA Escherichia coli mutants. The rate of recombination of circular dimer plasmids was at least 1000-fold higher in recB recC sbcB or recB recC sbcA mutants as compared to wild-type cells. The...

RecR, together with RecF and RecO, facilitates RecA loading in the RecF pathway of homologous recombinational DNA repair in procaryotes. The human Rad52 protein is a functional counterpart of RecFOR. We present here the crystal structure of RecR from Deinococcus radiodurans (DR RecR). A monomer of DR RecR has a two-domain structure: the N-terminal domain with a helix-hairpin-helix (HhH) motif a...

Genetic and biochemical studies on enzymes known to be involved in regulating DNA supercoiling yield a complex spectrum of effects on the Escherichia coli SOS system. Previous studies indicated that only inhibition of DNA gyrase by antibiotics that act on the DNA gyrase A subunit results in turning on the E. coli SOS system. Here we show that coumermycin, an antibiotic that acts on the DNA gyra...

In all cells, genetic recombination is used to repair DNA breaks and, as a result, genetic information is exchanged between homologous DNA molecules. Discontinuities in DNA strands, specifically double-strand DNA breaks and single-strand DNA gaps, attract the enzymes responsible for the initiation of homologous recombination. In wild-type Escherichia coli, two distinct pathways are responsible ...

The accurate recovery of replication following DNA damage and repair is critical for the maintenance of genomic integrity. In Escherichia coli, the recovery of replication following UV-induced DNA damage is dependent upon several proteins in the recF pathway, including RecF, RecO, and RecR. Two other recF pathway proteins, the RecQ helicase and the RecJ exonuclease, have been shown to a€ect the...