Structural Differences between the Genomes of Strains from Different Laboratories.

The bacterium is known to efficiently and accurately reassemble its genome after hundreds of DNA double-strand breaks (DSBs). Only at very large amounts of radiation-induced DSBs is this accuracy affected in the wild-type , causing rearrangements in its genome structure. However, changes in its genome structure may also be possible during the propagation and storage of cell cultures.

Impact of C-terminal domains of paralogous single-stranded DNA binding proteins from Streptomyces coelicolor on their biophysical properties and biological functions.

Single-stranded DNA-binding proteins (SSB) are crucial in DNA metabolism. While Escherichia coli SSB is extensively studied, the significance of its C-terminal domain has only recently emerged. This study explored the significance of C-domains of two paralogous Ssb proteins in S.

Chromosome Segregation and Cell Division Defects in Recombination Mutants Exposed to Different DNA-Damaging Treatments.

Homologous recombination repairs potentially lethal DNA lesions such as double-strand DNA breaks (DSBs) and single-strand DNA gaps (SSGs). In , DSB repair is initiated by the RecBCD enzyme that resects double-strand DNA ends and loads RecA recombinase to the emerging single-strand (ss) DNA tails. SSG repair is mediated by the RecFOR protein complex that loads RecA onto the ssDNA segment of gaped duplex.

Characterization of gross genome rearrangements in Deinococcus radiodurans recA mutants.

Genome stability in radioresistant bacterium Deinococcus radiodurans depends on RecA, the main bacterial recombinase. Without RecA, gross genome rearrangements occur during repair of DNA double-strand breaks. Long repeated (insertion) sequences have been identified as hot spots for ectopic recombination leading to genome rearrangements, and single-strand annealing (SSA) postulated to be the most likely mechanism involved in this process.

RecBCD- RecFOR-independent pathway of homologous recombination in Escherichia coli.

The RecA protein is a key bacterial recombination enzyme that catalyzes pairing and strand exchange between homologous DNA duplexes. In Escherichia coli, RecA protein assembly on DNA is mediated either by the RecBCD or RecFOR protein complexes. Correspondingly, two recombination pathways, RecBCD and RecF (or RecFOR), are distinguished in E.

RecF, UvrD, RecX and RecN proteins suppress DNA degradation at DNA double-strand breaks in Escherichia coli.

Double strand breaks (DSBs) in E. coli chromosome (such as those induced by gamma rays) are repaired by recombination repair, during which a certain amount of DNA gets degraded. We monitored DNA degradation in gamma-irradiated cells to assess processing of DSBs.

Elevated Rate of Genome Rearrangements in Radiation-Resistant Bacteria.

A number of bacterial, archaeal, and eukaryotic species are known for their resistance to ionizing radiation. One of the challenges these species face is a potent environmental source of DNA double-strand breaks, potential drivers of genome structure evolution. Efficient and accurate DNA double-strand break repair systems have been demonstrated in several unrelated radiation-resistant species and are putative adaptations to the DNA damaging environment.

RecQ helicase acts before RuvABC, RecG and XerC proteins during recombination in recBCD sbcBC mutants of Escherichia coli.

The RecQ helicase is required by the RecF recombination pathway that is operative in recBC(D) sbcB sbcC(D) mutants of Escherichia coli. Genetic data suggest that RecQ participates in resection of DNA ends during initiation of recombination. In vitro, RecQ can unwind a variety of DNA substrates, including recombination intermediates such as D-loops and Holliday junctions.

Exonuclease VII is involved in "reckless" DNA degradation in UV-irradiated Escherichia coli.

The recA mutants of Escherichia coli exhibit an abnormal DNA degradation that starts at sites of double-strand DNA breaks (DSBs), and is mediated by RecBCD exonuclease (ExoV). This "reckless" DNA degradation occurs spontaneously in exponentially growing recA cells, and is stimulated by DNA-damaging agents. We have previously found that the xonA and sbcD mutations, which inactivate exonuclease I (ExoI) and SbcCD nuclease, respectively, markedly suppress "reckless" DNA degradation in UV-irradiated recA cells.

RecF recombination pathway in Escherichia coli cells lacking RecQ, UvrD and HelD helicases.

In recBCD sbcB sbcC(D) mutants of Escherichia coli homologous recombination proceeds via RecF pathway, which is thought to require RecQ, UvrD and HelD helicases at its initial stage. It was previously suggested that depletion of all three helicases totally abolishes the RecF pathway. The present study (re)examines the roles of these helicases in transductional recombination, and in recombinational repair of UV-induced DNA damage in the RecF pathway.

RecA protein assures fidelity of DNA repair and genome stability in Deinococcus radiodurans.

Deinococcus radiodurans is one of the most radiation-resistant organisms known. It can repair hundreds of radiation-induced double-strand DNA breaks without loss of viability. Genome reassembly in heavily irradiated D.

Roles of ExoI and SbcCD nucleases in "reckless" DNA degradation in recA mutants of Escherichia coli.

Exponentially growing recA mutant cells of Escherichia coli display pronounced DNA degradation that starts at the sites of DNA damage and depends on RecBCD nuclease (ExoV) activity. As a consequence of this "reckless" DNA degradation, populations of recA mutants contain a large proportion of anucleate cells. We have found that both DNA degradation and anucleate-cell production are efficiently suppressed by mutations in the xonA (sbcB) and sbcD genes.

Bacillus subtilis strain deficient for the protein-tyrosine kinase PtkA exhibits impaired DNA replication.

Bacillus subtilis has recently come into the focus of research on bacterial protein-tyrosine phosphorylation, with several proteins kinases, phosphatases and their substrates identified in this Gram-positive model organism. B. subtilis protein-tyrosine phosphorylation system PtkA/PtpZ was previously shown to regulate the phosphorylation state of UDP-glucose dehydrogenases and single-stranded DNA-binding proteins.

Reassembly of shattered chromosomes in Deinococcus radiodurans.

Dehydration or desiccation is one of the most frequent and severe challenges to living cells. The bacterium Deinococcus radiodurans is the best known extremophile among the few organisms that can survive extremely high exposures to desiccation and ionizing radiation, which shatter its genome into hundreds of short DNA fragments. Remarkably, these fragments are readily reassembled into a functional 3.

sbcB15 And DeltasbcB mutations activate two types of recf recombination pathways in Escherichia coli.

Escherichia coli cells with mutations in recBC genes are defective for the main RecBCD pathway of recombination and have severe reductions in conjugational and transductional recombination, as well as in recombinational repair of double-stranded DNA breaks. This phenotype can be corrected by suppressor mutations in sbcB and sbcC(D) genes, which activate an alternative RecF pathway of recombination. It was previously suggested that sbcB15 and DeltasbcB mutations, both of which inactivate exonuclease I, are equally efficient in suppressing the recBC phenotype.

The RuvABC resolvase is indispensable for recombinational repair in sbcB15 mutants of Escherichia coli.

The RuvABC proteins of Escherichia coli play an important role in the processing of Holliday junctions during homologous recombination and recombinational repair. Mutations in the ruv genes have a moderate effect on recombination and repair in wild-type strains but confer pronounced recombination deficiency and extreme sensitivity to DNA-damaging agents in a recBC sbcBC background. Genetic analysis presented in this work revealed that the (Delta)ruvABC mutation causes an identical DNA repair defect in UV-irradiated recBC sbcBC, sbcBC, and sbcB strains, indicating that the sbcB mutation alone is responsible for the extreme UV sensitivity of recBC sbcBC ruv derivatives.