Identification of additional genes belonging to the LexA regulon in <i>Escherichia coli</i>

Henestrosa, Antonio R. Fernández de; Ogi, Tomoo; Aoyagi, Sakae; Chafin, David; Hayes, Jeffrey J.; Ohmori, Hitoshi; Woodgate, Roger

doi:10.1046/j.1365-2958.2000.01826.x

Cited by 510 publications

(490 citation statements)

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“…Because recombinational repair in E. coli is the major repair system to mend chromosomal lesions, RecA-dependent mutants should have higher levels of chromosomal lesions. SOS response is a reaction of bacterial cells to chromosomal lesions and includes increased expression of Ϸ30 genes and decreased expression of 20 more genes (25,26). The genes induced during the SOS response are repressed in the absence of chromosomal damage by the LexA repressor bound to their promoters (27).…”

Section: Resultsmentioning

confidence: 99%

RecA-dependent mutants in Escherichia coli reveal strategies to avoid chromosomal fragmentation

Kouzminova

Rotman

Macomber

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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RecA-and RecBC-catalyzed repair in eubacteria assembles chromosomes fragmented by double-strand breaks. We propose that recA mutants, being unable to repair fragmented chromosomes, depend on various strategies designed to avoid chromosomal fragmentation. To identify chromosomal fragmentation-avoidance strategies, we screened for Escherichia coli mutants synthetically inhibited in combination with recA inactivation by identifying clones unable to lose a plasmid carrying the recA ؉ gene. Using this screen, we have isolated several RecA-dependent mutants and assigned them to three distinct areas of metabolism. The tdk and rdgB mutants affect synthesis of DNA precursors. The fur, ubiE, and ubiH mutants are likely to have increased levels of reactive oxygen species. The seqA, topA mutants and an insertion in smtA perturbing the downstream mukFEB genes affect nucleoid administration. All isolated mutants show varying degree of SOS induction, indicating elevated levels of chromosomal lesions. As predicted, mutants in rdgB, seqA, smtA, topA, and fur show increased levels of chromosomal fragmentation in recBC mutant conditions. Future characterization of these RecA-dependent mutants will define mechanisms of chromosomal fragmentation avoidance. C hromosomal fragmentation due to double-strand DNA breaks and disintegrated replication forks is a major contributor to genome instability in all organisms (1, 2). The two major pathways used by eukaryotic cells to repair fragmented chromosomes are nonhomologous end joining and homologous recombination (3). Nonhomologous end joining is an imprecise repair, frequently involving loss of genetic information, but it is nevertheless an efficient way to repair double-strand breaks in cells of higher eukaryotes (4). However, disintegrated replication forks, having a single double-strand end, cannot be reassembled by nonhomologous end joining and require error-free recombinational repair (5, 6). The importance of recombinational repair in higher eukaryotes is illustrated by the inviability of recombinational repair mutants in mice (7) and by the rapid death of recombinational repair-defective vertebrate cells due to chromosomal fragmentation (8). In the model eubacterium Escherichia coli, recombinational repair of fragmented chromosomes is catalyzed by the RecA and RecBCD enzymes (9). RecBCD is an exonuclease͞helicase that prepares the doublestrand DNA ends of the break for RecA polymerization (10). RecA filament catalyzes homologous strand exchange of the broken DNA duplex with an intact sister duplex, thus creating an opportunity for double-strand break repair (11).In recA or recBC mutants of E. coli, double-strand DNA breaks are not repaired (12) and cause chromosomal loss and cell death (13,14). However, recA mutant E. coli strains are still 50% viable (15, 16), which indicates that the chromosomal fragmentation is not a frequent event in E. coli and suggests the existence of strategies designed to avoid chromosomal fragmentation. Inactivation of one of these hypothetical avoidance a...

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Section: Resultsmentioning

confidence: 99%

RecA-dependent mutants in Escherichia coli reveal strategies to avoid chromosomal fragmentation

Kouzminova

Rotman

Macomber

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…In both E. coli and B. subtilis, DNA damage results in the induction of Ͼ40 unlinked genes that comprise the SOS response (43)(44)(45)(46). The recA gene is regulated by LexA, and recA transcript levels increase after exposure to exogenous damage (43).…”

Section: Reca-gfp Foci Form Through a Redistribution Of Existing Protmentioning

confidence: 99%

Replication is required for the RecA localization response to DNA damage in Bacillus subtilis

Simmons

Grossman

Walker

2007

Proc. Natl. Acad. Sci. U.S.A.

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In both prokaryotes and eukaryotes, proteins involved in DNA repair often organize into multicomponent complexes that can be visualized as foci in living cells. We used a RecA-GFP fusion to examine the subcellular cues that direct RecA-GFP to assemble as foci in response to DNA damage. We used two different methods to inhibit initiation of DNA replication and determined that DNA replication is required for the cell to establish RecA-GFP foci after exposure to DNA-damaging agents. Furthermore, use of endonuclease cleavage to generate a site-specific double-strand break demonstrated that the replication machinery (replisome) and DNA synthesis are required for assembly of RecA-GFP foci during repair of a double-strand break. We monitored the cellular levels of RecA and found that focus formation does not require further induction of protein levels, suggesting that foci result from a redistribution of existing protein to sites of damage encountered by the replisome. Taken together, our results support the model that existing RecA protein is recruited to ssDNA generated by the replisome at sites of DNA damage. These results provide insight into the mechanisms that the cell uses to recruit repair proteins to damaged DNA in living cells.replisome ͉ focus ͉ double-strand break

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“…Once activated, RecA interacts with LexA protein, the repressor of the SOS genes (Wagner et al, 1999). This interaction triggers the autocatalytic cleavage of LexA and consequent destruction of its ability to function as a repressor, which results in the derepression of SOS genes (Mustard and Little, 2000;Fernandez De Henestrosa et al, 2000). By using DNA microarray techniques Courcelle et al (2001) have shown that in E. coli the expression of 43 genes is controlled by LexA.…”

Section: Sos Responsementioning

confidence: 99%

Several pathways of hydrogen peroxide action that damage the E. coli genome

Asad

Almeida

et al. 2004

Genet. Mol. Biol.

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Hydrogen peroxide is an important reactive oxygen species (ROS) that arises either during the aerobic respiration process or as a by-product of water radiolysis after exposure to ionizing radiation. The reaction of hydrogen peroxide with transition metals imposes on cells an oxidative stress condition that can result in damage to cell components such as proteins, lipids and principally to DNA, leading to mutagenesis and cell death. Escherichia coli cells are able to deal with these adverse events via DNA repair mechanisms, which enable them to recover their genome integrity. These include base excision repair (BER), nucleotide excision repair (NER) and recombinational repair. Other important defense mechanisms present in Escherichia coli are OxyR and SosRS anti-oxidant inducible pathways, which are elicited by cells to avoid the introduction of oxidative lesions by hydrogen peroxide. This review summarizes the phenomena of lethal synergism between UV irradiation (254 nm) and H 2 O 2 , the cross-adaptive response between different classes of genotoxic agents and hydrogen peroxide, and the role of copper ions in the lethal response to H 2 O 2 under low-iron conditions. Key words: hydrogen peroxide, cross-adaptive response, lethal synergism, copper and iron. General AspectsThe appearance of aerobic forms of life was an important step in the evolutionary process, since oxygen consumption leads to the production of ten-fold more energy from glucose than does anaerobic metabolism (Meneghini, 1987). However, this process imposes constraints on cell viability, because of the generation of reactive oxygen species during respiration.The consecutive univalent reduction of molecular oxygen to water produces three active intermediates: superoxide anion (O 2 -• ), hydrogen peroxide (H 2 O 2 ) and hydroxyl radical (OH • ). These intermediates, collectively referred to as reactive oxygen species (ROS) are potent oxidants of lipids, proteins, and nucleic acids (Halliwell and Gutteridge, 1984;Mello-Filho and Meneghini, 1985;Meneghini, 1988). Among the oxidative DNA lesions, one of the major classes of DNA damage leads to modification in purine and pyrimidine bases, together with oligonucleotide strand breaks, DNA-protein cross-links and abasic sites. Increasing evidence suggests that the cumulative damage caused by ROS contributes to numerous degenerative diseases associated with aging, such as atherosclerosis, rheumatoid arthritis and cancer (Ames et al., 1993;Halliwell and Gutteridge, 1999).Living organisms have developed specific mechanisms to prevent the production and effects of ROS. The reduction of O 2 by cytochrome oxidase without yielding ROS, the superoxide dismutase catalysis of O 2 -• into H 2 O 2 through a dismutation reaction, the decomposition of H 2 O 2 by catalase and peroxidases, and the scavenging of ROS by some vitamins comprise part of the set of cellular antioxidant defenses (Halliwell and Gutteridge, 1999). Synthesis of the enzymes that catalyze these reactions is a part of the adaptive response tr...

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Identification of additional genes belonging to the LexA regulon in Escherichia coli

Cited by 510 publications

References 46 publications

RecA-dependent mutants in Escherichia coli reveal strategies to avoid chromosomal fragmentation

RecA-dependent mutants in Escherichia coli reveal strategies to avoid chromosomal fragmentation

Replication is required for the RecA localization response to DNA damage in Bacillus subtilis

Several pathways of hydrogen peroxide action that damage the E. coli genome

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