@article {810,
	title = {Differential requirements of two recA mutants for constitutive SOS expression in Escherichia coli K-12.},
	journal = {PLoS One},
	volume = {3},
	year = {2008},
	month = {2008},
	pages = {e4100},
	abstract = {BACKGROUND: Repairing DNA damage begins with its detection and is often followed by elicitation of a cellular response. In E. coli, RecA polymerizes on ssDNA produced after DNA damage and induces the SOS Response. The RecA-DNA filament is an allosteric effector of LexA auto-proteolysis. LexA is the repressor of the SOS Response. Not all RecA-DNA filaments, however, lead to an SOS Response. Certain recA mutants express the SOS Response (recA(C)) in the absence of external DNA damage in log phase cells.

METHODOLOGY/PRINCIPAL FINDINGS: Genetic analysis of two recA(C) mutants was used to determine the mechanism of constitutive SOS (SOS(C)) expression in a population of log phase cells using fluorescence of single cells carrying an SOS reporter system (sulAp-gfp). SOS(C) expression in recA4142 mutants was dependent on its initial level of transcription, recBCD, recFOR, recX, dinI, xthA and the type of medium in which the cells were grown. SOS(C) expression in recA730 mutants was affected by none of the mutations or conditions tested above.

CONCLUSIONS/SIGNIFICANCE: It is concluded that not all recA(C) alleles cause SOS(C) expression by the same mechanism. It is hypothesized that RecA4142 is loaded on to a double-strand end of DNA and that the RecA filament is stabilized by the presence of DinI and destabilized by RecX. RecFOR regulate the activity of RecX to destabilize the RecA filament. RecA730 causes SOS(C) expression by binding to ssDNA in a mechanism yet to be determined.},
	keywords = {Escherichia coli K12, Escherichia coli Proteins, Gene Expression Regulation, Bacterial, Genes, Bacterial, Models, Biological, Mutation, Rec A Recombinases, SOS Response (Genetics)},
	issn = {1932-6203},
	doi = {10.1371/journal.pone.0004100},
	author = {Long, Jarukit Edward and Renzette, Nicholas and Centore, Richard C and Sandler, Steven J}
}
@article {813,
	title = {Requirements for ATP binding and hydrolysis in RecA function in Escherichia coli.},
	journal = {Mol Microbiol},
	volume = {67},
	year = {2008},
	month = {2008 Mar},
	pages = {1347-59},
	abstract = {RecA is essential for recombination, DNA repair and SOS induction in Escherichia coli. ATP hydrolysis is known to be important for RecA{\textquoteright}s roles in recombination and DNA repair. In vitro reactions modelling SOS induction minimally require ssDNA and non-hydrolyzable ATP analogues. This predicts that ATP hydrolysis will not be required for SOS induction in vivo. The requirement of ATP binding and hydrolysis for SOS induction in vivo is tested here through the study of recA4159 (K72A) and recA2201 (K72R). RecA4159 is thought to have reduced affinity for ATP. RecA2201 binds, but does not hydrolyse ATP. Neither mutant was able to induce SOS expression after UV irradiation. RecA2201, unlike RecA4159, could form filaments on DNA and storage structures as measured with RecA-GFP. RecA2201 was able to form hybrid filaments and storage structures and was either recessive or dominant to RecA(+), depending on the ratio of the two proteins. RecA4159 was unable to enter RecA(+) filaments on DNA or storage structures and was recessive to RecA(+). It is concluded that ATP hydrolysis is essential for SOS induction. It is proposed that ATP binding is essential for storage structure formation and ability to interact with other RecA proteins in a filament.},
	keywords = {Adenosine Triphosphate, Chromosomes, Bacterial, Escherichia coli, Escherichia coli Proteins, Hydrolysis, Mutation, Protein Binding, Rec A Recombinases, Ultraviolet Rays},
	issn = {1365-2958},
	doi = {10.1111/j.1365-2958.2008.06130.x},
	author = {Renzette, Nicholas and Sandler, Steven J}
}
@article {820,
	title = {Localization of RecA in Escherichia coli K-12 using RecA-GFP.},
	journal = {Mol Microbiol},
	volume = {57},
	year = {2005},
	month = {2005 Aug},
	pages = {1074-85},
	abstract = {RecA is important in recombination, DNA repair and repair of replication forks. It functions through the production of a protein-DNA filament. To study the localization of RecA in live Escherichia coli cells, the RecA protein was fused to the green fluorescence protein (GFP). Strains with this gene have recombination/DNA repair activities three- to tenfold below wild type (or about 1000-fold above that of a recA null mutant). RecA-GFP cells have a background of green fluorescence punctuated with up to five foci per cell. Two types of foci have been defined: 4,6-diamidino-2-phenylindole (DAPI)-sensitive foci that are bound to DNA and DAPI-insensitive foci that are DNA-less aggregates/storage structures. In log phase cells, foci were not localized to any particular region. After UV irradiation, the number of foci increased and they localized to the cell centre. This suggested colocalization with the DNA replication factory. recA, recB and recF strains showed phenotypes and distributions of foci consistent with the predicted effects of these mutations.},
	keywords = {Chromosomes, Bacterial, DNA Replication, DNA, Bacterial, Escherichia coli, Escherichia coli Proteins, Green Fluorescent Proteins, Mutation, Rec A Recombinases, Recombinant Fusion Proteins, Recombination, Genetic, Ultraviolet Rays},
	issn = {0950-382X},
	doi = {10.1111/j.1365-2958.2005.04755.x},
	author = {Renzette, Nicholas and Gumlaw, Nathan and Nordman, Jared T and Krieger, Marlee and Yeh, Su-Ping and Long, Edward and Centore, Richard and Boonsombat, Ruethairat and Sandler, Steven J}
}
