@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 {816,
	title = {A hand-off mechanism for primosome assembly in replication restart.},
	journal = {Mol Cell},
	volume = {26},
	year = {2007},
	month = {2007 Jun 22},
	pages = {781-93},
	abstract = {Collapsed DNA replication forks must be reactivated through origin-independent reloading of the replication machinery (replisome) to ensure complete duplication of cellular genomes. In E. coli, the PriA-dependent pathway is the major replication restart mechanism and requires primosome proteins PriA, PriB, and DnaT for replisome reloading. However, the molecular mechanisms that regulate origin-independent replisome loading are not fully understood. Here, we demonstrate that assembly of primosome protein complexes represents a key regulatory mechanism, as inherently weak PriA-PriB and PriB-DnaT interactions are strongly stimulated by single-stranded DNA. Furthermore, the binding site on PriB for single-stranded DNA partially overlaps the binding sites for PriA and DnaT, suggesting a dynamic primosome assembly process in which single-stranded DNA is handed off from one primosome protein to another as a repaired replication fork is reactivated. This model helps explain how origin-independent initiation of DNA replication is restricted to repaired replication forks, preventing overreplication of the genome.},
	keywords = {Binding Sites, DNA Helicases, DNA Replication, DNA, Bacterial, DNA, Single-Stranded, DNA-Binding Proteins, DNA-Directed DNA Polymerase, Escherichia coli, Escherichia coli Proteins, Genome, Bacterial, Models, Biological, Multienzyme Complexes, Protein Binding, Replication Origin},
	issn = {1097-2765},
	doi = {10.1016/j.molcel.2007.05.012},
	author = {Lopper, Matthew and Boonsombat, Ruethairat and Sandler, Steven J and Keck, James L}
}
