PMID:21764927

Citation	Vlašić, I, Šimatović, A and Brčić-Kostić, K (2011) Genetic requirements for high constitutive SOS expression in recA730 mutants of Escherichia coli. J. Bacteriol. 193:4643-51
Abstract	The RecA protein in its functional state is in complex with single-stranded DNA, i.e., in the form of a RecA filament. In SOS induction, the RecA filament functions as a coprotease, enabling the autodigestion of the LexA repressor. The RecA filament can be formed by different mechanisms, but all of them require three enzymatic activities essential for the processing of DNA double-stranded ends. These are helicase, 5'-3' exonuclease, and RecA loading onto single-stranded DNA (ssDNA). In some mutants, the SOS response can be expressed constitutively during the process of normal DNA metabolism. The RecA730 mutant protein is able to form the RecA filament without the help of RecBCD and RecFOR mediators since it better competes with the single-strand binding (SSB) protein for ssDNA. As a consequence, the recA730 mutants show high constitutive SOS expression. In the study described in this paper, we studied the genetic requirements for constitutive SOS expression in recA730 mutants. Using a β-galactosidase assay, we showed that the constitutive SOS response in recA730 mutants exhibits different requirements in different backgrounds. In a wild-type background, the constitutive SOS response is partially dependent on RecBCD function. In a recB1080 background (the recB1080 mutation retains only helicase), constitutive SOS expression is partially dependent on RecBCD helicase function and is strongly dependent on RecJ nuclease. Finally, in a recB-null background, the constitutive SOS expression of the recA730 mutant is dependent on the RecJ nuclease. Our results emphasize the importance of the 5'-3' exonuclease for high constitutive SOS expression in recA730 mutants and show that RecBCD function can further enhance the excellent intrinsic abilities of the RecA730 protein in vivo.
Links	PubMed PMC3165666 Online version:10.1128/JB.00368-11
Keywords	Escherichia coli/genetics; Escherichia coli Proteins/metabolism; Exodeoxyribonuclease V/metabolism; Exodeoxyribonucleases/metabolism; Gene Expression Regulation, Bacterial; Genes, Reporter; Mutation, Missense; Rec A Recombinases/genetics; SOS Response (Genetics); beta-Galactosidase/genetics; beta-Galactosidase/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ECOLI:RECA	involved_in	GO:0009432: SOS response	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete
ECOLI:RECA		GO:0009432 : SOS response	ECO:0000315:		P		Fig. 4: Shows effects of mutations in RecA loading functions on cSOS expression in recA730 mutants	complete CACAO 4431

References

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