Open AccessGenetic Evidence for the Requirement of RecA Loading Activity in SOS Induction after UV Irradiation in Escherichia coli
Author(s) -
Ivana Ivančić-Baće,
Ignacija Vlašić,
Erika SalajŠmic,
Krunoslav Brčić-Kostić
Publication year - 2006
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00130-06
Subject(s) - sos response , repressor lexa , recbcd , biology , escherichia coli , dna repair , helicase , mutant , microbiology and biotechnology , dna , repressor , regulon , dna damage , recq helicase , exonuclease , homologous recombination , genetics , gene expression , gene , dna polymerase , rna , genome instability
The SOS response inEscherichia coli results in the coordinately induced expression of more than 40 genes which occurs when cells are treated with DNA-damaging agents. This response is dependent on RecA (coprotease), LexA (repressor), and the presence of single-stranded DNA (ssDNA). A prerequisite for SOS induction is the formation of a RecA-ssDNA filament. Depending on the DNA substrate, the RecA-ssDNA filament is produced by either RecBCD, RecFOR, or a hybrid recombination mechansim with specific enzyme activities, including helicase, exonuclease, and RecA loading. In this study we examined the role of RecA loading activity in SOS induction after UV irradiation. We performed a genetic analysis of SOS induction in strains with a mutation which eliminates RecA loading activity in the RecBCD enzyme (recB1080 allele). We found that RecA loading activity is essential for SOS induction. In therecB1080 mutant RecQ helicase is not important, whereas RecJ nuclease slightly decreases SOS induction after UV irradiation. In addition, we found that therecB1080 mutant exhibited constitutive expression of the SOS regulon. Surprisingly, this constitutive SOS expression was dependent on the RecJ protein but not on RecFOR, implying that there is a different mechanism of RecA loading for constitutive SOS expression.