Genetic analysis of the requirements for SOS induction by nalidixic acid in Escherichia coli.
Nalidixic acid, the prototype antibacterial quinolone, induces the SOS response by a mechanism that requires the RecBCD nuclease/helicase. A key step inferred for this induction pathway is the conversion of a drug-induced gyrase cleavage complex into a DNA break that can be processed by RecBC. We tried to clarify the nature of this step by searching for additional gene products that are specifically necessary for SOS induction following nalidixic acid treatment. A transposon library of approximately 19,000 insertion mutants yielded 18 mutants that were substantially reduced for SOS induction following nalidixic acid but not UV treatment, and which were also hypersensitive to nalidixic acid. All 18 mutants turned out to have insertions in recB or recC. As expected, recA insertion mutants were uncovered as being uninducible by either nalidixic acid or UV treatment. Insertions in 11 other genes were found to cause partial defects in SOS induction by one or both pathways, providing possible leads in understanding the detailed mechanisms of SOS induction. Overall, these results suggest that nalidixic acid-induced DNA breaks are generated either by RecBC itself, by redundant activities, and/or by an essential protein that could not be uncovered with transposon mutagenesis.
Newmark
Kathryn G
KG
Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
O'Reilly
Erin K
EK
Pohlhaus
Jennifer Reineke
JR
Kreuzer
Kenneth N
KN
D000890:Anti-Infective Agents / Q000494:pharmacology; D017101:Bacteriophage P1 / Q000235:genetics; D027081:DNA Gyrase / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D016254:Mutagenesis, Insertional; D009154:Mutation; D009268:Nalidixic Acid / Q000494:pharmacology*; D013014:SOS Response, Genetics / Q000235:genetics*; D017422:Sequence Analysis, DNA; D059005:Topoisomerase II Inhibitors; D014161:Transduction, Genetic; D014466:Ultraviolet Rays
D000890:Anti-Infective Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D059005:Topoisomerase II Inhibitors; D009268:Nalidixic Acid; D027081:DNA Gyrase