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The epsilon subunit of DNA polymerase III Is involved in the nalidixic acid-induced SOS response in Escherichia coli.

Publication ,  Journal Article
Pohlhaus, JR; Long, DT; O'Reilly, E; Kreuzer, KN
Published in: J Bacteriol
August 2008

Quinolone antibacterial drugs such as nalidixic acid target DNA gyrase in Escherichia coli. These inhibitors bind to and stabilize a normally transient covalent protein-DNA intermediate in the gyrase reaction cycle, referred to as the cleavage complex. Stabilization of the cleavage complex is necessary but not sufficient for cell killing--cytotoxicity apparently results from the conversion of cleavage complexes into overt DNA breaks by an as-yet-unknown mechanism(s). Quinolone treatment induces the bacterial SOS response in a RecBC-dependent manner, arguing that cleavage complexes are somehow converted into double-stranded breaks. However, the only proteins known to be required for SOS induction by nalidixic acid are RecA and RecBC. In hopes of identifying additional proteins involved in the cytotoxic response to nalidixic acid, we screened for E. coli mutants specifically deficient in SOS induction upon nalidixic acid treatment by using a dinD::lacZ reporter construct. From a collection of SOS partially constitutive mutants with disruptions of 47 different genes, we found that dnaQ insertion mutants are specifically deficient in the SOS response to nalidixic acid. dnaQ encodes DNA polymerase III epsilon subunit, the proofreading subunit of the replicative polymerase. The deficient response to nalidixic acid was rescued by the presence of the wild-type dnaQ gene, confirming involvement of the epsilon subunit. To further characterize the SOS deficiency of dnaQ mutants, we analyzed the expression of several additional SOS genes in response to nalidixic acid using real-time PCR. A subset of SOS genes lost their response to nalidixic acid in the dnaQ mutant strain, while two tested SOS genes (recA and recN) continued to exhibit induction. These results argue that the replication complex plays a role in modulating the SOS response to nalidixic acid and that the response is more complex than a simple on/off switch.

Duke Scholars

Published In

J Bacteriol

DOI

EISSN

1098-5530

Publication Date

August 2008

Volume

190

Issue

15

Start / End Page

5239 / 5247

Location

United States

Related Subject Headings

  • beta-Galactosidase
  • SOS Response, Genetics
  • Nalidixic Acid
  • Mutagenesis, Insertional
  • Microbiology
  • Genetic Complementation Test
  • Genes, Reporter
  • Escherichia coli Proteins
  • Escherichia coli
  • DNA Polymerase III
 

Citation

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Pohlhaus, J. R., Long, D. T., O’Reilly, E., & Kreuzer, K. N. (2008). The epsilon subunit of DNA polymerase III Is involved in the nalidixic acid-induced SOS response in Escherichia coli. J Bacteriol, 190(15), 5239–5247. https://doi.org/10.1128/JB.00173-08
Pohlhaus, Jennifer Reineke, David T. Long, Erin O’Reilly, and Kenneth N. Kreuzer. “The epsilon subunit of DNA polymerase III Is involved in the nalidixic acid-induced SOS response in Escherichia coli.J Bacteriol 190, no. 15 (August 2008): 5239–47. https://doi.org/10.1128/JB.00173-08.
Pohlhaus JR, Long DT, O’Reilly E, Kreuzer KN. The epsilon subunit of DNA polymerase III Is involved in the nalidixic acid-induced SOS response in Escherichia coli. J Bacteriol. 2008 Aug;190(15):5239–47.
Pohlhaus, Jennifer Reineke, et al. “The epsilon subunit of DNA polymerase III Is involved in the nalidixic acid-induced SOS response in Escherichia coli.J Bacteriol, vol. 190, no. 15, Aug. 2008, pp. 5239–47. Pubmed, doi:10.1128/JB.00173-08.
Pohlhaus JR, Long DT, O’Reilly E, Kreuzer KN. The epsilon subunit of DNA polymerase III Is involved in the nalidixic acid-induced SOS response in Escherichia coli. J Bacteriol. 2008 Aug;190(15):5239–5247.

Published In

J Bacteriol

DOI

EISSN

1098-5530

Publication Date

August 2008

Volume

190

Issue

15

Start / End Page

5239 / 5247

Location

United States

Related Subject Headings

  • beta-Galactosidase
  • SOS Response, Genetics
  • Nalidixic Acid
  • Mutagenesis, Insertional
  • Microbiology
  • Genetic Complementation Test
  • Genes, Reporter
  • Escherichia coli Proteins
  • Escherichia coli
  • DNA Polymerase III