Isolation of SOS constitutive mutants of Escherichia coli.

Journal Article (Journal Article)

The bacterial SOS regulon is strongly induced in response to DNA damage from exogenous agents such as UV radiation and nalidixic acid. However, certain mutants with defects in DNA replication, recombination, or repair exhibit a partially constitutive SOS response. These mutants presumably suffer frequent replication fork failure, or perhaps they have difficulty rescuing forks that failed due to endogenous sources of DNA damage. In an effort to understand more clearly the endogenous sources of DNA damage and the nature of replication fork failure and rescue, we undertook a systematic screen for Escherichia coli mutants that constitutively express the SOS regulon. We identified mutant strains with transposon insertions in 42 genes that caused increased expression from a dinD1::lacZ reporter construct. Most of these also displayed significant increases in basal levels of RecA protein, confirming an effect on the SOS system. As expected, this collection includes genes, such as lexA, dam, rep, xerCD, recG, and polA, which have previously been shown to cause an SOS constitutive phenotype when inactivated. The collection also includes 28 genes or open reading frames that were not previously identified as SOS constitutive, including dcd, ftsE, ftsX, purF, tdcE, and tynA. Further study of these SOS constitutive mutants should be useful in understanding the multiple causes of endogenous DNA damage. This study also provides a quantitative comparison of the extent of SOS expression caused by inactivation of many different genes in a common genetic background.

Full Text

Duke Authors

Cited Authors

  • O'Reilly, EK; Kreuzer, KN

Published Date

  • November 2004

Published In

Volume / Issue

  • 186 / 21

Start / End Page

  • 7149 - 7160

PubMed ID

  • 15489426

Pubmed Central ID

  • PMC523190

International Standard Serial Number (ISSN)

  • 0021-9193

Digital Object Identifier (DOI)

  • 10.1128/JB.186.21.7149-7160.2004


  • eng

Conference Location

  • United States