Suppression of constitutive SOS expression by recA4162 (I298V) and recA4164 (L126V) requires UvrD and RecX in Escherichia coli K-12

Mol Microbiol. 2009 Jul;73(2):226-39. doi: 10.1111/j.1365-2958.2009.06765.x. Epub 2009 Jun 23.


Sensing DNA damage and initiation of genetic responses to repair DNA damage are critical to cell survival. In Escherichia coli, RecA polymerizes on ssDNA produced by DNA damage creating a RecA-DNA filament that interacts with the LexA repressor inducing the SOS response. RecA filament stability is negatively modulated by RecX and UvrD. recA730 (E38K) and recA4142 (F217Y) constitutively express the SOS response. recA4162 (I298V) and recA4164 (L126V) are intragenic suppressors of the constitutive SOS phenotype of recA730. Herein, it is shown that these suppressors are not allele specific and can suppress SOS(C) expression of recA730 and recA4142 in cis and in trans. recA4162 and recA4164 single mutants (and the recA730 and recA4142 derivatives) are Rec(+), UV(R) and are able to induce the SOS response after UV treatment like wild-type. UvrD and RecX are required for the suppression in two (recA730,4164 and recA4142,4162) of the four double mutants tested. To explain the data, one model suggests that recA(C) alleles promote SOS(C) expression by mimicking RecA filament structures that induce SOS and the suppressor alleles mimic RecA filament at end of SOS. UvrD and RecX are attracted to these latter structures to help dismantle or destabilize the RecA filament.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Alleles
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Gene Expression Regulation, Bacterial
  • Mutation, Missense
  • Rec A Recombinases / genetics
  • Rec A Recombinases / metabolism*
  • SOS Response, Genetics*
  • Substrate Specificity


  • Escherichia coli Proteins
  • RecX protein, E coli
  • Rec A Recombinases
  • UvrD protein, E coli
  • DNA Helicases