RecA protein of Escherichia coli has a third essential role in SOS mutator activity

J. B. Sweasy, E. M. Witkin, N. Sinha, V. Roegner-Maniscalco

Research output: Contribution to journalArticlepeer-review

156 Scopus citations


The DNA damage-inducible SOS response of Escherichia coli includes an error-prone translesion DNA replication activity responsible for SOS mutagenesis. In certain recA mutant strains, in which the SOS response is expressed constitutively, SOS mutagenesis is manifested as a mutator activity. Like UV mutagenesis, SOS mutator activity requires the products of the umuDC operon and depends on RecA protein for at least two essential activities: facilitating cleavage of LexA repressor to derepress SOS genes and processing UmuD protein to produce a fragment (UmuD') that is active in mutagenesis. To determine whether RecA has an additional role in SOS mutator activity, spontaneous mutability (tryptophan dependence to independence) was measured in a family of nine lexA-defective strains, each having a different recA allele, transformed or not with a plasmid that overproduces either UmuD' alone or both UmuD' and UmuC. The magnitude of SOS mutator activity in these strains, which require neiter of the two known roles of RecA protein, was strongly dependent on the particular RecA allele that was present. We conclude that UmuD'C does not determine the mutation rate independently of RecA and that RecA has a third essential role in SOS mutator activity.

Original languageEnglish (US)
Pages (from-to)3030-3036
Number of pages7
JournalJournal of bacteriology
Issue number6
StatePublished - 1990
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology


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