Highly mutagenic replication by DNA polymerase V (UmuC) provides a mechanistic basis for SOS untargeted mutagenesis

Proc Natl Acad Sci U S A. 2000 Jan 18;97(2):565-70. doi: 10.1073/pnas.97.2.565.


When challenged by DNA-damaging agents, Escherichia coli cells respond by inducing the SOS stress response, which leads to an increase in mutation frequency by two mechanisms: translesion replication, a process that causes mutations because of misinsertion opposite the lesions, and an inducible mutator activity, which acts at undamaged sites. Here we report that DNA polymerase V (pol V; UmuC), which previously has been shown to be a lesion-bypass DNA polymerase, was highly mutagenic during in vitro gap-filling replication of a gapped plasmid carrying the cro reporter gene. This reaction required, in addition to pol V, UmuD', RecA, and single-stranded DNA (ssDNA)-binding protein. pol V produced point mutations at a frequency of 2.1 x 10(-4) per nucleotide (2.1% per cro gene), 41-fold higher than DNA polymerase III holoenzyme. The mutational spectrum of pol V was dominated by transversions (53%), which were formed at a frequency of 1.3 x 10(-4) per nucleotide (1. 1% per cro gene), 74-fold higher than with pol III holoenzyme. The prevalence of transversions and the protein requirements of this system are similar to those of in vivo untargeted mutagenesis (SOS mutator activity). This finding suggests that replication by pol V, in the presence of UmuD', RecA, and ssDNA-binding protein, is the basis of chromosomal SOS untargeted mutagenesis.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • ATP-Binding Cassette Transporters*
  • Bacterial Proteins / metabolism
  • Base Sequence
  • Carrier Proteins / genetics
  • DNA Damage / genetics
  • DNA Replication / genetics*
  • DNA, Single-Stranded / genetics
  • DNA, Single-Stranded / metabolism
  • DNA-Binding Proteins / metabolism
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / genetics
  • Escherichia coli Proteins*
  • Frameshift Mutation
  • Maltose-Binding Proteins
  • Molecular Sequence Data
  • Monosaccharide Transport Proteins*
  • Mutagenesis
  • Mutation
  • Plasmids / genetics
  • Point Mutation
  • Rec A Recombinases / metabolism
  • Recombinant Fusion Proteins / genetics
  • SOS Response, Genetics / genetics*


  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • Carrier Proteins
  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Maltose-Binding Proteins
  • Monosaccharide Transport Proteins
  • Recombinant Fusion Proteins
  • maltose transport system, E coli
  • Rec A Recombinases
  • DNA polymerase V, E coli
  • DNA-Directed DNA Polymerase
  • UmuD protein, E coli