Replication of UV-irradiated single-stranded DNA by DNA polymerase III holoenzyme of Escherichia coli: evidence for bypass of pyrimidine photodimers

Proc Natl Acad Sci U S A. 1986 Jul;83(13):4599-603. doi: 10.1073/pnas.83.13.4599.


Replication of UV-irradiated circular single-stranded phage M13 DNA by Escherichia coli RNA polymerase (EC and DNA polymerase III holoenzyme (EC in the presence of single-stranded DNA binding protein yielded full-length as well as partially replicated products. A similar result was obtained with phage G4 DNA primed with E. coli DNA primase, and phage phi X174 DNA primed with a synthetic oligonucleotide. The fraction of full-length DNA was several orders of magnitude higher than predicted if pyrimidine photodimers were to constitute absolute blocks to DNA replication. Recent models have suggested that pyrimidine photodimers are absolute blocks to DNA replication and that SOS-induced proteins are required to allow their bypass. Our results demonstrate that, under in vitro replication conditions, E. coli DNA polymerase III holoenzyme can insert nucleotides opposite pyrimidine dimers to a significant extent, even in the absence of SOS-induced proteins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriophage phi X 174 / genetics
  • Coliphages / genetics
  • DNA Polymerase III / metabolism*
  • DNA Repair*
  • DNA Replication* / radiation effects
  • DNA, Single-Stranded / genetics
  • DNA-Directed DNA Polymerase / metabolism*
  • Escherichia coli / enzymology
  • Escherichia coli / genetics
  • Escherichia coli / radiation effects
  • Pyrimidine Dimers / genetics*
  • Templates, Genetic
  • Ultraviolet Rays


  • DNA, Single-Stranded
  • Pyrimidine Dimers
  • DNA Polymerase III
  • DNA-Directed DNA Polymerase