Alternate pathways of DNA replication in Escherichia coli

S. Bryan, H. Chen, Y. Sun, R. E. Moses

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


We have described the pcbA1 mutation which enables E. coli cells to replicate DNA in the absence of a functional dnaE gene product if DNA polymerase I (the polA gene product) is present. The pcbA1 mutation phenotypically suppresses multiple dnaEts and dnaEam alleles. The pcbA1 / PolI replication pathway differs from normal in sensitivity to certain DNA-damaging agents such as methylmethane sulfonate (MMS) and a lack of damage-directed mutagenesis. We report here cloning of the pcbA1 gene in a multicopy plasmid. The pcbA1 mutation is detected only in cis; therefore, cloning necessitated gene eviction. The pcbA1 gene lies closely- linked to gyrB. We have demonstrated the physical presence of DNA polymerase I in the replicating holoenzyme complex by immunoblotting using dnaEam strains. We conclude that E. coli has two alternate replisome structures: REP-A, in which DNA polymerase I is the functional synthetic subunit; and REP-E, in which the α-subunit, product of the dnaE gene, is functional. To investigate further the role of individual DNA polymerases in replication, we have isolated the polB gene on multicopy plasmids.

Original languageEnglish (US)
Pages (from-to)249-254
Number of pages6
JournalBBA - Gene Structure and Expression
Issue number2-3
StatePublished - Dec 20 1988


  • (E. coli)
  • DNA polymerase I
  • DNA replication pathway
  • pcbA1 cloning
  • polB

ASJC Scopus subject areas

  • Structural Biology
  • Biophysics
  • Biochemistry
  • Genetics


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