title: DNA polymerase II as a fidelity factor in chromosomal DNA synthesis in Escherichia coli.
abstract: Escherichia coli DNA polymerase III holoenzyme (HE) is the main replicase responsible for replication of the bacterial chromosome. E. coli contains four additional polymerases, and it is a relevant question whether these might also contribute to chromosomal replication and its fidelity. Here, we have investigated the role of DNA polymerase II (Pol II) (polB gene product). Mismatch repair-defective strains containing the polBex1 allele--encoding a polymerase-proficient but exonucleolytically defective Pol II--displayed a mutator activity for four different chromosomal lac mutational markers. The mutator effect was dependent on the chromosomal orientation of the lacZ gene. The results indicate that Pol II plays a role in chromosomal replication and that its role is not equal in leading- versus lagging-strand replication. In particular, the role of Pol II appeared larger in the lagging strand. When combined with dnaQ or dnaE mutator alleles, polBex1 showed strong, near multiplicative effects. The results fit a model in which Pol II acts as proofreader for HE-produced misinsertion errors. A second role of Pol II is to protect mismatched 3' termini against the mutagenic action of polymerase IV (dinB product). Overall, Pol II may be considered a main player in the polymerase trafficking at the replication fork.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5A, Warsaw, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Banach-Orlowska
authors.forename: Iwona J
authors.initials: IJ
authors.lastname: Fijalkowska
authors.forename: Roel M
authors.initials: RM
authors.lastname: Schaaper
authors.forename: Piotr
authors.initials: P
authors.lastname: Jonczyk
mesh_terms: D000483:Alleles; D001667:Binding, Competitive; D002876:Chromosomes, Bacterial; D004257:DNA Polymerase II / Q000502:physiology*; D004258:DNA Polymerase III / Q000235:genetics / Q000502:physiology; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000502:physiology*; D004269:DNA, Bacterial / Q000096:biosynthesis*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000502:physiology*; D005798:Genes, Bacterial; D017930:Genes, Reporter; D009154:Mutation; D001616:beta-Galactosidase / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C074904:DNA polymerase III, alpha subunit; D004257:DNA Polymerase II; D004258:DNA Polymerase III; C468316:dnaQ protein, E coli; D001616:beta-Galactosidase; D045643:DNA Repair Enzymes