title: Role of accessory DNA polymerases in DNA replication in Escherichia coli: analysis of the dnaX36 mutator mutant.
abstract: The dnaX36(TS) mutant of Escherichia coli confers a distinct mutator phenotype characterized by enhancement of transversion base substitutions and certain (-1) frameshift mutations. Here, we have further investigated the possible mechanism(s) underlying this mutator effect, focusing in particular on the role of the various E. coli DNA polymerases. The dnaX gene encodes the tau subunit of DNA polymerase III (Pol III) holoenzyme, the enzyme responsible for replication of the bacterial chromosome. The dnaX36 defect resides in the C-terminal domain V of tau, essential for interaction of tau with the alpha (polymerase) subunit, suggesting that the mutator phenotype is caused by an impaired or altered alpha-tau interaction. We previously proposed that the mutator activity results from aberrant processing of terminal mismatches created by Pol III insertion errors. The present results, including lack of interaction of dnaX36 with mutM, mutY, and recA defects, support our assumption that dnaX36-mediated mutations originate as errors of replication rather than DNA damage-related events. Second, an important role is described for DNA Pol II and Pol IV in preventing and producing, respectively, the mutations. In the system used, a high fraction of the mutations is dependent on the action of Pol IV in a (dinB) gene dosage-dependent manner. However, an even larger but opposing role is deduced for Pol II, revealing Pol II to be a major editor of Pol III mediated replication errors. Overall, the results provide insight into the interplay of the various DNA polymerases, and of tau subunit, in securing a high fidelity of replication.
authors.affiliation: Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA.
authors.forename: Damian
authors.initials: D
authors.lastname: Gawel
authors.forename: Phuong T
authors.initials: PT
authors.lastname: Pham
authors.forename: Iwona J
authors.initials: IJ
authors.lastname: Fijalkowska
authors.forename: Piotr
authors.initials: P
authors.lastname: Jonczyk
authors.forename: Roel M
authors.initials: RM
authors.lastname: Schaaper
mesh_terms: D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism; D004256:DNA Polymerase I / Q000235:genetics / Q000378:metabolism; D004257:DNA Polymerase II / Q000235:genetics / Q000378:metabolism; D004258:DNA Polymerase III / Q000235:genetics / Q000378:metabolism; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics* / Q000502:physiology; D004259:DNA-Directed DNA Polymerase / Q000235:genetics* / Q000378:metabolism; D043382:DNA-Formamidopyrimidine Glycosylase / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D010641:Phenotype; D011485:Protein Binding; D011938:Rec A Recombinases / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C094399:DinB protein, E coli; D029968:Escherichia coli Proteins; D014157:Transcription Factors; C074904:DNA polymerase III, alpha subunit; D011938:Rec A Recombinases; C041273:transcription factor tau; D004256:DNA Polymerase I; D004257:DNA Polymerase II; D004258:DNA Polymerase III; D019951:DNA Polymerase beta; D004259:DNA-Directed DNA Polymerase; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; D043382:DNA-Formamidopyrimidine Glycosylase; C468610:DNA-formamidopyrimidine glycosylase, E coli