Role of Escherichia coli DNA polymerase I in chromosomal DNA replication fidelity |
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| Authors: | Karolina Makiela‐Dzbenska Malgorzata Jaszczur Magdalena Banach‐Orlowska Piotr Jonczyk Roel M. Schaaper Iwona J. Fijalkowska |
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| Affiliation: | 1. Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawinskiego 5A, Warsaw, Poland.;2. Present address: International Institute of Molecular and Cell Biology, Warsaw, Poland.;3. Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA. |
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| Abstract: | We have investigated the possible role of Escherichia coli DNA polymerase (Pol) I in chromosomal replication fidelity. This was done by substituting the chromosomal polA gene by the polAexo variant containing an inactivated 3′→5′ exonuclease, which serves as a proofreader for this enzyme's misinsertion errors. Using this strain, activities of Pol I during DNA replication might be detectable as increases in the bacterial mutation rate. Using a series of defined lacZ reversion alleles in two orientations on the chromosome as markers for mutagenesis, 1.5‐ to 4‐fold increases in mutant frequencies were observed. In general, these increases were largest for lac orientations favouring events during lagging strand DNA replication. Further analysis of these effects in strains affected in other E. coli DNA replication functions indicated that this polAexo mutator effect is best explained by an effect that is additive compared with other error‐producing events at the replication fork. No evidence was found that Pol I participates in the polymerase switching between Pol II, III and IV at the fork. Instead, our data suggest that the additional errors produced by polAexo are created during the maturation of Okazaki fragments in the lagging strand. |
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