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Proc Natl Acad Sci U S A. 2018 Apr 17;115(16):4212-4217. doi: 10.1073/pnas.1720353115. Epub 2018 Apr 2.

High-accuracy lagging-strand DNA replication mediated by DNA polymerase dissociation.

Author information

1
Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709.
2
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland.
3
Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland iwonaf@ibb.waw.pl schaaper@niehs.nih.gov.
4
Genome Integrity and Structural Biology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709; iwonaf@ibb.waw.pl schaaper@niehs.nih.gov.

Abstract

The fidelity of DNA replication is a critical factor in the rate at which cells incur mutations. Due to the antiparallel orientation of the two chromosomal DNA strands, one strand (leading strand) is replicated in a mostly processive manner, while the other (lagging strand) is synthesized in short sections called Okazaki fragments. A fundamental question that remains to be answered is whether the two strands are copied with the same intrinsic fidelity. In most experimental systems, this question is difficult to answer, as the replication complex contains a different DNA polymerase for each strand, such as, for example, DNA polymerases δ and ε in eukaryotes. Here we have investigated this question in the bacterium Escherichia coli, in which the replicase (DNA polymerase III holoenzyme) contains two copies of the same polymerase (Pol III, the dnaE gene product), and hence the two strands are copied by the same polymerase. Our in vivo mutagenesis data indicate that the two DNA strands are not copied with the same accuracy, and that, remarkably, the lagging strand has the highest fidelity. We postulate that this effect results from the greater dissociative character of the lagging-strand polymerase, which provides additional options for error removal. Our conclusion is strongly supported by results with dnaE antimutator polymerases characterized by increased dissociation rates.

KEYWORDS:

DNA polymerase III holoenzyme; DNA polymerase dissociation; DNA replication fidelity; dnaE antimutators; leading and lagging strands

PMID:
29610333
PMCID:
PMC5910852
DOI:
10.1073/pnas.1720353115
[Indexed for MEDLINE]
Free PMC Article

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