Retention of replication fidelity by a DNA polymerase functioning in a distantly related environment.


The primary structures of the replicative DNA polymerases (gp43s) of bacteriophage T4 and its distant phylogenetic relative RB69 are diverged, retaining only 61% identity and 74% similarity. Nevertheless, RB69 gp43 substitutes effectively for T4 gp43 in T4 DNA replication in vivo. We show here that RB69 gp43 replicates T4 genomes in vivo with a fidelity similar to that achieved by T4 gp43. Furthermore, replication by RB69 gp43 in the distantly related environment does not enhance the mutator activities of mutations in T4 genes that encode other components of the multienzyme DNA replicase. We also show that the fidelities of RB69 gp43 and T4 gp43 are both high in vitro and that they are similarly and sharply reduced in vivo by mutations that eliminate the 3'-exonucleolytic proofreading function. We conclude that gp43 interactions with the other replication proteins are probably nonessential for polymerase fidelity.



Exonuclease Activity, Fidelity, Mutational Analysis

One line summary:

RB69 and T4 polymerase both have high fidelity in vitro, and in vivo, their fidelity is reduced by mutations that disable its exonuclease function. Accessory protein interaction with the polymerases is not likely to affect fidelity.


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Polymerase Reference Property Result Context
T4 D219AD324A Dressman HK1997 Nucleotide Substitution Rate 310 Mutation frequency (relative to WT) Technique: Forward mutational
RB69 D222AD327A Dressman HK1997 Nucleotide Substitution Rate 490 Mutation frequency (relative to WT) Technique: Forward mutational

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