Originally published as Genetics Published Articles Ahead of Print on February 1, 2008.

Genetics, Vol. 178, 661-673, February 2008, Copyright © 2008
doi:10.1534/genetics.107.083444

Templated Mutagenesis in Bacteriophage T4 Involving Imperfect Direct or Indirect Sequence Repeats

Gary E. Schultz, Jr.1 and John W. Drake2

Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709

2 Corresponding author: Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences, 111 South Alexander Dr., Research Triangle Park, NC 27709.
E-mail: drake{at}niehs.nih.gov

Some mutations arise in association with a potential sequence donor that consists of an imperfect direct or reverse repeat. Many such mutations are complex; that is, they consist of multiple close sequence changes. Current models posit that the primer terminus of a replicating DNA molecule dissociates, reanneals with an ectopic template, extends briefly, and then returns to the cognate template, bringing with it a locally different sequence; alternatively, a hairpin structure may form the mutational intermediate when processed by mismatch repair. This process resembles replication repair, in which primer extension is blocked by a lesion in the template; in this case, the ectopic template is the other daughter strand, and the result is error-free bypass of the lesion. We previously showed that mutations that impair replication repair can enhance templated mutagenesis. We show here that the intensity of templated mutation can be exquisitely sensitive to its local sequence, that the donor and recipient arms of an imperfect inverse repeat can exchange roles, and that double mutants carrying two alleles, each affecting both templated mutagenesis and replication repair, can have unexpected phenotypes. We also record an instance in which the mutation rates at two particular sites change concordantly with a distant sequence change, but in a manner that appears unrelated to templated mutagenesis.


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Genetics 2008 178: NP. [Full Text]