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Journal of Virology, July 1999, p. 5326-5332, Vol. 73, No. 7
Department of Microbiology and Immunology,
College of Medicine, State University of New York, Syracuse, New
York 13210,1 and School of Dentistry,
National Taiwan University, Taipei, Taiwan2
Received 9 December 1998/Accepted 30 March 1999
A mutagenesis system was developed for the in vivo study of the
fidelity of DNA replication mediated by wild-type herpes simplex virus
type 1 (HSV-1) strain KOS and its polymerase (Pol) mutant derivatives
PAAr5, Y7, and YD12. The pHOS1 shuttle plasmid, which
contained the SupF mutagenesis marker gene and the HSV
oris sequence, was used for analysis of the
mutation frequency and the mutation spectrum. All three Pol mutants
induced significant increases in the mutation frequencies of the target
gene, despite the fact that PAAr5 was previously shown to
have an antimutator phenotype by the thymidine kinase mutagenesis assay
(J. D. Hall, D. M. Coen, B. L. Fisher, M. Weisslitz, S. Randall, R. E. Almy, P. Gelep, and P. A. Schaffer, Virology
132:26-37, 1984; C. B. C. Hwang and J.-H. Chen, Gene
152:191-193, 1995). Altered spectra of mutated target genes induced by
these three mutants were also observed. The relative frequencies of
both deletion and complex mutations found in mutants induced by
exonuclease-proficient Pols were significantly higher than those
induced by exonuclease-deficient Pols. On the other hand, the
exonuclease-deficient Pols induced significant increases in the
frequency of base substitutions, which comprised predominantly G
· C-to-T · A transversions, as well as mutations at additional hot spots. These results suggest that the HSV-1 DNA Pol can incorporate purine-purine or pyrimidine-pyrimidine mispaired bases which may be
preferentially proofread by its intrinsic exonuclease activity. Furthermore, the effects of the sequence context of the target gene and
the assay method should also be considered carefully in any analysis of
replication fidelity.
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Effects of Exonuclease Activity and Nucleotide
Selectivity of the Herpes Simplex Virus DNA Polymerase on the
Fidelity of DNA Replication In Vivo
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, College of Medicine, State University of New York, Syracuse, NY 13210. Phone: (315) 464-8739. Fax: (315) 464-7680. E-mail: hwangc{at}vax.cs.hscsyr.edu.
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