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Journal of Virology, August 1999, p. 6424-6429, Vol. 73, No. 8
Department of Biology, Indiana University,
Bloomington, Indiana 47405,1 and
Department of Chemistry & Biochemistry, Ribozyme
Pharmaceuticals Inc., Boulder, Colorado 803092
Received 3 December 1998/Accepted 25 April 1999
All polynucleotide polymerases have a similar structure and
mechanism of catalysis, consistent with their evolution from one progenitor polymerase. Viral RNA-dependent RNA polymerases (RdRp) are
expected to have properties comparable to those from this progenitor
and therefore may offer insight into the commonalities of all classes
of polymerases. We examined RNA synthesis by the brome mosaic virus
RdRp on DNA, RNA, and hybrid templates and found that precise
initiation of RNA synthesis can take place from all of these templates.
Furthermore, initiation can take place from either internal or
penultimate initiation sites. Using a template competition assay, we
found that the BMV RdRp interacts with DNA only three- to fourfold less
well than it interacts with RNA. Moreover, a DNA molecule with a
ribonucleotide at position
0022-538X/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Use of DNA, RNA, and Chimeric Templates by a Viral
RNA-Dependent RNA Polymerase: Evolutionary Implications for the
Transition from the RNA to the DNA World

11 relative to the initiation nucleotide
was able to interact with RdRp at levels comparable to that observed
with RNA. These results suggest that relatively few conditions were
needed for an ancestral RdRp to replicate DNA genomes.
*
Corresponding author. Mailing address: Department of
Biology, Indiana University, Jordan Hall 138, Bloomington, IN 47405. Phone: (812) 855-7959. Fax: (812) 855-6705. E-mail:
ckao{at}bio.indiana.edu.
Present address: Life Sciences Division, Los Alamos National
Laboratory, Los Alamos, NM 87545.
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