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Originally published In Press as doi:10.1074/jbc.M408167200 on August 3, 2004
J. Biol. Chem., Vol. 279, Issue 43, 44858-44871, October 22, 2004
An Isatin- -thiosemicarbazone-resistant Vaccinia Virus Containing a Mutation in the Second Largest Subunit of the Viral RNA Polymerase Is Defective in Transcription Elongation*
Cindy Prins,
Steven G. Cresawn, and
Richard C. Condit
From the
Department of Molecular Genetics and Microbiology, University of Florida, Gainesville, Florida 32610-0266
The vaccinia virus RNA polymerase is a multi-subunit enzyme that contains eight subunits in the postreplicative form. A prior study of a virus called IBTr90, which contains a mutation in the A24 gene encoding the RPO132 subunit of the RNA polymerase, demonstrated that the mutation results in resistance to the anti-poxvirus drug isatin- -thiosemicarbazone (IBT). In this study, we utilized an in vitro transcription elongation assay to determine the effect of this mutation on transcription elongation. Both wild type and IBTr90 polymerase complexes were studied with regard to their ability to pause during elongation, their stability in a paused state, their ability to release transcripts, and their elongation rate. We have determined that the IBTr90 complex is specifically defective in elongation compared with the WT complex, pausing longer and more frequently than the WT complex. We have built a homology model of the RPO132 subunit with the yeast pol II rpb2 subunit to propose a structural mechanism for this elongation defect.
Received for publication, July 19, 2004
* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
To whom correspondence should be addressed. Tel.: 352-392-3128; Fax: 352-392-3133; E-mail: condit{at}mgm.ufl.edu.

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Copyright © 2004 by the American Society for Biochemistry and Molecular Biology.
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