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J. Biol. Chem., Vol. 283, Issue 29, 20535-20546, July 18, 2008

This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 283/29/20535    most recent M801490200v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Chinnaswamy, S. Articles by Kao, C. C. PubMed PubMed Citation Articles by Chinnaswamy, S. Articles by Kao, C. C. Social Bookmarking                      What's this?

A Locking Mechanism Regulates RNA Synthesis and Host Protein Interaction by the Hepatitis C Virus Polymerase^*

Sreedhar Chinnaswamy, Ian Yarbrough, Satheesh Palaninathan, C. T. Ranjith Kumar, Vinodhini Vijayaraghavan, Borries Demeler, Stanley M. Lemon^¶, James C. Sacchettini, and C. Cheng Kao¹

From the Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, the Department of Biochemistry, University of Texas, Health Science Center, San Antonio, Texas 78229-3900, and the ^¶Center for Hepatitis Research, Institute for Human Infections and Immunity, Department of Microbiology and Immunology, University of Texas Medical Branch, Galveston, Texas 77555-1073

Mutational analysis of the hepatitis C virus (HCV) RNA-dependent RNA polymerase (RdRp) template channel identified two residues, Trp³⁹⁷ and His⁴²⁸, which are required for de novo initiation but not for extension from a primer. These two residues interact with the 1 loop on the surface of the RdRp. A deletion within the 1 loop also resulted in comparable activities. The mutant proteins exhibit increased double-stranded RNA binding compared with the wild type, suggesting that the 1 loop serves as a flexible locking mechanism to regulate the conformations needed for de novo initiation and for elongative RNA synthesis. A similar locking motif can be found in other viral RdRps. Products associated with the open conformation of the HCV RdRp were inhibited by interaction with the retinoblastoma protein but not cyclophilin A. Different conformations of the HCV RdRp can thus affect RNA synthesis and interaction with cellular proteins.

Received for publication, February 25, 2008 , and in revised form, April 28, 2008.

^* This work was supported, in whole or in part, by National Institutes of Health, NIAID, Grants 1RO1AI073335 (to C. K.) and U19-AI40035 and N01-AI25488 (to S. M. L.). 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.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. 1-5.

¹ To whom correspondence should be addressed. Tel.: 979-458-2235; Fax: 979-845-9274; E-mail: ckao{at}tamu.edu.

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