AAC Accepts, published online ahead of print on 14 May 2007

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Deval, J. Articles by Götte, M. Search for Related Content PubMed PubMed Citation Articles by Deval, J. Articles by Götte, M.

 Previous Article  |  Next Article 

Antimicrob. Agents Chemother. doi:10.1128/AAC.00186-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

PYROPHOSPHOROLYTIC EXCISION OF NON-OBLIGATE CHAIN-TERMINATORS BY HEPATITIS C VIRUS NS5B POLYMERASE

Jérôme Deval, Megan H. Powdrill, Claudia M. D'Abramo, Luciano Cellai, and Matthias Götte^*

Departments of Microbiology & Immunology, Medicine, and Biochemistry, McGill University, Montreal, Quebec, Canada; Istituto di Cristallografia, Sede di Roma, CNR, Rome, Italy

^* To whom correspondence should be addressed. Email: matthias.gotte{at}mcgill.ca.

Non-obligate chain-terminators, such as 2'-C-methylated nucleotides, block RNA synthesis by the RNA-dependent RNA polymerase (RdRp) of the hepatitis C virus (HCV). Previous studies with related viral polymerases have shown that classical chain-terminators lacking the 3'-hydroxyl group can be excised in the presence of pyrophosphate (PPi), which is detrimental to the inhibitory activity of these compounds. Here we demonstrate that the HCV RdRp enzyme is capable of removing both obligate and clinically relevant non-obligate chain-terminators. Pyrimidines are more efficiently excised than purines. The presence of the next complementary, templated nucleotide literally blocks the excision of obligate chain-terminators through formation of a dead-end complex (DEC). However, 2'-C-methylated cytidine monophosphate (2'-C-Me-CMP) is still efficiently cleaved under these conditions. These findings show that a 2'-methylated primer terminus impedes nucleotide binding. The S282T mutation, that is associated with resistance to 2'-C-methylated-nucleotides, does not affect the excision patterns. Thus, the decreased susceptibility to 2'-C-methylated-nucleotides appears to be based solely on an improved discrimination between the inhibitor and its natural counterpart. In conclusion, our data suggest that the phosphorolytic excision of non-obligate, pyrimidine-based chain-terminators can diminish their potency. The templated nucleotide does not appear to provide protection from excision through DEC formation.

This article has been cited by other articles:

• Tchesnokov, E. P., Obikhod, A., Schinazi, R. F., Gotte, M. (2008). Delayed Chain Termination Protects the Anti-hepatitis B Virus Drug Entecavir from Excision by HIV-1 Reverse Transcriptase. J. Biol. Chem. 283: 34218-34228 [Abstract] [Full Text]