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Hepatitis C virus NS3 helicase contributes to (−) strand RNA synthesis.

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Titel: Hepatitis C virus NS3 helicase contributes to (−) strand RNA synthesis.
Autoren: Ralfs, Philipp, Bressanelli, Stéphane, Günter, Lina M., Gabel, Alexander, Rothhaar, Paul, Price, Kyle J., Tubiana, Thibault, Munschauer, Mathias, Frick, David N., Lohmann, Volker
Quelle: Nature Communications; 8/27/2025, Vol. 16 Issue 1, p1-21, 21p
Schlagwörter: HEPATITIS C, RNA synthesis, GENETIC mutation, HAIRPIN (Genetics), VIRAL replication, RNA replicase, RNA helicase
Abstract: Many positive strand RNA viruses encode helicases, but their distinct functions in viral replication cycles is poorly understood. Here, we identify a mutation in the helicase domain of HCV non-structural protein 3 (NS3h), D1467G, which specifically affects (−) strand synthesis, phenocopying mutations in the 3' untranslated region of the genome. D1467G does not impair helicase activity in vitro or the binding of NS3h to critical cis-acting RNA elements, but reduces the interaction of NS3h and NS5B polymerase, potentially contributing to defective (−) strand synthesis. AlphaFold predictions of complexes between NS3h, RNA and/or NS5B suggest that NS3h both remodels the cis-acting RNA elements and unwinds the terminal stem-loop of the HCV genome rendering the template accessible for de novo initiation of (−) strand synthesis by NS5B. Overall, our study provides evidence for a defined function of a viral helicase in (−) strand genome synthesis of a positive strand RNA virus. Specific functions of viral helicases in genome replication of RNA viruses are widely unknown. This study suggests that hepatitis C virus NS3 helicase unwinds stem loop structures at the 3'end of the genome, thereby facilitating (−) strand synthesis. [ABSTRACT FROM AUTHOR]
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Abstract:Many positive strand RNA viruses encode helicases, but their distinct functions in viral replication cycles is poorly understood. Here, we identify a mutation in the helicase domain of HCV non-structural protein 3 (NS3h), D1467G, which specifically affects (−) strand synthesis, phenocopying mutations in the 3' untranslated region of the genome. D1467G does not impair helicase activity in vitro or the binding of NS3h to critical cis-acting RNA elements, but reduces the interaction of NS3h and NS5B polymerase, potentially contributing to defective (−) strand synthesis. AlphaFold predictions of complexes between NS3h, RNA and/or NS5B suggest that NS3h both remodels the cis-acting RNA elements and unwinds the terminal stem-loop of the HCV genome rendering the template accessible for de novo initiation of (−) strand synthesis by NS5B. Overall, our study provides evidence for a defined function of a viral helicase in (−) strand genome synthesis of a positive strand RNA virus. Specific functions of viral helicases in genome replication of RNA viruses are widely unknown. This study suggests that hepatitis C virus NS3 helicase unwinds stem loop structures at the 3'end of the genome, thereby facilitating (−) strand synthesis. [ABSTRACT FROM AUTHOR]
ISSN:20411723
DOI:10.1038/s41467-025-63498-9