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Hepatitis C virus NS2 protein contributes to virus particle assembly via opposing epistatic interactions with the E1-E2 glycoprotein and NS3-NS4A enzyme complexes.

ABSTRACT: The hepatitis C virus NS2 protein has been recently implicated in virus particle assembly. To further understand the role of NS2 in this process, we conducted a reverse genetic analysis of NS2 in the context of a chimeric genotype 2a infectious cell culture system. Of 32 mutants tested, all were capable of RNA replication and 25 had moderate-to-severe defects in virus assembly. Through forward genetic selection for variants capable of virus spread, we identified second-site mutations in E1, E2, NS2, NS3, and NS4A that suppressed NS2 defects in assembly. Two suppressor mutations, E1 A78T and NS3 Q221L, were further characterized by additional genetic and biochemical experiments. Both mutations were shown to suppress other NS2 defects, often with mutual exclusivity. Thus, several NS2 mutants were enhanced by NS3 Q221L and inhibited by E1 A78T, while others were enhanced by E1 A78T and inhibited by NS3 Q221L. Furthermore, we show that the NS3 Q221L mutation lowers the affinity of native, full-length NS3-NS4A for functional RNA binding. These data reveal a complex network of interactions involving NS2 and other viral structural and nonstructural proteins during virus assembly.

SUBMITTER: Phan T

PROVIDER: S-EPMC2738163 | biostudies-literature | 2009 Sep

REPOSITORIES: biostudies-literature

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Hepatitis C virus NS2 protein contributes to virus particle assembly via opposing epistatic interactions with the E1-E2 glycoprotein and NS3-NS4A enzyme complexes.

Phan Tung T Beran Rudolf K F RK Peters Christopher C Lorenz Ivo C IC Lindenbach Brett D BD

Journal of virology 20090610 17

The hepatitis C virus NS2 protein has been recently implicated in virus particle assembly. To further understand the role of NS2 in this process, we conducted a reverse genetic analysis of NS2 in the context of a chimeric genotype 2a infectious cell culture system. Of 32 mutants tested, all were capable of RNA replication and 25 had moderate-to-severe defects in virus assembly. Through forward genetic selection for variants capable of virus spread, we identified second-site mutations in E1, E2, ...[more]

PMID: 19515772

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Project description:Hepatitis C virus (HCV) nonstructural protein 2 (NS2) is a multifunctional protein implicated in both HCV RNA replication and virus particle assembly. NS2-encoded cysteine protease is responsible for autoprocessing of NS2-NS3 precursor, an essential step in HCV RNA replication. NS2 also promotes HCV particle assembly by recruiting envelope protein 2 (E2) to the virus assembly sites located at the detergent-resistant membranes (DRM). However, the fundamental mechanism regulating multiple functions of NS2 remains unclear. In this study, we discovered that NS2 is palmitoylated at the position 113 cysteine residue (NS2/C113) when expressed by itself in cells and during infectious-HCV replication. Blocking NS2 palmitoylation by introducing an NS2/C113S mutation reduced NS2-NS3 autoprocessing and impaired HCV RNA replication. Replication of the NS2/C113S mutant was restored by inserting an encephalomyocarditis virus (EMCV) internal ribosome entry site (IRES) between NS2 and NS3 to separate the two proteins independently of NS2-mediated autoprocessing. These results suggest that NS2 palmitoylation is critical for HCV RNA replication by promoting NS2-NS3 autoprocessing. The NS2/C113S mutation also impaired infectious-HCV assembly, DRM localization of NS2 and E2, and colocalization of NS2 with Core and endoplasmic reticulum lipid raft-associated protein 2 (Erlin-2). In conclusion, our study revealed that two major functions of NS2 involved in HCV RNA replication and virus assembly, i.e., NS2-NS3 autoprocessing and E2 recruitment to the DRM, are regulated by palmitoylation at NS2/C113. Since S-palmitoylation is reversible, NS2 palmitoylation likely allows NS2 to fine tune both HCV RNA replication and infectious-particle assembly.IMPORTANCE Chronic infection with hepatitis C virus (HCV) is a major cause of severe liver diseases responsible for nearly 400,000 deaths per year. HCV NS2 protein is a multifunctional regulator of HCV replication involved in both viral-genome replication and infectious-virus assembly. However, the underlying mechanism that enables the protein to participate in multiple steps of HCV replication remains unknown. In this study, we discovered that NS2 palmitoylation is the master regulator of its multiple functions, including NS2-mediated self-cleavage and HCV envelope protein recruitment to the virus assembly sites, which in turn promote HCV RNA replication and infectious-particle assembly, respectively. This newly revealed information suggests that NS2 palmitoylation could serve as a promising target to inhibit both HCV RNA replication and virus assembly, representing a new avenue for host-targeting strategies against HCV infection.

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Dataset Information

Hepatitis C virus NS2 protein contributes to virus particle assembly via opposing epistatic interactions with the E1-E2 glycoprotein and NS3-NS4A enzyme complexes.

Publications

Hepatitis C virus NS2 protein contributes to virus particle assembly via opposing epistatic interactions with the E1-E2 glycoprotein and NS3-NS4A enzyme complexes.

Similar Datasets

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