Interaction of Hepatitis C Virus Core Protein with Viral Sense RNA and Suppression of Its Translation

Abstract

To clarify the binding properties of hepatitis C virus (HCV) core protein and its viral RNA for the encapsidation, morphogenesis, and replication of HCV, the specific interaction of HCV core protein with its genomic RNA synthesized in vitro was examined in an in vivo system. The positive-sense RNA from the 5′ end to nucleotide (nt) 2327, which covers the 5′ untranslated region (5′UTR) and a part of the coding region of HCV structural proteins, interacted with HCV core protein, while no interaction was observed in the same region of negative-sense RNA and in other regions of viral and antiviral sense RNAs. The internal ribosome entry site (IRES) exists around the 5′UTR of HCV; therefore, the interaction of the core protein with this region of HCV RNA suggests that there is some effect on its cap-independent translation. Cells expressing HCV core protein were transfected with reporter RNAs consisting of nt 1 to 709 of HCV RNA (the 5′UTR of HCV and about two-thirds of the core protein coding regions) followed by a firefly luciferase gene (HCV07Luc RNA). The translation of HCV07Luc RNA was suppressed in cells expressing the core protein, whereas no significant suppression was observed in the case of a reporter RNA possessing the IRES of encephalomyocarditis virus followed by a firefly luciferase. This suppression by the core protein occurred in a dose-dependent manner. The expression of the E1 envelope protein of HCV or β-galactosidase did not suppress the translation of both HCV and EMCV reporter RNAs. We then examined the regions that are important for suppression of translation by the core protein and found that the region from nt 1 to 344 was enough to exert this suppression. These results suggest that the HCV core protein interacts with viral genomic RNA at a specific region to form nucleocapsids and regulates the expression of HCV by interacting with the 5′UTR.

Efficient trans -Encapsidation of Hepatitis C Virus RNAs into Infectious Virus-Like Particles

“…Given the extensive RNA secondary structures observed within the NTRs of the HCV genome, these stretches may mediate a specific interaction with HCV core protein and thus initiate packaging. Although not undisputed (67), various reports identified a direct and specific binding of HCV core to the IRES modulating its activity (5,53,54). The latter findings are in principal in line with the hypothesis that the HCV RNA comprises specific packaging signals and further suggest that the interaction between core and these sequences may be regulated to permit translation by ribosomes, replication by HCV NS proteins, and packaging by core in a coordinated manner.…”

Exploiting cis -Acting Replication Elements To Direct Hepatitis C Virus-Dependent Transgene Expression

“…If this is the case, an additive antiviral effect may be expected. Additionally, given that the HCV-responsive expression construct described here contains the 5Ј (nucleotides 1 to 377) region of the HCV genome, which was reported to interact with HCV nucleocapsid (core) protein and play an important role in viral encapsidation (11,33,35,41), it is tempting to speculate that the HCV minigenome may also be packaged inside the virion and budded from infected cells and, if so, it could direct secondary transgene expression by sequential infection, ultimately augmenting its anti-HCV effect.…”

Non-encapsidation activities of the capsid proteins of positive-strand RNA viruses

“…The Hepatitis C virus (HCV; Flaviviridae) core protein can specifically bind the internal ribosome entry site (IRES) in the 5′ UTR of the viral genome to suppress the translation of genes downstream (Boni et al, 2005;Shimoike et al, 1999). Positivelycharged residues in the N-terminal portion of the HCV core protein are required for the translation repression (Li et al, 2003;Shimoike et al, 2006).…”