Hepatitis C virus (HCV) isHepatitis C virus (HCV) is a leading cause of chronic liver disease, which affects around 170 million people worldwide. Infections are initially acute, and in many cases the symptoms are mild. However, around 80% of patients eventually develop a persistent chronic infection which can result in steatosis, fibrosis, cirrhosis, liver failure, and, in some cases, hepatocellular carcinoma. The main treatments currently available for chronically infected patients use a combination of pegylated alpha interferon and ribavirin, but these still result in a sustained antiviral response in only about 50% of genotype 1 infections (4). Consequently, more effective antivirals that target either the virus proteins directly or the host cell proteins required during HCV replication are currently being developed. In order to ensure that successful antivirals are generated, it is important that all aspects of the HCV life cycle and HCV-associated pathology are well understood.One way in which the different host processes that are an essential part of the HCV replication cycle can be studied is to investigate the effect that HCV infection has on cellular gene expression. RNA microarray hybridization is routinely used to investigate host gene expression and allows the entire transcriptomic profile of the cell to be characterized. Microarray analysis of HCV-infected cells can provide an insight into the genes involved in host cell antiviral responses, genes that are essential for the HCV replication cycle, and genes that contribute to HCV-associated liver pathology. Microarray expression profiling has already been used to study host gene expression in cells transfected with RNA encoding either individual HCV genes, HCV subgenomic replicons, or the full-length HCV genome. These studies have demonstrated that the replication of the HCV genome results in the regulation of a small number of host genes involved in lipid metabolism, cellular immunity, proliferation, apoptosis, and molecular transport (2,5,15,32). These studies have provided interesting insights into the HCV replication cycle. However, the biological significance of gene expression patterns identified is less clear, since the full virus replication cycle, including the processes of viral entry, assembly, and exit, does not take place.The recent discovery of JFH-1, a genotype 2a HCV clone that can undergo a complete infection cycle in cell culture, provides the opportunity to characterize the true effect of HCV infection on host gene expression (51). A recent study investigated the effects that a J6/JFH-1 chimera had on the gene expression profile of Huh7.5 cells during a time course infection with time points of 24, 48, 72, 96, and 120 h (53). The number of host genes regulated during infection was much higher than that previously observed for cells permitting only genome replication, indicating that the full replication cycle has additional effects on host gene expression.In this study, we present the results from an investigation

Staufen1 is a dsRNA-binding protein involved in the regulation of translation and the trafficking and degradation of cellular RNAs. Staufen1 has also been shown to stimulate translation of human immunodeficiency virus type 1 (HIV-1) RNA, regulate HIV-1 and influenza A virus assembly, and there is also indication that it can interact with hepatitis C virus (HCV) RNA. To investigate the role of Staufen1 in the HCV replication cycle, the effects of small interfering RNA knockout of Staufen1 on HCV strain JFH-1 replication and the intracellular distribution of the Staufen1 protein during HCV infection were examined. Silencing Staufen1 in HCV-infected Huh7 cells reduced virus secretion by around 70 %, intracellular HCV RNA levels by around 40 %, and core and NS3 proteins by around 95 and 45 %, respectively. Staufen1 appeared to be predominantly localized in the endoplasmic reticulum at the nuclear periphery in both uninfected and HCV-infected Huh7 cells. However, Staufen1 showed significant co-localization with NS3 and dsRNA, indicating that it may bind to replicating HCV RNA that is associated with the nonstructural proteins. Staufen1 and HCV core protein localized very closely to one another during infection, but did not appear to overlap, indicating that Staufen1 may not bind to core protein or localize to the core-coated lipid droplets, suggesting that it may not be directly involved in HCV virus assembly. These findings indicate that Staufen1 is an important factor in HCV replication and that it might play a role early in the HCV replication cycle, e.g. in translation, replication or trafficking of the HCV genome, rather than in virion morphogenesis.

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