Staufen1 promotes HCV replication by inhibiting protein kinase R and transporting viral RNA to the site of translation and replication in the cells

Abstract

Persistent hepatitis C virus (HCV) infection leads to chronic hepatitis C (CHC), which often progresses to liver cirrhosis (LC) and hepatocellular carcinoma (HCC). The molecular mechanisms that establish CHC and cause its subsequent development into LC and HCC are poorly understood. We have identified a cytoplasmic double-stranded RNA binding protein, Stau1, which is crucial for HCV replication. In this study, Stau1 specifically interacted with the variable-stem-loop region in the 3′ NTR and domain IIId of the HCV-IRES in the 5′ NTR, and promoted HCV replication and translation. Stau1 coimmunoprecipitates HCV NS5B and a cell factor, protein kinase R (PKR), which is critical for interferon-induced cellular antiviral and antiproliferative responses. Like Stau1, PKR displayed binding specificity to domain IIId of HCV-IRES. Stau1 binds to PKR and strongly inhibits PKR-autophosphorylation. We demonstrated that the transport of HCV RNA on the polysomes is Stau1-dependent, being mainly localized in the monosome fractions when Stau1 is downregulated and exclusively localized in the polysomes when Stau1 is overexpressed. Our findings suggest that HCV may appropriate Stau1 to its advantage to prevent PKR-mediated inhibition of eIF2α, which is required for the synthesis of HCV proteins for translocation of viral RNA genome to the polysomes for efficient translation and replication.

Hepatitis C virus plays with fire and yet avoids getting burned. A review for clinicians on processing bodies and stress granules

“…HCV can also exploit other RNP proteins that form part of the replication complex and assist in assembly and secretion. These processes can be tracked by a relocation of several P‐bodies and SGs components such as DDX6, PatL1, LSm1‐7, DDX3, Xrn1, TIA‐1, TIAR, G3BP, Ago1‐4 (Ago2 is the most convincing example) and Stau1, inside hepatocytes . The complexity of HCV‐host interaction can also be found in several manipulations of PKR‐based stress responses which, again, may seem contradictory .…”

“…These processes can be tracked by a relocation of several P‐bodies and SGs components such as DDX6, PatL1, LSm1‐7, DDX3, Xrn1, TIA‐1, TIAR, G3BP, Ago1‐4 (Ago2 is the most convincing example) and Stau1, inside hepatocytes . The complexity of HCV‐host interaction can also be found in several manipulations of PKR‐based stress responses which, again, may seem contradictory . Nevertheless, these intimate molecular mechanisms are still not completely understood, particularly in the wake of discoveries that both formation and dissolution of P‐bodies and SGs are extremely fine processes with very specific physical properties .…”

“…This is what seems to occur with Stau1, a protein present in SGs that is possibly involved in SG disaggregation. Stau1 binds to IRES and may not only facilitate viral translation and replication, but also block PKR …”

“…45,51,52,[56][57][58][59][60][64][65][66][67]81,86 The complexity of HCV-host interaction can also be found in several manipulations of PKR-based stress responses which, again, may seem contradictory. 66,[75][76][77]80,81 Nevertheless, these intimate molecular mechanisms are still not completely understood, particularly in the wake of discoveries that both formation and dissolution of P-bodies and SGs are extremely fine processes with very specific physical properties. [19][20][21] The consequences of all these alterations on the liver are unknown, but might be of importance after long-term infections, since gene expression is affected by RNA granules (Figure 3).…”

Modulation of HCV replication and translation by ErbB3 binding protein1 isoforms

“…Two sets of Huh7.5 cells grown overnight in 6-well culture plates were transfected with PKR siRNA. Twenty-four hours later, cells were infected with HCV-JFH1 virions in the presence of 5-µg/ml polybrene (Dixit et al, 2016). At 6 h, cells after infection, cells were washed two times with PBS and supplemented with fresh medium.…”