MicroRNA 122 Affects both the Initiation and the Maintenance of Hepatitis C Virus Infections

Abstract

A liver-specific microRNA, miR-122, anneals to the HCV genomic 5’ terminus and is essential for virus replication in cell culture. However, bicistronic HCV replicons and full length RNAs with specific mutations in the 5’ UTR can replicate, albeit to low levels, without miR-122. In this study, we have identified that HCV RNAs lacking the structural gene region or having EMCV IRES-regulated translation had reduced requirements for miR-122. In addition, we found that a smaller proportion of cells supported miR-122-independent replication when compared a population of cells supporting miR-122-dependent replication, while viral protein levels per positive cell were similar. Further, the proportion of cells supporting miR-122-independent replication increased with the amount of viral RNA delivered, suggesting that establishment of miR-122-independent replication in a cell is affected by amount of viral RNA delivered. HCV RNAs replicating independent of miR-122 were not affected by supplementation with miR-122, suggesting that miR-122 is not essential for maintenance of a miR-122-independent HCV infection. However, miR-122 supplementation had a small positive impact on miR-122-dependent replication suggesting a minor role in enhancing ongoing virus RNA accumulation. We suggest that miR-122 functions primarily to initiate an HCV infection but has a minor influence on its maintenance, and we present a model in which miR-122 is required for replication complex formation at the beginning of an infection, and also supports new replication complex formation during ongoing infection and after infected cell division. IMPORTANCE: The mechanism by which miR-122 promotes the HCV life cycle is not well understood, and a role in directly promoting genome amplification is still debated. In this study, we have shown that miR-122 increases the rate of viral RNA accumulation and promotes the establishment of an HCV infection in a greater number of cells than in the absence of miR-122. However, we also confirm a minor role in promoting ongoing virus replication and propose a role in the initiation of new replication complexes throughout a virus infection. This study has implications for the use of anti-miR-122 as potential HCV therapy.

The cellular poly(rC)-binding protein 2 prevents the early steps of hepatitis C virus virion assembly

“…RLuc-GNN also bears and inactivating GNN mutation within the NS5B RNA polymerase active site (Jones et al, 2007). The pJ6/JFH-1 mono RLuc-NS2 (“ Δcore-p7”) and pJ6/JFH-1 E1-p7 del (“ΔE1-p7”) plasmids – truncated versions of the Renilla reporter virus with deletions of structural genes through p7 – were provided by Dr. Joyce Wilson (University of Saskatchewan, Saskatoon, SK, Canada) (Panigrahi et al, 2022). The pJ6/JFH Δcore (“ΔCore”) plasmid consists of a truncated version of the Renilla reporter virus with a deletion of the core-coding gene that retained the first 15 codons (necessary for a functional HCV IRES) and the final 14 codons (which orient the E1 protein in the ER) of the core-coding sequence.…”

“…Specific mutations in the 5’ UTR can circumvent some of these roles, by enabling the spontaneous formation of the functional SLII structure and/or by increasing base-pairing at the 5’ terminus to protect the viral genome from exoribonuclease-mediated decay, even in the absence of miR-122 (Chahal et al, 2021). In addition to these roles, miR-122 has been proposed to modulate viral RNA replication by facilitating the formation of replication organelles, potentially by facilitating the switch from translation to viral RNA replication, although the mechanism by which this occurs has not yet been fully elucidated (Panigrahi et al, 2022; Ono et al, 2017; Masaki et al, 2015; Li et al, 2019).…”

Current Advances in RNA Therapeutics for Human Diseases

“…For example, miravirsen has completed Phase II clinical trials for the treatment of Hepatitis (Hep) C [ 58 ]. Miravirsen is a miR-122 inhibitor that sequesters miR-122, which has been implicated in the promotion of the Hep C virus (HCV) life cycle [ 140 ]. Clinical trials to date have shown a significant reduction of HCV viral load in patients treated with miravirsen [ 58 ].…”

MicroRNAs: Small Molecules with Significant Functions, Particularly in the Context of Viral Hepatitis B and C Infection

“…Advanced reports have established that miRNAs have a pivotal role in HCV infection and pathogenesis. Many cellular miRNAs suppress the HCV RNA replicative cycle, while others enhance it [ 60 , 61 ].…”