Article

Stabilization of hepatitis C virus RNA by an Ago2-miR-122 complex

Lineberger Comprehensive Cancer Center and Division of Infectious Diseases, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7292, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 01/2012; 109(3):941-6. DOI: 10.1073/pnas.1112263109
Source: PubMed

ABSTRACT MicroRNAs (miRNAs) are small noncoding RNAs that regulate eukaryotic gene expression by binding to regions of imperfect complementarity in mRNAs, typically in the 3' UTR, recruiting an Argonaute (Ago) protein complex that usually results in translational repression or destabilization of the target RNA. The translation and decay of mRNAs are closely linked, competing processes, and whether the miRNA-induced silencing complex (RISC) acts primarily to reduce translation or stability of the mRNA remains controversial. miR-122 is an abundant, liver-specific miRNA that is an unusual host factor for hepatitis C virus (HCV), an important cause of liver disease in humans. Prior studies show that it binds the 5' UTR of the messenger-sense HCV RNA genome, stimulating translation and promoting genome replication by an unknown mechanism. Here we show that miR-122 binds HCV RNA in association with Ago2 and that this slows decay of the viral genome in infected cells. The stabilizing action of miR-122 does not require the viral RNA to be translationally active nor engaged in replication, and can be functionally substituted by a nonmethylated 5' cap. Our data demonstrate that a RISC-like complex mediates the stability of HCV RNA and suggest that Ago2 and miR-122 act coordinately to protect the viral genome from 5' exonuclease activity of the host mRNA decay machinery. miR-122 thus acts in an unconventional fashion to stabilize HCV RNA and slow its decay, expanding the repertoire of mechanisms by which miRNAs modulate gene expression.

Download full-text

Full-text

Available from: Rohit Jangra, Jul 22, 2015
1 Follower
 · 
156 Views
  • Source
    • "Unique to this virus is a dependence on the liver-specific microRNA-122 (miR-122) (Jopling et al., 2005). Whereas miRNAs typically interact with the 3 0 UTRs of mRNAs to promote mRNA destabilization and/or translational repression (Bartel, 2009), the binding of miR-122 to two binding sites (seed site S1 and S2) in the 5 0 UTR of HCV genomic RNA is critical for viral replication (Jopling et al., 2008; Machlin et al., 2011) by moderately stimulating viral protein translation (Henke et al., 2008) and, in concert with Argonaute (AGO), by stabilizing and protecting the uncapped HCV RNA genome from degradation (Li et al., 2013b; Sedano and Sarnow, 2014; Shimakami et al., 2012). As the predominant miRNA in the liver, miR-122 has multiple roles to regulate lipid metabolism (Esau et al., 2006), iron homeostasis (Castoldi et al., 2011), and circadian rhythms (Gatfield et al., 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hepatitis C virus (HCV) uniquely requires the liver-specific microRNA-122 for replication, yet global effects on endogenous miRNA targets during infection are unexplored. Here, high-throughput sequencing and crosslinking immunoprecipitation (HITS-CLIP) experiments of human Argonaute (AGO) during HCV infection showed robust AGO binding on the HCV 5'UTR at known and predicted miR-122 sites. On the human transcriptome, we observed reduced AGO binding and functional mRNA de-repression of miR-122 targets during virus infection. This miR-122 "sponge" effect was relieved and redirected to miR-15 targets by swapping the miRNA tropism of the virus. Single-cell expression data from reporters containing miR-122 sites showed significant de-repression during HCV infection depending on expression level and site number. We describe a quantitative mathematical model of HCV-induced miR-122 sequestration and propose that such miR-122 inhibition by HCV RNA may result in global de-repression of host miR-122 targets, providing an environment fertile for the long-term oncogenic potential of HCV. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell 03/2015; 160(6):1099-1110. DOI:10.1016/j.cell.2015.02.025 · 33.12 Impact Factor
  • Source
    • "Nascent RNA genomes are translated to produce new viral proteins, serve as new/additional RNA templates for further RNA replication and are progressively assembled to form infectious virions. HCV replication is dependent on microRNA 122 (miR-122) [97], a liver-specific microRNA that recruits Argonaute 2 to the 5 0 end of the viral genome [98], stabilizing it and slowing its degradation by the 5 0 exonuclease Xrn1 [99]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hepatitis C virus (HCV) is an important human pathogen that causes hepatitis, liver cirrhosis and hepatocellular carcinoma. It imposes a serious problem to public health in the world as the population of chronically infected HCV patients who are at risk of progressive liver disease is projected to increase significantly in the next decades. However, the arrival of new antiviral molecules is progressively changing the landscape of hepatitis C treatment. The search for new anti-HCV therapies has also been a driving force to better understand how HCV interacts with its host, and major progresses have been made on the various steps of the HCV life cycle. Here, we review the most recent advances in the fast growing knowledge on HCV life cycle and interaction with host factors and pathways.
    Journal of Hepatology 11/2014; 61(1). DOI:10.1016/j.jhep.2014.06.031 · 10.40 Impact Factor
  • Source
    • "In addition to miR-122 itself, Dicer and TRBP, which process pre-miR-122 into mature miR-122, are required for the activation of HCV replication (Zhang et al., 2012a). Ago2 is also required for the miR-122 regulation of HCV RNA accumulation and translation (Wilson et al., 2011; Shimakami et al., 2012a). Localization of Ago2 to the HCV replication complex suggests its possible role in the subsequent steps of miR-122 activity (Ariumi et al., 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Hepatitis C virus (HCV) infection is a worldwide health problem and is one of the main causes of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma (HCC). However, only limited therapeutic options and no vaccines are currently available against HCV infection. Recent studies of microRNAs (miRNAs), which are able to regulate HCV replication and its related liver diseases by directly interacting with the HCV genome or indirectly controlling virus-associated host pathways, have broadened our understanding of the HCV life cycle. HCV utilizes host cellular miRNAs and modulates expression of miRNAs in infected hepatocytes for its infection and propagation. Moreover, such miRNAs directly or indirectly alter HCV replication efficiency and induce liver diseases including liver fibrosis, cirrhosis, or HCC. Representatively, miR-122 directly modulates the HCV life cycle by increasing HCV translation and genomic RNA stability. Recently, a phase IIa clinical trial with miravirsen, an LNA form of antimiR-122 oligonucleotides, showed significant reduction in serum HCV levels in patients chronically infected with HCV with no detectible evidence of resistance. In addition to miR-122, other miRNAs involved in the regulation of HCV propagation could be targeted in strategies to modulate HCV replication and pathogenesis. In this review, we summarize the features of miRNAs critical for HCV replication and HCV-mediated liver abnormalities and briefly discuss their potential application as therapeutic reagents for the treatment of HCV infection and its related diseases.
    The Journal of Microbiology 06/2014; 52(6):445-51. DOI:10.1007/s12275-014-4267-x · 1.53 Impact Factor
Show more