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Nucleic Acids Res. 2018 Jun 1;46(10):5139-5158. doi: 10.1093/nar/gky273.

miR-122 does not impact recognition of the HCV genome by innate sensors of RNA but rather protects the 5' end from the cellular pyrophosphatases, DOM3Z and DUSP11.

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1
Department of Microbiology & Immunology, University of Saskatchewan, Saskatoon, SK, Canada.
2
Department of Microbiology & Immunology, McGill University, Montréal, QC, Canada.
3
Department of Biochemistry, McGill University, Montréal, QC, Canada.

Abstract

Hepatitis C virus (HCV) recruits two molecules of the liver-specific microRNA-122 (miR-122) to the 5' end of its genome. This interaction promotes viral RNA accumulation, but the precise mechanism(s) remain incompletely understood. Previous studies suggest that miR-122 is able to protect the HCV genome from 5' exonucleases (Xrn1/2), but this protection is not sufficient to account for the effect of miR-122 on HCV RNA accumulation. Thus, we investigated whether miR-122 was also able to protect the viral genome from innate sensors of RNA or cellular pyrophosphatases. We found that miR-122 does not play a protective role against recognition by PKR, RIG-I-like receptors, or IFITs 1 and 5. However, we found that knockdown of both the cellular pyrophosphatases, DOM3Z and DUSP11, was able to rescue viral RNA accumulation of subgenomic replicons in the absence of miR-122. Nevertheless, pyrophosphatase knockdown increased but did not restore viral RNA accumulation of full-length HCV RNA in miR-122 knockout cells, suggesting that miR-122 likely plays an additional role(s) in the HCV life cycle, beyond 5' end protection. Overall, our results support a model in which miR-122 stabilizes the HCV genome by shielding its 5' terminus from cellular pyrophosphatase activity and subsequent turnover by exonucleases (Xrn1/2).

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