MiR-122 modulates type I interferon expression through blocking suppressor of cytokine signaling 1

MiR-122 is a liver-specific miRNA. Recent studies demonstrated that the interferon (IFN) therapy efficacy is poor in the hepatitis C virus (HCV)-infected patients with lower miR-122 abundance in the livers. The hepatocarcinoma patients also have low miR-122 levels in their livers. We previously found that the IFN expression was reduced when miR-122 was knocked down in human oligodendrocytes. The mechanism is unclear. In this study, the miR-122-abundant cell Huh7 was used to explore the regulatory mechanism of miR-122 on type I IFN expression. We found that miR-122 significantly increased the type I IFN expression in Huh7 cells, while knocking down miR-122 decreased the type I IFN expression. By screening potential miR-122 targets among the negative regulators in IFN signaling pathways, we found that there were putative miR-122 targets in the suppressor of cytokine signaling 1 (SOCS1) mRNA. Over-expressing miR-122 decreased the SOCS1 expression by 50.55% in Huh7 cells, while knocking down miR-122 increased SOCS1 expression by 62.56%. Using a green fluorescence protein (EGFP) fused SOCS1-expressing plasmid, the SOCS1-EGFP fluorescence intensity and protein were lower in miR-122 mimic-treated cells than those in mock-miRNA-treated cells, while miR-122 knockdown significantly increased the SOCS1-EGFP fluorescence intensity and protein expression. Mutations in the nt359-nt375 region abandoned the impact of miR-122 on SOCS1-EGFP expression. Taken together, SOCS1 is a target of miR-122. MiR-122 can regulate the type I IFN expression through modulating the SOCS1 expression.