Suppression of dual specificity phosphatase I expression inhibits hepatitis C virus replication.

It was reported that dual specificity phosphatase 1 (DUSP1) is specifically upregulated in the liver of patients with chronic hetpatitis C virus (HCV) infection who do not respond to peginterferon (PegIFN) treatment. Here, we have investigated the role of DUSP1 in HCV replication in hepatoma cells stably expressing the full HCV replicon (FK). DUSP1 was silenced in cells harboring the FK replicon using a lentiviral vector encoding a DUSP1-specific short hairpin RNA (LV-shDUSP1). We demonstrated that knock-down of DUSP1 significantly inhibited HCV RNA and protein expression. Also, DUSP1 silencing enhanced the expression of phosphorylated signal transducer and activator of transcription 1 (phosho-STAT1) and facilitated the translocation of STAT1 into the nucleus. The mRNA expression levels of myxovirus resistance protein A (MxA), 2'-5'-oligoadenylate synthetase 1 (OAS1), ISG15 ubiquitin-like modifier (ISG15), chemokine C-X-C motif ligand 10 (CXCL10), and ubiquitin-specific protease 18 (USP18) were also accelerated by silencing of DUSP1. Furthermore, combined with the IFN treatment, DUSP1 silencing synergistically decreased the levels of HCV RNA. These results suggest that suppression of DUSP1 expression enhances phosphorylation and nuclear translocation of STAT1, resulting in increasing expression of interferon-stimulated genes (ISGs), which synergizes with IFN's antiviral effect against HCV. In conclusion, DUSP1 is involved in the antiviral host defense mechanism against a HCV infection and thus DUSP1 might be a target to treat chronic HCV infection.