Hepatitis C Virus Core Protein Down-Regulates p21^Waf1/Cip1 and Inhibits Curcumin-Induced Apoptosis through MicroRNA-345 Targeting in Human Hepatoma Cells

<div><p>Background</p><p>Hepatitis C virus (HCV) has been reported to regulate cellular microRNAs. The HCV core protein is considered to be a potential oncoprotein in HCV-related hepatocellular carcinoma, but HCV core-modulated cellular microRNAs are unknown. The HCV core protein regulates <i>p21^Waf1/Cip1</i> expression. However, the mechanism of HCV core-associated <i>p21^Waf1/Cip1</i> regulation remains to be further clarified. Therefore, we attempted to determine whether HCV core-modulated cellular microRNAs play an important role in regulating <i>p21^Waf1/Cip1</i> expression in human hepatoma cells.</p> <p>Methods</p><p>Cellular microRNA profiling was investigated in core-overexpressing hepatoma cells using TaqMan low density array. Array data were further confirmed by TaqMan real-time qPCR for single microRNA in core-overexpressing and full-length HCV replicon-expressing cells. The target gene of microRNA was examined by reporter assay. The gene expression was determined by real-time qPCR and Western blotting. Apoptosis was examined by annexin V-FITC apoptosis assay. Cell cycle analysis was performed by propidium iodide staining. Cell proliferation was analyzed by MTT assay.</p> <p>Results</p><p>HCV core protein up- or down-regulated some cellular microRNAs in Huh7 cells. HCV core-induced microRNA-345 suppressed <i>p21^Waf1/Cip1</i> gene expression through targeting its 3′ untranslated region in human hepatoma cells. Moreover, the core protein inhibited curcumin-induced apoptosis through p21^Waf1/Cip1-targeting microRNA-345 in Huh7 cells.</p> <p>Conclusion and Significance</p><p>HCV core protein enhances the expression of microRNA-345 which then down-regulates <i>p21^Waf1/Cip1</i> expression. It is the first time that HCV core protein has ever been shown to suppress <i>p21^Waf1/Cip1</i> gene expression through miR-345 targeting.</p>