Interferon-inducible ribonuclease ISG20 inhibits hepatitis B virus replication through directly binding to the epsilon stem-loop structure of viral RNA
(A) HepDES19 cells were seeded in 35 mm-dish and cultured with tet-free medium to induce HBV pgRNA transcription. 24 h later, cells were transfected with 4 μg of control vector or plasmid F-ISG20 for 36 h, then tet was added back to the culture medium to shut down pgRNA transcription. Cells were harvested at indicated time points. HBV RNA was extracted from harvested samples and analyzed by Northern blot. Expression of FLAG-tagged ISG20 was detected by Western blot. The results are representative of three separate trials. (B) HepG2 cells in 12-well-plate were co-transfected with 0.7 μg of pTREHBVDES and 0.1 μg of pTet-off, plus 0.7 μg of control vector or plasmid F-ISG20. Four days post transfection, tet was added back and cells were harvested at indicated time points and subjected to HBV RNA qPCR analysis. The relative levels of HBV total RNA normalized to β-actin mRNA levels in each samples were expressed as the percentage of the RNA levels from the corresponding sample at 0 h time point (Mean ± SD, n = 4). The half-life of HBV RNA was marked on the plot.