Fig. 3. Post-transcriptional down-regulation of viral capsids. (A) Control and PKR-si Huh-7 cells transfected with pHBV1.2 were treated with 500 U/ml of IFN-α for two days. Total cellular RNA was extracted and viral transcripts were measured by Northern blotting. Expected sizes of the four viral transcripts are indicated on the right. Analyzed in parallel was mRNA of a co-transfected CAT gene construct controlled by the HBV enhancer I and the HBX promoter. The latter construct also served a control for transfection efficiency. (B) Control and PKR-si Huh-7 cells transfected with pHBV1.2 were treated with 500 U/ml of IFN-α for four days. Viral capsid immunoprecipitated with anti-core antibody was subjected to the endogenous polymerase assay. Radiolabelled DNA products were extracted and electrophoresed on a 1% agarose gel. An autoradiograph of three similar experiments was shown with quantified signal intensity. (C) Control and PKR-si Huh-7 cells were treated for two days with 1,000 U/ml of IFN-α, and cellular proteins were immunoblotted with the antibodies against PKR, phospho-PKR, STAT-1, phospho-STAT-1, or actin (as a loading control).