Effect of FEN1 inhibition on HBV-replicating cells. Hep38.7-Tet cells were treated with dimethylsulfoxide (DMSO) as a vehicle control, PTPD (5 μM), or 3TC (50 μM) in the absence of tetracycline for 5 days. At day 5, levels of HBV DNA, HBV RNA (pgRNA normalized by HPRT) and pre-C mRNA were analyzed. qPCR analysis of HBV DNA in (A) culture supernatant, (B) cytoplasmic NC-DNA, (C) cccDNA, and (D) pgRNA. Each result represents the mean ± SEM of three independent experiments. Asterisks indicate statistically significant differences; *P < 0.05, **P < 0.01, ***P < 0.001 compared with DMSO (A–D). (E) RT-PCR analysis for pre-C mRNA transcribed from cccDNA in Hep38.7-Tet cells. β-actin was used as a loading control.