Doxorubicin promotes HBV replication depending on the EP element of HBV enhancer I. (A) The sequences of wild‐type, EPM1‐, and EPM2‐mutated EP elements. Enh I: enhancer I; 2c, GB, EP, and E are the HNF3, HNF4/RXR, RFX1/MIBP1, and basic leucine zipper‐binding sites, respectively. (B) HepG2 cells were cotransfected with pGL3‐HBV Enh I (wild‐type, EPM1 or EPM2)‐luciferase, TRL‐PK and pCMV‐HA‐RFX1 expression plasmids, or vector control pCMV‐HA using lipofectamine 2000 in a 12‐well plate. The role of the EP element in RFX1‐mediated activation of the HBV enhancer I was evaluated by a dual‐luciferase assay. HepG2 cells were transfected with wild‐type, EPM1, or EPM2 mutant 1.2 × HBV expression plasmid. After 24 h of transfection, the cells were treated with 1 μmol/L Dox for 1 h. The levels of total HBV RNA (C) and RFX1 mRNA (D) were detected by qRT‐PCR at 48 h post‐Dox treatment.