Introduction:
Emerging evidence identifies that microRNAs (miRNAs) are associated with hepatitis B virus (HBV) infection. In the current study, we mainly focus on the functions and underlying mechanisms of miR-212-3p in HBV replication in hepatocellular carcinoma (HCC).

Material and methods:
The levels of miR-212-3p, nuclear factor I A (NFIA) and HBV DNA copies were measured by qRT-PCR. The level of core particle-associated HBV DNA, the production of hepatitis B surface antigen (HBsAg) and hepatitis B e-antigen (HBeAg), and the expression of NFIA were detected via southern blot assay, ELISA and western blot assay, respectively. The putative target of miR-212-3p was predicted by TargetScan and Pictar, followed by the dual luciferase reporter assay and RNA immunoprecipitation (RIP) assay to validate the interaction. The interaction between miR-212-3p and enhancer I/X promoter (EnI/Xp) reporter was also verified by dual luciferase reporter assay. In addition, the cell viability and apoptotic rate were detected by MTT and flow cytometry, respectively.

Results:
miR-212-3p mimics or NFIA knockdown inhibited HBV expression and replication in HepG2.2.15 cells, while miR-212-3p inhibitor or NFIA overexpression showed the opposite trend. NFIA was confirmed as a direct target of miR-212-3p. Furthermore, miR-212-3p impeded HBV expression and replication by suppressing NFIA. Also, miR-212-3p lowered EnI/Xp activity by regulating NFIA. In addition, miR-212-3p retarded cell viability and induced apoptosis through targeting NFIA.

Conclusions:
miR-212-3p targets NFIA to down-regulate its expression, thereby inhibiting HBV replication and tumorigenesis in HCC. Our findings might provide a promising therapeutic target for HBV infection.