The Effect Of Hbx On Remodelling Of Minichromosomes Related To Hepatitis B Virus Replication

Background and objective: Viral minichromosomes are organized byhepatitis B virus (HBV) covalently closed circular DNA (cccDNA), histoneand non-histone proteins. Remodelling of minichromosomes is crucial forregulation of HBV replication, which is dependent on the presence of HBVX protein (HBx). The objective was to determine whether HBx regulatesother remodelling of minichromosomes related to HBV replication inaddition to acetylation of cccDNA-bound histones.Methods: The HBx-deficient muant plasmid was constructed bysite-directed mutagenesis. The effect of HBx on HBV replication,transcription, antigen secretion and cccDNA-bound methylated,phosphorylated and acetylated histone H3were then investigated bytransfecting human HepG2cells with the linear full-length HBV genome(wild-type) or the HBx-deficient mutant HBV DNA (HBx mutant).Results: Although the formation of cccDNA was not affected by HBx,HBV replication, transcription and antigen secretion were all significantlyreduced resulting from the absence of HBx. The acetylation,mono-methylation and phosphorylation of cccDNA-bound histone H3wereassociated with HBV replication. In addition, the levels of cccDNA-boundmethylated, phosphorylated and acetylated histone H3decreased sharply inHBx mutant HBV DNA. HBx modulated not only the status of acetylation but also methylation and phosphorylation of histone H3bound to thecccDNA during HBV replication in HepG2cells.Conclusions: HBx plays an important role in regulating remodelling ofminichromosomes related to HBV replication.