Ten-eleven translocation (Tet) methylcytosine dioxygenase-dependent viral DNA demethylation mediates in vivo hepatitis B virus (HBV) biosynthesis

Liver-specific ten-eleven translocation (Tet) methylcytosine dioxygenases 2 and 3 (Tet2 plus Tet3)-deficient hepatitis B virus (HBV) transgenic mice fail to support viral biosynthesis. The levels of viral transcription and replication intermediates are dramatically reduced. Hepatitis B core antigen is only observed in a very limited number of pericentral hepatocytes in a pattern that is similar to glutamate-ammonia ligase (Glul), a beta-catenin target gene. HBV transcript abundance in adult Tet-deficient mice resembles that observed in wild-type neonatal mice. Furthermore, the RNA levels of several beta-catenin target genes including Glul, Lhpp, Notun, Oat, Slc1a2, and Tbx3 in Tet-deficient mice were also similar to that observed in wild-type neonatal mice. As HBV transcription is regulated by beta-catenin, these findings support the suggestion that neonatal Tet deficiency might limit beta-catenin target gene expression, limiting viral biosynthesis. Additionally, HBV transgene DNA displays increased 5-methylcytosine (5mC) frequency at CpG sequences consistent with neonatal Tet deficiency being responsible for decreased developmental viral DNA demethylation mediated by 5mC oxidation to 5-hydroxymethylcytosine, a process that might be responsible for the reduction in cellular beta-catenin target gene expression and viral transcription and replication.