Avian hepatitis B viruses: Molecular and cellular biology, phylogenesis, and host tropism

Figure 3 Model of the hepadnaviral life cycle. The hepadnaviral particle binds the hepatocyte via a specific receptor complex/molecule. It then enters the cell via endocytosis and is transported intracellularly in a MT-dependent fashion. After release out of the endosomal compartment, the nucleocapsid containing the viral DNA binds the nuclear pore complex and the viral genome is released into the nucleus. It is also possible that the whole nucleocapsid enters the nucleus and releases the viral DNA inside. Afterwards, the viral rcDNA is converted into cccDNA and viral transcripts are made. These are exported into the cytosol where the pgRNA is packaged together with the viral polymerase into the nucleocapsid. Inside the capsid, the RNA is reverse transcribed into the viral DNA genome. These matured nucleocapsids can then either be transported to the nucleus to add to the cellular cccDNA pool or they interact with viral surface proteins on the cellular ER membrane. There, the nucleocapsid buds into the lumen of the ER and is then transported in a yet undefined fashion to the cell surface where the viral particle is released into the cell exterior.