Localization of hepatitis B virus core protein and viral DNA at the nuclear membrane.

An early step in the replication of the hepatitis B virus (HBV) genome is the transport of the viral DNA into the nucleus of the infected cell. So far only little is known about the events and mechanisms at the nuclear membrane required for entry of the viral genome into the nucleus. Using a hepatoblastoma cell line that constitutively produces hepatitis B virions and in so doing displays intracellular viral amplification, we showed that nonparticulated HBV core protein is associated with nuclear membrane pore complexes. Additionally, viral DNA has been detected firmly attached to the nuclear membrane. Small amounts of viral core protein, as well as viral DNA, were detectable within the cell nucleus. However, core particles could not be shown at the nuclear membrane or within the nuclei of these cells. Our observations on localization of HBV DNA and core protein at the nuclear membrane thus provide a suggestion for further examinations of the transfer of the viral genome from the cytoplasm into the nucleus of the infected cell.