Duck hepatitis B virus polymerase acts as a suppressor of core protein translation.

Nucleocapsid assembly in hepadnavirus replication requires selective encapsidation of the pregenomic RNA template and the viral polymerase by the core proteins. It has been shown that an encapsidation signal located at the 5' end of the pregenomic RNA is responsible for its interaction with the polymerase. In the present study, we have shown that a region located at the 3' periphery of the core open reading frame may interact with the viral polymerase in duck hepatitis B virus. By using an in vitro rabbit reticulocyte lysate translation system, we found that interaction of the polymerase with this region resulted in selective suppression of core mRNA translation. Insertion of this putative inhibitory sequence into the CD4 gene also led to a selective inhibition of CD4 mRNA translation in the presence of polymerase. Specific inhibition of core protein synthesis was observed in a chicken hepatoma cell line (LMH) cotransfected with core and polymerase plasmid DNA.