The majority of duck hepatitis B virus reverse transcriptase in cells is nonencapsidated and is bound to a cytoplasmic structure

The hepadnavirus reverse transcriptase binds cotranslationally to the viral pregenomic RNA. This ribonucleoprotein complex is then encapsidated into n ascent viral core particles, where the reverse transcriptase copies the vir al RNA into DNA. Here we report that 75% of the duck hepatitis B virus reve rse transcriptase present in transfected LMH cells does not follow this wel l-known pathway but rather exists in the cell separate from the core protei n or nucleocapsids. The nonencapsidated reverse transcriptase is also abund ant in infected duck liver. The nonencapsidated reverse transcriptase exist s as a complex set of isoforms that are mast likely produced by posttransla tional modification. Interestingly, only the smallest of these isoforms is encapsidated into viral care particles. The nonencapsidated reverse transcr iptase is bound to a large cellular cytoplasmic structure(s) in a detergent -sensitive complex. The cellular distribution of the reverse transcriptase only partially overlaps that of the core protein, and this distribution is unaffected by blocking encapsidation. These observations raise the possibil ities that the metabolic fate of the reverse transcriptase may be posttrans criptionally regulated and that the reverse transcriptase may have roles in the viral replication cycle beyond its well-known function in copying the viral genome.