Posttranscriptional Regulation of Gene Expression in Hepadnaviruses

The hepadnaviruses utilize multiple nested promoters on the same DNA strand to transcribe several mRNA species, all of which terminate at the same polyadenylation site. While most studies of hepadnaviral gene expression have concentrated on transcriptional initiation, it has become clear that there exist viralcis-elements that are important in posttranscriptional events. This review will describe recent data on transcriptional elongation, transcriptional termination, and RNA export in hepadnaviruses and compare them with the corresponding processes in the distantly related retroviruses.