COORDINATE REGULATION OF REPLICATION AND VIRUS ASSEMBLY BY THE LARGE ENVELOPE PROTEIN OF AN AVIAN HEPADNAVIRUS

We have used linker scanning and site-directed mutagenesis in an attem pt to distinguish among the known functions of the duck hepatitis B vi rus large envelope protein, p36. We found that tinker-encoded amino ac id substitutions in at least one region of the pre S envelope protein p36 produced defects in both the production of enveloped virus and the regulation of covalently closed circular DNA (cccDNA) synthesis. Most linker substitutions, typically in the 5' two-thirds of the pre-S reg ion of the p36 gene did not affect either cccDNA regulation or envelop ed virus production but did destroy the infection competence of the en veloped particles produced. Single amino acid substitutions of residue s 128 and 131 demonstrated a similar correlation between defects in th e ability of p36 to support enveloped virus production and to control cccDNA levels. We concluded from these studies that virus production a nd cccDNA regulation probably require a common activity of p36.