2 REGIONS OF AN AVIAN HEPADNAVIRUS RNA PREGENOME ARE REQUIRED IN CIS FOR ENCAPSIDATION

We have constructed a series of deletion mutants spanning the genome o f duck hepatitis B virus in order to determine which regions of the vi ral genome are required in cis for packaging of the pregenome into cap sid particles. Deletion of sequences within either of two nonadjacent regions prevented replication of the mutant viral genomes expressed in a permissive avian hepatoma cell line in the presence of functionally active viral core and P proteins. Extraction of RNA from cells transf ected with these replication-defective mutants showed that the mutants retained the capacity to be transcribed into a pregenomic-size viral RNA, but that these RNA species were not packaged into viral capsids. The two regions defined by these deletions are located 36 to 126 (regi on I) and 1046 to 1214 (region II) nucleotides downstream of the 5' en d of the pregenome and contain sequences which are required in cis for encapsidation of the duck hepatitis B virus pregenome.