In Step A. transcription starts and continues through the polyadenylated and self-cleavage sites. Polyadenylation processes the RNA and releases the HDAg mRNA that travels to the cytoplasm (Step B). The antigenomic RNA strand undergoes self-cleavage and continues transcribing for another 1.7kb(the length of the genomic RNA). Self-cleavage somehow prevents normal downstream fragment degradation. Usually after mRNA processing, the unused RNA is degraded. Not in this case! During this continued transcription, polyadenylation is suppressed (Step C). After transcribing 1.7kb, the second self-cleavage occurs. This releases the unit-length antigenome RNA (StepD). The antigenome (+) undergoes self-ligation to form the circular template for the genomic RNA (-) (Step E). The virus uses RNA polymerase II again to transcribe copies of the genome.
Assembly of the HDV virion requires the envelope proteins (HBsAg) of the helper hepadnavirus, HBV. Without the envelope the virus cannot replicate properly. This is why coinfection or super infection with HBV is necessary.