Promotes both transcription and replication of genomic RNA. Following virus entry into host cell, provides nuclear import of HDV RNPs thanks to its nuclear localization signal. May interact with host RNA polymerase II thereby changing its template requirement from DNA to RNA. RNA pol II complex would then acts as an RNA-directed RNA polymerase, and transcribe and replicate HDV genome (By similarity). Homodimer. Homooctamer. Interacts with host RNA polymerase II complex, and with host NPM1. Phosphorylated at serines and threonines by host MAPK1/3, PKR, and CK2. Acetylation modulates nuclear localization. Neo-synthesized genomic RNA migrates from the nucleus to the cytoplasm, where they interact with S-HDAg, which once acetylated redirect both partners to the nucleus (By similarity). Methylation plays a role in viral genome replication. Partially edited. RNA editing at this position occurs on the antigenomic strand and consists of a conversion of A to G catalyzed by the cellular enzyme ADAR1. The unedited RNA version gives rise to the small delta antigen, which ends with a nonsense codon at position 196. In the edited version, this amber codon is modified to a tryptophan codon and gives rise to the large delta antigen protein (AC P0C6L9). S-HDAg suppresses editing of non-replicating antigenomic RNA, thereby regulating the extent of editing (By similarity). This strain belongs to the genotype II found only in East Asia. Belongs to the hepatitis delta antigen family.