Following virus entry into host cell, provides nuclear import of HDV RNPs thanks to its nuclear localization signal. Needs co-infection with hepatitis B virus to provide surface proteins, otherwise there is no packaging or budding. Packages the HDV ribonucleoprotein in hepatitis B virus empty particles. Interacts with both HDV genomic RNA and cytoplasmic tail of HBsAg. May inhibit viral RNA replication (By similarity). Homodimer. Homooctamer. Interacts with HBV HBsAg. May interact with clathrin to induce virion budding (By similarity). isoprenylated in the cytoplasm, and translocates in the nucleus possibly after phosphorylation. Translocates after to nuclear speckle, then to the ER membrane where interaction with Hepatitis B virus antigene takes place (By similarity). Prenylated by host farnesyl-transferase in the cytoplasm prior to nucleus translocation. Phosphorylated at serines by host CK2 and other kinases. phosphorylation does not seem to be important for its function (By similarity). 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 (AC P06934), 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. S-HDAg suppresses editing of non-replicating antigenomic RNA, thereby regulating the extent of editing (By similarity). This strain belongs to the genotype I found in North America, Europe, Africa, East and West Asia and the South Pacific. Belongs to the hepatitis delta antigen family.