Fig. 3.

Differential expression of S- and L-HDAg as a consequence of antigenome RNA editing by ADAR-1. The HDV antigenomic RNA has one single open reading frame from which the two isoforms of HDAg are expressed. Adenosine deaminase acting on RNA-1 (ADAR1) catalyses editing of the amber/W site on the antigenomic HDV RNA and adenosine 1012 is converted to inosine. After replication and mRNA transcription, the original stop codon (AUG, terminating the synthesis of S-HDAg) is converted into UGG, coding for a tryptophan (Trp) residue and allowing translation to proceed until the next stop codon, which results in the addition of 19 amino acids (L-HDAg).