Fig. 2

HDV RNA editing mechanism. Genomic RNA (gray rounded rectangle) serves as a template for mRNA synthesis which is translated into HDAg-S, which is necessary for synthesis of new RNAs. The genome serves as a template for the synthesis of the antigenome (rounded black rectangle), which also serves as a template for new genomic RNAs. A fraction of antigenomic RNAs are edited by the enzyme adenosine deaminase (ADAR-1) at the UAG site (stop codon), also called the Amber/W site (wavy and dotted arrow), wherein an adenine is replaced by inosine. The edited antigenomes serve as templates for the edited genomes (rounded rectangle edited for ACC). Edited genomes serve to synthesize edited messenger RNAs (with UGG – Tryptophan instead of UAG-stop codon) encoding HDAg-L, which is the key factor for enveloping the virus and inhibiting replication. The edited genome and antigenomes are simultaneously synthesized by a replication mechanism called rolling-circle. This way the editing levels accumulate replication products. Note that the numbering scheme is intended to indicate an increasing repertoire of activities that persist as replication occurs, rather than a gradual progression in which the above processes are terminated. (Source: [28]. Curr Top MicrobiolImmunol, our translation, modified)