viruses

Deltaviruses, such as the notorious Hepatitis D virus (HDV), share characteristics with viruses, satRNAs, and viroids. Formally, HDV is a satellite virus of Hepatitis B virus limited to human hosts, although deltaviruses with hosts ranging from ducks to snakes to fish and insects have recently been discovered. Unlike other viruses, HDV has a circular structured genome and replicates via a rolling circle mechanism in which self-cleavage is accomplished using a unique ribozyme in both genomic polarities. Like viroids, HDV uses host polymerase II for (+) strand synthesis, though there is currently no consensus on the polymerase for (−) strand synthesis. Unlike the other viroid-like RNA agents in this database, deltaviruses encode a single open reading frame coding for two isoforms of the delta antigen protein in the (−) polarity.

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